4. Page | 3
I. Executive Summary
quasar energy group has assessed the feasibility of a regional anaerobic digester facility located in Athens,
Ohio. For this study, it was assumed that the digester facility would be located at the Athens‐Hocking
Recycling Center. This co‐location allows AHRC to take advantage of biogas produced by the digester and
as an industrial zoned area, is well suited for the type of activities that would take place at a regional
digester facility. Two scenarios were analyzed, one where the facility processes only municipal
wastewater biosolids and septic to produce compressed natural gas (CNG) as an alternative fuel for
AHRC’s truck fleet, and an alternative scenario where biosolids, septic, food waste and FOG are all
produced to make electricity to offset both the digester and AHRC electric load, and sell the excess electric
to other tenants in the industrial park.
While a regional anaerobic digestion facility will provide numerous environmental benefits to the region,
and has the potential to provide significant savings in wastewater treatment plant operations to several
municipalities, the project economics for both scenarios are not promising. In the surrounding rural area,
there is not enough material to make the project large enough to benefit from economies of scale with
anaerobic digestion and biogas utilization technologies. Furthermore, there are challenges of finding low
cost means to manage the residual byproduct from the digestion facility.
In order to make the project financially feasible, SOPEC will need to pursue creative partnerships with
funding sources. At this time no immediate grant opportunities appear applicable. In our estimation, in
order to be cash flow positive and cover interest payments on long term, state or federal low‐cost
financing programs, the project will need to solicit cash contributions to be made by nearby partnering
municipalities from their operational savings realized by sending their biosolids to the digestion facility.
Initially the most promising candidates for a regional partnership appear to be the cities of Athens,
Marietta, and Jackson, however other municipalities should be approached as well. If there is a genuine
interest in a long term commitment and partnership the facility may be possible, however without such
contributions this project will not be financially viable and should not be pursued at this time.
A summary of the project’s capital costs, annual revenue and operating expenses and simple payback
period is shown below for both scenarios, with and without municipal contributions.
Table 1: Project Financial Summary
No Contributions With Contributions ($225K/yr)
RNG Electric RNG Electric
Annual Revenue $798,861 $615,803 $1,023,861 $840,803
Annual Expenses ‐$646,990 ‐$553,017 ‐$646,990 ‐$553,017
Annual EBITDA $151,871 $62,785 $376,871 $287,785
Annual Interest Expense1
‐$259,492 ‐$252,179 ‐$259,492 ‐$252,179
Annual Earnings after Interest ‐$107,621 ‐$189,393 $117,379 $35,607
Total Capital Costs $7,588,667 $7,374,787 $7,588,667 $7,374,787
Simple Payback Period 50 117 20 26
1
Assuming USDA’s Water and Waste Disposal Loan program financing terms of 40 years at 1.63% interest
6. Page | 5
Biomass Availability Summary and Initial Digester Design Basis
The summary results of the biomass availability research and resulting initial digester design basis is
shown below in Table 3, categorized by food waste and fats oils and grease (FOG), biosolids from
wastewater treatment plants, and septic waste. Values were prescribed to % of total solids, % of volatile
solids, tip fees, and biogas standard cubic feet per minute (scfm) to estimate the material characteristics,
revenue potential and gas potential by category. These results and assumptions will be discussed in
greater detail in each corresponding section.
Table 3: Biomass Availability Summary and Initial Digester Design Basis Summary
Annual
Wet Tons
%TS %VS
Tip Fee
($/wet ton)
Annual Tip
Fee
Biogas
SCFM
Food Waste & FOG (All) 13,078 8% 92% $20.00 $174,954 51
Biosolids (All) 50,929 20% 64% $25.00 $1,273,223 185
Septic (All) N/A 1% 50% $12.00 N/A N/A
Total 64,007 17% 70% $1,448,177 235
Food Waste & FOG (Potential) 4,465 8% 91% $20.00 $0 16
Biosolids (Potential) 34,060 20% 64% $25.00 $981,768 127
Septic (Potential) N/A 1% 50% $12.00 N/A N/A
Total 38,525 19% 67% $981,768 143
Food Waste & FOG (Secured) 0 8% 91% $20.00 $0 16
Biosolids (Secured) 13,624 20% 64% $25.00 $340,599 51
Septic (Secured) 10,000 1% 50% $12.00 $120,000 1
Total 23,624 12% 58% $460,599 68
Notes:
All = All material identified within the research area
Potential = material identified within the research area for which a digester cited at AHRC could have potential to be
competitive for and secure given existing disposal costs, anticipated transportation expense and expected tip fee.
