USER'S MANUAL:
CO-DIGESTION ECONOMIC
ANALYSIS TOOL
Office of Research and Development
National Risk Mangement Research Laboratory
Land Remediation and Pollution Control Division

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Table of Contents
Model Objective:	2
Intended Audience:	2
Background:	2
Model Overview:	3
Model Components (see below for more detailed explanations):	4
Model Outputs:	4
Types of Organic Waste Considered:	5
Using the Model:	5
First Time Users	6
Graphical User Interface (GUI)	6
Excel Worksheets	6
Opening the Model	6
Collecting Data	7
Navigation	7
Entering Your Data:	8
Customizingthe model:	8
GUI Components:	8
1.	Digester	9
2.	Feedstocks	9
3.	Economics	10
4.	Biosolids	10
5.	Heating	11
Worksheet Components:	12
1.	Current Parameters	12
2.	Future Parameters	13
3.	Comparison	13
4.	Biogas Use	15
5.	Digester and Ancillary Equip	15
Input Variables	16
Data Sheet	16
Glossary	16
Saving Data	16
Results Interpretation	16
Appendix A	17
Appendix B	19

o

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Model Objective:
The Co-Digestion Economic Analysis Tool (Co-EAT) 2016, for which this manual applies, has three
primary objectives:
1.	Provides an initial economic feasibility assessment for co-digestion of organic wastes at a Water
Resource Recovery Facility (WRRF) using anaerobic digestion (AD) to manage wastewater solids.
The analysis can also be conducted to assess the feasibility of co-digestion at facilities that do not
yet use, but are considering, anaerobic digestion, including dairies and stand-alone digesters.
2.	Compare the relative merits of three uses of biogas: heating, electrical generation, and
compressed natural gas for vehicle fuel.
3.	Provide a clear comparison of the economic implications of co-digestion, given multiple
performance assumptions, and unique physical and cost parameters provided by the tool-user.
Note: This model is not intended to be a final evaluation of a food waste co-digestion project. Tool
users should perform community and situation specific analyses of project viability prior to
implementation.
Intended Audience:
Decision makers who are considering adding food waste or another organic feedstock into existing anaerobic digester
systems at a water resource recovery facility, farm, or food processer. It will help to have input from people with
technical and finance background to help with input and interpretation of results. It is intended to be used by utility
and city managers with specific information provided by engineers, WRRF managers, and operators.
Background:
Many WRRFs have AD systems that have excess capacity, sometimes significant excess capacity. This is
often a result of changes in service area population not rising to match design expectations. Having AD
capacity could be an opportunity to create or enhance income streams for the facility while at the same
time helping to divert organic material from landfills. This tool can help calculate the cost of upgrading a
facility, the expected increase in biogas production, and the enhanced income from tipping fees and
increased energy production.
Wasted food and similar organic materials make up more than 30% of the waste reaching landfills in the
U.S.1 In a landfill, organic materials produce methane, a potent greenhouse gas. Through anaerobic
digestion, food waste can be transformed into a source of renewable energy as microorganisms break
down the food waste and release biogas as a product.2
5
<
73
\
£L '
$b)
V pro^N
1 U.S. Solid Waste Characterization 20013.
https://www.epa.gov/smm/advancing-sustainable-materials-management-facts-and-figures
2Organics: Anaerobic Digestion.
https://www.epa.goV/anaerobic-digestion/basic-information-about-anaerobic-digestion-ad#HowADworks
November 2016	2
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official	^
EPA approval, endorsement, or recommendation.	*
Printed on 100% recycled paper - process chlorine-free.
PIICH**1"

