bioenergy assessment in the caribbean. report on promising … · 2016. 2. 23. · bioenergy...

Bioenergy Assessment in the

Caribbean. Report on Promising

Bioenergy Projects Concepts

Authors: Carsten Linnenberg, Kwasi Glover, Kay Schaubach, Elliott

Lincoln, Walter Stinner, Andreas Ortwein

DBFZ Deutsches Biomasseforschungszentrum

gemeinnützige GmbH

Torgauer Straße 116

04347 Leipzig

Phone: +49 (0)341 2434-112

Fax: +49 (0)341 2434-133

www.dbfz.de

[email protected]

Date: 24.07.2015

http://www.dbfz.de/

Bioenergy Assessment in the Caribbean. Report on Promising Bioenergy

Projects Concepts

Report_Project-Concepts.docx II

Project Supporting Institutional Structures to promote Renewable Energy and

Energy Efficiency in the Caribbean Region

Activity Activity: Assessment of bioenergy resource potentials, framework conditions,

technology options and development of bioenergy investment projects in the

Caribbean

GIZ ID VN: 81176707

PN: 10.2262.3-001.00

Report for Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH

OE 5340, room ED 21024

Dag-Hammarskjöld-Weg 1–5,

65760 Eschborn

Supplier DBFZ Deutsches Biomasseforschungszentrum gemeinnützige GmbH

Torgauer Straße 116

04347 Leipzig

Germany

Represented in joint management by:

Prof. Dr. mont. Michael Nelles and Daniel Mayer

Phone: +49 (0)341 2434-112

Fax: +49 (0)341 2434-133

E-Mail: [email protected]

Internet: www.dbfz.de

Contact person Kay Schaubach

Phone: +49 (0)341 2434-468

Fax: +49 (0)341 2434-133

E-Mail: [email protected]

http://www.dbfz.de/

Table of Content

Report_Project-Concepts.docx III

Table of Content

1 Background .......................................................................................................................................................... 7

2 Concept overview ................................................................................................................................................. 8

3 Biogas plant for Barnwell Farms, Barbados ................................................................................................... 10

3.1 Business Case and Framework ............................................................................................................................. 10

3.2 Site description......................................................................................................................................................... 11

3.3 Feedstock supply ..................................................................................................................................................... 12

3.4 Preliminary plant design ......................................................................................................................................... 13

3.5 Cost estimation ........................................................................................................................................................ 16

3.6 Impact estimation.................................................................................................................................................... 19

3.7 Project development plan ...................................................................................................................................... 21

3.8 Risk analysis and recommendations.................................................................................................................... 21

4 Biogas plant for Armag Farms, Barbados ...................................................................................................... 22





4.5 Cost estimation ........................................................................................................................................................ 27




5 Biogas from water plants for GSWMA, Guyana ............................................................................................. 38





5.5 Cost estimation ........................................................................................................................................................ 44


5.7 Project development plan – main issues to be considered .............................................................................. 49


6 Antigua Distillery, Antigua and Barbuda......................................................................................................... 51




6.4 Preliminary plant design - biogas utilization in CHP unit ................................................................................... 54

6.5 Cost estimation ........................................................................................................................................................ 56


6.7 Recommendations for improvement and development of the project .......................................................... 61

Figures

Report_Project-Concepts.docx IV

7 Fairfield Rice Inc, Guyana ................................................................................................................................ 63





7.5 Cost estimation ........................................................................................................................................................ 67



8 Saw mill bioenergy for Wood bv, Guyana ....................................................................................................... 70





8.5 Cost estimation ........................................................................................................................................................ 73


8.7 Further project development .................................................................................................................................. 74

Figures

Figure 1: Defunct biogas plant at Barnwell Farms, Barbados ..................................................................... 12

Figure 2: Pig barn with residential area in the background at Barnwell Farms, Barbados ....................... 12

Figure 3: Pig shed at Barnwell ....................................................................................................................... 13

Figure 4: Slurry tanker .................................................................................................................................... 13

Figure 5: Simplified flow diagram biogas plant ............................................................................................ 14

Figure 6: Simplified flow diagram biogas plant scenario 1 and scenario 2 ............................................... 26

Figure 7: Close up of waterplants in Georgetown channels. ....................................................................... 40

Figure 8: Removal of waterplants in Georgetown channels ........................................................................ 41

Figure 9: Simplified flow diagram GSWMA biogas plant .............................................................................. 43

Figure 10: Land slot for biogas plant in St. Johns, Antigua, Distillery plant to the left and empty

production building to the right for potential bottling plant (2012) ..................................... 52

Figure 11: Simplified flow diagram biogas plant .......................................................................................... 55

Figure 12: General principle of an ORC power plant with one working medium cycle .............................. 65

Figure 13: General principle of a water steam cycle for biomass CHP ....................................................... 66

Tables

Report_Project-Concepts.docx 5

Tables

Table 1: Overview of the elaborated project concepts .................................................................................. 8

Table 2: Estimated biogas potential of Barnwell Farms manure ................................................................ 15

Table 3: Investment cost BARNWELL FARMS BIOGAS SYSTEM .................................................................. 16

Table 4: Operational cost Barnwell Farms biogas system for first full year of operation .......................... 17

Table 5: Estimated annual income BARNWELL FARMS BIOGAS SYSTEM .................................................. 18

Table 6: Estimated biogas potential of Armag Farms Ltd substrates ......................................................... 25

Table 7: Investment cost Armag Farms Ltd. biogas system ........................................................................ 27

Table 8: Operational cost Armag Farms Ltd biogas system (scenario 1) for first full year of

operation .................................................................................................................................. 28

Table 9: Estimated annual income Armag Farms Ltd. biogas system ........................................................ 29

Table 10: Investment cost ARMAG FARMS LTD BIOGAS SYSTEM .............................................................. 31

Table 11: Operational cost Armag Farms Ltd biogas system for first full year of operation ..................... 32

Table 12: Estimated annual income ARMAG FARMS LTD BIOGAS SYSTEM .............................................. 33

Table 13: Estimated biogas potential of GSWMA substrate ....................................................................... 41

Table 14: Investment cost GSWMA biogas system ...................................................................................... 44

Table 15: Operational cost GSWMA biogas system for first full year of operation .................................... 45

Table 16: Estimated annual income GSWMA biogas system ...................................................................... 46

Table 17: Estimated biogas potential of Antiguan substrates .................................................................... 54

Table 18: Investment cost Antigua Distilleries, Ltd. BIOGAS SYSTEM ........................................................ 56

Table 19: Operational cost Antigua Distilleries, Ltd. biogas system for first full year of operation .......... 57

Table 20: Estimated annual income Antigua Distilleries, Ltd. BIOGAS SYSTEM ........................................ 58

Abbreviations


Abbreviations

Abbreviation Explanation

BGP Biogas Plant

BIDC Barbados Investment and Development Corporation

BNOC Barbados National Oil Company

BOD Biochemical oxygen demand

CARICOM Caribbean Community

CHP Combined heat and power

CNG Compressed natural gas

COD Chemical oxygen demand

DM Dry Matter

EAC Equivalent annual costs

Enprocon Environmental Project Consulting GmbH

FM Fresh Matter

GIZ Gesellschaft für internationale Zusammenarbeit

GSWMA Guyana Solid Waste Management Authority

HRT Hydraulic Retention Time

IDB Inter-American Development Bank

kW Kilowatt

oDM Organic Dry Matter

ORC Organic Rankine Cycle

PPA´s Power Purchase Agreements

REETA Renewable Energy and Energy Efficiency Technical Assistance

Background


1 Background

The Caribbean region faces a range of problems related to the generation, distribution and use of

energy. The region depends heavily on imported fossil fuels, creating dependency, a drain of currency,

high energy prices and environmental problems. A range of projects and initiatives have been started or

carried out to promote sustainable and affordable energy, but have not yet had the impact of energy

system transition (Auth et al., 2013).

CARICOM (Caribbean Community), with its 15 member states Antigua and Barbuda, The Bahamas,

Barbados, Belize, Dominica, Grenada, Guyana, Haiti, Jamaica, Montserrat, St. Kitts and Nevis, St. Lucia,

St. Vincent and the Grenadines, Suriname, and Trinidad and Tobago have established the so far

missing long term vision and the coordinated regional approach to promote renewable energy systems

in form of the Caribbean Sustainable Energy Roadmap and Strategy (C-SERMS) after a decade of

development. (Auth et al., 2013)

In this context, the CARICOM Energy Unit together with the GIZ project Renewable Energy and Energy

Efficiency Technical Assistance (REETA) commissioned a bioenergy assessment study for the CARICOM

region and the Dominican Republic.

The specific tasks to be performed were:

1. Legal Framework Assessment

2. Study Screening

3. Gap Analysis

4. Baseline Development

5. Potential Analysis

6. Potential Location Research

7. Stakeholder Mapping

8. Capacity Building

9. Project Concepts Development

GIZ contracted DBFZ in cooperation with GFA to perform the work, which was implemented by a team of

German and Caribbean experts covering the broad spectrum of this assessment study.

Several hundred documents spanning laws, statistics, studies etc. from 1942 up to today have been

screened, more than 40 stakeholders (such as ministries, universities, farmers, associations)

interviewed and a survey on national potentials has been conducted as a basis for the given tasks. This

work has been efficiently supported through the dedication of the local project partners. Further

experiences were exchanged through the cooperation with regional organizations and contacts to

international organizations (e.g. FAO, GIZ, Caribbean Climate Change Centre, CARIRI, Barbados

Agricultural Society, Guyana Energy Agency).

Concept overview


The work resulted in following documents

a report on the legal framework and its appropriateness for bioenergy projects spanning the 16

countries of the target region (available separately)

a collection of more than 300 document with an overview (Excel based)

a report on baseline and monitoring development as well as a gap analysis (available separately)

snapshots of each country giving an overview about biomass potentials and potential locations

(available separately)

a country specific collection of stakeholders including contact data and categorisation, e.g.

authority, biomass provider, plant operator (Excel document, not publically available for privacy

issues)

a report containing six concepts (up to pre-feasibility) for promising bioenergy projects (this

document)

These outputs are obtainable through the CARICOM secretariat, GIZ, DBFZ and GFA.

This document is dedicated to the promising bioenergy project concepts.

2 Concept overview

Within the six focus regions of this project (Trinidad and Tobago, Barbados, Guyana, Suriname, Belize

and Jamaica), the projects (Table 1) were chosen based on probability of implementation, geographical,

technological and feedstock spread as well as their replicability or development initiation power.

Table 1: Overview of the elaborated project concepts

Concept Name Country Technology Biomass

Barnwell Farm pig

manure digester

Barbados Lagoon biogas digester,

CHP

pig manure

Armag a) biomethane

plant, b) CHP plant

Barbados Biogas digester, biogas

upgrading

Agricultural residues,

energy plants

GSWMA, biogas from

ditch waterplants

Guyana Biogas digester, CHP Waterplants,

Antigua Distillery Antigua and Barbuda Biogas digester Vinasse, grasses, pig

gut content

Fairfield Rice Inc, Guyana Steam turbine, CHP Rise husks

Wood bv Saw mill

residues

Guyana High pressure steam

turbine

Saw mill residues

In Trinidad and Tobago as well as Suriname, no project was chosen due to the comparatively extremely

low electricity prices, which result in a less competitiveness of bioenergy as long as there are no

governmental incentives in place.

Jamaica showed a beneficial framework but the possible projects appeared as not implementable in

the near future. A large fruit plantation with attached juice production stated that there are almost no

Concept overview


residues which are not yet used (mostly fodder). Furthermore, a disease is spreading among the citrus

species which will result in lower production rates now and in the future. A large sugar factory with an

adjacent distillery was promising as a showcase but the equipment, especially the boiler of the sugar

factory proved to be several decades old (eight, in the case of the boiler). The owner expressed little

interest in investments, with or without extended bioenergy.

Another sugar plant project (Barbados) was discarded as the owners also drew back during the talks.

One reason might be the plan to build a new sugar factory. Little is known about the project, except the

estimated costs of USD 250m, that it will use more sugar cane than is available on the island right now

and that it will integrate several products.

Breweries, being wide spread in the region and therefore interesting to be subjected to bioenergy

assessment, were also very reluctant in cooperation. Thus, brewery concepts have to be evaluated in

another project.

In summary, the here assessed projects span 3 countries (Barbados, Belize, Guyana), one small and

one larger biogas plant with combined heat and power (CHP), one biomethane plant, and two different

solid biofuels concepts. Each project uses different feedstock (manure, agricultural residues, energy

plants, water plants, rise husks, wood residues). Thus, the widest possible spread has been chosen to

showcase implementable bioenergy projects.

Biogas plant for Barnwell Farms, Barbados


3 Biogas plant for Barnwell Farms, Barbados

Operator: Barnwell Farms Ltd.

Location: Rockhall

St. Thomas

Barbados

Feedstock: Pig manure

Technology: Lagoon anaerobic digester with CHP

Business model: Odour avoidance

Maximum generation of electricity

Coverage of own electricity demand, feed in of excess power

3.1 Business Case and Framework

Barnwell Farms is the largest pig farm in Barbados and the only pig farm with in-house artificial

insemination capabilities. The farm installed two ninety cubic metre digesters approximately twenty five

years ago to digest the slurry produced by 400 pigs. The project was originally supported by GTZ, as part

of a biogas program, however subsequently the digesters were mothballed due to operational and

maintenance issues. The project ensured that Barnwell Farms has experience of operating this type of

system.

More recently the company has been facing significant pressure from nearby residents because of the

unpleasant odours emanating from the property. The pressure intensified with the development of a

private residential housing project in close proximity to the farm.

In addition to tremendous waste disposal challenges at the farm, the company also struggles with high-

energy costs as well as the opportunity cost of failing to convert organic waste material into energy

despite a ready supply of raw material and the availability of tried and tested conversion technologies.

Currently the company collects pig slurry in a large lagoon on the property and is desirous of

implementing a solution to its odour problems by treating the waste slurry and realising the benefits of

substituting high cost - fossil fuelled energy with energy derived from waste.