Secured = assumptions for average annual material secured and delivered to the digester facility cited at AHRC
While there is a large amount of material in the surrounding area, not all of the material will ultimately be
delivered to the digester facility. A list of potential reasons, though not exhaustive are described below:
o Material is too far away to be economically transported to the digester facility
o Waste generators already have an existing treatment process or disposal outlet that is cheaper
o A competing disposal facility will win the business of servicing the customer
o A customer is not interested or motivated to make a change from their current disposal method
Therefore the category of ‘Secured’ is what was used for the digester design basis, as it is the assumption
of how much of the identified material is estimated to be delivered to the digester facility.
7. Page | 6
As shown in the table above, the most prominent sources of biomass in Athens County and the
surrounding area are biosolids from wastewater treatment plants and septic waste. There are not many
food and beverage manufacturing facilities located in southeastern Ohio or neighboring West Virginia.
Given the lack of population density there is not much food waste or FOG generated from residential
sources or commercial establishments such as grocery stores, institutions, or restaurants. The food waste
that is generated is typically mixed with other waste streams and is categorized as municipal solid waste
(MSW) and not suitable for anaerobic digestion given the high level of contamination with non‐digestible
materials.
Note on Data Collection and Completeness
While this research gives an approximation of the potential for feedstock within the given area around
which a project can be modeled, it should not be seen as absolute or exhaustive. Not all data was readily
available from the contacts made and assumptions were used to approximate some values of material.
Our experience also shows that some sources of biomass material become available following the
construction and operation of a digester facility. Especially with private food waste and FOG generators,
many sources are unwilling to give out waste information. With the realization of a sustainable and cost‐
effective solution for waste management, generators are more willing to consider the option as an
alternative to their current outlets and there may be some material unaccounted for in this study that will
become available.
Biosolids Market
Material Overview
Wastewater treatment plants generate significant volumes of organic waste material that is removed
from the wastewater which the facilities treat each day before the cleaned water is discharged back into
waterways. This material, often referred to as biosolids, comes in a variety of forms, but most typically its
physical property is a liquid sludge which is then put through a mechanical separation device such as a
belt filter press, screw press, or centrifuge which removes a significant portion of water and changes the
material consistency to a wet solid, soil like substance, often referred to in the industry as “cake”. This
dewatered cake biosolids material can serve as a reliable base load for regional anaerobic digesters as it
is often very consistent and regular in nature. Though the biogas potential from biosolids is not as high
as food waste and FOG, the biology is consistent and neutral enough that it can serve as a buffer to higher
strength and more acidic feedstock and can stabilize digester health. Biosolids also have the benefit of
having a higher renewable credit value when used to create transportation fuel, which is described in
further detail in Section III.
Market Overview
Sixty‐two (62) wastewater treatment plants were identified in the 50 mile radius surrounding the AHRC
site, with an estimated volume of nearly 51,000 wet tons of biosolids produced annually. Of that subset,
26 facilities were determined to not be viable opportunities for the Athens located digester due to either
their long distance from the AHRC site or because they already have a reliable and cost effective solution
for biosolids management that would be difficult to compete with. It was estimated that of the remaining
36 facilities and 34,000 wet tons, approximately 40% of that material could be secured by the digester
facility.
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Table 4: Biosolids Market Summary
# of
Facilities
Annual
Wet Tons
%TS %VS
Tip Fee
($/wet
ton)
Annual Tip
Fee
Biogas
SCFM
Biosolids (All) 62 50,929 20% 64% $25.00 $1,273,223 185
Biosolids (Potential) 36 34,060 20% 64% $25.00 $981,768 127
Biosolids (Secured) TBD 13,624 20% 64% $25.00 $340,599 51
The geographic location of the various biosolids sources from nearby waste water treatment plants can
bee seen in Figure 1 below. Within the immediate vicinity of Athens (25 miles) there are several
wastewater treatment plants that have good potential to participate in the regional digester facility. To
the north and northwest there are several other opportunities, however competition becomes more
fierce with competitor facilities in the Columbus and Zanesville markets. To the southwest, near Jackson,
to the south, near Gallapolis, and to the east, near Parkersburg and Marietta, there are clusters of
potential targets as well.