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Food waste can be digested anaerobically to create renewable energy using a variety of methods,
including:
¦	Co-digestion at a wastewater treatment plant3
¦	Co-digestion in a farm digester
¦	Digestion in a stand-alone digester
Many water resource recovery facilities have successfully implemented co-digestion of post-consumer
food waste and other organic wastes with biosolids at their main wastewater treatment plant.4 The
following key benefits of digesting food waste and other organics were identified:
¦	Food waste has 3 to 3.5 times the methane production potential per volume than biosolids.
The methane production potential of biosolids was 120 m3 gas/ton and food waste around
367 m3 gas/ton.
¦	Food waste is more readily biodegradable and requires less residence time and digester volume
than municipal biosolids.
Municipalities are increasingly interested in evaluating the viability of implementing co-digestion in their
service area as a way to reduce the amount of landfills, generate renewable energy, and mitigate climate
change. Currently, there are many wastewater treatment facilities with excess digester capacity that
may be ideal for co-digestion. This Co-Digestion Economic Analysis Tool was developed to provide a
way to make a quick assessment of the economic feasibility of adding external feedstocks (especially
food waste) to an existing anaerobic digester system at a WRRF.
Model Overview:
The Co-Digestion Economic Analysis Tool (Co-EAT) provides an initial look at the economic and physical
feasibility of organic waste co-digestion at Water Resource Recovery Facilities (WRRF) for the purpose of
biogas production, for increased fees from new feedstocks, and for changing the nature of
biosolids/digestate.The Co-Digestion Economic Analysis Tool (Co-EAT') utilizes the current publicly-
available data on the emerging practice of co-digestion at WRRFs.
Co-EAT can be used with existing or projected digesters, and will calculate results with no pre-existing
digester in place, however the model was intended to help WRRF operators assess the viability of
implementing co-digestion with existing anaerobic digesters. Because empirical data are not available for
a wide variety of food waste co-digestion projects in the U.S., the model uses the best current data and
should be considered a screening tool for initial evaluation as real feedstocks will have specific
characteristics that will effect digester system performance.
Co-EAT does not provide a rigorous feasibility study, but does identify the various logistical, operational,
and equipment considerations within an "economic cost model" resulting in the calculation of the Net
Annual Worth of the project. The model is flexible and users can adjust assumptions and costs to fit their
circumstances. Wherever available, source data is provided for further research and evaluation. For the
best results, users should input measured operating parameters instead of using model assumptions.
3	The Benefits of Anaerobic Digestion.
https://www.epa.gov/anaerobic-digestion/environmental-benefits-anaerobic-digestion-ad
4	Food Waste to Energy: How Six Water Resource Recovery Facilities are Boosting Biogas Production
https://www.epa.gov/anaerobic-digestion/food-waste-nergy-how-six-water-resource-recovery-facilities-are-boosting-
3 November 2016	3
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
$
<
73
\
£L '
£b)
V pro^N

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Model Components (see below for more detailed explanations):
1.	Graphical User Interface
•	Home
•	1 - Digester
•	2 - Feedstocks
•	3-Economics
•	4-Biosolids
•	5 - Heating
2.	Excel Worksheets
•	Overview
•	1. Current Parameters
•	2. Future Parameters
•	3. Comparison
•	4. Biogas Use
•	5. Digester and Ancillary Equip.
•	Input Variables
•	Data Sheet
•	Glossary
•	References
The following schematic, Figure 1, graphically depicts which components are considered as part of the
tool. This tool models wet digestion and should not be used as a proxy for determining the feasibility
of dry digestion.	Key components which are not included as part of the tool are:
•	Off-Site Pre-Processing of Feedstock
•	Biogas Air Emissions Reductions
•	Greenhouse Gas Emissions Reductions from Renewable Energy Generation
•	Avoided Transportation Costs to Landfill
5
<
73
\
£L '
$b)
V pro^N
Figure 1. Schematic of Co-Digestion Economic Analysis Tool (Co-EAT) - Identifies key components of the model.
Model Outputs:
Co-EAT calculates the economic, environmental and operational outputs for an organic waste co-digestion
system including:
¦	Fixed and recurring costs
¦	Solid waste diversion savings
4 November 2016	4
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
\
A •
SEZJ
<0
Capital investments
Biogas production
Avoided Utility/Vehicle Fuel Costs
Collection
Digestion
~
Feedstock Characteristics
-	Food Waste
-	Fats, Oils, & Grease (FOG)
Feedstock Receiving
-	Landfill Tipping Fees
-	Tipping Fee at Digester
Feedstock Processing
-	Equipment
-	Operations & Maintenance
Digester Infrastructure
-	Excess Capacity
-	Needed Capacity
-	Ancillary Equipment
Operations &
Maintenance
-	Repair, cleaning, etc.
-	Labor
-	Operating Parameters
Residual Management
• Transportation
- Tipping Fees
Biogas
Types of
Organic
Waste
Characteristics
Quantity
Value
-	Heating
-	Combined Heat and Power (CHP)
-	Renewable Natural Gas (RNG)
Cleaning
Considered:
¦	Food waste
¦	Fats, oils and grease (FOG)
¦	Other (If user has minimal feedstock characteristics, any organic feedstock can be modeled)
Using the Model:
5 November 2016
5
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
m

