Federal University of Itajubá – UNIFEI

Mechanical Engineering Institute – IEM

Excellence Group in Thermal Power and Distributed Generation – NEST

MS.c Mateus Henrique Rocha

LIFE CYCLE ANALYSIS OF DIFFERENT ALTERNATIVES FOR THE TREATMENT AND

DISPOSAL OF ETHANOL VINASSE

1st Brazil-U.S. Biofuels Short Course

Providing Interdisciplinary Education in Biofuels Technology

São PauloJuly-August 2009

• Ethanol production through sugar juice or finalmolasses fermentation has a serious problem related tothe quantities and high organic content of its mainresidue called vinasse or stillage.

• For each liter of ethanol, 10-13 liters of vinasse areproduced using conventional technologies.

• Ethanol vinasse is a dark, brown colour liquid, of acidnature, that remains after alcoholic distillation at 107ºC,with a smell that goes from astringent to nauseating.

• Vinasse is classified as a class II residue, not inert butnot dangerous.

• The chemical composition of sugarcane ethanolvinasse is variable and depends of the wine rawmaterials.

• The wine characteristics depends also of the mustpreparation, alcoholic fermentation system, type ofyeast, distillation and flegma separation.

Chemical and physical properties of vinasse

• Return to the farm, as a partial or total substitution ofmineral nutrients (fertirrigation).

• Anaerobic digestion, using methanogenic bacterias, forthe production of biogas, process (anaerobic digestion).

• Vinasse concentration by evaporation, for return tofarm as fertilizer.

• Vinasse concentration by evaporation for combustionaiming at energy recovery.

The possible forms of vinasse disposal

Fertigation

Concrete typical channel Vinasse application rate (300 m³/ha)

Distributed system by truck.

Anaerobic digestion

Anaerobic digestion plant:

• Flow = 5.000 m³/day• Diameter = 26,0 m

• Height = 4,75 m

Jenbacher Generator

Vinasse concentrated at 40%

Vinasse concentration by evaporation for combustion

Vinasse concentration

plants (Vogelbusch)

Concentrated vinasse at 60%.

• Life Cycle Analysis (LCA) is a technique ofenvironmental analysis that allows the minimization ofenvironmental problems.

• LCA is a process of evaluation of the environmentalimpacts associated with a system of products orservices, that allows the identification and evaluation ofthe impacts throughout the life cycle of the product.

• Environmental impacts are determined based on theinputs and outputs of materials and energy in eachphase of the product life cycle, and can be associatedwith different categories.

Life Cycle Analysis

Main stages of a life cycle analysis study

Goal and Scope Definition

Goal and Scope

Definition

Inte

rpre

tation

Impact Assessment

Inventory Analysis

Definition of the function, functional unit and reference flow

Product system establishment

Definition of the allocation procedures

Selection of environmental impacts

Data categorization

Studies supositions and limitations

Quality data requirements

Selection of the peer review process

Report definition

To establish the

limits of the study.

Goal and Scope

Definition

Inte

rpre

tation

Impact Assessment

Inventory Analysis

Inventory Analysis

Goal and scope definition

Preparation for data collection

Data collection

Data validation

Unit process data

Functional unit data

Data agreggation

Refining

To quantify the inputs and outputs of a product system.

Allocation and recycling

Goal and Scope

Definition

Impact Assessment

Inventory Analysis

Impact Assessment

Indicators

NormalizationAggregationWeighting

Data quality analysis Inte

rpre

tation

Characterization

Characterization

Normalization

Normalization: contribution to the total impact

h

hh~

&=

Climate change 0.05%

Acidification 0.02%

Weighting (Single score)

• Giving importance for each environmental impact

• Subjective

• Not to be used without appropriate Peer review for public purposes

∑ =⋅=i ii

h~

wh~

wW

(Non dimensional units)

Goal and Scope

Definition

Impact Assessment

Inventory Analysis

Inte

rpre

tati

on

Interpretation

• Sensitivity Analysis

• Evaluation

– Materials selection

– Supply chain management

– Establish infrastruture for recycling

Case study• The objective of this work is to determine the environmental

impact of disposal vinasse options and to compare them.

• Functional unit: 1.0 m³ of vinasse treated.

• System boundary: for inputs on the process the criterion of cut

will be mass flow, or potential of environmental impact of the

product.

• Selection of the methods of environmental impact evaluation:

Eco-Indicator 99.

• Requirement of the data: the data will be collected throughprimary sources (direct sample) or secondary (bibliographical

research).

• Used software: for elaboration of the LCA data of vinasse will beused SimaPro 7.0 software elaborated by Pre Consultants, a

dutch Company.

Environmental impacts characterization

Environmental impacts characterization

Single score

Single score

Some remarks about LCA tool in cases studies

The application of LCA for the evaluation of environmental impacts related to

vinasse treatment and disposal does not allow for a complete analysis, due to

the uncertainties associated to the leaching and volatilization of the vinasse

applied to the soil as fertilizer.

The presence of ions in vinasse, mainly potassium, phosphorus (phosphate)

and nitrogen compounds (nitrite and nitrate) could cause groundwater

salinization.

The great obstacle concerning the quantification of this impact is the lack of

reliable information about what actually happens with vinasse components

when applied to the soil.

There are different possibilities in face of real situations: ions can behave as

inert compounds and remain in the ground, to be converted into metabolites by

microorganisms, extracted through roots for sugarcane nutrition, leached,

volatilized to atmosphere, etc. Even when such information is available there is

a great need of specialized scores for the correct evaluation of the related

impacts.

Some remarks about LCA tool in cases studies

The LCA results evaluation is also difficult due to the high amount of impact

scores proposed in evaluation models, and the existing doubts in relation to

which of them preference must be given. Therefore, at the beginning of the

study, while goal and scope were being defined, the impact evaluation models

must be clearly set, including the categories selection that would be considered,

as well as, the compounds that would be taken into account during impact

quantification.

Organic fertilizers, such as vinasse, present several advantages in relation to

mineral fertilizers, as they promote nutrient recycling in ecosystems, and cause

less environmental impacts during production. Currently great efforts are being

applied in the research of renewable energy inputs, such as biogas and

concentrated vinasse, which contribute to the GHG reduction and climate

change mitigation.

Some remarks about LCA tool in cases studies

Life cycle inventory and associated energy balance do not allow

for the highlight of the advantages of cogeneration with thecommercialization of surplus electricity, due to the fact that

residues energy potential is quantified using its heating value as

reference. Final impacts evaluation must be carried out in order tocompare alternatives including cogeneration as by-product

allocation method.

The comparison between these two environmental benefits, thatexclude each other, is a real gap in the ethanol sustainability

evaluation. The cause of this is the existing uncertainties in co-

products allocation and in the evaluation of fertirrigation

secondary impacts. Such gap has not been possible to be fulfilled

using LCA methodology in its current developing stage.

Thank you for attention!Thank you for attention!