Figure 1: Biosolids Market Map
13. Page | 12
Table 9: Top Food Waste Prospects
Name
Distance
to AHRC
(Miles)
Type of
Material
Annual
Quantit
y (wet
tons)
Disposal
Location
Notes
City of Athens
Commercial and
Residential
Organics
0
Pre‐ and post‐
consumer
waste
1,000
Landfill/
AHRC
Compost
The expanding
organics collection
program would be a
good high energy
potential feedstock
source
Sickle’s
Sanitation
17 FOG 1,300
Land
Application
Eager to participate
in the program if
pricing is
competitive
Liquid
Environmental
Solutions
Varies FOG 2,166
FOG
Processing
Facility
Typically haul
material back to
Cincinnati to their
own facility but may
participate to save
hauling expense
Jackie O’s2
8
Food and
beverage
manufacturing
residuals
N/A
Sewer
Disposal
Large load on sewer
system‐would have
to collaborate with
City and Jackie O’s
to reach an
equitable
agreement on cost
Ohio University Note
quasar reached out to Ohio University to inquire about waste material that they currently compost on
campus. They have two streams being utilized in their process: back‐of‐house, pre‐consumer waste from
their kitchens, and post‐consumer food waste and compostable service ware that are collected primarily
during events. They utilize their compost across campus and, without an arrangement with AHRC to
receive this material, would not likely outsource their back‐of‐house waste stream. However, they have
contamination issues with material collected at events and would be willing to redirect this waste stream
to an outside operation. At this time, this waste stream would average approximately 2 tons/day. quasar
has not included this material in the market summary as the high contamination would likely require too
expensive of processing to justify its inclusion. Processing this material through anaerobic digestion would
likely be more expensive than the tip fee and value of the gas that it could produce. However, there could
be an opportunity for AHRC to incorporate this material directly into the composting operation, or to
arrange for a future partnership with Ohio University to accept their back‐of‐house waste stream.
2
Not yet included in market summary due to low cost disposal via sewer system and not able to reach to validate
volumes of waste
14. Page | 13
Septic Market
Material Overview
Septic waste from residential septic systems is traditionally not a sought after material for anaerobic
digestion. However, due to the rural nature of southeastern Ohio and the need for a dilute liquid stream
to blend into the cake biosolids to create a pumpable liquid feed to the digester, it may prove to beneficial
to incorporate. Where cake biosolids are traditionally upwards of 20%TS; septic tank material is
approximately 1%TS and therefore a good agent to dilute to the target 10‐12%TS feed for the digester.
Market Overview
quasar did not perform exhaustive research into the septic market but rather used a high level analysis to
determine that sufficient quantity would be available to utilize septic as a dilution source. In the 23 county
Southeast District, the Ohio Department of Health states that there are nearly 90,000 existing systems
reported through regular survey activities. At an average of 1,000 gallons per tank and a cleanout at a
conservative rate of once every 5 years this equates to an estimate of 18,000,000 gallons or nearly 75,000
tons of septic waste per year. Not all of this material would be accessible to the digester given
transportation costs, competitor disposal facilities, and some haulers who choose to land apply material,
but at a capture rate of approximately 15% of this figure there would be sufficient septic to dilute the
expected biosolids.
Figure 2: Southeast District Ohio EPA/Ohio Department of Health
Tip Fee Pricing
Tip fees for receiving septic material range between $.04 and $.08 per gallon. At this stage a tip fee of
$.05/gallon was used for the analysis.
16. Page | 15
geographies, the tip fees will need to stay low to attract sufficient volumes of material given the
transportation distance.
Table 11: Competitor Facilities
Company Name
Facility
Type
City
Accept
Biosolids?
Accept
Liquids?
Estimated
Tip Fees
($/wet ton)
SWACO Landfill Columbus, OH Yes No $50
Athens‐Hocking
Reclamation Center
Landfill Nelsonville, OH Yes N/A $25‐$35
Pine Grove Landfill
(Republic Services)
Landfill Amanda, OH Yes Yes N/A
Tunnel Hill Landfill Landfill New Lexington, OH Yes No $25‐$40
Northwestern Landfill
(Waste Management)
Landfill Parkersburg, OH Yes N/A $25‐$35
Beech Hollow Landfill
(Rumpke)
Landfill Wellston, OH Yes N/A N/A
Central Ohio Bioenergy
(COBE)
Digester Columbus, OH Yes Yes $35‐$45
Zanesville Energy Digester Zanesville, OH Yes Yes $25‐$40
Zanesville Tree Farm Tree farm Zanesville, OH Yes No $25‐$30
Charleston Landfill
(Waste Management)
Landfill Charleston, WV Yes No N/A
Gallia County Landfill
(Waste Management)
Landfill Bidwell, OH Yes No N/A
Sycamore Landfill
(Republic)
Landfill Hurricane, WV Yes No N/A
DSI Landfill (Waste
Management)
Landfill Hurricane, WV Yes No N/A
The geographic location of these competitor facilities can be found in Figure 1 on page 7.