A detailed feasibility study is required to calculate the potential for digesting pig slurry at Barnwell

Farms, especially as the company is restructuring. The study should include an assessment of biogas

potential, likely reduction in odour emissions from the property and the likely composition of (and

potential applications for) the resultant digestates. The assessment should also examine the potential

financial impact of this intervention on the business and consider the following options for energy

utilisation:

Option 1: Conversion of Pig Slurry for Base Load Electricity Generation

Barnwell Farms would convert its animal slurry to electrical energy via biogas production, with a view to

supplying its base load electricity demand. In this scenario Barnwell would continue to purchase peak



electricity demand from the grid. This ‘off-grid’ approach would be the least complicated, as it would

neither involve the sale of power nor would it require grid access. The company would be required to

obtain a license from the Minister Responsible for Energy to generate electricity for self-consumption

and is likely to receive support from the Barbados Investment Development Corporation (BIDC) in the

form of duty and tax exemptions on equipment and inputs.

Option 2: Maximum Generation and Sell Excess Power to the Grid

Barnwell Farms would develop biodigester and power generation capabilities in order to satisfy all of its

electricity and steam requirements. Excess power would be sold to the grid, which would require that

the company negotiate the terms of a PPA with both the utility and the Government’s Minister

responsible for Energy. In this regard, the Minister has discretion over the granting of a license to

produce electricity, which is a prerequisite to the awarding of a power purchase agreement.

In this study, option 2 is chosen for a prefeasibility check.

3.2 Site description

The Barnwell farm, located in Rock Hall, St. Thomas, Barbados is the largest pig farm in the country with

approximately 3,000 animals.

This means therefore, that each mast animal producing 1.5 m3 of pig manure per year could produce

an annual amount of 4,500 m3 or 4,635 tons per year. This amount offers avenues for the energetic

and thereafter bio-fertilizer use of both resources. It suffices for use for mono-substrate digestion in all

types of fermenters taking the final goal of bioenergy production for the main part into consideration.

Otherwise, an understanding of a comprehensive integrated bio-fertilizer production will have to be

considered for a multipurpose use of both the bioenergy and bio-fertilizer for sustainability purposes.

In an appropriate environment of optimized productivity and production of biogas of high quality, not

only the nutrients are important. It is vital to fix a desired system of fermentation and as such stabilize

the temperature of the system. Although in the tropics, with average temperatures fluctuating between

20-34°C could drastically affect the quality (in particular lower the methane content) and constancy of

the gas produced (quantity) and so the daily or hourly productivity unless the aim of such a venture is to

produce energy independently of the constancy.

Based on the location, it is important to select a modern biogas plant of little or no emissions as any

emissions could drive the farm out of business due to emitted biogas odour that could affect the

inhabitants of the locality.

Ignoring the aforementioned particularities could also lead to problems in the CHP operation which

adds up to costs for e.g. a frequent change of filters etc.

A practical value of ca. 35-40% methane/m³ should be presumed for feasible economic calculations.

It is vital to carry out an environmental impact assessment, especially to the extent of which such a

project could impact the communities both in helping to augment their agricultural productivity through

the use of the digestate as a bio-fertilizer, thus reducing their input costs as well as raising the quality of

their produce, as well as adjacent positive effects of indiscriminate dumping of the pig manures either

in the see or landfills. These are the dimensions such an environmentally sound project should have.



It is important to iterate that though the lagoon system might be deemed as the ideal solution for pig

slurry digestion in this part of the world, further feasibility studies into the topic covering possible

available co-substrates could change the type of system towards more holistic solutions.

The following pictures show the defunct biogas plant at Barnwell Farms (Figure 1) and the pig barn with

the residential area in the background (Figure 2).

Figure 1: Defunct biogas plant at Barnwell Farms, Barbados

Figure 2: Pig barn with residential area in the background at Barnwell Farms, Barbados

3.3 Feedstock supply

To the effect of a constant and optimized bioenergy production, feedstock supply including quality goes

along with a comprehensive integrated management.

The availability of an on-farm residue on Barnwell Farms is a premise to a constant supply of a valuable

feedstock. However, under optimized production and end use agricultural premises, a co-digestion

should be considered in a second step. This accounts for higher biogas as well as bio-fertilizer qualities.

Under tropical conditions, a 7% dry matter (DM) content of 80% organic dry matter (oDM) can be

expected of pig manure. These values depend on the hygienic and maintenance standards of the pig

farm, as well as on-farm nutritional programs.

A theoretical biogas potential of almost 95,000m³ per year can be estimated with a possible content of

60% CH4. However, to determine practical potential, a detailed feasibility study is required.

© Kay Schaubach / DBFZ




The proposed lagoon biodigester is usually used to treat liquid biomass and it works with a maximum

dry matter content of less than 3% due to technical challenges caused by sedimentation.

Adjustment for higher biogas production can also be made directly by regulating the water supply for

cleaning the pigsties or indirectly increasing the fresh organic dry matter in pig manure by adapting

animal diet. Economic cost benefits should be considered. Inserting inorganic parts or pieces to raise

the internal surface of the biodigester might cause positive effects on the biogas production. As the

Barnwell pig farm has around 6 ha of agriculture land, harvest residues or organic waste could be

studied and silaged for year round administration to the input mix of the biodigester. A feedstock

mixture of pig manure and for example agricultural waste materials or fodder residues would lead to a

higher biogas potential and quality.

3.4 Preliminary plant design

Figure 3: Pig shed at Barnwell

Figure 4: Slurry tanker

For the daily amount of 22t/d of pig manure plus 35m³/d spilling water a preliminary plant layout is

considered in this report consisting of the following plant components (see Figure 5: Simplified flow

diagram biogas plant):

a) Reception tank/collecting pit:

Reinforced concrete or coated steel

Storing capacity 60m3

Equipped with mixing equipment to avoid phase separation

Covered and equipped with bio filter to minimize odour emissions

b) Central pumping station:

Equipped with two pumps for improved reliability of operation

Including pipes, valves and accessories

c) Control office:

With control cabinet

Project documentation

d) Digester:

Reinforced concrete, stainless or coated steel

Active volume approx. 1,100m³ (hydraulic retention time [HRT] 19 days)

Mixers/agitators

Gas storage

Biological desulphurization

Measuring equipment and valves

© Carsten Linnenberg © Carsten Linnenberg



e) Biogas flare:

Combustion capacity of 15m3/h

f) CHP unit:

35kWel capacity

g) Digestate separation unit:

57m3/d capacity

h) Storage lagoon for the liquid fraction of digestate:

Storing capacity of approx. two months equalling 1,500m3

Figure 5: Simplified flow diagram biogas plant

One potential location for the biogas plant is available on the premises in the western part of Barnwell

Farms. Soil analysis will have to determine if the plot is suitable for the construction of a biogas system.

3.4.1 Gas production & theoretical utilization

The potential daily gas production of Barnwell Farms biogas system is estimated to be 386m3 of biogas

(based on an estimated dry matter content of manure of ~5%. Daily biogas production can

increase/decrease considerably if the dry matter content is higher/lower as expected) with an average

methane content of 60%.



If utilized in a 35kW CHP unit it is assumed, that during 7,852 hours per year a total 274,800kWh/a

electrical energy and 340,000kWh/a thermal energy could be generated.

5% of produced electricity is estimated to being consumed during the daily operation of the biogas plant

itself and around 1% of it is lost due to transformation processes during grid feed in.

Approx. 27% of the produced heat is required for the heating of the biogas system.

Excess heat could be used for working processes at the farm requiring heat.

The following table shows the estimated biogas potential of Barnwell Farms using big manure.

Table 2: Estimated biogas potential of Barnwell Farms manure

Pig manure

Daily

production

Dry matter

content

Volatile

solids

Biogas

yield

Biogas

production

Methane

content

Methane

production

[tFM/d] [%] [%DM] [m3/tVS] [m3/d] [%] [m3/d]

Pig manure 22 5,0% 78,0% 450 386,1 60% 231,7

Water 35 0,0% 0,0% 0,0 0,0 0% 0,0

Total 57 1,93% 78,0% 450,0 386,1 60% 231,7

3.4.2 Revenues of the Barnwell Farms biogas plant

Three different products produced by the biogas plant could be commercialized (taking into account

transformation of biogas in a CHP to electrical and thermal energy):

a) Gas/electricity:

Either substitution of own electricity demand or sale to the national grid, this could generate a steady

income to subsidize operation costs of the farm.

b) Heat:

In this report no income from produced heat is considered.

c) Fertilizer:

Fertilizer could be sold to local farmers and local municipalities; price connected to world market prices

of nutrients. For this report a sales price of 25.00 US$ per ton of solid digestate and 1.00 US$ per ton

of liquid digestate is considered. Values are empirical values of the consultant. This consideration is

crucial to calculate an economic viability of this project.

Reduction of odour molestation and environmental protection could also be considered as products but

are not taken into account due to their non-tradability.



3.5 Cost estimation

3.5.1 Invest costs for biogas system

Cost for the planned biogas system at Barnwell Farms for the treatment of a daily amount of 22m3 pig

manure plus 34m3 spilling water is estimated to range around 363,000 US$ (see Table 3). These

figures base on values of the Leitfaden Biogas, 6th edition, 2013, chapter 8.2, table 8.10 (FNR, 2013)

and empirical values of the consultant (a fixed exchange rate of 1 EUR=1.123705 US$ is assumed).

Table 3: Investment cost BARNWELL FARMS BIOGAS SYSTEM

Investment

Manufacturing costs for the plant

Substrate storage and loading 56,185.00 US$

Digester and civil works 121,568.00 US$

Gas utilization and control 84,278.00 US$

Digestate storage 33,711.00 US$

Total Manufacturing costs for the plant

295.742 US$

Further expected costs

Planning, permits/licensing and commissioning 56,185.00 US$

Start-up cost 11,237.00 US$

Total further expected costs 67,422.00 US$

Total investment costs 363,165.00 US$

3.5.2 Costs for substrate procurement/transport

Since the substrate to be treated is manure evolving at Barnwell Farms itself no costs for substrate

procurement are considered.

3.5.3 Operational and maintenance costs biogas system

Table 4 shows the estimated annual operational cost of BARNWELL FARMS BIOGAS SYSTEM. The

annual sum of money to be spent for maintenance and servicing of the biogas system is estimated to

be approx. 7,260 US$/a plus additional 2,750 US$/a for servicing and maintaining the CHP unit.

Cost for separation of digestate is estimated to be approx. 5,200 US$/a.

Amortization and interest payments are estimated to be approx. 54,100 US$/a.



Table 4: Operational cost Barnwell Farms biogas system for first full year of operation

Costs per year

Amortization + Interest

payments

Mixed interest

borrowed capital:

8,00% 10 years 54,122 US$

Operating expense separator 20,645 t/a 0.25 US$/t 5,219 US$

Maintenance/servicing BGP Part: 2% Total investment costs 7,263 US$

Maintenance/servicing costs

CHP

274,807 kWh/a 0.01 US$/kWh 2,748 US$

Personnel costs 365d/a 12h/d 5.00 US$/m 21,900 US$

Biological support 3,360 US$

Business management 5,000 US$

Insurance 1,816 US$

Total annual operational costs 101,428 US$

Operational staff of BARNWELL FARMS BIOGAS SYSTEM is estimated to get an hourly payment of

5.00 US$/h and is assumed to work on 4,380 hours per year generating an annual cost of

21,900 US$/a.

Since the biological process will need frequent servicing, the amount of 3,360 US$/a is taken into

account for laboratory analyses and similar.

An annual lump sum of 5,000 US$/a is assumed for business management of BARNWELL FARMS

BIOGAS SYSTEM plus 1,816 US$/a insurance payments.

This is leading to a total of 101,428 US$ operational costs for the first full year of operation.

3.5.4 Income from electricity sale

Produced biogas could be, via combustion, turned into electric energy and be sold to the power grid to

generate an income.

With an estimated daily biogas production of 386 m3/d and a methane content of 60% a 35 kW CHP

unit could be operated during 7,852 hours per year generating approx. 274,800 kWh/a.

Auxiliary power demand of the BARNWELL FARMS BIOGAS SYSTEM itself and transformation losses

during feed in are estimated to range around 16,351 kWh/a, leaving 258,450 kWh/a to be sold.

This could generate an annual income of approx. 51,690 US$/a.

3.5.5 Income from heat sale

In this report no income from heat sale is considered.



3.5.6 Income from fertilizer sale

After being processed inside the digester substrate could be commercialized as a liquid organic

fertilizer. After separating the digestate, it is estimated to have an annual production of 20,168 m³ per

year of liquid organic fertilizer. It is considered in this report that the liquid fraction is being sold at

1.00 US$/m³, generating an annual income of 20,168 US$/a.

The solid fraction of separated fertilizer could be commercialized and due to its high solid content would

even be suitable for transport over longer distances. An estimated amount of 450t/a at a sale price of

25.00 US$/t could generate incomes in the range of 11,491 US$/a.

Table 5: Estimated annual income BARNWELL FARMS BIOGAS SYSTEM

Annual income

Total electrical

work CHP 1

start-

up:

2016 274,807 kWh/a 7,852 h/a

On-site power -13,740 kWh/a

Transformation

and feed-in losses

-2,611 kWh/a

Actual fed-in

electricity

258,456 kWh/a

Electricity sale 100% 258,456 kWh/a 20 US$cent/kWh 51,691 US$

Fertilising value

(solid)

457 t/a 25.00 US$/t 11,491 US$

Fertilising value

(liquid)

20,168 t/a 1.00 US$/t 20,168 US$

Total annual

income

81,351 US$

3.5.7 Profitability assessment

The cost estimation for the presented concepts is based on calculating equivalent annual costs (EAC).

