CH2MHill Deskins Green House Gas Study view report here:https://issuu.com/jeffreywidner/docs/ghg_deskins_comparison_tm_final_3-1

https://issuu.com/jeffreywidner/docs/ghg_deskins_comparison_tm_final_3-1

T E C H N I C A L M E M O R A N D U M

Deskins Greenhouse Gas Comparison Study

PREPARED FOR: F. D. Deskins, Inc.

PREPARED BY: CH2M HILL

DATE: March 19, 2010

Introduction

Greenhouse Gas (GHG) mitigation and regulation are becoming focal points for many

municipalities and utilities across the United States and around the world. Representatives

from utilities are now requesting that carbon footprint be added to criteria for alternative

evaluation to focus on system sustainability and to receive stimulus funding that has been set

aside for “green” projects. Many utilities will have to report their emission inventories

annually, and their GHG emissions may be regulated in the future. Therefore, it is important

to evaluate the carbon footprint of potential wastewater treatment plant (WWTP) liquid

treatment and biosolids processing facilities to address these potential regulatory issues and

avoid negative environmental impacts.

This technical memorandum (TM) provides a summary of the comparison of the GHG

emissions associated with the construction and operation of three commonly used

wastewater biosolids dewatering processes: the Deskins filter bed system (new and

retrofitted), a belt filter press dewatering system, and a centrifuge dewatering system.

Process assumptions, using common thickening and digestion facilities, were made to

develop generic 5, 10 and 20 MGD WWTP GHG comparisons of the three selected

dewatering system alternatives. Although no two WWTPs are entirely alike and these

facilities do not actually exist, this approach provides a common basis for comparison, and

the general results from this comparison are applicable to many actual facilities throughout

the United States. This approach assuming average and typical design criteria and

operating conditions was used for evaluation of the biosolids dewatering systems in order

to present the F. D. Deskins, Inc. Company (Deskins Company) with independent and

unbiased GHG emission data.

Overall Greenhouse Gas Emissions Accounting Methodology

The methodology used to develop readily comparable estimates of GHG emissions from the

design criteria for the various wastewater biosolids dewatering systems is largely based on

the General Reporting Protocol (v1.0) published by The Climate Registry modified to

include significant supply chain GHG emissions and GHG emissions during construction.

This methodology is largely consistent with ISO 14040 Life Cycle Assessment and ISO

14064-1 Greenhouse Gases, but is not designed to include those life cycle sources deemed de d

minimis. Some downstream GHG emissions are neglected, but assumed to be substantially

equivalent for the alternatives. The methodology is designed to be largely compatible with

PAS-2050, Bilan Carbone, and other global standards but not entirely equivalent.

CH2M HILL Parametric Cost Estimating System

The CH2M HILL Parametric Cost Estimating System (CPES) is a proprietary tool developed

by CH2M HILL staff, capable of producing parametric facility designs. The tool allows users

to specify each component, or module, of the facility including treatment technologies,

chemicals, electric power, natural gas, and others. Each individual module within CPES has

been developed using generic design parameters and materials quantities developed from

previous projects. These parameters allow for dimensional accuracy in regards to the

building footprint associated with each module.

Once the modules have been selected that will compose the proposed facility, the user then

enters design criteria specific to the project. These criteria can vary from flow or loading

rates to the number and size of the biosolids dewatering equipment. Once all pertinent

design criteria have been entered into CPES, material quantities and facility dimensions are

calculated. These values provide a summary for all materials, equipment, and construction

activities required to produce the proposed facility. The approximate capital cost, if needed,

can also be calculated. This allows the user to determine the carbon footprint associated

with all construction activities required to produce the completed facility.