18. Page | 17
Biogas Production
Following the generation of the digester design basis based on the determination of the most likely
feedstock sources, quasar relied on our operational experience and input from our laboratory to estimate
the biogas potential (cubic feet of gas production per pound of volatile solids) and methane content for
each feedstock. quasar was able to estimate the gas production and energy potential of the digester as
follows.
Table 13: Energy Potential per Feedstock
Biogas
SCFM
CHP
(kwh)
RNG‐
CNG
(DGE)
Food Waste & FOG (Secured) 16 584,159 40,822
Biosolids (Potential) 51 1,798,876 125,708
Septic (Secured) 1 26,996 1,887
Total 68 2,410,031 168,417
Combined Heat and Power (CHP) Option
The combined heat and power (CHP) option includes a gas cleaning skid to remove impurities such as
moisture, hydrogen sulfide and siloxanes from the biogas before being burned in either an internal
combustion engine or microturbine which is connected to a generator to produce electricity. The waste
heat that comes from the combustion engine or microturbine can be captured and utilized to meet the
head needs of the anaerobic digester.
With this energy production, the facility can completely cover the electric load of the digester operation,
100% of the electric consumption at the Athens‐Hocking Recycling Center, and have excess electric for
sale. The table below shows the proposed distribution of the electric produced by the CHP, assuming a
90% equipment uptime. The CHP would cover the onsite electric and thermal load of the digester
operations. Per information received from AHRC, the recycling facility’s annual electric consumption is
approximately 102,000 kWh or an average load of 12kW. The table below illustrates this distribution of
electric.
Table 14: Project Electric Distribution
kW kWh
Total Electric Production 236 2,068,093
Average Digester Parasitic Load ‐158 ‐1,382,471
Average AHRC Electric Usage ‐12 ‐102,000
Balance of Electric for Sale 132 583,622
The digester parasitic load and AHRC electric usage should be valued at the generation cost of electricity,
approximately $.08/kwh for the Athens area. The balance of electric should try to be sold behind the
meter to other tenants of the industrial park so to maintain the relatively higher value of $.08/kwh versus
19. Page | 18
the wholesale rate. Renewable Energy Credits (RECs) can be sold into out of state markets, currently that
value is around $7‐$8 per MWh.
The CHP should be able to cover 100% of the thermal load of the digester with excess heat left over for
use at AHRC.
Table 15: Project Thermal Load
MMBTU
Total Thermal Production 10,171
Average Digester Parasitic Load 4,326
Balance of Thermal Heat for Use 5,845
Renewable Natural Gas (RNG) – On Site Compressed Natural Gas (CNG) Vehicle Fueling Option
Renewable natural gas is an industry term for a natural gas equivalent fuel that is produced typically from
anaerobic digestion or landfill gas facilities. To get to natural gas grade the biogas must pass through
several cleaning steps to remove not only moisture, hydrogen sulfide and siloxanes but also carbon
dioxide. Furthermore the gas must be pressurized to be utilized as compressed natural gas (CNG) as an
alternative vehicle fuel to diesel or gasoline. There are several different technologies that could be utilized,
the most common for small scale applications such as these are membrane and pressure swing adsorption
(PSA) systems. A summary of the differences between biogas and renewable natural gas (RNG) can be
seen below.