They can be defined as:

𝐸𝐴𝐶𝑡𝑜𝑡𝑎𝑙 = 𝐸𝐴𝐶𝑖𝑛𝑣 − 𝑎𝑛𝑛𝑢𝑎𝑙 𝑖𝑛𝑐𝑜𝑚𝑒 + 𝑎𝑛𝑛𝑢𝑎𝑙 𝑐𝑜𝑠𝑡𝑠

with EACinv being the equivalent annual costs of the investment:

𝐸𝐴𝐶𝑖𝑛𝑣 = 𝐼𝐶 ∗(1 + 𝑖𝑘)𝑛 ∗ 𝑖𝑘

(1 + 𝑖𝑘)𝑛 − 1

Here, IC are the actual costs of the investment, ik is the nominal interest rate, and n is the depreciation

or recovery period (in years).



Annual income is calculated as the sum of all monetary cash flows to the operator/owner (including

absolute earnings from power sale, feed-in-tariffs where applicable, by-product sale).

Annual costs include labour costs, maintenance (e.g. spare parts) and operation (e.g. lubrication oils),

insurances, administration and unexpected costs.

For the economic calculations, the following assumptions are made:

depreciation or recovery period: n=10 years

nominal interest rate: ik=8%

reference electricity costs: cr=0.2US$/kWh

annual service and maintenance BGP: csmBGP=2% (of IC)

annual service and maintenance CHP unit: csmCHP=0.01US$/kWhproduced

annual administration, insurances and unexpected costs: caiu=as indicated in Table 4

hourly wages for plant operators: chw=3US$/h

total investment costs: IC=363,165US$

total annual operation costs: cOPtotal=47,306US$/a

total annual income: Incometotal=83,351US$/a

annual benefit (income-costs): =36,045US$/a

Specific power production costs: Csp=0.27US$/kWh



𝐸𝐴𝐶𝑖𝑛𝑣 = −(363,164 ∗(1 + 0.08)10 ∗ 0.08

(1 + 0.08)10 − 1)

𝐸𝐴𝐶𝑖𝑛𝑣 = −54,122

𝐸𝐴𝐶𝑡𝑜𝑡𝑎𝑙 = −54,122 + 83,351 − 47,306

𝑬𝑨𝑪𝒕𝒐𝒕𝒂𝒍 = −𝟏𝟖, 𝟎𝟕𝟕

3.6 Impact estimation

3.6.1 Local economy

There are several points, which will strengthen the local economy. One very important point is the

emission reduction, which becomes sensitive due to rising conflicts between population settlement and

tourist economy on the one side and animal production on the other side. To be able to minimize these

conflicts the development in both sectors is forced. As the tourist economy has a high demand for meat

products, this enables the optimization of local economy.



The additional employment and added value generation is also a brick for the local economy. As it is all

year production with less direct impact by fluctuating tourist economy it is a factor for economic

stabilization. The replacement of fossil fuels as well as the replacement of mineral fertilizer by the

optimized characteristics of the digestate products will reduce the countries money outflow.

3.6.2 Environmental and hygiene aspects

Greenhouse gas emissions

The manure treatment in a biogas plant has a couple of direct and indirect benefits for environment

and hygiene. Globally the reduction of greenhouse gas emissions, especially the direct greenhouse

gases methane and nitrous oxide are important. Both are generated by normal manure storage and

then emitted to the atmosphere. Methane has a 28-fold greenhouse effect compared to carbon dioxide,

nitrous oxide is 365 times stronger (global warming potential over 100 years) (IPCC, 2014). The

anaerobic digestion in a biogas fermenter avoids the generation of nitrous oxide, which is formed

especially under semi-oxic conditions, when nitrogen rich substrates are degraded. The methane

generation is enhanced, but in a controlled process with utilization of the generated gas. In this way, the

methane is transferred to CO2 by the factor of 25. This carbon dioxide is climate neutral as it is

generated from manure as a renewable resource.

Replacing electricity production from fossil fuels means a further reduction of greenhouse gas

emissions. The amount depends on the used fossil fuel and on the conversion efficiencies of the

technologies.

Avoiding greenhouse gas emissions is a crucial point for a sustainability strategy especially for islands

or low-lying coastal regions. Rising sea level or rising risk for thunderstorms endangers their physical

and economic existence.

Not the least, for touristic regions like Barbados an authentic sustainable policy enhances the image

and standing.

Further emissions

The biogas process takes place in gastight tanks. This reduces emissions of odour and ammonia. Odour

substances like fatty acids and further organic compounds are degraded in the process. So even after

processing the odour emissions are reduced when the digestate is handled to be used as fertilizer. This

allows a more equal fertilisation of the cropping areas, even near to the settling areas. By this way and

by some changes of the fertilizer characteristics the fertilizer efficiency can be enhanced and mineral

fertilizers can be replaced. Both mean a reduction of nutrient losses to the environment.

Ammonia emissions are in total more difficult. As named before, these emissions are avoided during

the process as it takes place in a closed tank. After digestion the viscosity is reduced (=quicker

infiltration into soil), but the partial pressure of ammonia is enhanced, as protein is degraded.

Furthermore the pH value is enhanced from ca. 6.5 to ca. 7.5. Therefore, the equilibrium between NH3

and NH4+ is shifted to NH3. So the emission risk is enhanced after the process, if the further handling

does not care for these aspects.

Hygiene aspects

There are a couple of direct and indirect hygiene effects due to manure and organic waste treatment in

biogas plants. Maybe the indirect effects are of higher importance than the direct ones. As named

before, the manure and organic wastes are processed in anoxic closed tanks and the organic matter is



degraded to biogas therein. This has two indirect effects on hygiene. At first, vectors like rodents,

insects etc. which are in the substrate will die and will be degraded during the process. Furthermore,

these vectors as well as further ones lose their nutrient base and some of them their habitat as the

organic matter is degraded after the process.

The extend of the direct effects is strongly dependent on technical parameters such as temperature,

temperature steps, average and secure retention time, pre-treatment etc. pathogen organisms are

reduced by the process.

3.7 Project development plan

The shown project is one of the “waste to energy” projects, which are always named as exemplary for

sustainability reasons. There is no competition for any resources, but a couple of positive impacts.

Unfortunately, the shown project is quite small and the loans are quite high with 8%, which has strong

effects on the economic base of the project. Finding a good solution for implementation as business

case would open the options for a couple of further plant options like this.

For this reason the following plan is recommended. A feasibility improvement consultation is

recommended to evaluate and concretize data, to proof and optimize the plant concept and business

model. This project should also enhance local capacity for efficient plant implementation.

Actor involvement is a key point to develop this sector of small waste to biogas plants. The one group of

actors to be involved are the stakeholders, who are affected by the emissions. This is the farmer, who

gets pressure on his production and the neighbours who do not like the smell. Maybe the inclusion of

these as shareholders can be a brick of the business case.

Discussions seem to be fruitful with the Barbados and local government, with banks and with

international development organisations. The goal of such discussions is to create programs for smaller

loans for such investments and to build up a knowledge based infrastructure (laboratory and

consultancy service, own research at local universities etc.). This shall lead to enhanced reliability of the

plants and so to reduced risks and enhanced yields.

3.8 Risk analysis and recommendations

On the current stage there are a couple of risks in the feasibility of that plant:

The basic data are not clear (e.g. dry matter concentration of manure, biogas yield, own consumption of

energy, different prices for sold and exchanged energy), especially as the company is restructuring;

The marketability of the resulting fertilizers is seen as a very critical point, especially for the liquid

fertilizer this seems to be very optimistic due to estimated high handling costs.

On the other side there seem to be some options for cost reduction.

Biogas plant for Armag Farms, Barbados


4 Biogas plant for Armag Farms, Barbados

Operator: Cooperative around Armag Farms Ltd

Location: Sunbury Plantation

St. Philip

Barbados

Feedstock: Agricultural residue, energy plants

Technology: Anaerobic digester with biomethane upgrade

Business model: Collection of residues of several farms

Introduction of energy crops to enhance crop rotation for soil improvement

Biomethane feed-in into national gas grid in a bilateral contract with BNOC


Armag Farms manages 900 acres of arable land at its Sunbury Estate and Colleton Plantation. The

plantation is focused on growing root crops such as sweet potatoes, yams and cassava and has recently

begun processing operations to include sweet potato fries and other value added products.

The farm like many agricultural/agri-processing operations faces significant challenges from high

operational costs. These include the cost of energy (amongst the highest in the Caribbean), waste

disposal costs and the consequent opportunity costs associated with failing to offset a proportion of its

energy demand with cheaper, more sustainable energy resources.

There is potential for Armag Farms to convert its agricultural residues into compressed natural gas (Bio-

CNG) by a process of anaerobic digestion. The farm has already begun the process of exploring Napier

Grass and other short rotation crops to augment existing residues, which would further enhance the

quality of digestates from the process, creating opportunities for organic soil conditioners and fertilizers.

There is also the possibility to source feedstock from neighbouring farmers for the digester and the

principals at Armag Farms are already in discussion with their farming neighbours about the planting of

up to 2,000 additional acres of Napier Grass. In addition, there is potential for rehabilitating a

significant acreage of idle cane fields.

Barbados has significant natural gas resources that are developed by the Barbados National Oil

Company (BNOC). BNOC are able to produce 36,000m³ per day, however, peak period demand has

been greater than supply and as a result the country has been experiencing gas shortages during these

periods. The BNOC appear keen to explore alternative sources of natural gas including biogas and have

been looking at an example project in St. Croix using Napier Grass as a short rotation energy crop.

A more detailed feasibility study would be required to determine the technical viability and commercial

potential for Bio-CNG. At this stage it is felt that the following alternative to the “Do Nothing (Business

as Usual)” scenario should be further explored:

Armag Farms would convert the agricultural residues and short rotation crops from its operations along

with those from neighbouring farms to biomethane by a process of anaerobic digestion. The resultant

biogas would then be sold to BNOC. The project is likely to receive support from the Barbados

Investment Development Corporation (BIDC) in the form of duty and tax exemptions on equipment and



inputs. Project financing could come from a public private partnership and GIZ/REETA should explore

the possibilities for partnering with established German biogas companies.

The island Barbados has a comparatively huge natural gas grid sourced by domestic gas. Barbados gas

sources are continuously decreasing by what during Christmas 2014 the national gas company was not

able to serve all clients with the gas amount required. Thus, several industrial and service clients claim

for loss of profit and future development of gas business is getting limited.

On the other hand Barbados sugar industry is internationally not competitive, thus has to be subsidized

by the state to survive economically. Therefore, sugar cane farmers are highly interested to produce

energy crops like Napier grass as catch crop to improve soil vitality respectively yields per hectare and

to generate an additional income independent on sugar cane production.

Rum distilleries in Barbados so far pump the produced spent wash (organically high contaminated

wastewater from distillation process) directly into the sea. Besides high energy content this kind of

wastewater contains high concentration of nutrients (especially Potassium) which potentially could be

used for fertilizing issues in case of its anaerobic treatment.

BNOC)as well as sugar cane farmers are highly interested to produce Bio-CNG to feed it into BNOC gas

grid and hence to provide it to present as well as to future clients of BNOC.

A further feasibility study, including PPP models, to show economical and technical viability of the

project should be prepared and thus convince decision makers at BNOC, famers and at the political

side to advance this project.

Armag Farms and Armag Manufacturing Ltd. sell under the brand “Sunbury Harvest”. Products are

convenient foods based on sweet potato (100 acres at Armag), corn, cassava, breadfruit and eddie.

Further types are tested. Purchasing fitting equipment poses a problem. They use a steam blancher,

which is fast and keeps nutrients. A blast freezer is used to cool the produce down, which is energy

intensive. Food processing as such is energy intensive which causes financial problems as they have to

compete with imports such as potatoes from the UK and Ireland.

The Barbados gas company is seen as the main partner in the most likely option. As the main product

will be biomethane served to one possible customer, good and reliable contracts are needed. Ideally the

gas company will become a shareholder. The digestate should be used as a fertilizer on the fields of the

contracted farms. As the substrates are generated from permanent crops, humus reproduction on

these fields is even balanced without the digestate. This means an option for merchandising the

digestate.

In this study, both biomethane and CHP options are assessed.


The Sunbury, St. Phillip area is the home for agriculture crop production of sweet potatoes, corn,

cassava, breadfruit etc. Armag Farms manages ca. 900 acres of arable land at its Sunbury Estate and

Colleton Plantation growing short-term crops with a harvest residue that could be used for anaerobic

fermentation if properly pre-treated. Planning could help in the use of ca. 2,000 additional acreage for

Napier grass cultivation for biomass availability and all-year-round throughput feedstock assurance. In

addition, idle cane farms of adjacent former sugar producer companies could equally serve as sources

of biomass cultivation, thus supply.



The main focus of Armag Farms is to use harvest residues for energy provision as the country’s energy

demand is growing steadily and prices are at top levels. The multipurpose target of energy and

biofertilizer production could well propel the bioenergy industry looking at it from both points of view of

Barbados being a net importer for mineral fertilizer and cost of electric energy.

Based on the long-term plantation sugarcane production and few crop rotational alternatives and

activities, Barbados agriculture will continue demanding higher quantities of fertilizer. From the

agronomical point of view, those soils need to be brought back to have their microorganisms that

naturally carry out very important organic matter decomposition and soil amelioration. Bioenergy

production could lead the way.

Symbiotic effects of multiple source biomass input and the output of energy and bio-fertilizer should be

considered by not only looking for electric energy repayment but also with bio-fertilizer to assure higher

agriculture productivity and lower imported inorganic fertilizers.

One potential location for the biogas plant is available on the premises of Armag Farms Ltd. Soil

analysis will have to determine if the plot is suitable for the construction of a biogas system.


Feedstock supply has the task of guaranteeing sustainable biogas productivity and other adjacent

benefits of anaerobic digestion. Using the agriculture residues as the base feedstock guaranties an

annual high carbon input supply, however, these residues have to be studied and a pre-treatment

method for all-year-round management strategy developed for their upkeep and supply. A feasibility

study towards the establishment of such a plant will also focus deeper into other available useable

substrates of value for the digestion process namely poultry dropping, pig manure, spent wash water

from the local distilleries etc.

The opportunity of using high yielding Napier Grass biomass opens up new possibilities of alternative

energy generation. After establishing the culture, low amounts of fertilizers and pesticides are needed.