Another feature of CPES is the life cycle analysis tool. The life cycle module imports data

from the parametric facility design and cost estimate to produce a summary of annual costs

and resource consumption associated with the operations and maintenance (O&M) of the

proposed facility. Resource consumption such as energy, fuel, chemicals, and replacement

of consumable materials are calculated and reported on an annual basis within the life cycle

tool. This allows the user to quantify the carbon footprint associated with O&M activities at

the facility for a full year of operation. The CPES life cycle module differs from ISO 14040 in

that it is not a full four phase assessment process. The module only addresses the inventory

analysis phase. The tool simply creates an inventory of materials that can be further

analyzed according to the four phase assessment. Scope definition, impact assessment, and

interpretation are all contained to the greenhouse gas module discussed below.

Both the parametric facility design and life cycle analysis modules are linked to the

Greenhouse Gas (GHG) Calculation Module, also developed by CH2M HILL staff. The

values obtained from the parametric facility design and life cycle modules are directly

imported into the GHG module so that all emissions from construction and O&M can be

quantified. However, no comparative capital, annual or present worth costs were generated

using the CPES for the three biosolids dewatering systems for the three generic WWTPs in

accordance with the scope of work of this project.

Documentation and Assumptions

Given the complexity and scope of the proposed facilities and alternatives, some

assumptions were required in order to develop the facility designs and accountings of GHG

emissions. The following section includes a summary and discussion of these assumptions,

and provides documentation of the emission factors and values used in the emission

calculations.

General

In order to compare emissions from varying sources, all emissions must be converted into a

common unit. The commonly accepted unit is carbon dioxide equivalents, or CO2e, due to

the abundance of CO2 in the atmosphere. When looking at the concentrations of GHG in the

atmosphere, CO2 is by far the most abundant. Converting gases in smaller quantities to

CO2e allows for the simplest calculation of total GHG emissions.

These emission factors are applied uniformly within the GHG module. The two factors

below in Exhibit 1 are the global warming potentials (GWP) for the non-carbon dioxide

(CO2) gases of concern, methane (CH4) and nitrous oxide (N2O). The GWPs are based on

the degradation time of each molecule in the atmosphere in comparison to the most

prevalent GHG, CO2. By multiplying each gas by its GWP, that gas can then be converted to

CO2e.

EXHIBIT 1

Global Warming Potential

Gas Global Warming Potential (GWP)

CO2 1

CH4 21

N2O 310

Source: California Climate Action Registry, General Reporting Protocol, Reporting Entity Wide Greenhouse Gas

Emissions, Version 3.0, April 2008

GHG Emissions Categories

Direct

Direct emissions are GHG sources which the entity directly owns or controls. These

emissions are put into four categories: stationary combustion, mobile combustion, processrelated,

and fugitive emissions. Direct emissions are commonly referred to as scope 1

emissions by many reporting protocols.

Indirect

These emissions are a result of the purchase and consumption of electricity. Although these

emissions are outside the organization’s boundary, most reporting protocols require

quantification of these emissions in order to provide incentives for energy efficiency and

conservation. Indirect emissions from electrical purchase are typically referred to as scope 2

emissions in most reporting protocols.

rect (Optional)

Optional indirect emissions are sources in which an organization has significant control or

influence, and occur within its boundaries. Most of these GHG emissions result from

contracted services for upstream and downstream activities such as product manufacturing,

transportation, and disposal. These emissions sources are referred to as optional indirect, or

scope 3 emissions, because most reporting protocols do not require organizations to report

these emissions as a part of their inventory.

De Minimis

De Minimis emissions are considered to be sources that are small or negligible in

comparison to the overall inventory of the organization. Typically, most protocols do not

require any documentation or supporting data regarding these emissions.

Direct Emissions from Mobile Combustion

GHG emissions associated with transportation are a Scope 1, or direct emission. The GHG

module also accounts for Scope 3 optional indirect emissions from transportation. This is

done by taking into account transportation for outsourced activities such as hauling and

delivery of construction materials and chemicals. These emissions are not required in all

reporting protocols, but these emissions have a significant impact on the total carbon

footprint for the facility and should be calculated whenever possible. All transportation

associated with hauling and delivery of materials is assumed to be optional indirect

emissions. The only direct emissions accounted for within the module are those associated

with on-site construction activities such as excavation and backfill. These emissions are

discussed further below. The emission factors for mobile combustion emissions, along with

the assumptions for vehicle fuel economy are summarized in Exhibit 2.

