unknown - 2008 - landfill gas to energy feasibility report

7/29/2019 Unknown - 2008 - Landfill Gas to Energy Feasibility Report

1/134

Landfll Gas to Energy

Feasibility Report

August 2008 | FINAL DRAFT

PREPARED FOR: CITY OF EL PASOENVIRONMENTAL SERVICES DEPARTMENT


2/134


3/134

FINALDRAFT

LANDFILL GAS TO ENERGY FEASIBILITY REPORT

City of El Paso Environmental Services Department

Table of Contents

Letter of Transmittal

Table of Contents

List of AppendicesList of Tables

List of Figures

EXECUTIVE SUMMARYOverview .........................................................................................................ES-1

Section 1: Site Descriptions.............................................................................ES-2Section 2: Landfill Gas Generation .................................................................ES-3Section 2 provides R. W. Becks analysis of landfill gas generation..............ES-3

RWB Model Results Summary..............................................................ES-4Section 3: Landfill Gas to Energy Possibilities...............................................ES-5

LFGTE Possibilities Summary ..............................................................ES-6

Direct Use (Medium-Btu)..........................................................ES-7High-Btu Processing ..................................................................ES-7

Section 4: Landfill Gas Collection ..................................................................ES-7LFG Collection Capital Cost .................................................................ES-8LFG Collection Operations and Maintenance (O&M) Costs ................ES-9

Section 5: LFGTE Ownership Options ...........................................................ES-9

Ownership Decision Matrix.................................................................ES-10

Section 6: Assessment of Grants and Funds..................................................ES-10Section 7: Financial Pro Forma Analysis ......................................................ES-11

Methodology........................................................................................ES-11

Basis of Comparison............................................................................ES-11Options Summary ................................................................................ES-12

Alternate Analysis of Scenario 1A ......................................................ES-13

Section 8: Conclusions and Recommendations.............................................ES-14Summary of LFGTE Possibilities........................................................ES-14

General Conclusions ES-16


4/134

TABLE OF CONTENTS FINAL DRAFT

1.1.3 Clint 1482 North.......................................................................... 1-3

1.1.4 Clint 2284 .................................................................................... 1-4

Section 2 LANDFILL GAS GENERATION2.1 LFG Generation Modeling ...................................................................... 2-12.2 LFG Generation Variables....................................................................... 2-2

2.2.1 Waste Characterization................................................................ 2-2

2.2.2 Moisture Content ......................................................................... 2-32.2.3 Temperature................................................................................. 2-4

2.2.4 Landfill Size and Geometry......................................................... 2-5

2.2.5 Landfill Construction Materials and Techniques ........................ 2-52.3 Site Characteristics and Waste Receipts.................................................. 2-6

2.3.1 McCombs Landfill....................................................................... 2-6

2.3.2 Clint 1482 South .......................................................................... 2-7

2.3.3 Clint 1482 North.......................................................................... 2-82.3.4 Clint 2284 .................................................................................... 2-9

2.4 LFG Generation Model Results............................................................. 2-11

2.4.1 McCombs................................................................................... 2-11

2.4.2 Clint 1482 South ........................................................................ 2-132.4.3 Clint 1482 North........................................................................ 2-14

2.4.4 Clint 2284 .................................................................................. 2-152.4.5 RWB Model Results Summary ................................................. 2-18

Section 3 LANDFILL GAS TO ENERGY POSSIBILITIES3.1 Electricity Generation.............................................................................. 3-1

3.1.1 End Users..................................................................................... 3-3

3.1.2 Capital Costs................................................................................ 3-43.1.3 O&M Costs.................................................................................. 3-6

3.2 Direct Use (Medium-Btu)........................................................................ 3-73.2.1 End Users..................................................................................... 3-8

International Paper El Paso Containment Plant........................... 3-9

Roberto Bustamante WWTP (Lower Valley WaterDistrict).......................................................................... 3-9

Valley Feed Mills ........................................................................ 3-9

3.2.2 Capital Costs................................................................................ 3-93.2.3 O&M Costs................................................................................ 3-10

3.3 High-Btu Processing.............................................................................. 3-10

3.3.1 End Users................................................................................... 3-11

EPNG Pipeline........................................................................... 3-11LNG/CNG P d ti 3 11


5/134

FINAL DRAFT TABLE OF CONTENTS

Section 4 LANDFILL GAS COLLECTION4.1 LFG Collection Conceptual Design Variables ........................................ 4-2

4.1.1 Refuse Depths .............................................................................. 4-24.1.2 Vertical and Horizontal Extraction Wells.................................... 4-2

4.1.3 Condensate Management ............................................................. 4-3

4.1.4 Flare Station ................................................................................. 4-34.2 LFG Collection Capital Cost ................................................................... 4-3

4.3 LFG Collection O&M Costs.................................................................... 4-5

Section 5 LANDFILL GAS TO ENERGY OWNERSHIP OPTIONS

5.1 Ownership Decision Matrix..................................................................... 5-1

Section 6 ASSESSMENT OF GRANTS AND FUNDS6.1 Survey of Funding Options...................................................................... 6-1

6.1.1 Section 45 Renewable Energy Production Tax Credit ................ 6-1

6.1.2 Clean Renewable Energy Bonds (CREBs) .................................. 6-2

6.1.3 Renewable Energy Production Incentive (REPI) ........................ 6-26.1.4 Renewable Energy Credits (RECs).............................................. 6-2

6.1.5 Greenhouse Gas Emission Credits............................................... 6-36.1.6 Federal Alternative Fuels Tax Credit........................................... 6-46.1.7 Federal Alternative Fuels Excise Tax Credit ............................... 6-4

6.1.8 Alternative Fuel Grant (Texas) .................................................... 6-4

6.2 Summary of Funding Options.................................................................. 6-4

Section 7 FINANCIAL PRO FORMA ANALYSIS7.1 Introduction.............................................................................................. 7-1

7.2 Methodology for Financial Analysis ....................................................... 7-17.3 Basis of Comparison................................................................................ 7-2

7.4 Scenario 1 Electricity Generation ......................................................... 7-37.4.1 Scenario 1A Clint 2284 Only.................................................... 7-3

7.4.2 Scenario 1B Clint 2284 and Clint 1482 North.......................... 7-47.5 Scenario 2 Direct Use (Medium Btu) ................................................... 7-5

7.6 Scenario 3 High Btu Processing ........................................................... 7-6

7.6.1 Other High-Btu Processing Considerations ................................. 7-7

7.7 Options Summary .................................................................................... 7-87.8 Alternate Analysis of Scenario 1A .......................................................... 7-9

Section 8 CONCLUSIONS AND RECOMMENDATIONS8.1 Summary of LFGTE Possibilities............................................................ 8-1

8 1 1 Electricity Generation (Financial Scenarios 1A 1B and


6/134


List of Appendices

Appendix A LFG Generation Model OutputAppendix B LFG End Users

Appendix C Engineering opinion of Probable Cost

Appendix D Cash Flow Model

This report has been prepared for the use of the client for the specific purposes identified in thereport. The conclusions, observations and recommendations contained herein attributed to


7/134

FINAL DRAFT TABLE OF CONTENTS

List of Tables

Table ES-1 Report Content and Organization ................................................................2Table ES-2 Landfill Area Descriptions...........................................................................2

Table ES-3 Gas Modeling Summary Table ....................................................................5Table ES-4 LFG Collection System Yearly Capital Cost Estimates ...........................9

Table ES-5 NPV Summary Including Revenue from Credits ...................................13

Table ES-6 NPV of Scenario 1C Wait Five Years before Implementation...............14Table 1-1 Landfill Area Descriptions ......................................................................... 1-1

Table 2-1 Historical Waste Receipt Data - McCombs Landfill (tons)........................ 2-6

Table 2-2 LFG General Assumptions - McCombs Landfill ....................................... 2-7Table 2-3 Historical Waste Receipt Data - Clint 1482 South (tons)........................... 2-8Table 2-4 LFG General Assumptions - Clint 1482 South .......................................... 2-8

Table 2-5 Historical Waste Receipt Data - Clint 1482 North (tons)........................... 2-9Table 2-6 LFG General Assumptions - Clint 1482 North .......................................... 2-9

Table 2-7 Historical and Projected Waste Receipt Data - Clint 2284 (tons) ............ 2-10

Table 2-8 LFG General Assumptions - Clint 2284................................................... 2-11Table 2-9 Gas Modeling Summary Table................................................................. 2-18