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
The model is comprised of a graphical user interface (GUI) and several linked worksheets. The GUI provides
an easy to follow, interactive variable input screen guiding the user through entering the necessary
parameters to run the model. The worksheets are responsible for a majority of the calculations and
organization of the data. The model can be customized according to individual circumstances, allowing the
model to be applicable to many city's or organization's situation. It is designed to compare current
operating parameters to future operating parameters. Providing "what if" scenarios to weigh different
options for biogas use.
First Time Users
A first time user's tutorial can be found in
Appendix B. The tutorial provides clear
guidance that navigates users through
their first use of the model.
Graphical User Interface (GUI)
The GUI provides a central location for the
user to input data, Figure 2. The interface
makes it easier to manage data and store
it all in one place. The GUI performs two
major calculations: annual heating
demand and composite feedstock. Once
data is entered and the 'Run' button
clicked, the input variables are
transported to the worksheets to perform
calculations and generate an output. It
should be noted that the GUI does not
present the assumed variables located
within the worksheets. The GUI only
includes fields that require input from the
user. It is recommended that the user
becomes familiar with the assumed variables and calculations embedded in the worksheets to further
tweak the model to their specific needs.
Excel Worksheets
The Excel Worksheets provide a majority of the calculations and organize the data. Through the open
worksheets, the user has the ability to review the formulas and assumptions and/or copy and paste
information to be compared to a later run. If default variables are change, it is possible to restore the
worksheets back to default using the designated buttons located on each worksheet. If a value and/or
formula is changed and not restored, this value and/or formula will be used for every run until the default
formulas are restored.
Opening the Model
Once the model is downloaded from https://www.epa.gov/anaerobic-digestion/anaerobic-digestion-tools-and-
resources#CoEAT, the model can be opened by double clicking the file. After the file loads, a selection screen will
pop-up only if macros are enabled. Having macros enabled is required to run the GUI. To do so, please follow
Microsoft's procedure for enabling macros. Once macros are enabled, the pop-up window appears. The user will be
^ November 2016	6
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
$
<
73
\
£L '
£b)
V pro^N
S3
Co-EAT: Co-Digestion
Economic Analysis Tool
An analysis tool to assess the economic feasibiltiy of co-digestion at a
Water Resource Recovery Facility
sr*,.
»•o \
%pbo^°
Facility:
To get started you will need to collect the input data for the model.
The required input data can be accessed using the buttons below:
Lets Begin!
Developers:
Steve Rock
Jonathan Ricketts
Last Updated: 9/22/2016
Disclaimer: Co-EAT is a screening tool for initial evaluation and does not provide a rigorous feasibility study. The
model identifies the various logistical and equipment considerations within a simple spreadsheet calculator. The
model compares current operating parameters to theoretical future operating parameters (selected by user)
in order to help the user evaluate which options should be further researched. The model is flexible. Users can
adjust assumptions and costs to fit their circumstances.
Figure 2. Home tab of the graphical user interface.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
asked to start new or load previously saved data.
Collecting Data
The necessary data must be collected before using the model. If new was selected in the opening pop-up window,
the GUI will start with the "Home" tab. Two buttons, "Print" and "Spreadsheet", are located here allowing the user
to either print or use a spreadsheet to collect all of the necessary data for the model. Some of the values on the "Co-
EAT Input Data Sheet" are marked with an 'X' in the 'Model' column indicating the model has default values for
these parameters which should only be used if the user does not have their own information.
Navigation
The GUI contains buttons (Perform Actions) and tabs (Receive Inputs). The button logic is displayed in
Figure 3. The tabs are navigable using buttons or by clicking. The input boxes located in the tabs can be
navigated using the 'tab' key or by clicking. Worksheets are accessible while the GUI is open. Data will
not be imported into the worksheets until 'Run' is clicked. Once in the worksheets, the GUI can be
accessed using multiple buttons located throughout the workbook. For example, the button named
'Calculate Composite Feedstock' takes the user back to the GUI. As illustrated in Figure 3, for data to
remain in the GUI and be imported into the worksheet, the user must select run. If the GUI is closed
using the 'X', all data in the GUI will be lost and not imported into the worksheets. Once the user returns
to the worksheets, normal navigation of an Excel workbook is restored.
The model includes explanations and references so you can work through it without having to use
significant outside reference materials.
£
<
73
\
£L '
$b)
V pro^N
1 November 2016
7
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
jp*sr^
0&)
PRO^&

-------
Co-Digestion Economic Analysis Tool (Co-EAT)