EXHIBIT 2

Emission Factors for Mobile Combustion

Item Value

Truck Type Heavy Duty

Percentage of Highway Driving 55

Percentage of City Driving 45

Highway Fuel Economy (miles/gal) 10

City Fuel Economy (miles/gal) 8

CO2 Emission Factor (lbs/gal) 21.958

CH4 Emission Factor (tons/mile) 5.51X10-6

N2O Emission Factor (tons/mile) 6.61X10-6

Source: California Climate Action Registry, General Reporting Protocol, Reporting Entity Wide Greenhouse Gas

Emissions, Version 3.0, April 2008

DESKINS GREENHOUSE GAS COMPARISON STUDY

DESKINS GHG COMPARISON TM 4

COPYRIGHT 2010 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

Indirect (Optional)

Optional indirect emissions are sources in which an organization has significant control or

influence, and occur within its boundaries. Most of these GHG emissions result from

contracted services for upstream and downstream activities such as product manufacturing,

transportation, and disposal. These emissions sources are referred to as optional indirect, or

scope 3 emissions, because most reporting protocols do not require organizations to report

these emissions as a part of their inventory.

De Minimis

De Minimis emissions are considered to be sources that are small or negligible in

comparison to the overall inventory of the organization. Typically, most protocols do not

require any documentation or supporting data regarding these emissions.

Direct Emissions from Mobile Combustion

GHG emissions associated with transportation are a Scope 1, or direct emission. The GHG

module also accounts for Scope 3 optional indirect emissions from transportation. This is

done by taking into account transportation for outsourced activities such as hauling and

delivery of construction materials and chemicals. These emissions are not required in all

reporting protocols, but these emissions have a significant impact on the total carbon

footprint for the facility and should be calculated whenever possible. All transportation

associated with hauling and delivery of materials is assumed to be optional indirect

emissions. The only direct emissions accounted for within the module are those associated

with on-site construction activities such as excavation and backfill. These emissions are

discussed further below. The emission factors for mobile combustion emissions, along with

the assumptions for vehicle fuel economy are summarized in Exhibit 2.

EXHIBIT 2

Emission Factors for Mobile Combustion

Item Value

Truck Type Heavy Duty

Percentage of Highway Driving 55

Percentage of City Driving 45

Highway Fuel Economy (miles/gal) 10

City Fuel Economy (miles/gal) 8

CO2 Emission Factor (lbs/gal) 21.958

CH4 Emission Factor (tons/mile) 5.51X10-6

N2O Emission Factor (tons/mile) 6.61X10-6

Source: California Climate Action Registry, General Reporting Protocol, Reporting Entity Wide Greenhouse Gas

Emissions, Version 3.0, April 2008

For the Scope 1 emissions for on-site activities, as well as the Scope 3 emissions related to

outsourced activities such as hauling and delivery of materials, assumptions were made for

travel distances for each category. These mileage assumptions are kept the same for all

scenarios and alternatives evaluated for this study. These assumptions are listed in Exhibit

3.

EXHIBIT 3

Assumptions for Transportation

Item Miles

Chemical Delivery 100

Concrete Delivery 25

Structural Backfill Delivery 50

Haul Distance of Excess Dirt 25

Process Piping Delivery 100

Biosolids Hauling to Landfill/Land Application 25

Note: All distances are one way, not roundtrip. Roundtrip distances are accounted for in the module.

The last source for mobile combustion is diesel consumption related to earthwork activities

such as excavation, backfill and the biosolids retrieving tractor usage for the Deskins filter

bed process. In order to calculate total diesel consumption to complete all earthwork

activities, assumptions were made in regards to the efficiency of these machines in varying

types of soil. These assumptions are listed below in Exhibit 4.