Based on its high growth, its fast growing rate and its abundant forage, the high organic matter can be

used for anaerobic digestion. Consideration should be given to the fact that the use of Napier grass for

bioenergy generation poses certain risks: high cost of harvesting and transportation, opportunity cost

for animal nutrition and the possible conflict of producing energy crops instead of animal feed.

The main task should be establishing a permanent nutritional program of easily available and

compatible feedstock by controlling the logistic and energetic costs, as concentration of biomass from

different locations could boost or dictate the size of the plant to be considered and quality to be

attained for both biogas and biofertilizer. Theoretical calculations could approximate to a reality of what

to expect, but laboratory residue analysis could give certainty of plant establishment and economics.




For this report a daily amount of 282 m³/d of substrate mixture, with values indicated in Table 6 is

considered. All values are empirical values of the consultant and shall be checked for with the actual

substrates.

Table 6: Estimated biogas potential of Armag Farms Ltd substrates

Pig manure

Daily amount Dry matter

content

Volatile

solids

Biogas

yield

Biogas

production

Methane

content

Methane

production

[tFM/d] [%] [%DM] [m3/tVS] [m3/d] [%] [m3/d]

Napier

grass

226.03 18.0% 90.0% 400 14,646.6 55% 7,762.7

Poultry

dropping

1.97 45.0% 75.0% 500 332.9 60% 199.7

Food

leftovers

2.85 18.2% 92.9% 438 211.0 64% 135.0

Gut content

(pigs)

1.32 14.0% 80.0% 438 64.5 64% 41.3

Spent wash 49.86 7.0% 85.0% 400 1,186.7 65% 771.4

Total 282.03 16.23% 89.3% 406.8 16,630 54.2% 9,013

4.4.1 Preliminary plant layout

For the daily amount of 282t/d of substrate mixture a preliminary plant layout is considered in this

report consisting of the following plant components (see Figure 6):









c) Control office:



d) Digester (multiple):


Active volume approx. 15,928m³ (HRT 56 days)

Mixers/ agitators

Gas storage





e) Biogas flare:

Combustion capacity of 800m3/h

f) CHP unit (scenario 1) or gas upgrading (scenario 2):

1,700 kWel (scenario 1) / 700m3n/h capacity


300m3/d capacity

Storage lagoon for the liquid fraction of digestate:

Storing capacity of approx. two months equalling 17,000m³

Figure 6: Simplified flow diagram biogas plant scenario 1 and scenario 2

Gas production & theoretical utilization scenario one

The potential daily gas production of Armag Farms Ltd. biogas system is estimated to be 16,630m³ of

biogas with an average methane content of 54.2%.

If utilized in two CHP units with a total capacity of 1,690kW it is assumed that during 8,000 hours per

year a total of 13,360,000kWh/a electrical energy and 14,200,000kWh/a thermal energy could be

generated.

8% of the produced electricity is estimated to being consumed during the daily operation of the biogas

plant itself and around 1% of it is lost due to transformation processes during grid feed in.

Approx. 29% of produced heat is required for the heating of the biogas system.



Gas production & theoretical utilization scenario two

The potential daily gas production of Armag Farms Ltd biogas system is estimated to be 16,630m³ of

biogas with an average methane content of 54.2%.

If utilized in a bio methane gas upgrading unit it is assumed, that an average of 318mn³/h biomethane

could be generated and fed into the national gas grid.

18% of produced biogas is estimated to being consumed by an installed CHP unit to cover the biogas

plant’s auxiliary electricity demand.

4.5 Cost estimation

4.5.1 Economic calculations of the Armag Farms Ltd biogas plant scenario

one (CHP utilization)

Invest costs for biogas system

Cost for the planned biogas system at Armag Farms Ltd. for the treatment of a daily amount of 226t/d

Napier grass, 1,97t/d poultry droppings, 2,85t/d food leftovers, 1,32t/d gut content of pigs plus

49,86t/d spent wash is estimated to range around 4.800.000 US$ (see Table 7)

These figures base on values of the Leitfaden Biogas, 6th edition, 2013, chapter 8.2, table 8.10 (FNR,

2013) and empirical values of the consultant (a fixed exchange rate of 1 EUR=1.123705 US$ is

assumed).

Table 7: Investment cost Armag Farms Ltd. biogas system

Investment



Digester and civil works 1,400,000.00 US$

Gas utilization and control 1,800,000.00 US$


Total Manufacturing costs for the plant 4,000,000 US$


Planning, permits/licensing, infrastructure provision and

commissioning

700,000.00 US$


Total further expected costs 800,000 US$

Total investment costs 4,800,000 US$

Costs for substrate procurement/transport

An annual production of approx. 82,500t/a Napier grass is considered to range around

1,485,000 US$/a including cropping and transportation to the biogas system.



Table 8 shows the estimated annual operational cost of Armag Farms Ltd. biogas system. Annual sum

of money to be spent for maintenance and servicing of the biogas system is estimated to be approx.

81,974 US$/a plus additional 85,200 US$/a for servicing and maintaining the CHP unit.



Table 8: Operational cost Armag Farms Ltd biogas system (scenario 1) for first full year of operation

Costs per year


payments

Mixed interest borrowed

capital: 8.00% 10 years 715,342 US$




CHP

13,364,379 kWh/a 0.012 US$/kWh 160,973 US$




Insurance 24,000 US$

Cost crop production Napier

grass

82,500t/a 18 US$/t 1,485,000 US$

Total annual operational costs 1,552,463 US$

Operational staff of Armag Farms Ltd. biogas system is estimated to get an hourly payment of


52,560 US$/a.

Since biological process will need frequent servicing, the amount of 3,360 US$/a is taken into account

for laboratory analyses and similar.

An annual lump sum of 15,000 US$/a is assumed for business management of Armag Farms Ltd.

biogas system plus 24,000 US$/a insurance payments.

Cropping of Napier grass is considered to range around 1,485,000 US$/a, Leading to a total of

2,548,622 US$ operational costs for the first full year of operation.

Income from electricity sale


generate an income.

With an estimated daily biogas production of 16,630 m³/d and a methane content of 54.2% two CHP

units with a total capacity of 1,690 kW could be operated during 8,000 hours per year generating

approx. 13,364,000 kWh/a.

Auxiliary power demand of the Armag Farms Ltd. biogas system itself and transformation losses during

feed in are estimated to range around 1,192,103 kWh/a, leaving 12,172,276 kWh/a to be sold.

This could generate an annual income of approx. 2,434,455 US$/a.



Income from heat sale


Income from fertilizer sale

It is assumed that most of the produced digestate is utilized to fertilize Napier grass cultivations;

therefore no income from digestate/fertilizer sale is considered.

Table 9: Estimated annual income Armag Farms Ltd. biogas system

Annual income

Total electrical

work CHP 1

start-

up:

2016 13,364,379 kWh/a 8,000 h/a

On-site power -1,069,150 kWh/a

Transformation

and feed-in

losses

-122,952 kWh/a

Actual fed-in

electricity

12,172,276 kWh/a

Electricity sale 100% 12,172,276 kWh/a 20 US$cent/kWh 2,434,455 US$

Fertilising value

(solid)

14,146 t/a US$/t

Fertilising value

(liquid)

53,805 t/a US$/t

Total annual

income

US$

2.434.455

Profitability assessment scenario one






(1 + 𝑖𝑘)𝑛 − 1












reference electricity costs: cr=0.2US$/kWh


annual service and maintenance CHP unit: csmCHP=0.01US$/kWhproduced

annual administration, insurances and unexpected costs:

caiu=as indicated in Table 8, hourly wages for plant

operators: chw=6 US$/h

total investment costs: IC=4,800,000 US$

total annual operation costs: cOPtotal=1,833,281 US$/a

total annual income: Incometotal=2,434,455 US$/a

annual benefit (income-costs): =601,175 US$/a

Specific power production costs: Csp=0.10 US$/kWh



𝐸𝐴𝐶𝑖𝑛𝑣 = −(4,800,000 ∗(1 + 0.08)10 ∗ 0.08

(1 + 0.08)10 − 1)

𝐸𝐴𝐶𝑖𝑛𝑣 = −715,342

𝐸𝐴𝐶𝑡𝑜𝑡𝑎𝑙 = −715.342 + 2.434.455 − 1.833.281

𝑬𝑨𝑪𝒕𝒐𝒕𝒂𝒍 = −𝟏𝟏𝟒. 𝟏𝟔𝟕

4.5.2 Economic calculations of the Armag Farms Ltd biogas plant scenario

two (gas upgrading)

Invest costs for biogas system

Cost for the planned biogas system at Armag Farms Ltd for the treatment of a daily amount of 226t/d

Napier grass, 1.97t/d poultry droppings, 2.85t/d food leftovers, 1.32t/d gut content of pigs plus

49.86t/d spent wash is estimated to range around 5,600,000 US$ (see Table 10).

These figures base on values of the Leitfaden Biogas, 6th edition, 2013, chapter 8.2, table 8.10 (FNR,

2013) and empirical values of the consultant (a fixed exchange rate of 1 EUR=1.123705 US$ is

assumed).



Table 10: Investment cost ARMAG FARMS LTD BIOGAS SYSTEM

Investment



Digester and civil works 1,400,000.00 US$

Gas utilization and control 2,600,000.00 US$




Planning, permits/licensing, infrastructure provision and commissioning 700,000.00 US$




Costs for substrate procurement/transport

An annual production of approx. 82.500t/a Napier grass is considered to range around

1.485.000 US$/a including cropping and transportation to the biogas system.

Operational and maintenance costs biogas system

Table 11 shows the estimated annual operational cost of ARMAG FARMS LTD BIOGAS SYSTEM. Annual

sum of money to be spent for maintenance and servicing of the biogas system is estimated to be

approx. 112,000 US$/a plus additional 30,000 US$/a for servicing and maintaining the CHP unit and

76,376 US$/a for maintenance and servicing of the gas upgrading unit.





Table 11: Operational cost Armag Farms Ltd biogas system for first full year of operation

Costs per year


payments



Operating expense separator 94,867

t/a

0.25 US$/t 23,717 US$



CHP

2,000,000 kWh/a 0.015

US$/kwh

30,000 US$

Maintenance, operation and

servicing costs Gas

upgrading

76,376 US$

Personnel costs 365d/a 24h/d 6.00US$/h 52,560 US$



Insurance 28,000 US$

Cost crop production Napier

grass

82,500t/a 18US$/t 1,485,000 US$

Total annual operational costs 2,660,578 US$

Operational staff of Armag Farms Ltd biogas system is estimated to get an hourly payment of


52,560 US$/a.



An annual lump sum of 15,000 US$/a is assumed for business management of ARMAG FARMS LTD

BIOGAS SYSTEM plus 28,000 US$/a insurance payments.

Cropping of Napier grass is considered to range around 1,485,000 US$/a.

Leading to a total of 2,660,578 US$ operational costs for the first full year of operation.

Income from bio methane sale

Produced biogas could be, via gas upgrading, turned into bio methane and be sold to the power grid to

generate an income.

With an estimated annual biomethane production of 2,640,528 m³/d and a purity of 97.0% could be

sold at a rate of 0.70 US$/m³.

This could generate an annual income of approx. 1,787,540 US$/a.

Income from heat sale




Income from fertilizer sale

It is assumed that most of the produced digestate is utilized to fertilize Napier grass cultivations;

therefore no income from digestate/fertilizer sale is considered.

Table 12: Estimated annual income ARMAG FARMS LTD BIOGAS SYSTEM

Annual income

Produced

biomethane

start-

up:

2016 25,536,281 kWh/

a

8,00

0

h/a

Biomethane

sale

100

%

25,536,281 kWh/

a

7.0 US$cent/kW

h

US$ 1,787,540

Fertilising

value (solid)

12,431 t/a US$/t

Fertilising

value (liquid)

82,436 t/a US$/t

Total annual income US$ 1.787.540

Profitability assessment scenario two






(1 + 𝑖𝑘)𝑛 − 1










reference electricity costs: cr=0.2 US$/kWh


annual service and maintenance CHP unit: csmCHP=0.015 US$/kWhproduced


caiu=as indicated in Table 11

hourly wages for plant operators: chw=6 US$/h




total annual operation costs: cOPtotal=1,826,013 US$/a

total annual income: Incometotal=1,787,540 US$/a

annual benefit (income-costs): =-38,473 US$/a




𝐸𝐴𝐶𝑖𝑛𝑣 = −(5,600,000 ∗(1 + 0.08)10 ∗ 0.08

(1 + 0.08)10 − 1)

𝐸𝐴𝐶𝑖𝑛𝑣 = −834,565

𝐸𝐴𝐶𝑡𝑜𝑡𝑎𝑙 = −834,565 + 1,787,540 − 1,826,013

𝑬𝑨𝑪𝒕𝒐𝒕𝒂𝒍 = −𝟖𝟕𝟑, 𝟎𝟑𝟖 $𝑼𝑺


The impact needs to be analysed differently because of the different concept aspects and options.

4.6.1 Environmental and hygiene aspects by digestion of the organic wastes

Greenhouse gas emissions

The organic wastes and manure treatment in a biogas plant has a couple of direct and indirect benefits

for environment and hygiene. Globally the reduction of greenhouse gas emissions, especially the direct

greenhouse gases methane and nitrous oxide are important. Both are generated by normal manure

storage and then emitted to the atmosphere. Methane has a 25-fold greenhouse effect compared to

carbon dioxide, nitrous oxide is 300 times stronger. The anaerobic digestion in a biogas fermenter

avoids the generation of nitrous oxide, which is formed especially under semi-oxic conditions, when

nitrogen rich substrates are degraded. The methane generation is enhanced, but in a controlled

process with utilization of the generated gas. In this way the methane is transferred to CO2 by the factor

of 25. This carbon dioxide is climate neutral as it is generated from manure as a renewable resource.


emissions. The amount is depending on the used fossil fuel and on the conversion efficiencies of the

technologies.






Not the least for touristic regions like Barbados an authentic sustainable policy enhances the image

and standing.