Table 16: Biogas and RNG Constituents
Biogas RNG
CH4 50‐65% >97%
CO2 34%‐50% < 2%
O2 < 2% < .2%
N2 < 5 % < 1%
H2S < 500 ppm < 4 ppm
Pressure < 1 psi > 3600 psi
AHRC Fleet Fueling
Once in the format above, the RNG can be used as an alternative fuel to diesel to fuel AHRC’s 16 trash
trucks which consume on average 75,000 gallons diesel per year. However, AHRC must first convert their
vehicles, to CNG. The 16 vehicles are on lease and over the next 3‐5 years as the digester is being
developed and built could be converted over to CNG. At an outright purchase the CNG vehicles would be
approximately $35‐$40K more than the current diesel truck costs, representing a cumulative expense of
$600,000 above the capital cost of diesel vehicles. There may be a grant or low cost financing
opportunities available for this investment as well as tax credits and incentives. Without incentives, the
fuel savings alone (assuming a sale price of $2.25 per diesel gallon equivalent of CNG) is $41,250 a year,
representing a payback of approximately 15 years. There are added environmental benefits of running a
CNG fleet which has fewer emissions that diesel vehicles. The vehicles would be fueled via a time fill
22. Page | 21
RIN Pricing
Table 19: February 2020 RIN Pricing ($/RIN)
D3 D4 D5 D6
$1.58 $0.48 $0.48 $0.34
While RIN trading can be extremely lucrative for a renewable fuel project, the market is variable based on
supply and demand, and so there is a significant amount of risk associated with this revenue source. The
figure below shows the average RIN pricing trends since 2013 for all four fuel types. This also demonstrates
the substantial value that D3 RINs have when compared to other categories.
Figure 4: Historical RIN Prices
24. Page | 23
IV. Effluent Management
Effluent Volumes
Within the digestion process, the methanogenic bacteria reduce the volume of volatile solids by an
estimated 50‐60% depending on feedstock inputs, however the non‐volatile solids and the water pass
through the system without any volume reduction. This means that generally ~93% of the inputs come
out of the backend of the digester as outputs. The management of the post‐digestion effluent can often
prove to be the most challenging aspect of a potential digestion project, depending on the location and
the available outlets for beneficial reuse. Based on the volumes in the design basis, if all feedstock types
are included, we have predicted the following effluent streams for post‐digestion. The table below also
shows solid and liquid streams, following a potential dewatering process that could be implemented
following digestion.
Table 20: Digester Effluent Volumes
DIGESTER FEED
Feedstock Wet Tons %TS %VS Dry Tons Gal
Tons
VS
Food Waste / FOG 12 8% 91% 1 2,937 1
Biosolids 37 20% 64% 4 8,962 3
Septic 27 1% 50% 5 6,578 4
Total Blended Biomass 77 12.4% 85.6% 10 18,477 8
EFFLUENT Per Day Basis (based on 7 day/wk digester feeding and dewatering)
EFFLUENT Wet Tons %TS %VS Dry Tons Gal
Tons
VS
Effluent out of Digester Before Dewatering 72 6.5% 70% 4.65 17,297 3
Per Day Basis (7 days of feeding)
26. Page | 25
As shown in the table above, most of the effluent management options require further concentrating the
solids in the effluent through a mechanical separation process with equipment such as a screw press, belt
filter press or a centrifuge. When this process takes place the resulting liquids that are separated from the
material need to be managed in some way, most commonly through discharge to the local sewer system.
The challenge is that these liquids are high in nutrients that may exceed the capacity of the small
wastewater treatment plants in the area. The expected effluent characteristics can be seen below.
Table 22: Effluent Characteristics
BOD (mg/L) TN (mg/L) P (mg/L)
Digester Effluent 10,025 7,600 3,994
In conversations with wastewater treatment plant in The Plains, which the AHRC site is connected to‐
there is no ability to accept this material due to its high strength. Furthermore, a similar conversation as
had with the City of Athens to explore trucking the material to a discharge point, but initial indications are
that they would not be able to accept this liquid stream either. There are options to put in pre‐treatment
systems to further reduce the nutrient load, however in order to get to a level that may be acceptable to
the plants it would likely require a significant capital investment that drives the cost of effluent
management higher than is economically feasible. In effect, it would require building a mini wastewater
treatment plant on site to be able to discharge to small nearby wastewater plant. Given these limitations
of the nearby sewer infrastructure the most viable alternative appears to be liquid land application.
Liquid Land Application
Class A
Land application can be a challenging avenue for management residual effluent, but can be successful if
done correctly. The first recommendation would be to install a Class A thermal treatment system which
pasteurizes the material, reduces the pathogen count and creates an exceptional quality Class A product
that is recognized by the Ohio EPA. Achieving this Class A product, instead of producing the Class B
material that is typical of most digester operations in Ohio opens up much more avenues for land
application as there are no permits required for fields and farmers are more receptive to the higher quality
product. A significant marketing and educational effort will need to be made to alert farmers to the
availability of this material and to explain the agronomic benefits of using the material.