EXHIBIT 4

Assumed Efficiency of Earthwork Activities

Load Factor Efficiency

Medium Load Factor (Natural Bed Clay) 25 cy/gal

Deskins Biosolids Retrieving Tractor 1.63 gal/hr; 45 HP

Source: Means Productivity Standards for

Construction, Third Edition, 1994

Direct Emissions from Solids Disposal at Landfill or Beneficial Use as

Fertilizer/Soil Condition on Agricultural Land

GHG emissions associated with disposal of the dewatered biosolids at a landfill were

calculated based on volume of the biosolids cake assuming the total cake solids

concentration and the biological content of the solids. It was assumed that all dewatered

solids would be sent to a landfill site located a one-way distance of 25 miles from the generic

WWTP. Offsite GHG emissions from the landfill were included in the total GHG emissions

estimate. However, these offsite GHG emissions were negligible compared to the onsite

GHG emissions and were considered equal for the three biosolids dewatering alternatives.

The offsite GHG emissions would be the same if the biosolids were beneficially land applied

as a fertilizer/soil conditioner versus disposed of in a landfill.

Indirect Emissions from Electricity

The purchase of electricity, considered scope 2 indirect emissions, must be considered when

accounting for the GHG emissions of a facility under most globally-accepted reporting

protocols. To determine the total CO2e from the purchase of electricity, CH2M HILL staff

uses the Environmental Protection Agency’s (EPA) eGRID data that averages emission

factors for twenty-six sub regions across the United States. See Exhibit 5 below for the

United States national average emission factors used in this study. It should be noted that

eGRID factors are defined for a specific point in time. No adjustments in these factors were

made due to a potentially changing mix of power supply fuels over the life cycle of the

alternatives. Some standard global protocols call for the analysis of operating and build

margins to derive these factors. It was assumed for this analysis the EPA eGRID factors

would suffice.

EXHIBIT 5

Emission Factors for Electrical Consumption

Emission Factor Value (lbs/MWh)

CO2 1363.00

CH4 0.0196

N2O 0.0298

Source: Environmental Protection Agency Climate Leaders, Greenhouse Gas Inventory Protocol Core Guidance

Module, Indirect Emissions from Purchases/Sales of Electricity and Steam, June 2008.

Optional Indirect Emissions from Chemical Consumption

The optional indirect emissions from chemical consumption are considered to be scope 3

emissions. These emissions account for the production of the chemical, primarily polymer

for this study, at the manufacturing site, and transportation of the chemical to the facility forDESKINS GREENHOUSE GAS COMPARISON STUDY

DESKINS GHG COMPARISON TM 7

COPYRIGHT 2010 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

consumption. These emission factors account for the production of the chemical from

existing materials and do not account for emissions associated with obtaining or producing

the raw materials required production. As discussed in Exhibit 3 above, a one-way chemical

transportation distance of 100 miles was assumed for all chemicals. The emission factors for

the production of chemicals associated with these proposed facilities are listed in Exhibit 6.

EXHIBIT 6

Emission Factors for Chemical Production (Polymer)

Chemical Emission Factor (lbs CO2/lb chemical)

Liquid Emulsion Polymer 2.082

Source: Life-cycle Energy and Emissions for Municipal Water and Wastewater Services: Case Studies of

Treatment Plants in the U.S., Malavika Tripathi, April 2007.

Design Criteria for Biosolids Dewatering Systems

In order to estimate the GHG emissions for each alternative, the facility components specific

to each scenario must be specified. Once these assumptions were made, the CPES modules

were built. These assumptions address system capacity, equipment selection, and biosolids

thickening, storage and stabilization requirements. Three WWTP capacity scenarios – 5, 10

and 20 MGD - were evaluated for each dewatering system.