Further emissions







Hygiene aspects

The biogas digestion of organic wastes has several indirect and direct hygiene effects. As named

before, the process takes place in a closed tank under anoxic conditions. The easy degradable organic

compounds are degraded in the process. This means that insects, rodents and other animal vectors

lose their feed base and sometimes their habitat. If one of these vectors comes into a plant, it will die

and will be degraded. Those are very strong indirect effects to enhance the hygiene in organic waste

management.

There are also direct effects. In detail the reduction of pathogens by biogas process depends strongly

on some technical parameters like digestion temperature level, pre-treatment, heat step in between the

process, average and secure retention time, cascading and some more.

Water supply:

The current handling of the organic wastes will be considerably improved. Instead of disposing the

wastes into the environment, it will be treated, while producing energy and fertilizer. This will strongly

reduce water pollution.

Local economy

There are several points, which will strengthen the local economy. One very important point is the

emission reduction, which becomes sensitive due to rising conflicts between population settlement and

tourist economy on the one side and current handling of organic wastes on the other side. By

minimizing these conflicts the development in both sectors is forced. As the tourist economy has a high

demand for meat products and also for rum, this enables the optimization of local economy.

The improved ecologic situation and water supply will also be an advantage for the tourist economy,

especially for a higher level tourism.

The additional employment and added value generation is also a brick for the local economy. As the

biogas production is all year production with less direct impact by fluctuating tourist economy it is a

factor for economic stabilization. The replacement of diesel fuel for diesel generators as well as the

replacement of mineral fertilizer by the optimized characteristics of the digestate products will reduce

the countries money outflow.



4.6.2 Energy cropping

The best way of energy cropping should be proven. In the current concept, the inorganic nutrients are

needed for the energy crops (and additional fertilizers for the unavoidable losses). A legume option

would generate nitrogen, improve soil fertility in a stronger way and would enable to sell the fertilizers

(only fertilizing inorganic potassium and phosphate). The current status and vegetation of the planned

fields need to be considered as well.

4.6.3 CHP option of whole concept

The impact of the given biogas concept with CHP option needs to be proven against other options,

which seems to be favourable. It should be proven,

a) if the main electricity production can`t be provided in a much more feasible way (less costs, less

ecologic footstep for energy cropping, easy technology with low operation costs and risk). For

the time without sun, a storage should be considered.

The organic wastes should be digested in a biogas plant with big gas storage. In this way the gas

can be used to produce energy in a flexible way, the CHP shall be operated in the hours without

sun/wind power generation.

b) If the storage for electric energy is not feasible, the whole energy for the night time may be

produced by biogas. In this case the organic wastes and additional energy crops (but less

amount compared to the 24 hours option) should be digested for the estimated energy need. In

daytime, solar and wind plants would generate the electricity and in night time the CHP would

run gas storage for gas of day-time).

The enhancement of energy provision will enhance Barbados` chances for further development.

Depending on the communication strategy the way of energy sector development can be an important

point for Barbados tourist sector.

4.6.4 Biomethane option of whole concept

The seasonality of demand seems to be strong. It needs to be checked, how the BNOC likes to handle

this aspect – assessing flexibility option like storage and flexible production for the short times of high

demand. Measures like high pressure tanks with liquefied methane are possible but are assessed as

very costly.

In general, the biomethane option opens a couple of new development lines for Barbados and if done in

a good way it would be an important step for a total renewable country. That’s a very important point for

an island, as islands and coastal areas will be especially affected by climate change.


The project may be a very good show case after some clarification and improvements.

The first point to do is the proving of the two business options CHP and biomethane, regarding the

suggestions made in 2.6.3 and 2.6.4. As second step, the energy crop option needs to be checked in

detail as stated in 2.6.2. Some improvement seems to be necessary regarding the fertilizer marketing

importance of the financial concepts.



After those clarifications a feasibility check of the technical and economic concept can be done. The

technical viability will be checked with regard to the substrates.


As named before, the project may become very interesting after some clarifications and improvements

(see 2.2- 2.7.4). The business concepts cannot be really proven at the moment as shown in the named

chapters.

The main critical points of the concept are the following:

The additional gas need, which should be covered by the biomethane, is a peak load. Operating a

biomethane plant for a short number of days per year will not be feasible. Therefore, it needs to be

clarified, if the natural gas production is flexible enough or if there are gas storages in the existing

system to cover the variation of need. In this case the biomethane can be an additional baseload

feed in. Otherwise (and even in case of another solution to cover the gas need) there is a need to

invest in gas storage capacity at the biomethane plant or at any other place in the gas grid. It needs

to be ensured, that the piping system can take the peak load from the storage point. Such a storage

is an investment into the whole infrastructure. It needs to be covered by the gas company or be paid

back by a special high peak load price (for producers and consumers). The clarification of this point

is the base for a further planning of the project.

The cropping costs are a main part of the overall costs. Main parts of these costs are the harvest

including the logistics and the fertilizing. Optimizations of harvest and logistics should be proven.

Fertilizing costs can be reduced mainly to potassium (K) and phosphate (P), if legumes are used

instead of Napier Grass. In this case, the digestate can be sold as organic fertilizer, rich in nitrogen

(N), which is produced by the legumes by symbiotic N2 fixation from atmosphere. The solid part can

be composted for nursery substrate, if there is a market in Barbados. This option can generate

further income. Furthermore, legume cropping enhances soil fertility in the strongest way for the

following crops. It should be proven, if adequate legumes are available.

The discussed substrates are very challenging due to the fibrous behaviour. The technology should

be optimized to meet the challenges, which is cost efficient (investment and operational costs) and

which is reliable under the given maintenance service conditions.

Biogas from water plants for GSWMA, Guyana


5 Biogas from water plants for GSWMA, Guyana

Operator: Not yet decided

Location: Georgetown

Guyana

Feedstock: Water hyacinth, water lilies from drainage ditches,

mix with other substrates

Technology: Anaerobic digester with CHP

Business model: Diversion of ditch water plants from landfill

Use of water plants in biogas plant

Feed-in of electricity

Local heat use

Use of digestate as fertilizer

PPP model,


The city of Georgetown, Guyana faces ongoing challenges with the provision of municipal services to

manage waste, provide energy and improve public health. At present, the city has to dredge and clear

the numerous canals in the city of aquatic plants, most commonly the lotus flower (Nelumbo nucifera)

to ensure the effective functioning of the canal system and prevent flooding.

The wet biomass is transported by truck to the landfill for disposal, at significant costs to the city. There

is therefore an opportunity to offset at least a portion of the costs associated with maintaining the

canals by processing the wet biomass in a centralised biogas plant.

A detailed feasibility study is required to determine the technical viability of a centralised biogas plant,

to be located on or near the existing landfill. The biogas facility should be capable of processing wet

biomass from the cities’ canals as well as other organic waste streams that are presently ending up at

the landfill. There may also be opportunities to incorporate chicken waste from local poultry operations

as it is felt that this is a sizeable and reliable source of biomass. Also, increasing the diversity of

feedstock materials is likely to add to the quality of digestate produced at the plant, with the potential

for added value fertiliser production and therefore additional revenue generating opportunities.

The study would also assess the potential economic impact on waste management costs for the city.

Given the municipal nature of the project, it is believed that a model which brings existing publically

funded and operated waste management services together with private sector biogas expertise, is best

suited to the development of a centralised biogas facility.




It is suggested to locate the plant on the premises of the Haags Bosch Sanitary landfill, which is

situated close to Georgetown. The waterplants are dumped here already.

In an interview with the Guyana Solid Waste Management Authority (GSWMA), following information

about the landfill was gathered:

3,000 tons of MSW are available weekly

2,500 – 2,700 tons are collected and shipped to the Hong Bosch Sanitary Landfill

Waste is collected 7 days a week

There is a leachate draining pond at the landfill which was started in 2007

Around 54% is organic waste

About 40% of the organic waste is food

Handling of organic wastes is problematic

Lotus plants extracted from the canals are sent to the landfill

There is no legislation for waste treatment plants

No local market exists for organic fertilizers

IDB has provided a grant for development of composting sites

Composting is being considered at the landfill but the market is uncertain

An incinerator exists but was shut down due to soot related pollution. No electricity was produced.

Metal is sorted out at the landfill and sold in a scrap market

A recycling plant is being considered for plastics and glass

Corrugated cardboards are currently being recycled

A bill has been prepared for the banning of Styrofoam

Tipping fees are paid at the landfill of around 5 - 10 US$ per tonne

Waste collection tax is around 15,000 GYD$ per year for residential and 150 - 300 GYD$ per year

Both diesel and electricity are consumed on site

The landfill life is about 18 years

There is space available for other installations at the landfill

There is potential for a PPP arrangement for waste treatment


As feedstock water plants, sludge from channels and additional biomass if needed or available

(preferably from landfill, assuming sufficient quality) are foreseen. Poultry droppings appear to be an

adequate addition.

The composition of the water plants will be assumed as it is not known. An analysis of the composition

of the water plants will be part in a future bankable project elaboration for the technical planning and

environmental assessment. Following aspects need to be investigated:

The behaviour of the aquatic plants (sprouts can be longer than 2 m), especially the toughness of

the fibres, which may be challenging for the pumping, mixing and tubing system. This may require

adapted technical solutions



An analysis on the level and significant differences in the pollutant level (pathogens, organic and

inorganic pollutants) is necessary for the integration of adapted technical measures (e.g. water

disinfection step, different lines etc.) by adequate lab analysis from different parts of the canal

system. The aquatic plants and the sludge will be analysed separately.

Typically in the tropics parasites are more important. This need to be clarified on site. In current

analysis of aquatic plant material in an ongoing project (own analysis, not published) in Germany it

was found, that these plants (Elodea nuttalii) are rich in nutrients but poor in pollutants. This may

lead to a concept with regular clearing only of the aquatic plants by harvesting boat (see for

example http://www.berky.de/252.html). In this case the sludge will only be cleared every few years

by an excavator. This way of management may be a measure to save costs for disposal and

generate added value by fertilizer generation. The decision can lately be done on the base of the

analyses.

Gas yields (batch tests and associated chemical analysis)

Nutrient contents (esp. N, P, K)

The following two figures show the waterplants in the channels of Georgetown and their removal.

Figure 7: Close up of waterplants in Georgetown channels.




Figure 8: Removal of waterplants in Georgetown channels


For this report it is assumed to use 80t/d of water plants plus 3t/d of poultry droppings as feed for the

biogas system.

The potential daily gas production of GSWMA biogas system is estimated to be 1,926m³ of biogas

(based on an estimated dry matter content of water plants of ~8%. Daily biogas production can

increase/decrease considerably if dry matter content is higher/lower as expected) with an average

methane content of 60%.

If utilized in a 250kW CHP unit it is assumed, that during 6,700 hours per year a total 1,675,000kWh/a

electrical energy and 1,982,600kWh/a thermal energy could be generated.




Table 13: Estimated biogas potential of GSWMA substrate

GSWMA substrates

Daily

production

Dry matter

content

Volatile

solids

Biogas

yield

Biogas

production

Methane

content

Methane

production

[tFM/d] [%] [%DM] [m3/tVS] [m3/d] [%] [m3/d]

Water

plants

80.0 8.0 85.0 270 1,468.8 60 881.3

Poultry

droppings

3.0 55.0 72.0 385 457.4 60 274.4

Total 83.0 9.70 82.3 290.6 1,926.2 60 1,155.7




For the daily amount of 80t/d of water plants plus 3t/d poultry droppings a preliminary plant layout is

considered in this report consisting of the following plant components (see Figure 9):

a) Reception tank/collecting pit & solid feeding unit:





Solid feeder to feed water plants into digester




c) Control office:



d) Digester:



Mixers/ agitators

Gas storage



e) Biogas flare:

Combustion capacity of 90m³/h

f) CHP unit:

250kWel capacity


83m³/d capacity





Figure 9: Simplified flow diagram GSWMA biogas plant



5.5 Cost estimation

5.5.1 Invest costs for the biogas system

Cost for the planned biogas system at GSWMA for the treatment of a daily amount of 80t water plants

plus 3t poultry droppings is estimated to range around 1,265,000 US$ (see Table 14). These figures

base on values of the Leitfaden Biogas, 6th edition, 2013, chapter 8.2, table 8.10 (FNR, 2013) and

empirical values of the consultant (a fixed exchange rate of 1 EUR=1.123705 US$ is assumed).

Table 14: Investment cost GSWMA biogas system

Investment






Total Manufacturing costs for the plant

942,566 US$


Planning, permits/licensing and commissioning 302,368.00 US$





Since the water plants to be treated is waste that has to be collected in any case, no costs for the water

plants procurement are considered.




Table 15 shows the estimated annual operational cost of GSWMA biogas system. The annual sum of

money to be spent for maintenance and servicing of the biogas system is estimated to be approx.

25,298 US$/a plus additional 16,746 US$/a for servicing and maintaining the CHP unit.



Table 15: Operational cost GSWMA biogas system for first full year of operation

Costs per year


payments






CHP

1,674,679 kWh/a 0.01 US$/kWh 16,746 US$

Substrate costs poultry

droppings

1,095t/a 2.00 $/t 2,190 US$




Insurance 6,324 US$


Operational staff of GSWMA biogas system is estimated to get an hourly payment of 5.00 US$/h and is

assumed to work on 5,840 hours per year generating an annual cost of 29,200 US$/a.



An annual lump sum of 5,000 US$/a is assumed for business management of GSWMA biogas system

plus 6,324 US$/a insurance payments.

This leads to a total of 283,971 US$ operational costs for the first full year of operation.



generate an income.

With an estimated daily biogas production of 1.926m³/d and a methane content of 60% a 250 kW CHP

unit could be operated during 6,700 hours per year generating approx. 1,674,679 kWh/a.

Auxiliary power demand of the GSWMA biogas system itself and transformation losses during feed in

are estimated to range around 99,643 kWh/a, leaving 1,491,301 kWh/a to be sold at 0.20 US$/kWh.







After being processed inside the digester the substrate could be commercialized as high grade organic


year of solid organic fertilizer. It is considered in this report that the solid fraction is being sold at

100 US$/t (reference http://ecuadorbalsa.com/organic-fertilizer.htm sold for 150 US$/t), generating

an annual income of 391,653 US$/a.