Table 3-1 EPE Estimated Avoided Energy Cost1 PUCT Substantive Rule

25.242 (e)(2)(A) c/KWh........................................................................... 3-4Table 3-2 Engineering Estimate of Probable Cost CAT 3516 Engine

Installation (2009 Dollars).......................................................................... 3-6

Table 4-1 Gas Modeling Summary Table................................................................... 4-1Table 5-1 City of El Paso LFGTE Feasibility Ownership Decision Matrix ............... 5-1

Table 6-1 Summary of LFG Credits, Bonds, Grants and Incentives .......................... 6-1

Table 7-1 Sample NPV Calculation............................................................................ 7-2Table 7-2 NPV of Scenario 1A ................................................................................... 7-3Table 7-3 NPV of Scenario 1A Including Revenue from Credits ........................... 7-4

Table 7-4 NPV of Scenario 1B ................................................................................... 7-4

Table 7-5 NPV of Scenario 1B Including Revenue from Credits............................ 7-5Table 7-6 NPV of Scenario 2...................................................................................... 7-5

Table 7-7 NPV of Scenario 2 Including Revenue from Credits .............................. 7-6

Table 7-8 NPV of Scenario 3...................................................................................... 7-7

Table 7-9 NPV of Scenario 3 Including Revenue from Credits .............................. 7-7Table 7-10 NPV Summary Including Revenue from Credits .................................. 7-8

Table 7-11 NPV of Scenario 1C Wait Five Years before Implementation.............. 7-9


8/134


List of Figures

Figure ES-1. Conceptual LFG Collection (Source: US EPA LMOP)....................ES-8Figure 1-1. McCombs ................................................................................................ 1-2

Figure 1-2. Clint 1482 South ..................................................................................... 1-3Figure 1-3. Clint 1482 North ..................................................................................... 1-4

Figure 1-4. Clint 2284................................................................................................ 1-5

Figure 2-1. LFG Generation vs. Time Example ........................................................ 2-4Figure 2-2. LFG Generation vs. Time using R. W. Beck model and

LandGEM model...................................................................................... 2-12

Figure 2-3. LFG Generation/Collection vs. Time (City provided tonnagesand assumed 75% collection efficiency) .................................................. 2-13

Figure 2-4. LFG Generated/Collected vs. Time (City provided tonnages and

assumed 75% collection efficiency)......................................................... 2-14Figure 2-5. LFG Generated/Collected vs. Time (City provided tonnages and

assumed 75% collection efficiency)......................................................... 2-15

Figure 2-6. LFG Generation vs. Time using R. W. Beck model andLandGEM model...................................................................................... 2-16

Figure 2-7. LFG Generation/Collection vs. Time (City provided tonnages

and assumed 75% collection efficiency) .................................................. 2-17Figure 3-1. Electricity Generation Technology Trends ............................................. 3-2

Figure 3-2. Electricity Generation Technology Trends ............................................. 3-2

Figure 3-3. Schematic Diagram of Typical Direct-Use Arrangement....................... 3-7Figure 3-4. Natural Gas Price Forecasts (West Texas Area) ..................................... 3-8

Figure 3-5. Schematic drawing of CO2 Wash Process (Courtesy of

FirmGreen, Inc.) ....................................................................................... 3-10Figure 4-1. Conceptual LFG Collection (Source: US EPA LMOP)......................... 4-2


9/134

FINAL DRAFT

EXECUTIVE SUMMARY

OverviewThe City of El Paso (City) owns two municipal solid waste landfill facilities: theMcCombs landfill at 13600 McCombs Street, and the Clint landfill at 2300 DarringtonRoad. Until 2005, the City was operating both facilities to accept municipal solidwaste generated in the City and surrounding areas. Currently, only the Clint landfill

facility is in operation. The McCombs landfill (McCombs) began receiving waste in1977 and is currently inactive (as of February 3, 2005 except for limited City clean-up waste in 2006) and not projected to receive waste until 2032. The Clint landfill(Clint) is comprised of two separately permitted facilities. MSW Permit #1482(referred to as Clint 1482) received waste from 1983 to 2007. MSW Permit #2284(referred to as Clint 2284) is the currently active disposal facility that began acceptingwaste in 2005 and is scheduled to be developed and receive waste until 2032.

At present, none of the City landfills actively collect landfill gas for destruction orbeneficial use. Landfill gas generated at this time is naturally venting out of thelandfill and into the atmosphere. The City retained R. W. Beck to evaluate the landfillgas (LFG) generation potential of the City landfill facilities and to explore thefeasibility of utilizing the LFG as an energy source. This Landfill Gas to Energy(LFGTE) Feasibility Report (report) reviews the existing and future LFG generationpotential of the landfill sites and evaluates recovery and energy utilization alternatives.

This report focuses on LFG generation potential and three general utilization

alternatives:

1. On-site generation of electricity for use on site or to sell to an electric utility;2. Direct thermal utilization of the LFG by piping the gas to a nearby end-user; or3. Processing of LFG on-site to produce natural gas quality for pipeline sale or

other alternative fuel use.

The evaluations in this report are based on the technical and economic potential of the

three alternative projects. Also discussed are ownership options (City-owned versusthird party-owned), and risk allocation for potential LFGTE projects. An assessmentof the grants and funds potentially available for these projects is also included.

Report Content and Organization


10/134

EXECUTIVE SUMMARY FINAL DRAFT

Table ES-1

Report Content and Organization

Section Content

1 Site descriptions.

2 Determination of estimated LFG generation potential based on wastetonnages and gas generation variables and modeling.

3 Discussion and evaluation of general LFGTE alternatives: i.e. electricity

generation, direct thermal utilization, and processing of the LFG tonatural gas quality.

4 Conceptual identification of LFG collection strategies and associatedcapital costs for collection of viable LFG for beneficial end use.

5 Discussion of ownership options and the sharing of project risk withother parties.

6 General assessment of grants and funds that could be available forLFGTE projects.

7 Financial pro formas that model conceptual LFGTE projects based onestimated capital costs, revenue over time, and operations costs overtime.

8 Conclusions and recommendations for future actions to be taken by theCity to ensure successful implementation of the LFGTE project thatprovides the most overall benefit to the City.

Section 1: Site DescriptionsSection 1 provides a description of the landfill areas evaluated during this study.The areas (listed from oldest to newest waste placement activity) include thefollowing:

Table ES-2Landfill Area Descriptions

Area Name Descripti on Waste Placement

McCombs All cells of the McCombs landfill regulated by MSWPermit #729A.

Waste placement from1977 to 2006.

Clint 1482 South Area of the Clint landfill south of the utility easementth t bi t th it R l t db MSWP it #1482

Waste placement from1983 t 1999


11/134

FINAL DRAFT EXECUTIVE SUMMARY

Section 2: Landfill Gas Generation

Section 2 provides R. W. Becks analysis of landfill gas generation.

LFG Generation ModelingLFGTE projects are based on the anaerobic decay of solid waste that naturally occursin landfills, which generates LFG at various rates and quality based on certainvariables. In order to appropriately design LFG collection systems and/or beneficial

end uses for the gas, engineering estimates must be made regarding the current andfuture generation of LFG at a particular site, or from a particular waste mass. This isknown as LFG generation modeling. The City is familiar with the U.S. EnvironmentalProtection Agencys (US EPA) LandGEM model. This program allows for input ofgeneral tonnages, two kinetic variables, and the site-specific non-methane organiccompound (NMOC) content of the LFG. These variables are commonly based onnationwide averages (Clean Air Act or AP-42 published values). The LandGEMmodel output tabulates total LFG production over time.

Similarly, R. W. Beck has developed the RWB LFG Generation Model (RWB Model)based on a polynomial solution of the first-order time dependent relationship betweenLFG generation and the decomposition of organic waste material. It has been usedand continually refined for over 20 years. In addition, it has been used successfully inmodeling LFG generation and recovery at over 100 landfills. There are several well-known and distinct stages of LFG generation for municipal solid waste (MSW)depending on numerous characteristics of the site and waste composition. The

RWB Model uses a series expansion to curve fit these stages to known or assumedvalues of each characteristic. The variety of conditions encountered in a MSW landfillcan then be modeled by adjusting the coefficients in the polynomial solution toapproximate the characteristics of the particular site.