The assumptions for the solids thickening and anaerobic digestion processes that preceded

dewatering common to each generic 5, 10 and 20 MGD WWTP were as follows:

1. Primary and activated sludge liquid stream treatment

2. A 40:60 ratio of primary to secondary waste activated sludge.

3. Total combined solids production of 2,000 pounds per million gallons of WWTP

capacity

4. Primary solids thickened in primary clarifiers to 5 percent solids concentration with

80% volatile solids concentration

5. Secondary waste activated sludge thickened in gravity belt thickeners to 5 percent

solids concentration with 75 percent volatile solids concentration

6. Anaerobic digestion of combined primary and WAS sized for 15 day SRT with 30

minute turnover time for hydraulic mixing and 2.5% feed solids concentration to

dewatering

7. 50% volatile solids destruction of combined primary and WAS

8. A class “B” biosolids product was achieved from the anaerobic digestion process.

8. One story 37.5 foot by 23 foot building assumed for polymer storage and feeding

equipment for Deskins filter beds 9. One story building (exact building dimensions included in the following tables)

assumed for belt filter press and centrifuge equipment.

A summary of the facility component assumptions for each alternative is shown in the

following exhibits.

New Deskins Filter Bed System

The design criteria for the new Deskins Filter Bed biosolids dewatering system are shown in

Exhibit 7.

EXHIBIT 7

New Deskins Filter Bed System - Design Criteria

5 MGD 10 MGD 20 MGD

Component Value Units Value Units Value Units

Anaerobically Digested Biosolids to

Deskins Filter Beds

8,610 lbs/d 17,220 lbs/d 34,440 lbs/d

Feed Solids Concentration to Deskins

Filter Beds

2.5 % 2.5 % 2.5 %

Deskins Filter Bed Solids Loading Rate 2.0 lbs/sf 2.0 lbs/sf 2.0 lbs/sf

Deskins Filter Bed Length 100 ft 100 ft 100 ft

Deskins Filter Bed Width 80 ft 80 ft 80 ft

Number of Deskins Filter Beds 4 # 8 # 15 #

Solids Capture 99 % 99 % 99 %

Dewatered Biosolids Cake Concentration

from Deskins Filter Beds (percent as dry

weight basis)

30 % 30 % 30 %

Deskins Filter Bed Drying Cycle Time 7 days 7 days 7 days

Total Electrical Load 1.5 BHP 1.5 BHP 1.5 BHP

Hours of Operation (per week) for

retrieving biosolids cake material

8 hr 14 Hr 24 hr

Polymer Consumption 11 lbs/dry ton 11 lbs/dry ton 11 lbs/dry ton

Belt Filter Press

The design criteria for the belt filter press (BFP) biosolids dewatering system are shown in

Exhibit 8.

EXHIBIT 8

Belt Filter Press – Design Criteria

5 MGD 10 MGD 20 MGD

Component Value Units Value Units Value Units

Anaerobically Digested Biosolids to BFPs 8,610 lbs/d 17,220 lbs/d 34,440 lbs/d

Percent Dry Solids to BFP 2.5 % 2.5 % 2.5 %

BFP Solids Loading Rate 600 lbs/hr/m 600 lbs/hr/m 600 lbs/hr/m

BFP Hydraulic Loading Rate 50 gpm/m 50 gpm/m 50 gpm/m

BFP Belt Width 2.0 M 2.0 m 2.0 m

Number of Operating Belt Filter Presses 1 # 1 # 2 #

Dewatering Building Length 78 ft 78 ft 90 ft

Dewatering Building Width 56 ft 56 ft 80 ft

Dewatered Biosolids Cake

Concentration from BFP (percent on dry

weight basis)

17 % 17 % 17 %

Solids Capture 90 % 90 % 90 %

Total Electrical Load 3.1 BHP 6.3 BHP 7.9 BHP

Hours of Operation (per day) 7 hr 7 hr 14 hr

Polymer Consumption 15 lbs/dry ton 15 lbs/dry ton 15 lbs/dry ton

DESKINS GHG COMPARISON TM 10

COPYRIGHT 2010 BY CH2M HILL, INC. • COMPANY CONFIDENTIAL

Centrifuge

The design criteria for the centrifuge biosolids dewatering system are shown in Exhibit 9.