The liquid fraction of separated fertilizer is not considered to be commercialized, since no local market

is available.

Table 16: Estimated annual income GSWMA biogas system

Annual income

Total electrical

work CHP 1

start-

up:

2016 1,674,679 kWh/a 6,699 h/a


Transformation

and feed-in

losses

-15,909 kWh/a

Actual fed-in

electricity

1,491,301 kWh/a

Electricity sale 100% 1,491,301 kWh/a 20 US$cent/kWh 298,260 US$

Fertilising value

(solid)

3,917 t/a 100.00 US$/t 391,653 US$

Fertilising value

(liquid)

25,452 t/a 0,00 US$/t 0 US$

Total annual

income

689,913 US$







(1 + 𝑖𝑘)𝑛 − 1



http://ecuadorbalsa.com/organic-fertilizer.htm















annual administration, insurances and unexpected costs: caiu=as indicated in Table 15



total annual operation costs: cOPtotal=95,459 US$/a

total annual income: Incometotal=689,913 US$/a


Specific power production costs: Csp=-0.07 US$/kWh



𝐸𝐴𝐶𝑖𝑛𝑣 = −(1,264,934 ∗(1 + 0.08)10 ∗ 0.08

(1 + 0.08)10 − 1)

𝐸𝐴𝐶𝑖𝑛𝑣 = −188,512

𝐸𝐴𝐶𝑡𝑜𝑡𝑎𝑙 = −188,512 + 689,913 − 95,459

𝑬𝑨𝑪𝒕𝒐𝒕𝒂𝒍 = 𝟒𝟎𝟓, 𝟗𝟒𝟐




5.6.1 Local economy

The overall plant size is estimated for around > 5m m3 of methane per year, correlating to an installed

power of a CHP plant of around 3 MW (8,000 operating hours per year) based on a very sustainable

concept. This means a very large plant option for the region with a large impact on energy supply, waste

management an environment protection.

There are several points, which will strengthen the local economy. An important point is the large

additional renewable energy production which can be used for several purposes such like biomethane

for cooking, as traffic fuel for decentralized CHP plants etc. This large amount of renewable energy

allows also a renewable electricity production. If CHP plants are operated flexible to complete

fluctuating renewables, it opens the option for large amounts of renewables in a reliable electricity

supply system. A further important point is the reduction of pollution, e.g. the emission reduction, which

becomes sensitive due to the not yet fully developed tourism economy on the one side and current

handling of organic wastes on the other side. By minimizing these conflicts the development in both

sectors is forced. A major advantage of this concept is the extension of the landfills lifetime.

The improved ecologic situation and water supply will also be an advantage for the tourist economy,

especially for a higher level tourism.



factor for economic stabilization. The replacement of diesel fuel for diesel generators as well as the

replacement of mineral fertilizer by the optimized characteristics of the digestate products will reduce

the countries money outflow.

5.6.2 Environmental and hygiene aspects by digestion of the organic wastes

Greenhouse gas emissions:

The organic wastes and manure treatment in a biogas plant has a couple of direct and indirect benefits

for environment and hygiene. Globally the reduction of greenhouse gas emissions, especially the direct

greenhouse gases methane and nitrous oxide are important. Both are generated by normal manure

storage and then emitted to the atmosphere. Methane has a 25-fold greenhouse effect compared to

carbon dioxide, nitrous oxide is 300 times more strong. The anaerobic digestion in a biogas fermenter

avoids the generation of nitrous oxide, which is formed especially under semi-oxic conditions, when

nitrogen rich substrates are degraded. The methane generation is enhanced, but in a controlled

process with utilization of the generated gas. In this way the methane is transferred to CO2 by the factor

of 25. This carbon dioxide is climate neutral as it is generated from the residues waterplants and

poultry droppings as a renewable resource.


emissions. The amount is depending on the used fossil fuel and on the conversion efficiencies of the

technologies.

Avoiding greenhouse gas emissions is a crucial point for a sustainability strategy especially for low-lying

coastal regions like Georgetown, Guyana. Rising sea level or rising risk for thunderstorms endangers

their physical and economic existence.



Further emissions:







Hygiene aspects:






management.




Water supply:

The current handling of the organic wastes will be improved considerably. Instead of disposing the

wastes at the landfill, it will be treated, while producing energy and fertilizer. This will strongly reduce

pollution.

5.7 Project development plan – main issues to be considered

A major part of a future project is the analysis of following aspects in order to derive at a feasible

project:

the current waste management needs to be checked in detail

an adapted management option needs to be developed with regard to the local conditions

Quality aspects of the different mass flows needs to be analysed; Such aspects like pollutant risk

parasites etc. needs to be answered by the process chain. This will be the prerequisite for a long

term concept for marketing of the fertilizers and to avoid the deposit costs and pollution effects.

For that size of a plant the energy utilization concept needs to be secured. One line of investigation

could be a biomethane option which might prove more feasible due to the scaling aspects.

This concept involves a range of different actors. It is advisable to involve these stakeholders from the

beginning to improve the chances of success:

Local government, government of Georgetown

Guyana administration

GIZ and REETA

Private waste generators (companies, households)

Companies responsible for clearing the canals

Companies responsible for the organization of waste collection, transport and handling

Informal waste sector, if available



If there is a pollution problem for the digestate, companies, which integrates harmful waste water

into the canals

Energy companies (for different energy markets)

Guyana agriculture actors or outside customers for fertilizers

Tourist industry, which will profit from optimization

Possible investors (ideally for PPP-concept)

Possible plant operators

Stakeholders for building up a knowledge based infrastructure (adequate lab capacity, consulting

and maintenance service)

Founding organizations

Banks


This project shows large overall chances and no general risk of a biogas plant treating these wastes.

Nevertheless, a thorough substrate analysis is necessary to define the optimal mixture and process

parameters. The given price for energy (0.2 US$/kWh of electric energy, methane price currently not

available) and the avoiding of disposal costs are a good base for a profitable project, if it will be created

in the right way. A key point for this will be an adequate mass flow management, which will take care

and minimize pollution risks of digestate and enables the fertilizer marketing instead of disposal of

digestate.

Antigua Distillery, Antigua and Barbuda


6 Antigua Distillery, Antigua and Barbuda

Operator: Antigua Distilleries, Ltd.

Location: Antigua

Feedstock: Vinasse, energy crops,

Technology: Anaerobic digester with CHP for electricity and thermal energy production

Business model: Treatment of highly contaminated wastewater (vinasse)

Maximum generation of electrical and thermal energy

Coverage of own electricity and thermal energy demand, feed in of excess

power

This concept is based on the study of Enprocon “Alternative Energy Production Proposals and Integrated

Waste Management Solutions for Eastern Caribbean States” from 2012(Enprocon, 2012). The data

have been updated, checked and applied with the methodology of this study.


Antigua Distillery was formed in Antigua in 1932 by a number of small independent rum producers.

Within a few years of its formation the company principals had purchased sugar cane estates and a

sugar factory that enabled Antigua Distillery to both produce sugar and the molasses required for its

rum production.

Today, the distillery faces significant operational costs such as the costs of electricity, which it

purchases from the grid and process steam, which it generates from fuel oil. In addition the company

faces significant opportunity costs associated with failing to capture the energy potential of 14,400

gallons of vinasse, which it produces daily for eight months of the year. Vinasse is a key waste by-

product of the rum making process.

There is potential for Antigua Distillery to convert the vinasse produced into biogas by a process of

anaerobic digestion. The biogas produced could then be used to produce electrical power and heat.

There are additional opportunities for the distillery to enhance both the quantity and quality of

substrates that could be utilized in the biogas facility by supplementing the vinasse with pig manure

and short rotation crops that are readily available on the island. A suitably constructed biogas facility

could also produce organic fertilizers and soil conditioners resulting in additional revenue potential.

This option would require that the biogas facility be located adjacent to the distillery. The project would

likely receive support from the Government of Antigua and Barbuda as long as it remained off-grid and

smaller than 1 MWel in size. Governmental support could include import duty and tax concessions on

plant and equipment.




Material supply chains and logistics will determine the positioning of the Antiguan project. As envisaged

in the Enprocon project document, the project is best located in the direct vicinity of the distillery, which

was stated as possible. Further details can be found in the mentioned Enprocon study.

One potential location for the biogas plant currently owned by the government and to be contributed to

the biogas project, is shown in Figure 10. Soil analysis will have to determine if the plot is suitable for

the construction of a biogas system.

Figure 10: Land slot for biogas plant in St. Johns, Antigua, Distillery plant to the left and empty production building to the right

for potential bottling plant (2012)


As in many parts of the Caribbean, the Enprocon project identified some key input materials, which

although might be readily available, might prove some real challenges in the urge to use all available

materials to obtain as much biogas as possible. A mention was made of leguminous leaves, lemon

grass and elephant grass which could be collected and brought to the facility from road cuttings and

through private delivery. Leguminous plants are very special in being used for biogas production for

many reasons unless adequate management of pre-treatment avenues like special ways of mixing

these materials during silage before use as their presence will definitely increase the protein content

and thus incur higher levels of propionic acid are explored. Notably, acetic and propionic acids are the

two quantitatively predominant acids in biogas plants. The possible ratio of 2:1 in favour of acetic acid

should stabilize an optimal production of high quality biogas. Eventually, it all gets down to pre-

treatment management and during fermenter feeding and process control management.

© Enprocon



Understandably, mowed grass if harvested at the right time could also prove to be a special co-

substrate as their frequency of regrowth in the typically tropical Caribbean is rapid and uniform. In most

cases, the collected mowed grass must be given a closer look especially when they are from

uncontrolled areas as contents of varieties could be so varied that high other leguminous plants could

be inherent of the mix causing not only problems in the digestion process but in the ensilaging process.

It is also important to include some oil plants that are also available and grow in the wild like whole

plant Ricinus comunis (castor plant). The process will use the oil yielding plants as an easy access to

boost the energy of the inherent microorganisms and thus a resounding biogas yield.

Slaughter house waste from local production is as well a valuable material and should form part of the

co-digestion mix for optimum. As afore mentioned, care should be taken in handling such highly

proteinaceous materials, in order to avoid lower acetic/propionic acid ratios for optimal biogas quality

and thus continuum in standardized electricity generation and provision.

Vinasse from both the distillery and other small scale rum distilleries are rather a challenging substrate

and co-digestion is advisable. Vinasse is an acidic liquid with pH between 4 and 5 and high chemical

oxygen demand (COD) content. It frequently poses serious disposal challenges for the industry as

evidenced by its high biochemical oxygen demand (BOD). It also requires high pre-treatment to work in

an anaerobic fermenter to reach adequate levels of pH for effective fermentation. Co-digestion is

helpful in such a process also and for the breakdown of all valuable nutrients it entails for biofertilizer

use. In a co-digestive system alternate subsequent processes and thus responsible microorganisms

carry out the process much more effectively. Its availability is taken into consideration; it will be what

definitely defines the location of the biogas plant taking logistics into consideration.

Although cattle slurry or manure might be in limited quantities in terms of availability and supply, if

periodically used as a constant microorganisms’ additive, it will help in the process of microbial

development apart from helping also as an energy source for especially the methanogenic bacteria.

In a pure biogas production system, in order to obtain acceptable amounts of quality biogas (with high

levels of methane), it is ideal to effect the co-digestion approach for system alternate subsequent

processes and thus responsible microorganisms to carry out the process much more effectively.

Using co-digestion of surplus yeast and wastewater adds a valuably adequate substrate to the mix for

the project.

The above materials in their mix should generate enough biogas with an end digestate that will market

as a valuable bio-fertilizer involving a close loop system of nutrient replenishment for both project and

sustainability purposes. However, it is always vital to carry out a thorough laboratory analysis of

feedstock before and after pre-treatment to find the right mix and dosage for each plant.

Note should be taken though of the use of the digestate and its quantities of application especially in

the Caribbean as there seem to be no fertilizer acts and implementation regulations covering what is

applied and how it is applied. Dependent on the contents of the co-digestion mix as discussed afore,

higher contents of nutrients could apply which could affect productivity of crops.



Table 17: Estimated biogas potential of Antiguan substrates

Pig manure

Daily amount Dry matter

content

Volatile

solids

Biogas

yield

Biogas

production

Methane

content

Methane

production

[tFM/d] [%] [%DM] [m3/tVS] [m3/d] [%] [m3/d]

Vinasse 35.87 9.9% 85.0% 400.0 1207.4 65.0% 784.8

Elephant

grass

10.96 13.0% 82.0% 550.0 642.5 52.0% 334.1

Leucaena 10.96 18.0% 90.0% 550.0 976.4 52.0% 507.7

Lemon

grass

10.96 18.0% 91.0% 550.0 987.3 52.0% 513.4

Gut content

(pigs)

3.29 14.0% 80.0% 350.0 128.9 60.0% 77.3

Total 72.03 13.02% 86.6% 485.2 3,942.5 56.2% 2,217.4

For this report a daily amount of 72 tons/d of substrate mixture, with values indicated in Table 17 is

considered. All values are empirical values of the consultant and shall be checked for with the actual

substrates.

6.4 Preliminary plant design - biogas utilization in CHP unit

For the daily amount of 72 tons/d of substrate mixture a preliminary plant layout is considered in this

report consisting of the following plant components (see Figure 11):









c) Control office:



d) Digester:



Mixers/ agitators

Gas storage





e) Biogas flare:

Combustion capacity of 250m³/h

f) CHP unit:

400kWel


100m³/d capacity



Figure 11: Simplified flow diagram biogas plant

Gas production & theoretical utilization

The potential daily gas production of Antiguan biogas system is estimated to be 3,942m³ of biogas with

an average methane content of 56.2%.

If utilized in a 400kW CHP unit it is assumed, that during 8,000 hours per year a total of

2,960,000kWh/a electrical energy and 3,392,615kWh/a thermal energy could be generated.