Info, not Imported
or Saved
Navigate to Next
Tab Right

t


i
Tab left
IB
V HPS	J
Data Not Saved
and Imported


¦
Yes
I
Data Saved
and Imported
\
/®S\
A •
SEZJ
<0
Key
Data does not remain in GUI
Data remains in GUI
GUI Buttons
GUI Interface
Actions
Figure 3. Logic diagram for the navigation of the main and options graphical user interface
Entering Your Data:
The GUI is the main location for entering data about your facility. "1. Current Parameters", "2. Future
Parameters", and "4. Biogas Use" worksheets can also be used for entering data but is not required.
Entered data is then used in calculations throughout the model to produce the output. Calculations for
the current and future parameters are located at the bottom of the corresponding worksheets. Biogas use
calculations are located in "4. Biogas Use" in the specific biogas use location, which is labeled on the left
hand side of the worksheet.
Customizing the model:
All worksheets contain assumptions and default values that provide the underlying functionality of the
model. Once familiar with the inputs, outputs, and data used to calculate values, you can customize the
mode! for individual circumstances by modifying data in the worksheets.
GUI Components:
Many of the model components in the GUI are briefly described below.
1 November 2016	8
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official	^
EPA approval, endorsement, or recommendation.	\
Printed on 100% recycled paper - process chlorine-free.
^ PR0^° ^

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
<
73
\
£L '
$b)
V pro^N
1. Digester
Input information about the digester's physical parameters, annual operations and maintenance cost,
and performance.

Performance
The model uses percent volatile solids reduction as the

metric for digester performance.
2. Feedstocks
Input current and future feedstock information and calculate composite feedstock parameters. Percent
solids of homogenized feedstock and hydraulic retention time are also entered here.
Feedstock
User can select from a list of default feedstocks or
input their own. The default feedstocks also contain
all of the required feedstock parameters.
Time of Use
Current - Feedstock that is currently being digested
and will not be digested with proposed
feedstock
Future - Proposed feedstock to be digested
Both - Feedstock that is currently being digested and
will continue to be digested along with
proposed feedstocks
Percent Solids of Homogenized Feedstock
User can input the calculated present solids from the
composite feedstock or enter their targeted percent
solids. This value is used to calculate hydraulic
retention time, available capacity, and other volume
calculations.
9 November 2016
9
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
jp*sr^
0&)
PRO^&

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
<
73
\
£L '
$b)
V pro^N
Input utility rates, feedstock tipping fees, and plant upgrade costs.
Utility Rates
Utility rates are based on average rates and do not
account for peak shaving. This assumption provides a
conservative estimate for the value of avoided utility
fees.
Project Upgrading Costs
Project upgrade costs can be calculated using the "5.
Digester & Ancillary Equip." worksheet or directly input.
The worksheet is accessible by clicking the 'Estimate
Cost' button or navigating the workbook. Once in "5.
Digester & Ancillary Equip.", the 'Return to Scenario
Inputs/Import Total' button must be clicked to import
the calculated value.
Biosolids
[
Input information for biosolids disposal and/or revenue and determine future economics of
biosolids.
Percent Solids of Biosolids
Value used to calculate volume of biosolids produced.
Should be the averaged value over the year.
Revenue or Cost
Revenue and/or cost are based on a $/ton basis. The
user has the ability to alter the amount of biosolids that
are sold or disposed for their future operations.
l°November 2016
10
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
jp*sr^
0&)
PRO^&

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
<
73
\
£L '
$b)
V pro^N
Input information about location, tank materials and dimensions, and feedstock quantity to
calculate heating demand.
Location
Location is based on a U.S. 5-digit zip code. Zip codes are
linked to the temperature difference between the
average annual temperature and the digester operating
temperature. Map located in Appendix A.
Digester Dimensions
Used to calculate the exposed surface area of the
digester.
Tank Materials
The user can select from default tank materials to obtain
a heat transfer coefficient for that material. The user can
also input their own information.
Surface Area
Surface area is calculated based on a cylindrical tank
with a flat roof and floor. The calculated surface area can
be overwritten with an equivalent surface area if the
digester is not cylindrical. In that case, the surface area
would need to be calculated by hand.
Heat Transfer Coefficient
Heat transfer coefficients are available for many
materials. The user can use the default values for the
default tank materials or calculate and input their own.
Specific Heat of Homogenized
Feedstock
Specific heat is used to calculate the amount of energy
needed to raise incoming feedstock to operating
temperatures. If value is unknown, it can be assumed
the same as water.
^November 2016
11
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
jp*sr^
0&)
PRO^&