EXHIBIT 9

Centrifuge – Design Criteria

5 MGD 10 MGD 20 MGD

Component Value Units Value Units Value Units

Anaerobically Digested Biosolids to

Centrifuges

8,610 lbs/d 17,220 lbs/d 34,440 lbs/d

Percent Dry Solids to Centrifuge 2.5 % 2.5 % 2.5 %

Centrifuge Solids Loading Rate 1435 lbs/hr 1435 lbs/hr 1435 lbs/hr

Centrifuge Hydraulic Loading rate 115 gpm 115 gpm 115 gpm

Centrifuge Power 125 BHP 125 BHP 125 BHP

Number of Operating Centrifuges 1 # 1 # 2 #

Centrifuge Bowl Diameter 20 in 20 in 20 in

Centrifuge Bowl Length 100 In 100 in 100 in

Centrifuge Building Length 77 Ft 77 ft 77 ft

Centrifuge Building Width 77 Ft 77 ft 77 ft

Solids Capture 95 % 95 % 95 %

Dewatered Biosolids Cake Concentration

from centrifuge (percent as dry weight

basis)

22 % 22 % 22 %

Total Electrical Load 131 BHP 131 BHP 259 BHP

Hours of Operation (per day) 6 Hr 11 hr 11 hr

Polymer Consumption 20 lbs/dry ton 20 lbs/dry ton 20 lbs/dry ton

Results

CH2M HILL staff calculated GHG emissions associated with the construction and operation

of three commonly used wastewater biosolids dewatering processes: the Deskins filter bed

system (new and retrofit), a belt filter press dewatering system, and a centrifuge dewatering

system based on the design criteria and GHG assumptions presented in the previous

sections of this memorandum.

Deskins Filter Bed Biosolids Dewatering System

The GHG emissions associated with the Deskins filter bed system (new and retrofit) for the

three capacity scenarios are shown in Exhibit 10. The average breakdown of GHG emissions

for the annual O&M activities for the three capacity scenarios for the new Deskins filter bed

system is shown in Exhibit 11.

The GHG emissions from the construction activities are a one-time event that should not be

added to the GHG emissions from the annual O&M activities.

Specific to the Deskins process, the majority (average of 47 percent) of the overall annual

O&M emissions for each of the three plant capacities are a result of polymer use; while the

second highest (average of 20 percent) was from diesel fuel use by truck transport of the

biosolids and land application of the biosolids; and the third highest (average of 19 percent)

was from power consumption of the biosolids feed pump and polymer system equipment

and heat, cool, ventilate and illuminate the polymer storage and feed building.

EXHIBIT 10

Deskins Filter Bed System GHG Summary

5 MGD 10 MGD 20 MGD

GHG Category Emissions Emissions Emissions Units

Electrical Power 14.52 14.64 14.76 Tons CO2e/yr

Chemicals (Polymer) 18.37 36.49 72.47 Tons CO2e/yr

Biosolids Retriever Tractor Diesel

Emissions

5.86 11.71 21.97 Tons CO2e/yr

Offsite GHG Emissions (Solids

Transport to and application at

Agricultural/ Landfill Site)

12.41 15.37 21.29 Tons CO2e/yr

Total Annual O&M GHG Emissions 51.16 78.21 130.49 Tons CO2e/yr

Construction GHG Emissions

New 42.75 80.78 145.17 Tons CO2e/yr

Retrofit 9.05 14.00 19.00 Tons CO2e/yr

Exhibit 11

Average Annual O&M GHG Emissions Chart for the Deskins Filter Bed System

Belt Filter Press Biosolids Dewatering System

A summary of the GHG emissions associated with the belt filter press biosolids dewatering

system is shown in Exhibit 12. The average breakdown of GHG emissions from annual

O&M activities for the three capacity scenarios for the BFP system is shown in Exhibit 13.

The majority of the overall emissions (66 percent) are attributed to the power required to

operate the biosolids feed pump, polymer system, and BFP equipment and heat, cool,

ventilate and illuminate the BFP dewatering building; while GHG emissions as a result of

polymer use is the second highest at 26 percent. However, as the generic plant size

increases in capacity from 10 to 20 MGD, GHG emissions as a result of electrical power

generation become a smaller percentage (57 percent) of the overall GHG emissions.