6.5 Cost estimation

6.5.1 Invest costs for biogas system

Cost for the planned biogas system at Antigua Distilleries, Ltd. for the treatment of a daily amount of

35.87t/d vinasse, 10.96t/d Elephant grass, 10.96t/d Leucaena, 10.96 t/d Lemon grass and 3.29t/d

gut content of pigs is estimated to range around 1,770,000 US$ (see

Table 18). These figures base on values of the Leitfaden Biogas, 6th edition, 2013, chapter 8.2, table

8.10 (FNR, 2013) (FNR, 2013)and empirical values of the consultant (a fixed exchange rate of

1 EUR=1.123705 US$ is assumed).

Table 18: Investment cost Antigua Distilleries, Ltd. BIOGAS SYSTEM

Investment








Planning, permits/licensing, infrastructure provision and

commissioning

400,000.00 US$





An annual production of approx. 4,000t/a Elephant grass, 4,000t/a Leucaena and 4.000t/a Lemon

grass is considered to range around 180.000 US$/a including cropping and transportation to the

biogas system.


Table 19 shows the estimated annual operational cost of Antiguan Distilleries, Ltd. biogas system.

Annual sum of money to be spent for maintenance and servicing of the biogas system is estimated to

be approx. 35,400 US$/a plus additional 29,600 US$/a for servicing and maintaining the CHP unit.





Table 19: Operational cost Antigua Distilleries, Ltd. biogas system for first full year of operation

Costs per year


payments



Operating expense separator 24,424

t/a

0.25 US$/t 6,179 US$



CHP

2,960,000 kWh/a 0.01 US$/kwh 29,600 US$




Insurance 8,850 US$

Cost crop production

Elephant grass, Leucaena,

Lemon grass

12,000t/a 15 US$/t 180,000 US$


Operational staff of Antigua Distilleries, Ltd. biogas system is estimated to get an hourly payment of


21.900 US$/a.



An annual lump sum of 10,000 US$/a is assumed for business management of Antigua Distilleries, Ltd.

biogas system plus 8,850 US$/a insurance payments.

Cropping of Elephant grass, Leucaena and Lemon grass is considered to range around 180,000 US$/a,

leading to a total of 559,072 US$ operational costs for the first full year of operation.



generate an income.

With an estimated daily biogas production of 3.940 m3/d and a methane content of 56.2% a 400 kW

CHP unit could be operated during 8.000 hours per year generating approx. 2,960,000 kWh/a.

Auxiliary power demand of the Antigua Distilleries, Ltd. biogas system itself and transformation losses

during feed in are estimated to range around 264,032 kWh/a, leaving 2,695,968 kWh/a to be sold.





It is assumed that 80% of the total thermal energy produced (2,691,887kWh/a) can be sold to the

distillery to substitute fossil fuel which are currently used to produce hot water/steam for the distillation

process. It is estimated that thermal energy produced could be sold for 5 US$cents/kWh what would

generate an annual income of approx. 107,676 US$/a.


After being processed inside the digester, the substrate could be commercialized as a liquid organic


year of liquid organic fertilizer. It is considered in this report that the liquid fraction is utilized to

substitute mineral fertilizer on farms close to the distillery and by this generating an income of

5.00 US$/m³, generating an annual income of 109,756 US$/a.

The solid fraction of separated fertilizer could be commercialized and due to its high solid content would

even be suitable for transport over longer distances. An estimated amount of 2,473t/a at a sale price of

50.00 US$/t could generate incomes in the range of 123,660 US$/a.

Table 20: Estimated annual income Antigua Distilleries, Ltd. BIOGAS SYSTEM

Annual income

Total electrical

work CHP

start-

up:

2016 2,960,000 kWh/a 8,000 h/a


Transformation

and feed-in

losses

-27,232 kWh/a

Actual fed-in

electricity

2,695,968 kWh/a

Electricity sale 100% 2,695,968 kWh/a 13 US$cent/kWh 350,476 US$

Heat sale 80% 2,153,510 kWh/a 5 US$cent/kWh 107,676 US$

Fertilising

value (solid)

2,473 t/a 50.00 US$/t 123,660 US$

Fertilising

value (liquid)

21,951 t/a 5.00 US$/t 109,756 US$

Total annual income 691,568 US$









(1 + 𝑖𝑘)𝑛 − 1














caiu=as indicated in Table 19: Operational cost

Antigua Distilleries, Ltd. biogas system for first full

year of operation



total annual operation costs: cOPtotal=295,289 US$/a

total annual income: Incometotal=691,568 US$/a





𝐸𝐴𝐶𝑖𝑛𝑣 = −(1,770,000 ∗(1 + 0.08)10 ∗ 0.08

(1 + 0.08)10 − 1)



𝐸𝐴𝐶𝑖𝑛𝑣 = −263,782

𝐸𝐴𝐶𝑡𝑜𝑡𝑎𝑙 = −263,782 + 691,568 − 295,289

𝑬𝑨𝑪𝒕𝒐𝒕𝒂𝒍 = 𝟏𝟑𝟐, 𝟒𝟗𝟔


6.6.1 Local economy

The local economic effects are of high importance for Antigua. The project will create a stable source of

energy on a stable cost base for the distillery, and effective fertilizer for crops. In case of integration of

municipal organic wastes and slaughterhouse wastes this will be combined with an improved

environmental and hygiene (see below).

So there are several points, which will strengthen the local economy. Important points are the coverage

of the current energy consumption of the distillery, additional renewable energy production which can

be used for several purposes such like cooking, reliable electricity production, optionally combined with

fluctuating renewables.

If CHP plants are operated flexible to complete fluctuating renewables, it opens the option for larger

amounts of renewables in a reliable electricity supply system. This might be a later option for the

distillery in case of larger contributions to the grid. A further important point is the reduction of pollution,

e.g. the emission reduction, which becomes sensitive due to rising sensitivity of coastal regions to

climate change. So, climate protection is elementary for sustainable agricultural economy in the region.

The improved ecologic situation and water supply will also be an advantage for the whole economy.



factor for economic stabilization. The replacement of external energy for the distillery as well as the

replacement of mineral fertilizer for agricultural production by the optimized characteristics of the

digestate products will reduce the money outflow and improve the economic stability of the distillery,

especially at fluctuating prices.

6.6.2 Environmental impact

Greenhouse gas emissions:

The vinasse and further organic wastes treatment in a biogas plant has a couple of direct and indirect

benefits for environment and hygiene. Globally the reduction of greenhouse gas emissions, especially

the direct greenhouse gases methane and nitrous oxide are important. Both are generated by normal

manure storage and then emitted to the atmosphere. Methane has a 25-fold greenhouse effect

compared to carbon dioxide, nitrous oxide is 300 times more strong. The anaerobic digestion in a

biogas fermenter avoids the generation of nitrous oxide, which is formed especially under semi-oxic

conditions, when nitrogen rich substrates are degraded. The methane generation is enhanced, but in a

controlled process with utilization of the generated gas. In this way the methane is transferred to CO2 by



the factor of 25. This carbon dioxide is climate neutral as it is generated from manure as a renewable

resource.

A special point of the vinasse digestion will be the protection of the water resources as after digestion

the vinasse will be used as an efficient fertilizer which does not cause plant damages.

Replacing energy production from fossil fuels means a further reduction of greenhouse gas emissions.

The amount is depending on the used fossil fuel and on the conversion efficiencies of the technologies.




Further emissions:







Hygiene aspects:






management.




Water supply:

The current handling of the organic wastes will be improved strongly. Instead of disposing the wastes

into the environment, it will be treated, while producing energy and fertilizer. This will strongly reduce

water pollution.

6.7 Recommendations for improvement and development of the project

During this study, some inconsistencies surfaced in the current project outline due to a lack of

information. It is recommended to clarify following issues in a more detailed project:

There are information about slaughterhouse wastes as a possible substrate. But there is no

exact information about amounts, composition, logistic framework, pressure to act for the

slaughterhouses, legal framework for hygiene management. Even no information is available

about possible treatment revenues.

Bagasse, filter mud and cane straw seem to be unused sources at the distillery. This can only be

estimated, as there is the information, that fossil fuels are used for steam production. Normally



distilleries produce steam by bagasse burning. These materials can be digested together with

the other residual energy crops in the current substrate list. As the C/N-ratio of the sugarcane

wastes is quite high, the combination with the legumes (see substrate list) would lead to a well

balanced nitrogen content in the process

From the current stage of knowledge, the process chain is planned with ensiling of crop

materials. It is unknown, if there is the possibility to replace those step by organising the logistic

in another way under the climatic conditions at the site.

Fairfield Rice Inc, Guyana


7 Fairfield Rice Inc, Guyana

Operator: Fairfield Rice Inc.

Location: 24 Water Street

Georgetown

Guyana

Feedstock: Rice husks

Technology: Burner or turbine

Business model: Diversion of rice husks from landfill, open burning or dumping

Process heat and power supply for rice mill/rice processing


Fairfield Rice was formed in Guyana in 1999. The company purchases paddy from local farmers and

processes it into high quality rice products that are marketed both locally and internationally. The

company’s rice milling operation is situated in the rice growing district of East Coast Demerara and

comprises a 7.5 metric ton per hour rice mill. Rice husks are considered by the Guyana Energy Agency

as priority no. 2 in terms of residues for bioenergy. Priority no. 1 is the cogeneration in the sugar

industry.

The company currently utilises a proportion of the waste rice husk from its operations to generate heat

for drying of the rice prior to milling. The rice typically starts off at 20% moisture and is dried to 12.0% to

12.5% moisture, which is the optimal moisture content for milling. Some of the waste rice husk is

utilised for poultry bedding and the remainder is disposed of by burning, which causes issues with

neighbours who complain about the smoke.

In addition to the waste management challenges associated with the burning of rice husk, Fairfield Rice

also faces high operational costs as a result of the high price of electricity in Guyana. Thus, failing to

convert its waste rice husk into usable heat and power at the same time as effectively disposing of this

waste stream represents a very significant opportunity cost to the business.

Conversion technologies that are currently deployed in the rice production sectors in several Asian

countries, suggest that Fairfield Rice could integrate either steam turbines or Organic Rankine Cycle

(ORC) engines to successfully utilize their rice husk waste. In this study, a steam turbine concept is

investigated.

In the event that excess electrical power is available for sale, the company would need to obtain the

relevant permissions and licenses from the Office of the Prime Minister in order to be able to produce

and sell power. Significantly, a number of cogeneration and distributed power schemes already exist in

Guyana, as do projects of this sort that have successfully obtained PPA’s from the Government.




The rice milling operation of Fairfield Rice Inc, is situated in the rice growing district of East Coast

Demerara. According to the company, there is space on the premises to accommodate a bioenergy

plant (depending on size). The resulting short transport distances are beneficial for the cost and energy

balances.

Depending on the chosen plant configuration and the resulting amount of energy being generated by

rice waste treatment, the heat can be used for drying rice before milling or other processes. In depth

chemical characterization and biogas potential analyses of the rice husks compounded with manure

should be made for optional use as fertilizers mixed up with ashes from combustion or for alternative

conversion via anaerobic fermentation.

Rice mills work 6 months during rice crops, and there are 2 crops a year. Energy and logistic balance

need to be analysed.

Additionally, the ashes can be used as an additive for fertilization in nutrition intense rice cultivation but

due to the high contents of silicium, further considerations should be given to their reuse on the field as

well as for bio-digestion.


According to the owners information, about 4,000 to 5,000 t of rice husk are produced every year.

Taking into account a heating value of 15 MJ/kg, this equals an amount of 30 – 33 GWh fuel heat

input. With a supposed 8,000 operating hours per year, this equals to a thermal power of a potential

installation of 3.65 to 4.15 MWth while potential electric power depends on electric efficiency.

Rice husks need careful adjusted process conditions for combustion. They are difficult to ignite and do

not burn easily. Air must be blown through the husk until it burns into an open flame. The husk fuel is so

light that it mostly burns in suspension. As a more efficient procedure, reburning the unburnt ash by

reintroducing it into the combustion chamber may be much more feasible.

Due to its high resistance to moisture penetration due to some level of lignification thus microbial

decomposition in the shortest time, anaerobic digestion may only be practicable when a thorough pre-

treatment is given.

However, it is interesting to note that the net calorific values are around 16 MJ/kg and it is estimated

that 8,000 tons of husk can produce 1 MW of energy. Logistical issues like the determination of the

position and dimension of the steam turbine, feedstock supply and total energy balances highly depend

on the latter. For better combustion performance, production capacity of the rice mill might be

increased as well.

A feasibility study should advise the company as to whether to adapt storage, and transportation of the

rice residues to best steam turbine use and to capitalize energy sales or to customize the combustion

engine according to production standards.


There are several options for the combined production of heat and power from rice husk. Considering

the available amount of rice husk, there are two general options that should be considered for the site.



The first option is based upon the so-called Organic Rankine Cycle (ORC), while the second one is using

a water steam cycle and a gas turbine.

Figure 12: General principle of an ORC power plant with one working medium cycle

Typical combined heat and power (CHP) systems with Organic Rankine Cycle (ORC) start at a nominal

power of 0.5 MWel. Organic Rankine Cycles (ORC) make use of some specific features of certain thermal

and silicon oils. While the thermal oil can be used to transfer heat from a furnace at a specific

temperature, the silicon oil has some advantageous properties in regard of the thermodynamic Rankine

cycle.

In an ORC plant, biomass is burnt within a furnace. Afterwards, heat is transferred to thermal oil, e.g. via

coils. By this way, the heat can be transferred at low pressure level since the oil has a higher boiling

temperature which will not be reached in the process. Depending on the process design, there can be

one or two thermal oil cycles (see Figure 12) (Bini, 2010).

Within the so-called turbogenerator, heat from the thermal oil is transferred to a specific silicon oil (the

type of which is depending on the temperature of the hot thermal oil). The silicon oil will boil and drive a

power generator. In a further heat exchanger, the oil is cooled down and condensed.

Typical electrical power outputs are in the range of 400 to 2,200 kW, with an efficiency of 15-20 %.