In the RWB Model, empirical data and assumed variables are used (as discussedbelow) based on observations and experience from the project landfill and multiplesimilar landfills to estimate LFG generation over approximately 20 years. To checkthe assumptions and estimates used in the RWB Model, a comparison is madebetween the lifetime LFG generation output and the biochemical methane potential(BCMP) for the assumed organic quantity of MSW on site. The BCMP is thelaboratory theoretical maximum LFG production from a unit of MSW, expressed incubic feet per pound of dry organic MSW. Multiplying the BCMP by the estimatedMSW dry organic tonnage gives a value of lifetime LFG generation. This can be

d ith th d th d l d lif ti ti A ti


12/134


R. W. Beck has performed LFG modeling worldwide since 1989. The financing forseveral of the largest energy recovery projects in the United States and Canada have

relied on the RWB Model for LFG generation and recovery forecasting, including: McCarty Road Landfill, Houston, TX McCommas Bluff Landfill, Dallas, TX Coyote Canyon Landfill, Orange County, CA Gazmont Landfill, Montreal, Canada Cedar Hills Landfill, King County, WA Edgeboro, Edison Township, and Industrial Land Reclaiming Landfills, Middlesex

County, NJ

While every recovery project stages the installation of gas collectors with widevariability, the RWB Model information provided by R. W. Beck has consistentlytracked expectations without serious shortfall or over-estimation. Of the over 150projects modeled, R. W. Beck is not aware of any deviations greater than 30% ofmodeled outcome without serious attendant shortfalls in waste receipts, installation of

collectors, or problems with flooded collectors. Generally, when the waste receiptsfollow the estimated projections by the landfill owners, the RWB Model providesconsistent recovery forecasts.

R. W. Beck is currently involved in modeling LFG generation and recovery at fiveenhanced leachate recirculation and bioreactor landfills from Texas to South Dakota.At several of these projects R. W. Beck has tracked the recovered gas quantities versusthe RWB Model for over ten years. Each project currently has, or is in the process of

developing, energy recovery facilities with the engineering and assistance ofR.W. Beck. In each case, the RWB Model has consistently provided accurate andreasonable forecasts.

RWB Model Results SummarySections 2.3 and 2.4 summarize the RWB Model results. In general, three of the fourareas are in a declining phase of their gas generation curve. Due to lack of incoming

waste in current and future years, gas generation is on the decline in these areas. Inareas of declining gas generation it becomes difficult to justify the capital expenses forLFGTE projects based on the declining amount of fuel to provide revenue in futureyears. In general, it is R. W. Becks experience that landfill areas with less than 500SCFM initially, and in a declining gas generation phase, are not promising LFGTEprojects. This is especially valid in the case of the City sites, in which LFG collection


13/134


Table ES-3Gas Modeling Summary Table

Area LFG Generation Feasibi li ty Notes

McCombsDeclining LFGGeneration

Difficult to justify a landfill gas to energyproject for this area.

Clint 1482 South Declining LFGGeneration

Located across the utility easement from

current operations. Gas collection for thelandfill gas to energy project difficult to

justify for this area

Clint 1482 NorthDeclining LFGGeneration

Gas collection for landfill gas to energyproject difficult, but worth exploring inconjunction with Clint 2284. The

collection of gas from this area is modeledfinancially in Section 7.

Clint 2284Increasing LFGGeneration through2032.

Gas collection system feasible andexpandable for all phases at this site.Gas collection and landfill gas to energyrecommended for this site. The collection

of gas from this area is modeledfinancially in Section 7.

Based on these findings and R. W. Becks experience in the LFGTE industry, theprimary focus of LFGTE feasibility is recommended to be concentrated on the Clintlandfill area. Specifically, Clint 2284 is anticipated to be the future of LFGTE for theCity. The balance of this report focuses on exploration of the LFGTE possibilities andfeasibility modeling of gas generated from this site. Additional analysis is done withsupplemental gas collection from Clint 1482 North as well. This is based on theproximity of Clint 1482 North to Clint 2284 and the possibility of collecting additionalgas for a minimum incremental cost. It is important to note that the greatest variablefor LFG production modeling is the waste acceptance rate of a particular landfill. Iffuture waste receipts are not as predicted and modeled in the RWB Model(i dditi l t i t d t th Cli t d/ M C b l dfill ) th LFG


14/134


naturally occurring byproduct of the anaerobic stabilization within the waste mass of amunicipal solid waste landfill. In the past twenty years, significant influence in both

government and private sectors has been placed on finding viable options for thebeneficial use of this resource. In general, there are three primary end use categories:

1. On-site generation of electricity for sale to an electric utility;2. Direct thermal utilization of the LFG by piping the gas to a nearby thermal

energy-user; or

3. Processing of LFG on-site to produce natural gas quality for pipeline sale orother alternative fuel use.

These three end use categories have individual benefits and drawbacks, and all have avariety of particular technologies and usages which will be discussed in this section.

LFG is comprised mainly of methane (CH4), carbon dioxide (CO2), and several otherconstituents lumped together as balance gases. Methane is the most prominentconstituent with an average percentage by volume of approximately 50%. Thiscorresponds to an average heating content of 500 Btu/ft

3(on a Higher Heating Value

basis). This energy content allows the LFG to be utilized in the variety of ways which

will be discussed in the following subsections. LFG is commonly either vented to theatmosphere or combusted in a flare in order to destroy environmentally harmful airpollutants and greenhouse gases. By reusing the LFG, not only is there anenvironmental benefit with the destruction of this waste stream, there is also apotential economic benefit for the landfill.

The following subsections focus on the potential end uses for the LFG that can begenerated and collected at the City sites. Each subsection will introduce basic

technologies, explore local end users/buyers, and discuss capital andoperations & maintenance (O&M) costs. The potential end use options discussed inthis report represent the most common, practical uses for landfill gas based on currenttechnologies. Other specialized LFG recovery options exist (i.e. LNG or carbondioxide production), but these require somewhat experimental technologies or specificconditions, locations, and end users; and therefore, they have not been discussed inthis report.

LFGTE Possib ilit ies SummaryThe options discussed in this section are generally considered the most practicaloptions for LFG end use. Based on the predicted LFG generation at Clint 2284, all ofthe end use options discussed could be utilized by the City. Section 7 analyzes theseoptions financially and Section 8 provides opinions and recommendations based on


15/134


LFG. Operationally, engine generators are relatively straightforward to maintain anddo not have stringent LFG quality or high-pressure requirements. Capital and O&M

costs are well established and predictable for projects of this type. Electricity can besold to the local electric utility or to non-local utilities by means of wheeling powerover the shared grid.

Direct Use (Medium-Btu)

Direct thermal utilization of the medium-Btu LFG by a nearby end user is also a verycommon LFGTE project in the United States and often the most economically viable.These projects also do not have very stringent LFG quality requirements. Direct useof the medium-Btu LFG can be very attractive if an end user can be located that hasconsistent (24 hours/day, 7 days/week) and adequate (quantity needs match the LFGoutput) requirements for the fuel. Pipeline costs vary depending on distance to the enduser and right-of-way requirements. Compression and dehydration of the LFG isrelatively straightforward and costs are well established. Unfortunately, R. W. Beckdid not find a perfect fit user for the LFG produced at Clint 2284 that would be anoptimum customer for the gas. In all of the cases explored, the operations are not

continuous.

High-Btu Processing

Most high-Btu processes are proprietary, as various companies are still working tomake this an economically feasible solution. End uses for high-Btu gas can rangefrom direct injection to a near-by pipeline, such as the El Paso Natural Gas (EPNG)pipeline that bisects the property, to conversion to liquefied natural gas (LNG) orcompressed natural gas (CNG) for alternative vehicle fuel. Because of the advanced

technology required to construct the facility as well as refine the gas, the capital andO&M costs are relatively high. Additionally, the costs per SCFM for smaller facilitiesincrease (relatively) due to the loss of economy of scale and minimum equipmentsizing for specialized plant equipment. R. W. Beck is not aware of any commercially-viable high-Btu projects with LFG flow rates similar to the predictions for Clint 2284.LFG collection system operations have additional considerations for high-Btu LFGTEprojects. In order to arrive at pipeline-quality natural gas, the oxygen content of theinput LFG must be strictly controlled. In turn, this means that the LFG collectionsystem and wellfield must be operated with virtually zero air intrusion. Operation atthis level may be difficult to impossible at the City sites, based on the lack of finalclosure capping and the sandy soil available for interim cover material.

Section 4: Landfill Gas Collection


16/134


Figure ES-1. Conceptual LFG Collect ion (Source: US EPA LMOP)

This section identifies general variables associated with LFG collection system designand defines a conceptual collection system for the Clint 2284 and Clint 1482 North

areas that informs the cost estimates in the pro-forma analyses.