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Worksheet Components:
Each worksheet provides calculations modeling the different aspects of anaerobic digestion. The worksheet
functions and calculations are briefly described below.
1. Current Parameters
Calculations for biogas and biosolids generation, economics, and available capacity for the current
operating conditions are found within this worksheet.
Data
The data is brought into the worksheet from the GUI
inputs. There is no need to alter the worksheets unless
assumptions in the calculations do not match your
facilities process. For example, if you would like to give a
lower heating value to methane to calculate a more
conservative estimate.
Digester Volume
The volume of the digester is calculated assuming a
cylindrical digester with a flat floor. The model also takes
into account volume consumed by objects within the
digester. This volume is incorporated into the effective
operating capacity percentage.
Feedstock
The composite feedstock values are brought in from the
GUI. To make changes to the feedstock (say to compare
different amounts and save them as separate files) use
the "Calculate Composite Feedstock" button located
next to the feedstock information.
Biogas
Biogas production is calculated using an empirically
derived conversion constant based on % volatile solids
destroyed.
Biosolids
Biosolids generation is based on the percent solids of
biosolids and the amount of volatile solids destroyed.
Heating
Heating demands are calculated in the GUI and used to
determine an economic value for biogas.
5
<
73
\
£L '
$b)
V pro^N
^November 2016	12
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official	^
EPA approval, endorsement, or recommendation.	*
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
<
73
\
£L '
$b)
V pro^N
2. Future Parameters
Calculations for biogas and biosolids generation, economics, and available capacity for the future
operating conditions are found within this worksheet. All of the calculations are the same as the
current parameters worksheet but using the future values from the GUI.
Data
The data is brought into the worksheet from the GUI
inputs. As previously mention, there is no need to alter
the worksheets unless assumptions in the calculations
do not match your facilities process.
3. Comparison
This worksheet compiles all of the important calculated information from the other worksheets and
presents the data for comparison. The current conditions are compared to four future scenarios.
Current
The "Current" column displays the information
calculated for the current operating parameters. This
option assumes all of the biogas is used to heat the
digester. Biogas is given value based on avoided natural
gas for heating.
Future A
This column displays the information for future
operating parameters assuming there will be no change
in biogas use (Biogas will only be used to heat the
digester in the existing boiler). Cost and incomes
associated with accepting external feedstocks are
included.
Future B
This column displays the same operating parameters as
'Future A' except that this scenario assumes all biogas
will be used to run a combined heat and power engine
(CHP). Value is given to the electricity generated and
heat recovered by the CHP. Costs and incomes
associated with accepting external feedstocks and
purchasing a CHP are included.
Future C
Displays information for using the same operating
parameters as the other future scenarios but assumes
biogas will be used to meet the heating demand of the
digester and any remaining biogas will be converted into
vehicle fuel. Costs and incomes associated with
accepting external feedstocks, a gas upgrading system,
and truck upgrades are included.
^November 2016	13
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official	^
EPA approval, endorsement, or recommendation.	*
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
<
73
\
£L '
$b)
V pro^N
3. Comparison Cont'd
Future D
Displays the same information as 'Future C' except the

model assumes all biogas will be used as vehicle fuel.

Biogas value is based on the amount of gallon of gas

equivalent (GGE) of biogas produced. Costs and incomes

associated with accepting external feedstocks, a gas

upgrading system, and truck upgrades are included.
Net Annualized Value
The net annualized value (NAV) of the projected cash

inflows and outflows including initial capital costs, is

calculated for each scenario.
Capital Costs
Fixed capital costs required to update and/or increase

capacity of the digesters with additional costs

(engineering and O&M costs) calculated as a percentage

of capital cost.
O&M Costs


Cost may include operating personnel, collection

containers and vehicles, processing equipment, digester

cleaning, and disposal vehicles.
Revenue


Potential revenue streams from organic co-digestion

are calculated based on organic waste volume and

characteristics and known biosolids revenue.