EXHIBIT 12

Belt Filter Press GHG Summary

5 MGD 10 MGD 20 MGD

GHG Category Emissions Emissions Emissions Units

Electrical Power 111.76 119.03 163.92 Tons CO2e/yr

Chemicals (Polymer) 25.21 49.64 99.28 Tons CO2e/yr

Offsite GHG Emissions (Solids

Transported to and application at

Agricultural/Landfill Site)

12.56 15.66 21.86 Tons CO2e/yr

Total Annual O&M GHG Emissions 149.53 184.33 285.06 Tons CO2e/yr

Construction Activities 17.9 18.04 23.91 Tons CO2e/yr

Exhibit 13

Average Annual O&M GHG Emissions Chart for the Belt Filter Press Dewatering System

Centrifuge Biosolids Dewatering System

A summary of the GHG emissions associated with the centrifuge biosolids dewatering

system is shown in Exhibit 14. The average breakdown of GHG emissions resulting from

annual O&M activities for the three capacity scenarios for the centrifuge system is shown in

Exhibit 15. The majority of the overall average emissions (75 percent) are attributed to the

power required to operate the equipment (significantly higher for the centrifuge compared

to the other two dewatering alternatives) and heat, cool, ventilate and illuminate the

centrifuge dewatering building; while GHG emissions as a result of polymer use is the

second highest at 20 percent. In fact, the GHG emissions that result from electrical power

consumption for the centrifuge alternatives is 2.8 to 5.5 times higher than the GHG

emissions associated with polymer use.

EXHIBIT 14

Centrifuge GHG Summary

5 MGD 10 MGD 20 MGD

GHG Category Emissions Emissions Emissions Units

Electrical Power 185.47 270.39 366.38 Tons CO2e/yr

Chemicals (polymer) 33.45 66.35 132.47 Tons CO2e/yr

Offsite GHG Emissions (Solids

Transported to and application at

Agricultural/Landfill Site)

12.50 15.55 21.64 Tons CO2e/yr

Total Annual O&M Emissions 231.42 352.29 520.49 Tons CO2e/yr

Construction Activities 40.78 40.78 40.78 Tons CO2e/yr

Exhibit 15

Average Annual O&M GHG Emissions Chart for the Centrifuge Dewatering System

Comparison of GHG Emissions for Biosolids Dewatering Systems

CH2M HILL staff compared the GHG emissions for the three biosolids dewatering systems

including Deskins filter beds, belt filter press dewatering and centrifuge dewatering for 5, 10

and 20 MGD WWTPs. The comparison is divided into two sections: 1) GHG emissions from

construction activities, and 2) GHG Emissions from annual O & M activities.

GHG Emissions from Construction Activities

The GHG emissions that are a result of the one-time construction activities are shown in

Exhibit 16. The GHG emissions that are associated with the construction of new Deskins

filter beds are equal to or significantly higher than the GHG emissions those are a result of

the construction of the BFP and centrifuge dewatering buildings for the three WWTP

scenarios. Note that the construction of 4, 8 and 15 Deskins filter beds, each with an area of

80,000 square feet, are required for the 5, 10 and 20 MGD WWTP scenarios, respectively.

However, nearly 60 percent of the total Deskins filter bed projects involve the retrofitting of

existing drying or evaporation beds rather than the construction of new filter beds. GHG

emissions from construction activities resulting from retrofitting existing drying beds to

Deskins filter beds are much lower than GHG emissions from construction of new filter

beds. A separate estimate of GHG emissions from construction activities related to

retrofitting of existing drying beds to Deskins filter beds (includes removal of existing media

and installation of new media, drainage panels, PVC liner and piping and adding taller

concrete walls to side of the filter beds) is also included in Exhibit 16. Note that the GHG

emissions from the construction activities resulting from retrofitting of existing drying beds

to Deskins filter beds is 4.7 to 7.6 times less than the GHG emissions from construction of

similar sized new Deskins filter beds. In addition, the GHG emissions from construction

activities resulting from retrofitting of existing drying beds with new Deskins filter beds are

the lowest of all the three dewatering alternatives and approximately 1.3 to 4.5 times less

when compared to belt filter presses and centrifuges.