LFG Collection Capital CostAppendix C presents the LFG collection system installation and expansion costestimates for the Clint 2284 and Clint 1482 North areas. The cost estimates assumeinitial construction and expansion to match gas production and operations expansioninto new waste disposal cells. The gas collection system expansion is modeled basedon the cell expansion predictions (based on future predicted tonnages) presented bythe City in the recent permitting effort (fugitive dust calculation section of the permitapplication).

Appendix C contains an engineering opinion of probable cost for each year in whichexpansion would take place until 2032 (approximately every 1-2 years). Thisinformation is used to develop the pro forma analyses in Section 7. Table ES-4,summarizes the yearly information found in Appendix C.


17/134


Table ES-4LFG Collection System Yearly Capital Cost Estimates

Year Estimated Capital Cost Year Estimated Capital Cost

2009 $2,082,972 2023 $200,687

2011 $778,403 2024 $270,856

2013 $474,548 2025 $270,856

2014 $604,354 2026 $200,687

2015 $298,595 2027 $607,2522017 $279,899 2028 $270,856

2018 $955,857 2029 $200,687

2019 $232,300 2030 $270,856

2020 $200,687 2031 $623,312

2021 $515,361 2032 $200,687

2022 $232,300

LFG Collection Operations and Maintenance (O&M) CostsFor the purposes of the analyses in this report, O&M costs were assumed for the LFGcollection system as it expands. The basis of the cost is an assumed factor of$25/acre/month. This accounts for miscellaneous parts, replacements, monitoring, and

labor for O&M of the gas collection system. In the pro-forma analyses, this costincreases accordingly as the gas collection system covers greater and greater acreages.O&M costs have been allocated to additional acreage starting the year after expansioninto that acreage.

Section 5: LFGTE Ownership Options

If the City ultimately decides to pursue a LFGTE project, a number of decisions willneed to be made regarding the Citys appetite for ownership, capital cost outlay, andrisk. Section 5 delineates the spectrum of ownership options that the City could

pursue in the development of a LFGTE project.

Commonly, a private party (Developer) will agree to participate in a project of thist ith th Cit Thi t ill ll th D l t b i t h i l


18/134


This flexibility in development structure makes the analysis of various projectsdifficult, due to the different rates, loans, and incentive programs available to public

versus private owners (see Section 6 for a discussion of grants and funds associatedwith these types of projects). Section 7 explores the financial merits of each type ofproject and makes the case that profitable projects (according to net present value) willbe a profitable solution regardless of the ownership entity.

Ownership Decision MatrixFigure 5-1, in Section 5 of the report, presents the Ownership Decision Matrix. This

matrix introduces the spectrum of ownership options along the top rows, and discussesthe implications of each to various project attributes in the columns. The City RiskOverview at the bottom of the figure characterizes the amount of relative risk the Citywould take on (depending on ownership option) for each situation in the first column.The City can use this matrix to get an idea of the level of responsibility, cost and riskthat might be associated with a project under various ownership scenarios. This tablecan also be used during negotiation with a possible Developer, to ensure that issues arebrought up, discussed, and agreed upon prior to signing any contracts.

Based on discussions with City staff and the specialized nature of LFGTE expertise, itis likely that the City will choose to have a Developer take on most of the risk for afuture LFGTE project. Since the LFG collection system is not yet in place at the Citylandfills, the City will need to decide whether to install and/or operate the LFGcollection system or let the Developer perform this service as well. Commonly,landfill entities choose to install and operate their own LFG collection system. Thisscenario is described in the middle column of the Ownership Decision Matrix.

Moving to the right in the figure describes projects owned and operated more by theDeveloper, and moving to the left in the figure describes projects owned and operatedmore by the City. The allocation of risk and costs in return for revenue is the purviewof the contract negotiations after the City has received responses from a future requestfor proposal, but the matrix gives an idea of the issues associated with these projects.

Section 6: Assessment of Grants and FundsSection 6 includes research of economic incentives that may be available for the Cityand/or Developer (depending on ownership options as discussed in Section 5) for aLFGTE project. R. W. Beck reviewed state and federal energy credits, productioncredits, incentives, bonds and tax credit programs. The following programs werediscovered:


19/134


Federal Alternative Fuels Tax Credits; Federal Alternative Fuels Excise Tax Credits; and Alternative Fuel Grant.Table 6-1, in Section 6, provides a concise summary of the fiscal opportunities thatmay be available to LFGTE projects.

Section 7: Financial Pro Forma AnalysisThis section outlines the methodology utilized in the financial pro forma analyses ofthe three general LFGTE project alternatives. The capital costs and O&M cost factorspreviously introduced are utilized and manipulated in the financial models as prudent.

MethodologyFor each end-use scenario, R. W. Beck estimated the revenue and required capital andO&M costs for a 20-year period. AfterR. W. Beck developed a 20-year projection of

cash flows for each end-use scenario,

1

the future cash flows were discounted so thatamounts are represented in 2008 dollars. These annual amounts were then summed tocalculate a net present value (NPV). For the initial evaluation of these scenarios,R. W. Beck used a discount rate of five percent for the electricity generation (Scenario1) and direct use medium Btu (Scenario 2), and 10 percent for high-Btu processing(Scenario 3). The amount for the first two scenarios represents what the City couldearn if it invested in 20-year United States Treasuries2 rather than one of these LFGTEprojects. R. W. Beck applied a higher discount rate for the high-Btu processing due to

the greater risk. If the NPV is negative for a project, this means investing in theTreasuries would be a better investment than the LFGTE project. If the NPV is

positive, then the LFGTE project would be the better investment. Section 7.7shows the effect of using higher discount rates, which a private company would likelydo in an analysis of these projects.

Basis of Comparison

As discussed in Section 6.1.5, the City is not required to meet the Federal New SourcePerformance Standard (NSPS) requirements during the 20-year planning period, basedon current assumptions. Therefore, the City is not required to install a LFG collectionsystem and there is no cost associated with management of LFG. Therefore, the NPVof the status quo is zero. Any LFGTE project considered should have an NPVgreater than zero if it is to be considered financially better than the status quo of


20/134


control system (i.e. odor control, subsurface gas migration control,

environmental stewardship, sustainability, etc.)

Options SummaryTable ES-5 summarizes the three end-use scenarios discussed in the section.R. W. Beck has also shown an alternative NPV with a higher discount rate applied tothe revenue, capital, and O&M costs of the LFGTE projects and provided those totalsat the bottom of the table. The result of increasing the discount rate is shown underPrivate Operator Perspective since private companies will typically use a higher

discount rate for future cash flows than a public sector entity. As discussed in Section7.6, R. W. Beck believes that the risk associated with Scenario 3 is greater thanScenario 1 and 2 and therefore a higher discount rate was used for Scenario 3.

All of these end-use projects assume the City would initiate the process of collectingand utilizing the LFG (either itself or via a private contractor) as soon as possible. Inorder to further analyze the most common LFGTE option of using engine generatorsto produce electricity, Section 7.8 provides an alternate scenario where the City wouldwait a period of years before implementing a LFGTE system of this type.


21/134


Table ES-5NPV Summary Including Revenue from Credits

Descripti on Scenario 1A1 Scenario 1B1 Scenario 2 Scenario 3

Revenue $16,725,216 $19,298,491 $6,679,691 $16,635,266

LFG Collection System ($7,254,541) ($8,350,477) ($7,254,541) ($5,244,713)

Gas System ($11,633,172) ($12,725,216) ($8,226,729) ($14,151,281)

Subtotal ($2,162,496) ($1,777,202) ($8,801,579) ($2,760,728)

GHG Credit Revenue $2,607,341 $3,148,845 $2,607,341 $2,607,341

REC Revenue $328,284 $410,007 $0 $0

Total NPV $773,129 $1,781,650 ($6,194,239) ($153,388)

Private Operator Perspective

Discount Rate2

15% 15% 15%

20%Adjusted NPV2 ($768,475) ($610,066) ($3,668,778) ($1,476,151)

1. Scenario 1A includes LFG collection from Clint 2284 only. Scenario 1B includes LFG collection from Clint 2284 and Clint 1482 North.2. These discount rates apply only to the LFGTE infrastructure, revenue, and operating costs. The discount rate for the GHG credits and REC were

kept constant at 15 percent.

Al ternate Analysis of Scenario 1A

As discussed in Section 7.7, R. W. Beck analyzed an alternate version of Scenario 1A.For the purposes of discussion, R. W. Beck refers to this alternate as Scenario 1C.