Other potential benefits like renewable energy credits

(REC) and net metering are location-specific. As such these

potential benefits are difficult to anticipate and calculate

and not calculated in the Model. Nonetheless, they could

be meaningful financial factors in the feasibility analysis

and therefore the model will allow the user to add the

data manually.
^November 2016
14
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
jp*sr^
0&)
PRO^&

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
<
73
\
£L '
$b)
V pro^N
4. Biogas Use
This worksheet calculates the biogas value and costs for each of the scenarios described in the "3.
Comparison" worksheet explanation. All of the assumptions for the calculations are found within
this worksheet.
Capital Recovery Factor
Net annual value is based on annual costs. Calculating
equivalent annual values for one-time expenditures
requires a discount rate and analysis period to obtain a
factor to multiply the one-time expenditure by.
Capital Costs
The cost associated with upgrading the digester to
optimize performance and upgrading/installing a
receiving station. Each of the future scenarios add costs
depending on the scenario. An engineering factor is used
to estimate costs for design and consultant work.
Biogas Options
The biogas options are described in the description of
worksheet "3. Comparison". All assumptions an
calculations are found in this worksheet.
5. Digester and Ancillary Equip.
This worksheet calculates costs not directly associated with the digester unit including three primary
areas. The total cost calculated in this worksheet is then imported into the GUI.
FOG Receiving Station
Necessary if the facility will be collecting and processing
FOG, a high-value feedstock that will require separate
handling and pre-processing.
Feedstock processing
External feedstocks typically require some level of
processing to optimize digestion. Processing includes
various methods such as mixing, dewatering, grinding,
sifting, etc.
Ancillary Equipment and Services
Other tasks required include engineering and
environmental studies associated with siting and
constructing the digesters.
^November 2016
15
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
Printed on 100% recycled paper - process chlorine-free.
jp*sr^
0&)
PRO^&

-------
o
m.
Co-Digestion Economic Analysis Tool (Co-EAT)	\ 1
Input Variables
This worksheet provides the user with a printable version of all of the input variables from the GUI
and worksheets allowing the user to save and compare inputs of multiple runs. User can print this
worksheet from "3. Comparison" or navigate to and print from the actual worksheet.
Data Sheet
This worksheet provides an "Items You Need Before You Get Started" list that contains all of the
inputs of the GUI. Users can print this worksheet using the GUI or navigate to and print from the
actual worksheet.
Glossary
This worksheet contains definitions for common terms used throughout the workbook.
Saving Data
All data input into the GUI can be saved using the 'Options' button or before the data is imported into the model. The
saved data is stored in a hidden worksheet and can be loaded at any time using the 'Options' button or when first
opening the model. Each run is saved under the name input for the facility name. There is no external file created for
the saved information. To export the input data, navigate to the 'Input Data' worksheet and print, copy and paste to
another workbook, or any other mean.
Results Interpretation
The main interpretation of the results is to determine if the economics of accepting external feedstocks is worth the
investment by comparing the net annualized value of the current process and future process with varying biogas use
options. This comparison can be found in "3. Comparison" in the 'Net Annualized Value' row. While this is the main
result, other conclusions can be drawn from the model. Following is a list that includes a few of the alternative results:
•	Amount of available capacity for external feedstock (Row 'Available Capacity' in "3. Comparison")
•	Amount of digester volume that needs to be added for processing additional feedstock (Row 'Additional
Volume Needed to Treat Feedstock' in "3. Comparison")
•	Percent increase in biogas (Analysis Box in "3. Comparison)
•	Percent increase in biosolids (Analysis Box in "3. Comparison)
•	Percent increase in heating demand (Analysis Box in "3. Comparison)
•	Size of CHP that can continuously run based on biogas production (Analysis Box in "3. Comparison)
•	Determine how changing parameters of your biosolids handling affects your current process
This is not a comprehensive list and other results may be determined from the model's output.
^November 2016	16
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official	^
EPA approval, endorsement, or recommendation.	*
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Appendix A
17
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or
recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
Anaerobic Digestion Temperature Regions for the United States
D 62.5125 250
I Mites
250 125 0	250 500
I Miles
Anaerobic Digestion Temp. Region
| 22.5 (H1) |	I 42.5 (R5) I	| 62.5 (RS) |
| 27.5  |	| 52.5 (R7) |	| 72.5 (R11)
¦ 37.5 (R4) I	j 57.5 (R6)	77.5 (R12)
82.5 (R13)
87.5 (R14)
Appendix A. Anaerobic digestion temperature regions map for the United States. Temperature regions are based on the difference between a
98 °F digester operating temperature and the mean annual temperature.
18
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or
recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------
Nt£D Sfy,.
Co-Digestion Economic Analysis Tool (Co-EAT)	/
*
*<¦ PRO^°
V
Appendix B: First Time User Tutorial
November 2016	19
i O \
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or	%
recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
i O *
i®J
1. Select 'New' in the first pop-up window.
2. Answer the first question.
Current Operations Question 1
23
Do you currently have an operating anaerobic treatment system?
Yes
No
November 2016	20
# o \
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or	%
recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
* O '
PRO^
if
3.	Print or locate the spreadsheet that provides a list of the required data to run the model. Retrieve the
data.
4.	input the facility name and click 'Let's Begin!'
Co-EAT: Co-Digestion
Economic Analysis Tool
An analysis tool to assess the economic feasibiltiy of co-digestion at a
Water Resource Recovery Facility