The one story BFP Dewatering Building dimensions range from approximately 80 foot X 80

foot to 80 foot by 90 foot; while the one story Centrifuge Dewatering Building dimensions

are 80 foot X 80 foot for all three scenarios. Also, the GHG emissions that are a result of the

construction of the BFP dewatering building are lower the GHG emissions from the

construction of the centrifuge dewatering building because the structural requirements

(structural excavation, backfill and slab thickness) are less.

Exhibit 16

Comparison of GHG Emissions from Construction Activities

GHG Emissions from Annual O&M Activities

A summary of the annual O&M emissions for each of the dewatering alternatives is shown

in Exhibit 17. This summary includes GHG emissions that result from the following: 1)

electrical power consumption, 2) chemical (polymer) use, 3) biosolids retriever tractor diesel

fuel use, and 4) diesel fuel use by truck transport of the biosolids and land application of the

biosolids. The GHG emissions from the annual O& M activities do not include GHG

emissions from one-time construction activities.

Exhibit 17 shows that the Deskins filter bed dewatering system should produce significantly

less GHG emissions as a result of annual O & M activities compared to belt filter press and

centrifuge dewatering systems. The Deskins filter bed system should produce 2.2 to 2.9

times less GHG emissions compared to BFP dewatering systems and 4 to 4.5 times less GHG

emissions when compared to a centrifuge dewatering system that are a result of annual

O & M activities for 5, 10, and 20 MGD WWTPs.

Exhibit 17

Comparison of GHG Emissions from Annual O&M Activities

Summary and Conclusions

The Deskins filter bed biosolids dewatering system produces less overall annual O & M

GHG emissions compared to both a belt filter press system and a centrifuge dewatering

system for 5, 10, and 20 MGD WWTPs, based on the reasonably and well accepted generic

WWTP solids processing facility design criteria and GHG emission assumptions in this

Technical Memorandum.

When GHG emissions from annual O&M activities are examined, it is apparent that the

Deskins filter bed biosolids dewatering system will be “greener” and have a significantly

smaller impact on the environment compared to belt filter press and centrifuge biosolids

dewatering systems. This is largely due to the relatively small electrical load (only biosolids

feed and polymer feed pumps) required for the Deskins system if the filtrate from the

process can be discharged by gravity. The GHG emissions that result from the use of

electrical power to operate the equipment and to heat, cool, ventilate and illuminate the

dewatering buildings for the belt filter press and the centrifuge alternatives are significant.

Only a small building to house polymer storage and feed systems that will use minimal

electrical power is required for the Deskins filter bed system.

The GHG emissions that are associated with the construction of new Deskins filter beds are

significantly higher than the GHG emissions those are a result of the construction of the BFP

and centrifuge dewatering buildings for the three WWTP scenarios. However, much lower

GHG emissions will result from the construction activities from retrofitting of existing

drying beds to Deskins filter beds compared with the GHG emissions that will result from

the activities from construction of new Deskins filter beds, belt filter press or centrifuge

dewatering facilities.

As municipalities attempt to decrease GHG emissions from WWTPs in the near future, it is

now important to consider GHG emissions from solids processing facilities. As our study

shows, it is beneficial to consider and choose the Deskins filter bed system as a biosolids

dewatering system over a belt filter press or a centrifuge biosolids dewatering system if the

reduction of GHG emissions is a priority and cost and other criteria are considered

approximately equal or less for the Deskins filter bed system.

This effort is not intended to endorse the Deskins Company or any other biosolids dewatering

processes and should not be presented on the Deskins Company literature or on the website

as such. The Deskins Company is to submit the summary of this study for review and

approval by CH2M HILL prior to using it in any Company literature or on the website. This

letter report is to be distributed as a complete document.