The Clint 2284 landfill is a relatively new landfill. Therefore, the LFG flow rate

is still at a relatively low level compared where to it is anticipated to be in future

years. R. W. Beck also analyzed the scenario in which no activity would be

conducted at the landfill, with regard to collecting and utilizing LFG, for a period

of five years. Table ES-6 summarizes the information for this Scenario 1C. Asshown in Table ES-6, waiting a period of five years has a significant impact on the

financial feasibility of using engine generators to produce electricity on site.


22/134


Table ES-6NPV of Scenario 1C Wait Five Years before Implementation

Descript ion Scenario 1C NPV

Revenue $21,260,451

LFG Collection System ($6,502,583)

Gas System ($13,592,129)

Subtotal $1,165,739

GHG Credit Revenue $2,136,987

REC Revenue $256,047

Total $3,558,772

Private Operator Perspective

Discount Rate1

15%Adjusted NPV1 $732,888

1. These discount rates apply only to the LFGTE infrastructure, revenue, and operating costs.The discount rate for the GHG credits and REC were kept constant at 15 percent.

Section 8: Conclusions and RecommendationsThis LFGTE feasibility report has been organized to follow the process of discovery,

investigation, and analysis of landfill gas estimation, collection and beneficial use.This section summarizes the conclusions of this report, re-iterates the informationgathered from this project, and provides recommendations for future actions thatprovide the most overall benefit to the City.

Summary of LFGTE Possibil itiesAs noted in the report, during the course of the next approximately 20 years, the Citymay have the opportunity to serve multiple end users and utilize a variety oftechnologies that may not be feasible at this time. Additionally, the City may be ableto take advantage of voluntary trading of landfill methane emission offset credits(GHG credits) if a collection and control system can be installed and operating beforethe regulatory requirement to do so. The following summarizes the financial and


23/134


NPV becomes positive for these Scenarios (project that provides greater financialbenefit than the do nothing alternative) when revenue from GHG credits andrenewable energy credits are included in the pro forma.

NPV is greater if the City decides to wait (5 years modeled in Scenario 1C) for gasproduction to increase at Clint 2284 before pursuing this LFGTE project.

Operationally, electricity generation by engine generators is the most commonlyutilized LFGTE electricity generation technology, and is quite reliable and proven.

Medium-Btu Direct Use (Financial Scenario 2):

NPV for a LFG collection system and direct use at one of the local industriessurveyed in this report (based on LMOP database) with only LFG sales revenue isnegative.

NPV remains negative even when revenue from GHG credits is modeled. This Scenario is highly dependent on the ability of the end user to take all the LFG

produced (i.e. a full-time process). This Scenario would be the most financiallyadvantageous LFGTE option if an end user could be located that could take the

full LFG flow from Clint 2284 for a larger percentage of the time.

Operationally, medium-Btu direct use by local pipeline is a very common LFGTEproject that is simple to operate and has a reasonable up-front capital cost. Thetechnology is simple and proven.

High-Btu Processing (Financial Scenario 3):

NPV for a LFG collection system and high-Btu processing with only LFG salesrevenue is negative. Capital and O&M costs are highly dependent on theproprietary design of the processing plant, the scale of the project, and theoperational practices of the Developer.

NPV is affected positively (but remains negative) when revenue from GHG creditsare modeled.

This Scenario models a high-Btu processing plant at a smaller scale than iscurrently commercially operational. Data is not available on the true effect of theloss of economy of scale.

Currently, fewer of these types of projects exist due to the uncertain commercialviability at smaller LFG flow rates.

Operationally, high-Btu processing plants require zero oxygen in the raw LFG,hi i i f h LFG ll i i h i i i



24/134


of energy (electricity or gas), GHG credits, and possibly RECs. Based on the Citysexpertise and appetite for risk, it is likely that a third party Developer will becontracted with for any LFGTE project at the City sites. This report provides the Citywith a solid foundation of knowledge regarding the potential of the LFG generated atthe Citys sites. This body of knowledge will be invaluable if the City receivesunsolicited offers for LFGTE projects, or when the City chooses to advertise with aRequest for Proposal (RFP) for a LFGTE project. Key considerations for an RFP andthe knowledge to critically analyze and compare financial pro formas advertised byDevelopers are added features of this report. This will be important, since it is likelythat Developers may approach the City with unsolicited offers that are based on

currently undiscovered end-users, and/or financial pro formas that make differentassumptions based on the Developers perspective or proprietary process. This RFPprocess is generally advantageous to the City, as it allows for flexible and inventivesolutions to be proposed, and the City can utilize the information in this report tocompare assumptions and solutions.

During the course of the next approximately 20 years, the City may have theopportunity to serve multiple end users and utilize a variety of technologies that maynot be feasible at this time. Additionally, the City may be able to take advantage ofvoluntary trading of landfill methane emission offset credits if a collection and controlsystem can be installed and operating before the regulatory requirement to do so.Based on the current Tier II report (report required by federal New SourcePerformance Standards using LandGEM gas modeling) performed by the City, a LFGcollection and control system is not required at Clint 2284 through the active life ofthe facility. This may change with future Tier II results, but any collection anddestruction of gas (by any means flare or end use) can be potentially traded as

emissions credits on various trading platforms, including the Chicago ClimateExchange, Blue Source, or other available services offering GHG crediting options.

Key Findings and RecommendationsBased on the specific and general conclusions noted above, R. W. Beck recommendsthat the City consider the following actions to follow-up this report and gain the mostvalue from this effort. These recommendations should be considered in conjunction

with the Citys other business, legal, policy, and financial considerations.1. Given that Clint 2284 is a relatively young landfill in the early stages of LFG

production, R. W. Beck would not recommend the development of an RFP for aLFGTE project at this time. The analyses in this report support the possibility thatmore financially advantageous results could be achieved if the City waits

i t l 5 It i i t t t t th t th fi i l f ibilit f th



25/134


incur little risk if an RFP was advertised. The creation of an RFP would require asmall effort and could yield interesting Developer ideas.

3. Within the proposed 5-year waiting period, the City should commission a LFGcollection and control system masterplan design for Clint 2284. This masterplanwould design a LFG collection system that effectively captures the gas generatedat the site and allows for a diverse array of LFG end use options from a centralizedcollection point. Additionally, a masterplan would ensure responsible design ofwells, piping, blower/flare station, sumps, etc. to accommodate known futuregrowth at the site. This masterplan could be used by the City or used to govern aDeveloper in how to expand gas collection at the site responsibly.

4. Within the proposed 5-year waiting period, the City should market the LFGpotential at the Clint 2284 site to businesses looking at possible locations formanufacturing or industrial facilities. As stated in Section 7, a direct-use medium-Btu project would be the most financially advantageous to the City if an end usercould be located near the Clint 2284 site that could use all of the LFG generated ona full time (eg. 24 hours/day, 7 days/week) basis.

5. Although high-Btu projects have not been viable at the relative scale of Clint 2284LFG production, high-Btu processing is an emerging technology that is constantlychanging. Additional impetus for research in this area is a result of rising naturalgas prices. The City should monitor this technology and be open to exploring newproprietary methods if proposed by Developers.

6. As the City nears the end of the 5-year waiting period to allow for increasedLFG production, the City should commission detailed design and construction of aPhase 1 LFG collection and control system at Clint 2284. This initial system

would conform to the LFG masterplan to allow for future expansion. After thefirst phase of the LFG collection and control system is in place, the City will beoptimally positioned to advertise an RFP for LFGTE at Clint 2284. The RFP willcontain information from this report and updated flow and design informationfrom the installed and operational LFG collection and control system.

7. It is important to note that the greatest variable for LFG production modeling is thewaste acceptance rate of a particular landfill. If future waste receipts are not aspredicted and modeled in the RWB Model (i.e. additional waste is accepted at theClint and/or McCombs landfills), the LFG generation model and the feasibility ofLFGTE projects at these sites can be greatly affected. For example, a significantincrease in the quantity of waste disposed could accelerate the feasibility of aLFGTE project.



26/134


(This page intentionally left blank)

FINAL DRAFT


27/134

FINAL DRAFT

Section 1SITE DESCRIPTIONS

1.1OverviewThe City of El Paso (City) owns two municipal solid waste landfill facilities: the

McCombs landfill at 13600 McCombs Street, and the Clint landfill at 2300 Darrington

Road. Until 2005, the City was operating both facilities to accept municipal solid

waste generated in the City and surrounding areas. Currently, only the Clint landfillfacility is in operation. The McCombs landfill (McCombs) began receiving waste in

1977 and is currently inactive (as of February 3, 2005 except for limited City clean-up waste in 2006) and not projected to receive waste until 2032. The Clint landfill

(Clint) is comprised of two separately permitted facilities. MSW Permit #1482

(referred to as Clint 1482) received waste from 1983 to 2007. MSW Permit #2284

(referred to as Clint 2284) is the currently active disposal facility that began acceptingwaste in 2005 and is scheduled to be developed and receive waste until 2032.