Facility:
To get started you will need to collect the input data for the model.
The required input data can be accessed using the buttons below:
Spreadsheet
Developers:
Steve Rock
Jonathan Ricketts
Last Updated: 12/7/2016
Disclaimer: Co-EAT is a screening tool for initial evaluation and does not provide a rigorous feasibility study. The
model identifies the various logistical and equipment considerations within a simple spreadsheet calculator. The
model compares current operating parameters to theoretical future operating parameters (selected by user)
in order to help the user evaluate which options should be further researched. The model is flexible. Users can
adjust assumptions and costs to fit their circumstances.
5. Multiple tabs will appear after 'Let's Begin!' is clicked. Navigate through the tabs and input the
necessary data.
November 2016
21
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or
recommendation.
Printed on 100% recycled paper - process chlorine-free.
I O
W
r->l PHQ.1*

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
* o '
PRO^
if
6. Use the 'Options' button, located in the top left corner of the GUI, to perform routine operations like
save, load, and delete.
7. Use the buttons and explanations throughout the GUI to aid with inputting the data. Click the question
marks next to variables to received further explanation of the variable.
Co-EAT
Options
Home [ 1 - Digester 2 - Feedstocks I 3 - Economics f 4 - Biosolids f 5 - Heating
Feedstocks: Sludge and External Soun
Table A
Feedstock Time of Use Quantity Units/Day
Speci
Gravi
-
¦ T 1



1 J
1 ~ 1



1 d
1 1 1
¦ ~ 1


¦
November 2016	22
# o \
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or	%
recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------
Co-Digestion Economic Analysis Tool (Co-EAT)
* O '
PRO^
if
8. Click 'Run', located in the top right corner of the GUI, to import the data and observe the results.
Co-EAT
9. Observe the results in '3. Comparison' worksheet.
s






Co- EAT_V8.1 .xlsm - Excel
R
File
Home
Insert
Page Layout
Formulas
Data
Review
View ACROBAT
0 Tell me what you want to do
as
^ Record Macro
bo
J Use Relative References
1=0 ^
Visual Macros
Basic	! Macro Security
Code
£ Eq. St
Add- Excel COM
ins Add-ins Add-ins
Add-ins
¦p fc/' ^ ProPerties [pi
- ' r—q!1 View Code
Insert Design _	Source
Mode \M\ Run Dialog
~ Map Properties f^?Import
Expansion Packs L*^ Export
Pj Refresh Data
XML
H83

Current
Future A
Future B
Future C
Future D
Biogas Produced (cf/yr)
1603,335
25,097,097
25,097,097
25,097,097
25,097,097
Total Biogas Heating Energy (MBTU/yr)
729
11,418
r 7,307
11,418
0
Total Energy Needed for Heating (MBTU/yr)
2,185
2,790
2,790
2,790
2,790
Max Capacity of Digester (gal)
250,000
250,000
250,000
250,000
250,000
Feedstock Feed Rate (gal/day)
7,650
12,772
12,772
12,772
12,772
% Solids of Feedstock Fed to Digester ['/.)
2.0'/.
8.0'/.
8.0*
8.0 %
8. OX
Percent Volatile Solids Reduction {'/.)
30 X
60 %
60%
60%
60%
Actual Hyraulic Retention Time (days)
30.7
18.4
18.4
18.4
18.4
Target Hydraulic Retention Time (days)
15.0
15.0
15.0
15.0
15.0
Available Capacity (Gal/dayT
8,030
2,908
2,908
2,908
2,908
Additional Volume Needed to Treat Feedstock (gal)
0
0
0
0
0
Mass of Biosolids (Tons/yr)
1151
4673
4673
4673
4673
Biosolids Cost ($/yr)
($40,269)
($163,568)
($163,568)
($163,568)
($163,568)
Biosolids Revenue ($/yr)
$0.00
$0.00
$0.00
$0.00
$0.00
Tipping Fees ($/yr)
$0.00
$268,019.50
$268,019.50
$268,019.50
$268,019.50
Avoided Natural Gas Costs ($/yr)
$9,514
$112,536
$58,922
$0
($36,391)
Avoided Electricity Costs ($/yr)
$0
$0
$106,188
$0
$0
Avoided Vehicle Fuel ($/yr)
$0
$0
$0
$205,507
$271,962
Annualized Cost of Plant Upgrades Wyr)
$0
($19,977)
($93,730)
($76,865)
($76,865)
Annual Operations and Maintenance ($/yr)
($2,500)
($2,500)
($2,500)
($2,500)
($2,500)
Net Annualized Value ($/yr)
($33,255)
$194,510
$173,332
$230,594
$260,658
Current: Use biogas to heat digester and incomming feedstock. Value is given to
is not met, ewpense for natural gas will incur.
Return to Inputs/ GUI
Restore Default Formulas
Print Input Values
Overview 1. Current Parameters
2. Future Parameters
5. Digester & Ancillary Equip.
November 2016
23
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or
recommendation.
Printed on 100% recycled paper - process chlorine-free.
I O
W
r->l PHQ.1*