An ORC based CHP fuelled by rice husk has been reported for Italy (Baresi, 2013). In Mortara (Region

Lombardy, Province Pavia), an ORC plant with an electric power of 600 kW and a thermal power of

2.8 MW has been installed and started in July 2008. It is fuelled by rice husk from rice mill Parboriz

Spa. Thermal power is used to the production of parboiled rice. The ORC part has been delivered by

Turboden (now part of Mitsubishi Heavy Industries), while the boiler was supplied by Classen

Apparatebau Wiesloch GmbH (“Classen Apparatebau Wiesloch GmbH - Referenzen. Dezentrale

Stromerzeugung ORC - Reisschalenverbrennung - Italien,” n.d.). It is reported to be running with 99%

availability (Baresi, 2013).

© DBFZ, 2015, base on (Bini, 2010)



Figure 13: General principle of a water steam cycle for biomass CHP

Typical combined heat and power (CHP) systems with steam cycle start at a nominal power of 1MWel.

At first, the fuel (here: rice husk) is burnt within a furnace (see Figure 13). There are several combustion

technologies, including a variety of grid furnaces as well as fluidized bed combustion systems. Also,

there might be a staging of the air to decrease emissions. The heat from the flue gas is transferred to

pressurized water within a boiler (which might have several stages) to produce superheated steam.

Within a steam turbine, the energy from the steam is transferred to a generator to produce power. Heat

from the steam can be used, e.g. for thermal processes. In bleeder type steam turbines, steam can be

extracted in several stages of the turbine. Before closing the cycle, the steam has to be condensed so it

can be pressurized again.

For this case study, a nominal power of 600 kWel is assumed, with an electric efficiency of 14 %.

© DBFZ, 2015



7.5 Cost estimation

The economic estimation for the presented concepts is based on calculating equivalent annual costs

(EAC). The annual benefit (BPA) can be calculated as

𝐵𝑃𝐴 = 𝑎𝑛𝑛𝑢𝑎𝑙 𝑖𝑛𝑐𝑜𝑚𝑒 − 𝐸𝐴𝐶𝑖𝑛𝑣 − 𝑎𝑛𝑛𝑢𝑎𝑙 𝑐𝑜𝑠𝑡𝑠



(1 + 𝑖𝑘)𝑛 − 1



The annual income is calculated as the sum of all monetary cash flows to the operator/owner (including

absolute earnings from power sale, feed-in-tariffs where applicable, by-product sale, but also additional

earnings e.g. from lower rice losses during drying) and of prevented spending (e.g. for electrical power

from the grid, diesel fuel).




Investment costs: IC = 3.8 Mio. € (about 4.33 Mio. US-$, at 1.1387 US-$/€)



reference electricity costs: cr=0.19 US-$/kWh

rice husk lower heating value: HI,RH=15 MJ/kg

annual service and maintenance: csm=8% (of IC)


caiu=2% (of IC)

monthly wages for plant operators: cmw=1,000 $

operating staff: nop=7 (3 shifts at 2 operators each, + 1 administrator)

fuel costs: cfuel=0 US$/tdry

With these assumptions, the following results can be achieved:

equivalent annual costs of investment are about 645,000 US-$,

annual labour force costs are 84,000 US-$,

overall annual costs are 1.16 Mio. US-$,

power production costs are 0.2420 US-$/kWh

annual fuel consumption: 8230 t



With a nominal interest rate of 10.5%, the results are as following:





For comparison, a calculation with more positive assumptions has been made (interest rate of 8%,

depreciation period of 20 years, service and maintenance only 3%). Under these assumptions, the

results change:



overall annual costs are 741,000 US-$,


Under positive frame conditions, power production costs can be reduced to a level below reference

electricity costs.


As described in the first chapter, rice husks are a major resource in Guyana and are left unused as a

resource, thus causing environmental damage. This will be partially alleviated through the energetic use

proposed in this study, improving water and air quality. The electricity production will replace fossil fuel

use, reducing CO2 emissions and imports. The operator will gain greater independence in energy supply

from the grid and, in an optimised scenario, cost saving. Additionally, fossil fuel can be saved when

eventually the heat generated alongside electricity is used in industrial processes.

If this showcase is implemented, it might initiate further project using rice husks, thus multiplying the

effects.


The next step for the implementation of a rice husk CHP project is a complete feasibility study. For this

study, following sections or steps are recommended (Wittmaier et al., 2006):

Definition of scope, aim and objectives of the study

Definition of options (e.g. locations or technical options)

Framework conditions

general,

legislative,

economic,

supportive regional development plans

assessment of existing energy supply

financing and investment

Assessment of feasibility



project design and technical assessment

economic assessment

environmental impact assessment

regulatory requirements, necessary permits

social impact

Risk assessment

Comparison of options

Recommendations

Saw mill bioenergy for Wood bv, Guyana


8 Saw mill bioenergy for Wood bv, Guyana

Operator: Wood bv

Location: In the counties of

Barama, Charity and

Parika

Guyana

Feedstock: Wood waste from saw mills: dust, chips and slabs

Technology: 1MWel high pressure steam turbine

Business model: Collection of wood residues at one central plant

Generation of heat and power

Power distribution to cooperating saw mills

Central Kill-and-Dry facility at power plant to utilize heat

Assessment: Purchase of pellets from Suriname to cover feedstock demand

Assessment: feed-in of excess power


There are several options for the combined production of heat and power from residues of wood

processing. They usually include some pre-treatment (usually mechanical or thermal), one or more

thermo-chemical process steps (e.g. gasification or combustion), and the power conversion step(s).

World Timber Products (WOOD bv) is a distributor of hardwoods, softwoods, engineered boards and

other manufactured wood products. The company is based in the Netherlands and has an international

supply chain that extends into wood concessions in both Guyana and Suriname. This has enabled its

operatives to gain experience in the Guyanese forestry sector and build key relationships within the

industry.

Wood bv collaborates with a network of sawmills in Guyana including clusters of mills in the Parika,

Charity and Barama districts, which are situated along the East Coast of the Demerara River. The vast

majority of these sawmills power their operations with diesel generators and bought power from the grid

to fulfil the remaining demand. Consequently, the cost of electricity is a large proportion of their

operational costs.

The wood waste produced by these sawmills comprises sawdust, woodchips and slabs and in most

instances is either spread onto lands surrounding the mill operations, given away or in some instances

ends up in the river. There is potential for Wood bv and its sawmill partners to convert the wood waste

that they produce into clean, sustainable heat and electrical energy. This requires a detailed study into

(i) the logistics of collecting the waste and transporting it to a central processing area, (ii) the most

appropriate technology for deployment, (iii) the feasibility of supplying electricity to the sawmills and (iv)

the potential for a centralised kiln drying facility for use by the sawmills. To this end, the following

options are thinkable:



Option 1: Conversion of Wood Waste for Distributed Power Generation plus Centralised Timber Drying

Services

Wood bv would contract with cooperating sawmills to store and then collect wood waste from their

facilities and deliver it to a centralised processing facility. The location of the facility would be chosen to

minimise transportation distances. The facility would convert wood waste into power that would be sold

to the sawmills at a reduced rate, reflecting the value of the raw material that they provide. The heat

produced would be utilised in a kiln dryer that would be made available to sawmill operators. This type

of distributed power generation would require government support and ‘point to point’ grid access in

order to transmit electricity from the central processing unit to the sawmills. Wood bv would therefore

need to first obtain a license to produce electricity from the Office of the Prime Minister and then

negotiate grid access and associated fees with the utility company, Guyana Power and Light.

Option 2: Conversion of Wood Waste and Electricity Feed-in to Grid Plus Centralised Timber Drying

Services

In this scenario, Wood bv would seek to enter into a PPA with the utility company for the sale of 100% of

the power produced to the grid. As in option 1, the heat produced would be made available to sawmill

operators in the form of timber drying services. This scenario is more complicated than option 1 as it

would require the company to negotiate feed-in-tariffs with the utility company.

Option 3: Maximum Conversion of Wood Waste for Distributed Power and Excess Power to Grid Plus

Centralised Timber Drying Services

In this scenario, Wood bv would seek to maximise power generation by augmenting wood waste from

local sawmills with pelletized wood waste sourced from neighbouring Suriname. The power produced

would be utilised by the processing facility and sold to local sawmills as in option 1. In addition, excess

power produced would be sold to the grid as in option 2. A number of large Guyanese corporations

generate power for their own needs and sell excess capacity to the grid and so there are precedents for

this type of model.

For this case study, steam turbine as technology option is chosen. The combination of biomass

combustion and a water steam cycle (with a steam turbine) is a common option for combined heat and

power.


Guyana’s land surface being covered by 75% forest, allows for residual wood usage for energy

purposes.

A big power plant in a centric position surrounded by sawmills should be the capable way for using

sawmill residues as an efficient fuel source. The sawmills have to be in closer ratio not only for

feedstock supply but also for the electric energy output of the suggested turbine. Waste handling,

treatment and combustion equipment charges have to be calculated carefully to not extend the plant's

operating costs.



This requires a detailed study into the:

logistics of collecting the waste and transporting it to a central processing area,

most appropriate technology for deployment,

feasibility of supplying electricity to the sawmills and

potential for a centralised kiln drying facility for use by the sawmills

The ashes can be used for organic fertilizers, considering increased amounts of chlorine, zinc and lead.

It is recommendable to blend the ashes with wood forage or wood waste for better fertilizing results.


At each sawmill, an average amount of 500 kg/h of wood residues is available according to previous

studies. With shifts of 8 h and 5 workdays per week, an annual amount of 1,040 t of biomass is

available per mill. This biomass is usually a mix of sawdust, chips, edgings, shavings and slabs, which

should be considered for technology choice.

The sawmilling industries produce between 40 - 55 % of waste from their incoming wood supply. These

residues contain heat values in the range of 17 to 23 MJ/kg of dry matter. As they are sub products of

timber production, energetic conversion is more than rationally even for production of electricity. Place

for covered outdoor storage and drying has to be planed as the high moisture content not only lowers

the heat value, but has an extremely negative impact on the overall combustion efficiency because of

the huge amount of energy needed to heat considerable quantities. Considering Guyana’s average

humidity of 80 - 90%, heat drying kilns are needed for an optimal combustion. A backup supply by

buying wood pellets from Surinam is needed to overcome problems.

It is advisable to consider closely forest policies and sustainability aspects in a future detailed study.

Depending on the feedstock supply, contracts with the partner sawmills and the energy generation

priorities adaptions have to be made. It is also possible to design a mobile power plant that could be an

option for better energy balance and less logistical costs on feedstock supply and power supply

systems.


The general principle for a power plant with steam cycle is the same as mentioned before (see Figure

13).

In accordance with previous studies, the following parameters were set for preliminary design:

1,000 kWel output

20% electrical efficiency

steam parameters: 420 °C and 30 bar



8.5 Cost estimation

The economic estimation for the presented concepts is based on calculating equivalent annual costs

(EAC). The annual benefit (BPA) can be calculated as

𝐵𝑃𝐴 = 𝑎𝑛𝑛𝑢𝑎𝑙 𝑖𝑛𝑐𝑜𝑚𝑒 − 𝐸𝐴𝐶𝑖𝑛𝑣 − 𝑎𝑛𝑛𝑢𝑎𝑙 𝑐𝑜𝑠𝑡𝑠



(1 + 𝑖𝑘)𝑛 − 1



The annual income is calculated as the sum of all monetary cash flows to the operator/owner and of

prevented spending (e.g. for electrical power from the grid, diesel fuel).




investment costs (including boiler, civil works, shredder, cooler etc.):

IC = 6,893,000 US-$


nominal interest rate: ik=10.5%

reference electricity costs: cr=0.19 US-$/kWh

lower heating value: HI,RH=15 MJ/kg (for absolute dry material)

moisture content: cH2O=25%

annual service and maintenance: csm=8% (of IC)


caiu=2% (of IC)

monthly wages for plant operators: cmw=1000 US-$

operating staff: nop=17 (5 shifts at 3 operators each, + 2 administrators)

fuel costs: cfuel=16.95 US$/tdry

It should be noted that the investment costs are the result of previous studies. Depending on the

technology chosen, they might also be lower.

With these assumptions, the following results can be achieved:

equivalent annual costs of investment are about 1.15 Mio. US-$,




annual fuel consumption: 8,000 t (dry) or 10,700 t (at 25% moisture content)



As it can be seen, the annual amount of wood needed for 8,000 operating hours considerably exceeds

the available amount of residual wood from one saw mill, actually the residues from 10 mills are

required for the supply of a 1 MWel power plant.

Power production costs are higher than electricity prices. For comparison, another comparative

calculation has been made with an interest rate of 8 %, only three plant operators and free fuel. Even

under these assumptions, power production costs are 0.2191 US-$/kWh.


The positive impacts here would also consist in the use of a local energy source, thus reducing imports

of fossil fuels. These will also lower the CO2 emissions. The sawmill operators will gain an independent

and stable energy source while also having a valuable option of clearing their premises of residues.

8.7 Further project development

The main reason for the high power production costs are investment, service and maintenance. For

further project development of a high-pressure steam turbine power plant with biomass, available

technology for medium scale CHP should be revised to reduce investment costs. Service and

maintenance might be overestimated in this study and should be revised.

References


References

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Bini, R., 2010. State of the Art of ORC Technology for Biomass Plants, (2010).

Classen Apparatebau Wiesloch GmbH - Referenzen. Dezentrale Stromerzeugung ORC -

Reisschalenverbrennung - Italien [WWW Document], n.d. URL http://www.caw-

wiesloch.de/index.php/de/referenzen (accessed 5.13.15).

Enprocon, 2012. Alternative Energy Production Proposals and Integrated Waste Management Solutions

for Eastern Caribbean States. Enprocon, Wien.

FNR (Ed.), 2013. Leitfaden Biogas, Von der Gewinnung zur Nutzung, 6. vollst. übera. Auflage. ed.

Gülzow.

IPCC, 2014. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the

Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team,

R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland.

Wittmaier, M., Schädlich, M., Langer, S., et al, 2006. Guidelines for the Preparation of Feasibility

Studies for the Generation of Renewable Energy from Organic Waste and Biomass for Vietnam

and other ASEAN Countries (project report).

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