The following subsections describe the Clint and McCombs landfill facilities in more

detail. This report generally analyzes and models the facilities according to the

following areas (listed from oldest to newest waste placement activity):

Table 1-1Landfill A rea Descriptions

Area Name

Descript ion Waste PlacementMcCombs All cells of the McCombs landfill regulated by MSW

Permit #729A.Waste placement from

1977 to 2006.

Clint 1482 South Area of the Clint landfill south of the utility easementthat bisects the site. Regulated by MSW Permit #1482.

Waste placement from1983 to 1999.

Clint 1482 North Area of the Clint landfill north of the utility easementthat bisects the site. Regulated by MSW Permit #1482.

Waste placement from1999-2007

Clint 2284 Area of the Clint landfill including all existing and futurecells regulated under MSW Permit #2284.

Waste placement from2005 to 2032 (predicted).

1.1.1McCombsM C b i l t d i t l 327 t th i t ti f M C b R d

Section 1 FINAL DRAFT


28/134


Based on filling activities from 1977 to 2006, McCombs has received approximately

2,083,806 tons of waste (approximately 4,327,364 cubic yards according to Citycalculations). Based upon information provided in the most recent Site Development

Plan, the approximate capacity of McCombs is estimated to be 12,768,742 tons (at full

build out).

D

C B

E F G

FutureSectors B-G

LinedSector A

UnlinedArea

Lined

Area

Figure 1-1. McCombs

Figure 1-1 shows the general plan of the McCombs landfill. The unlined area

shown on the drawing represents the oldest waste. The lined area shows cells thatwere lined in compliance with Subtitle D requirements. The last cell to be built at the

landfill was Sector A. Future Sectors B G are expected to be developed when this

landfill becomes operational again (currently estimated for 2032).

Relevant to this report, it is important to note that the McCombs facility has been

reading elevated gas readings in the perimeter monitoring probes located on the

western boundary of the facility (near McCombs Road). These elevated readings have

been a problem at the site for approximately 10 years. In an effort to address thesituation and to prevent any potential subsurface migration of LFG past the property

boundary, the City will be installing a blower/flare station to actively collect gas from

existing passive vents on the western portion of the unlined area shown onFigure 1-1.

FINAL DRAFT SITE DESCRIPTIONS


29/134


Clint 1482 South has received approximately 3,073,839 tons of waste. This area will

not be used for future waste disposal and the City has plans for final closure andcapping of this area.

CLINT1482NORTH

Unlined 102Acre Area

Lined 15Acre Ar ea

CLINT 2284

Figure 1-2. Clin t 1482 South

Figure 1-2 shows the general plan of the Clint 1482 South area. The unlined 102 acre

area shown on the drawing represents the oldest waste (filling from approximately1983 to 1995). The lined 15 acre area shows cells that were lined in compliance

with Subtitle D requirements and received waste from approximately 1995 to 1999.

1.1.3Clint 1482 NorthThe Clint 1482 North area includes the portion of the Clint landfill regulated by

Permit #1482 that lies north of the utility easement that bisects the site. This area

received waste from approximately 1999 to 2007, with older waste located in variouslocations that were used as landfills prior to permitting requirements. Based on

recorded filling activities in the years noted, Clint 1482 North has received

approximately 1,271,567 tons of waste. This area will not be used for future wastedisposal and the City has plans for final closure and capping of this area.



30/134


Figure 1-3. Clint 1482 North

CLINT1482SOUTH

Lined Cell A

Lined Cell B

UnlinedWaste

DisposalArea

CLINT 2284

Figure 1-3 shows the general plan of the Clint 1482 North area. The Cell A and

Cell B areas show the lined cells. The shaded area denotes an area of various older,unlined waste disposal locations.

1.1.4Clint 2284The Clint landfill regulated by Permit #2284 is located on approximately 311 acres onDarrington Road. Clint 2284 was originally permitted as a municipal solid waste

landfill on April 14, 2003. Based upon information provided in the permitting effort,

the approximate capacity of the Clint 2284 landfill is estimated to be 12,812,578 tons(at full build out assuming a compaction rate of 1,200 lb/cy). Full build out is

anticipated to include 20 waste cells in two phases. Similar to the Clint 1482 site,

Clint 2284 is bisected by the same utility easement that runs roughly east to west.Phase 1 is located north of the easement, and Phase 2 is located south of the easement.

The landfill first began receiving waste in 2005, and is currently filling in cells 5 and 6

of Phase 1. Based on filling activities from 2005 to 2007, Clint 2284 has received

910,495 tons of waste. This landfill expected to receive all future waste for the City



31/134

Figure 1-4. Clin t 2284

CLINT 1482 NORTH

ExistingCells 1-6

(PHASE 1)

FutureCells 7-10

CLINT 1482 SOUTH

Future Cells11-20

(PHASE 2)

Figure 1-4 shows the general plan of the Clint 2284 landfill. The existing and future

cells are shown, and the shaded cells 1-6 denote the existing developed area. Allexisting and future cells at Clint 2284 have and will be lined in compliance with

Subtitle D requirements.



32/134

(This page intentionally left blank)

FINALDRAFT


33/134

Section 2

LANDFILL GAS GENERATION

2.1LFG Generation ModelingLFGTE projects are based on the anaerobic decay of solid waste that naturally occurs

in landfills, which generates LFG at various rates and quality based on certain

variables. In order to appropriately design LFG collection systems and/or beneficial

end uses for the gas, engineering estimates must be made regarding the current andfuture generation of LFG at a particular site, or from a particular waste mass. This is

known as LFG generation modeling. The City is familiar with the U.S. EnvironmentalProtection Agencys (US EPA) LandGEM model. This program allows for input of

general tonnages, two kinetic variables, and the site-specific non-methane organic

compound (NMOC) content of the LFG. These variables are commonly based on

nationwide averages (Clean Air Act or AP-42 published values). The LandGEMmodel output tabulates total LFG production over time.

Similarly, R. W. Beck has developed the RWB LFG Generation Model (RWB Model)

based on a polynomial solution of the first-order time dependent relationship between

LFG generation and the decomposition of organic waste material. It has been usedand continually refined for over 20 years. In addition, it has been used successfully in

modeling LFG generation and recovery at over 100 landfills. There are several well-

known and distinct stages of LFG generation for municipal solid waste (MSW)depending on numerous characteristics of the site and waste composition.

The RWB Model uses a series expansion to curve fit these stages to known orassumed values of each characteristic. The variety of conditions encountered in aMSW landfill can then be modeled by adjusting the coefficients in the polynomial

solution to approximate the characteristics of the particular site.

In the RWB Model, empirical data and assumed variables are used (as discussed

below) based on observations and experience from the project landfill and multiplesimilar landfills to estimate LFG generation over approximately 20 years. To check

the assumptions and estimates used in the RWB Model, a comparison is madebetween the lifetime LFG generation output and the biochemical methane potential

(BCMP) for the assumed organic quantity of MSW on site. The BCMP is the

laboratory theoretical maximum LFG production from a unit of MSW, expressed incubic feet per pound of dry organic MSW. Multiplying the BCMP by the estimated

MSW dry organic tonnage gives a value of lifetime LFG generation This can be



34/134

R. W. Beck has performed LFG modeling worldwide since 1989. The financing for

several of the largest energy recovery projects in the United States and Canada haverelied on the RWB Model for LFG generation and recovery forecasting, including:

McCarty Road Landfill, Houston, TX

McCommas Bluff Landfill, Dallas, TX

Coyote Canyon Landfill, Orange County, CA

Gazmont Landfill, Montreal, Canada

Cedar Hills Landfill, King County, WA

Edgeboro, Edison Township, and Industrial Land Reclaiming Landfills, MiddlesexCounty, NJ

While every recovery project stages the installation of gas collectors with widevariability, the RWB Model information provided by R. W. Beck has consistently

tracked expectations without serious shortfall or over-estimation. Of the over 150

projects modeled, R. W. Beck is not aware of any deviations greater than 30% ofmodeled outcome without serious attendant shortfalls in waste receipts, installation of

collectors, or problems with flooded collectors. Generally, when the waste receiptsfollow the estimated projections by the landfill owners, the RWB Model providesconsistent recovery forecasts.

R. W. Beck is currently involved in modeling LFG generation and recovery at five

enhanced leachate recirculation and bioreactor landfills from Texas to South Dakota.