Land Availability
A large bank of land that the effluent will be applied on is required for a successful program as well. At an
application rate of 9,000 gallons per acre per year, a minimum of 750 acres would be needed, but ideally
a reserve of 2,000+ acres would be available in case farmers change their growing practices and to have
contingencies in place. One natural starting point would be to contact farmers that have existing
familiarity with biosolids land application. Below is a list of the total acres of Class B approved and
permitted fields in the area. Many of these fields should be available if the municipalities involved send
their biosolids to the regional digester instead of direct to land application. Key municipalities to target
for collaboration to transfer fields include Lancaster, Logan, Athens, Ravenswood, The Plains, and
Nelsonville. Combined these municipalities have 3,000 acres permitted.
27. Page | 26
Table 23: Existing Permitted Land Application Sites
County Facility Permitted Acres
Perry Zanesville Energy, LLC 3,067
Perry Newark WWTP 1,447
Perry Lancaster WPCF 509
Perry New Lexington WWTP 421
Perry New Lexington Tree Farm, LLC 311
Perry Central Ohio Bioenergy 192
Perry Columbus Southerly WWTP 83
Perry Somerset WWTP 47
Perry McConnelsville WWTP 41
Perry Heath WWTP 21
Perry Logan WWTP 7
Perry N/A 4
Perry Subtotal 6,150
Hocking Lancaster WPCF 784
Hocking Logan WWTP 552
Hocking Central Ohio Bioenergy 320
Hocking Subtotal 8,209
Meigs Ravenswood, WV WWTP 846
Meigs Pomeroy WWTP 383
Meigs Syracuse‐Racine Regional SD WWTP 149
Meigs Rutland WWTP 47
Meigs Athens WWTP 41
Meigs Subtotal 1,465
Athens Athens WWTP 674
Athens The Plains SD No 1 Buchtel 152
Athens Nelsonville WWTP 125
Athens Trimble Township WWTP 96
Athens Union STP 78
Athens Albany WWTP 63
Athens Chauncey 54
Athens Subtotal 1,242
Morgan McConnelsville WWTP 497
Morgan Stockport WWTP 192
Morgan Roseville WWTP 97
Morgan Beverly WWTP 70
Morgan Trimble Township WWTP 40
Morgan ODNR Burr Oak SP Marina No 1 WWTP 11
Morgan Subtotal 907
Vinton Columbus Southerly WWTP 110
Vinton Chilicothe WWTP 63
Vinton Subtotal 173
Grand Total 18,147
28. Page | 27
Storage
The other essential element to a successful land application program is having sufficient storage capacity
to allow for year round space to hold effluent production. Without storage capacity it is nearly impossible
to juggle the seasonal demands of farmers and weather limitations with the daily delivery of new
feedstock into the plant. Having storage allows for there to be a place for effluent to go year round and
then to have sufficient material to satisfy farmers needs seasonally when they need fertilizer. The most
common times of year for application are spring, fall and summer after hay cuts. We recommend a
minimum of 12 months of storage capacity, either in the form of a lagoon or a large tank. At the industrial
park where the AHRC is sited there is some land available for purchase or lease that could provide space
for a lagoon. It is not an ideal site given the neighboring businesses and limitations on set backs from
nearby roads and occupied buildings. However, given the lack of other alternative options at this stage a
lagoon has been considered. If the project is pursued alternative locations for a lagoon at nearby farm
fields could be considered.
Public Relations
There can be public relations challenges associated with building and operating a storage and land
application program. If a lagoon is constructed, it will occupy 3‐5 acres of land and material can be odorous
if not managed properly. Seasonally there will be large volumes of trucks taking material from the storage
facility to the fields. The benefit of the AHRC site is that it is an existing industrial park with a limited
population nearby. Nonetheless, an outreach effort with the other industrial park tenants should be
completed to mitigate any concerns.
31. Page | 30
Table 25: Cost of Work Estimate Detail
Cost of Work Detail Millions
Digester $0.71
Process Piping $0.17
Operations Building $0.43
Sitework $0.19
Solids & Liquids Receiving $0.47
Gas Upgrade $1.25
Class A $0.36
Lagoon $0.30
Electric $0.35
Feedstock Tank $0.16
Heating $0.18
Miscellaneous $0.08
Total Cost $4.65
Solids/Liquids Receiving
The facility will have capabilities for both solid and liquid feedstock receiving. The solids receiving module
includes a hopper with twin augers, an in‐line Muffin Monster grinder and shredder, and open hopper
pump. The macerator will reduce the size of solids material to less than ¼” particle size and blended with
liquid feedstocks if needed so that it is a pumpable slurry and can be sent into the feedstock equalization
tank. The solids receiving module is covered to reduce odors and for weather protection when not in use
and is constantly ventilated to an odor control system such as a biofilter.