-------
		£D ST4f-
Co-Digestion Economic Analysis Tool (Co-EAT)	/
ISK-
V PR^0
10. Return to the GUI at any time using the buttons located throughout the workbook.
B

-




Co- EAT_V8.1 .xlsm - Excel
R
File
Home
Insert
Page Layout
Formulas
Data
Review
View ACROBAT
C* Tell me what you want to do
*_™ Record Macro
No =
Code
J) KX* Hil Properties
¦B =Tt L < -
j] Use Relative References '***'	M	1	q! View Code
Visual Macros	Add- Excel COM Insert Design 		.	Source
Basic	* Macro Security	jns Add-ins Add-ins •* Mode LMj ^un Dialog
Controls
1-0 Map Properties Import
jU Expansion Packs \l\ Export
Refresh Data
XML
Current
Biogas Produced (cf/yr)	1,603,335
Total Biogas Heating Energy (MBTU/yr)	729
Total Energy Needed for Heating (MBTU/yr)	2,185
Man Capacity of Digester (gal)	250,000
Feedstock Feed Rate (gal/day)	7,650
% Solids of Feedstock Fed to Digester ['/.)	2.0%
Percent Volatile Solids Reduction ['/.)	30%
Actual Hyraulic Retention Time (days)	30.7
Target Hydraulic Retention Time (days)	15.0
Available Capacity (Gal/dayT	8,030
Additional Volume Needed to Treat Feedstock (gal)	0
Future C
17,037
Future D
25,037,097
0
2,730
250,000
250,000
250 JJDr
12,772
12,772
12,772
8.0 X
8.0%
8.0%
60%
60%
60%
18.4
18.4
18.4
15.0
15.0
15.0
2,908
2,908
2,908
Mass of Biosolids (Tons^yr)
Biosolids Cost ($/yr)
Biosolids Revenue ($fyr)
1151
($40,269)
$0.00
4673
($163,568)
$0.00
4673
($163,568)
$0.00
4673
($163,568)
$0.00
4673
($163,568)
$0.00
Tipping Fees ($Zyr)
Avoided Natural Gas Costs ($/yr)
Avoided Electricity Costs ($/yr)
Avoided Vehicle Fuel ($/yr)
$0.00
$9,514
$0
$0
$268,019.50
$112,536
$0
$0
$268,019.50
$58,922
$106,188
$0
$268,013.50
$0
$0
$205,507
$268,013.50
($36,331)
$0
$271,362
Annualized Cost of Plant Upgrades ($/yr)
Annual Operations and Maintenance ($/yr)
$0
($2,500)
($13,977)
($2,500)
($93,730)
($2,500)
($76,865)
($2,500)
($76,865)
($2,500)
Net Annualized Value (S/yr)
($33,255)
$194,510
$173,332
$230,534
$260,658
Return to Inputs/ GUI
Restore Default Formulas
Print Input Values
Current: Use biogas to heat digester and incomming feedstock. Value is given to excess heat. If digester heating demand
is not met, expense for natural gas will incur.
1. Current Parameters
2. Future Parameters 3. Comparison 4. Biogas Use
5. Digester & Ancillary Equip.
11. Save the workbook to save the work you have completed.
November 2016	24	***'»%
# o \
Mention of trade names, products, or services does not convey, and should not be interpreted as conveying official EPA approval, endorsement, or	%
recommendation.
Printed on 100% recycled paper - process chlorine-free.

-------