At several of these projects R. W. Beck has tracked the recovered gas quantities versusthe RWB Model for over ten years. Each project currently has, or is in the process of

developing, energy recovery facilities with the engineering and assistance of

R.W. Beck. In each case, the RWB Model has consistently provided accurate and

reasonable forecasts.

2.2LFG Generation VariablesAs discussed in the previous subsection, many site climatological, waste composition,

and geotechnical characteristics have significant impacts on LFG generation and

collection. To evaluate and forecast the availability of LFG at any of the project areas,it is necessary to consider the following variables and evaluate their impact on the

production and collection of LFG at each independent area of the project. Thefollowing subsections discuss, in general terms, the effects of these variables.

FINAL DRAFT LANDFILL GAS GENERATION


35/134

known). For the City sites, the following general waste characterization information

was known:

A waste characterization study was completed for both McCombs and Clint 1482in 1998-1999. Tonnage rates adjusted to reflect this information.

Known city cleanup/inert wastes were collected at specific times (Cheryl Ladd

waste and 2006 storm waste). Tonnage rates adjusted to reflect this information.

Curb-side recycling efforts commenced in 2007 will serve to lower future

tonnages to Clint 2284 as recyclable waste is diverted. Tonnage rates adjusted toreflect this information.

A certain percentage of the MSW will not contribute to LFG production. Kineticvariables adjusted to reflect this information.

Specific narration of how this information was modeled is included in the area-

specific discussion.

2.2.2Moisture Content

The moisture content of the waste volume is among the principal characteristics to beconsidered in determining the rate and duration of LFG generated by a given landfill.

The LFG industry widely accepts that landfills with high moisture levels (but not

saturated) generate LFG at a high rate for a relatively short duration. Conversely,landfills with low moisture levels generate LFG at a lower rate for a significantly

greater duration, sometimes well beyond 60 years. As shown in Figure 2-1, the rate of

LFG generation for a fixed waste volume can vary by more than 100% depending on

moisture content. The effect of moisture on duration of LFG generation is equally

significant but there is considerable debate over the long-term kinetics of thisrelationship. While the industry has not published a sufficient body of empirical data

to provide a proven long-term or post-closure LFG generation estimate, R.W. Beckhas significant experience and success in developing such forecasts in support of LFG

recovery projects.



36/134

0

0.05

0.1

0.15

0.2

0.25

0.3

-5 0 5 10 15 20 25

Years

Landf

illGasGeneration

(ft3/

lb/yr)

LANDFILL

CLOSURE

WET

AVERAGE

DRY

Figure 2-1. LFG Generation vs. Time Example

The relative moisture content within a landfill depends primarily on the moisturecontent of the MSW when it is placed, cover infiltration (rainfall), the acceptance of

sludges, and more recently the practice of leachate recirculation or bioreactor

technology. Wastes containing high levels of water include yard and food wastes andindustrial and sewage sludges. Rainfall can contribute to aggregate moisture during

landfill filling. Also a sites moisture characteristics can vary depending on the

intermediate soil permeability and on the ability of the site to drain or retain leachateentering and passing through the fill volume.

The City of El Paso has a dry climate (less than 25 inches of precipitation per year)

and therefore the annual amount of water added to the landfills due to precipitation is

less than average. Additionally, the City reports no sludges taken on a regular basis,and leachate recirculation is not generally practiced due to stipulations in the

permitting for these sites. These factors lead to assumptions of a relatively dry waste

mass that produces a gas generation model with a longer decay curve and the

possibility that conditions may not allow for every unit of organic waste todecompose. Future construction of landfill closure caps (as required) will further



37/134

causes of these variations are complex microbial interactions depending on waste

composition, moisture and the particular anaerobes present.

Estimating the effect of these temperature ranges in a LFG generation model isdifficult and probably of limited value in comparison with other characteristics which

affect the rate of LFG generation. However, most experts agree that landfills located

in warm-winter climates exhibit slightly higher overall LFG generation rates thanthose in cold-winter climates. Studies and data collected at sites in southern

California, Florida, northern Minnesota and Alaska indicate the effect is probably less

than a 5% variation in LFG generation rates, depending on a sites depth and average

year-round temperature. Temperature ranges were not explicitly taken into account in

the RWB Model, but temperature ranges will affect gas collection system design in thefuture.

2.2.4Landfill Size and Geometry

Increasing waste depth significantly enhances the collection or recovery of LFG from

within a landfill. Large, deep MSW landfills exhibit better overall LFG collection andgeneration characteristics than other sites. Although collection efficiencies are

impossible to measure, estimates range from 75% to over 90% for very tightlycontrolled landfills with extensive gas extraction systems. In the absence of existing

collection systems at the project sites for review, all of the gas models in this reportestimate collection efficiency at 75% (based on US EPA guidance and standards).

This means that the City is assumed to be able to collect at least 75% of the total LFG

generated at each site. The remainder of the gas will escape into the atmosphere orsubsurface. Generally, a landfill will be able to increase collection efficiency with the

installation of closure capping. Capping allows for the LFG wells to sustain increased

vacuum with less potential for air intrusion through the cap.

2.2.5Landfill Construction Materials and Techniques

Generally, the use of modern geosynthetic liners and leachate collection systems

(required for all MSW landfills, new or modified since 1994, under RCRA Subtitle DFederal Regulations) and advanced low permeability cover systems essentially isolate

the MSW fill volume in a landfill from the environment. In such sites, the conditions

for LFG generation theoretically remain relatively constant and recovery of LFG canbe a significant fraction of the total LFG generation. However, at the McCombs and

Clint landfills, the timing of development was such that some of the landfill areas were

Subtitle D lined and some were not. Additionally, most of the lined areas are not ableto re-circulate leachate due to specific permit stipulations. Also, the landfills have not



38/134

commencement of the next days waste placement. This allows for inert soil (material

that will not generate LFG) in the waste mass and these layers of soil could hindervertical travel of liquids and gas.

2.3Site Characteristics and Waste ReceiptsThis subsection compiles the historical and estimated future waste tonnage

information and site characteristics that affect the RWB Model. Each modeled areais attributed specific waste tonnages and characteristics based on City-provided

information, site visit knowledge gained, and R. W. Beck experience. These variables

feed the gas model and are customized for each area.

2.3.1McCombs Landfill

The McCombs landfill is currently not receiving waste. Table 2-1 summarizes the

historical waste receipt data for this site. The historical tonnages have been providedby the City. For the purposes of the RWB Model, 27.8% of the historical tonnage was

assumed to be inert tons that do not contribute to LFG production. The percent inert

tons is derived from the Citys 1998-1999 waste characterization study at the site andis comprised of approximately 12.6% plastics, 10.3% metals, and 4.9% glass.

Table 2-1Historical Waste Receipt Data - McCombs Landfill (tons)

Year

Historical

MSW

Modeled MSW

(inert removed) Year

Historical

MSW

Modeled MSW(inert

removed)

1977 30,639 22,121 1992 23,805 17.187

1978 31,265 22,573 1993 35,411 25,567

1979 31,903 23,034 1994 48,915 35,317

1980 32,554 23,504 1995 51,050 36,858

1981 33,218 23,983 1996 123,647 89,273

1982 33,896 24,473 1997 133,055 96,0661983 34,588 24,973 1998 127,574 92,108

1984 35,294 25,482 1999 98,407 71,050

1985 36,014 26,002 2000 65,046 46,963

1986 36,749 26,533 2001 152,081 109,802



39/134

In addition to the tonnage input, Table 2-2 summarizes the LFG generation modeling

input for: (i) the amount and age of MSW deposited at McCombs landfill, and (ii) theRWB Model assumptions regarding landfill composition, LFG energy content,

collection system efficiency and the anticipated duration of LFG generation.

Table 2-2LFG General Assumptions - McCombs Landfill

Composition Characteristic

MSW Moisture (by weight)1 25%

MSW Organics (by weight) 60%Sewage Sludge2 None

LFG Gen. Rate Coefficient (cubic ft. LFG/lb. MSW/year)3 0.144

BCMP4 (cubic ft LFG/lb. dry organic) 12.4

LFG Fuel Value (Btu/cubic ft HHV) 460

LFG Collection Efficiency (% of total generation) 75%Notes:

1 Percent Moisture as received2 Sludge generally not known to be accepted at this site3 MSW only. Inert waste does not contribute.4 BCMP - Biochemical Methane Potential

2.3.2Clint 1482 South

The Clint 1482 landfill is currently not receiving waste. Table 2-3 summarizes the

historical waste receipt data for this site. The historical tonnages have been provided

by the City. For the purposes of the RWB Model, 34.2% of the historical tonnage wasassumed to be inert tons that do not contribute to LFG production. The percent inert

tons is consistent with the Waste Characterization Study performed at the site by

Frontera Environmental (June 1999) and referenced in the Tier II analysis performedat the site in March, 2006.



40/134

Table 2-3Histor ical Waste Receipt Data - Clin t 1482 South (tons)

Year Histor ical MSWModeled MSW(inert removed) Year

HistoricalMSW

Modeled MSW(inert removed)

1983 114,705 75,533 1992 206,122 135,731

1984 175,569 115,612 1993 210,245 138,446

1985 179,152 117,972 1994 225,579 148,544

1986 182,808 120,379 1995 251,177 165,400

1987 209,862 138,194 1996 176,353 116,128

1988 190,425 125,395 1997 124,991 82,307

1989 194,234 127,903 1998 141,610 93,250

1990 198,118 130,461 1999 90,8080 59,797

1991 202,081 133,070Notes:1 1999 tonnage reflects half of total tonnage to the site.

2 Cell A (Clint 1482 North) began receiving waste that year.3 Tonnage was split.


input for: (i) the amount and age of MSW deposited at Clint 1482 South, and (ii) the

RWB Model assumptions regarding landfill composition, LFG energy content,

collection system efficiency and the anticipated duration of LFG generation.

Table 2-4

LFG General Assumpt ions - Clint 1482 South



MSW Organics (by weight) 60%

Sewage Sludge2 None

LFG Gen. Rate Coeff. - Max (cubic ft. LFG/lb. MSW/year)3 0.144



LFG Collection Efficiency (% of total generation) 75%Notes:1 Percent Moisture as received



41/134

by the City. For the purposes of the RWB Model, 34.2% of the historical tonnage was

assumed to be inert tons that do not contribute to LFG production. The percent inerttons is consistent with the Waste Characterization Study performed at the site by

Frontera Environmental (June 1999) and referenced in the Tier II analysis performedat the site in March, 2006.

Table 2-5Histor ical Waste Receipt Data - Clin t 1482 North (tons)

Year Histor ical MSWModeled MSW(inert removed) Year

HistoricalMSW

Modeled MSW(inert removed)

1999 90,8090 59,798 2004 46,851 30,851

2000 225,819 148,702 2005 54,345 35,786

2001 146,662 96,577 2006 141,246 93,010

2002 162,962 107,310 2007 237,873 75,4871

2003 165,000 108,653Notes:11999 tonnage reflects half of total tonnage to the site. Cell A began receiving waste that year. Tonnage was split with Clint 1482 South.

2 2007 modeled tonnage reduced by an additional 81,152 tons of inert waste, according to 2007 records of debris cleanup from 2006 storm.


input for: (i) the amount and age of MSW deposited at Clint 1482 North, and (ii) the

RWB Model assumptions regarding landfill composition, LFG energy content,collection system efficiency and the anticipated duration of LFG generation.

Table 2-6LFG General Assumptions - Clint 1482 North



MSW Organics (by weight) 60%

Sewage Sludge2 None


BCMP4 (cubic ft LFG/lb. dry organic) 12.4LFG Fuel Value (Btu/cubic ft HHV) 460

LFG Collection Efficiency (% of total generation) 75%Notes:1 Percent Moisture as received2Sludgegenerallynotknowntobeacceptedat thissite



42/134

waste. This landfill is expected to receive all future waste for the City and current

disposers until 2032. Table 2-7 summarizes the historical and future waste receiptdata for this site.

The historical tonnages have been provided by the City. For the future waste

tonnages, a 2% growth rate in total tonnage was assumed, consistent with City

permitting estimates. For the purposes of the RWB Model, 34.2% of the historical(years 2005 and 2006) tonnage was assumed to be inert tons that do not contribute to

LFG production. The percent inert tons is consistent with the Waste Characterization

Study performed at the site by Frontera Environmental (June 1999) and referenced in

the Tier II analysis performed at the site in March, 2006. This percentage was

adjusted for year 2007 and future years to account for the Citys recycling initiativethat started in 2007. The City reported an initial recycling diversion of approximately

10% of total tonnage in 2007 (assumption used in January, 2007 permitting effort).The RWB Model assumes an increase in recycling diversion at 2% per year for 2008

through 2010 to account for citizen learning curve and to match City recycling goals.

The future inert fraction is then assumed to stabilize at 17.6% (consistent with a wastecharacterization study performed for Clint 1482 in 1998-1999) to account for future

disposal of inorganic waste and City storm debris, since this is the Citys only

operational landfill.

Table 2-7Histor ical and Projected Waste Receipt Data - Clin t 2284 (tons)

Year

Historical/Projected

MSWModeled MSW(inert removed) Year

Historical/Projected

MSWModeled MSW(inert removed)

2005 333,841 219,834 2019 480,232 395,711

2006 256,164 132,2241 2020 489,837 403,626

2007 320,490 206,6321 2021 499,633 411,698

2008 386,233 300,682 2022 509,626 419,932

2009 393,958 314,575 2023 519,819 428,331

2010 401,837 328,904 2024 530,215 436,897

2011 409,873 337,735 2025 540,819 445,6352012 418,071 344,491 2026 551,636 454,548

2013 426,432 351,380 2027 562,668 463,638

2014 434,961 358,408 2028 573,922 472,912

2015 443660 365576 2029 585400 482370



43/134


input for: (i) the amount and age of MSW deposited (and estimated future waste) atClint 2284, and (ii) the RWB Model assumptions regarding landfill composition, LFG

energy content, collection system efficiency and the anticipated duration of LFGgeneration.

Table 2-8LFG General Assumptions - Clint 2284


MSW Moisture (by weight)1

25%MSW Organics (by weight) 60%

Sewage Sludge2 None




LFG Collection Efficiency (% of total generation) 75%

Notes:1 Percent Moisture as received2 Sludge generally not known to be accepted at this site3 MSW only. Inert waste does not contribute.4 BCMP - Biochemical Methane Potential

2.4LFG Generation Model Resul tsUsing the waste receipt and variable inputs described in the previous subsections, the

RWB Model has been utilized to estimate gas generation at the various sites. Thefollowing subsections present the model output for each area. When available, theRWB Model results are compared to the LandGEM model results obtained by the

City.

2.4.1McCombs

Figure 2-2 shows the McCombs landfill RWB Model LFG generation estimates. Also

provided for comparison on Figure 2-2 is the output of the LandGEM model. The

figure uses identical tonnage values in both models to allow for direct comparison.This is done to match the LandGEM model performed by the City in 2007.



44/134

LFG Generation/Collection Estimate - McCombs Landfill

All Ex is ting Cells

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

1977

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

2010

2013

2016

2019

2022

2025

2028

2031

Year

LandfillGas

(Std.

CubicFt./Min)

LFG Generated

City LandGEM LFG Generated

LFG Generated,R. W. Beck Model

LFG Generated,City LandGEM Model

Figure 2-2. LFG Generation vs. Time using R. W. Beck model and LandGEM model

Figure 2-2 illustrates the relationship between the RWB Model and the LandGEM

model. Both models show peak gas production in 2006 (final year of wasteplacement). The peak gas flow in the RWB Model is approximately 39% higher than

the LandGEM model, however, at about 10 years past the peak year, the RWB Modelpredicts less gas production than LandGEM. This shape of the curve and relationship

with the LandGEM model is consistent with the differing theories of the total gas

production in an arid climate. The LandGEM model assumes that gas production willcontinue until the production potential has been realized for each unit of waste. The

RWB Model assumes that gas production will occur where the micro-environment

allows for it, but all waste will not necessarily reach maximum LFG generationpotential. This is evidenced anecdotally by findings of old newspapers that have not

decomposed in older, arid landfills. The RWB Model curve is shaped to reflect thereality that waste in a micro-environment that can promote decomposition will do soand generate gas, whereas, waste that is not in the necessary micro-environment will

not decompose as fully. Ultimately, the decomposition of the total waste mass and

resulting LFG generation will be some fraction of the maximum potential that could

h b hi d d f di i



45/134

collection efficiency assumption that is appropriate for feasibility studies until an

actual gas collection system is installed.

LFG Generation/Collectio n Estim ate - McCombs Landfil lAll Ex ist ing Cel ls

0

50

100

150

200

250

300

350

400

450

500

550

600

650

1977

1980

1983

1986

1989

1992

unknown - 2008 - landfill gas to energy feasibility report

Documents