Figure 7: Solids Receiving Equipment
All outside liquid waste can be gravity fed directly from tankers through a screening operation to remove
any trash, rags or other contamination and then into a subgrade concrete liquid receiving pit. The liquids
receiving vessel can accept low total solids material, in the form of liquid food processing waste or fats,
oils and grease (FOG). Material will be pumped from the liquids receiving pit to the feedstock equalization
tanks and can also be pumped to the solids receiving pit to be used as dilution as needed for higher total
solids material.
32. Page | 31
Feedstock Equalization
Following receiving, feedstock will be pumped to a 75,000‐gallon feedstock equalization tank, which
provides a hydraulic short‐term storage buffer in front of the digester tank. This tank facilitates the onset
of the hydrolysis phase of anaerobic digestion and allows for a variable feedstock stream to mix together
so that the digesters are dosed with a steady, homogenous feed. The tank is a steel rolled tapered panel
(RTP) bolted design with an epoxy coating for corrosion prevention. The roof of the tank is a minimally
sloped steel cone. A side‐entry propeller mixer is included to prevent solids from settling to the bottom
of the tank.
Class A Pasteurization System
Prior to the digestion process, the incoming feedstock will pass through a series of heat exchangers and
three batch tanks while being pasteurized per the EPA’s 503 regulations for time and temperature. One
tank will fill, while one tank is held at a temperature of 160F for approximately 30 minutes to reduce
pathogen content in the material. This pasteurization step will allow the material to meet a Class A
designation.
Digestion
Following equalization, the feedstock stream will be heated to 100‐degrees using a glycol heat loop and
pumped to the digesters. quasar has sized one steel‐bolted, epoxy‐coated tank with a working capacity
of 500,000‐gallons for the project. This tank would have a flexible membrane roof that will serve to
regulate the gas pressure within the tank and to store biogas until it is piped to the gas upgrade during
the hours of fueling demand. The tank will have 2” of polyisocyanurate insulation with painted aluminum
sheathing affixed to the tank exterior. Mixing would be achieved through a hydraulic jet mix system where
the tank contents are recirculated through a series of nozzles within the tank. Feedstock temperature will
be maintained through a series of heat exchangers, with heat being provided by natural gas fed boilers.
Gas Upgrade & CNG Fueling
After digestion, the biogas will be routed to a gas upgrade facilities. The gas upgrade system will treat
inlet biogas to pipeline grade natural gas specifications. The anaerobic digester tanks will operate at a
pressure of 4”‐6” of water column and will be sent through a compressor to take the pressure to up to
150 psig. A dehydration step will remove moisture prior to entering the CO2 removal step. There will be
an upfront H2S removal step where the biogas will pass through an iron based bulk media to remove
Figure 8: Digester facility receiving solid and liquid feedstock loads
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H2S before further treatment. The main step in the gas upgrade process is removal of CO2, through a
membrane that separates the CH4 molecules from the CO2 molecules. A compressor will take the
product gas and raise the pressure to the required 36000+ psig for vehicle fueling. Ten slow fill posts
with two hoses each will fuel the AHRC trash trucks where they park overnight.
Flare and Odor Control
The odor from the solids and liquids receiving
areas will be captured and exhausted to an
onsite biofilter, approximately 15’x15’ in size.
The outside of the biofilter is constructed with
wooden slats with an impermeable
membrane inside to prevent any leakage of
untreated air. Air is diverted through the
bottom of the biofilter with perforated
drainage tile where it is forced through
hardwood mulch designed specifically to
capture and eliminate odor emanating from
the feedstocks. The wood chips develop a
biofilm on the surface of the media. As the
odorous air flows past the wood chips, the
odor particles are removed by the
microorganisms inhabiting the media. A
blower from each feedstock receiving pit will create a constant negative pressure out of the pit and to the
biofilter before it passes into the surrounding air.
Lagoon
An earthen, 6M gallon clay lined lagoon will be constructed adjacent to the digester system at the AHRC
site. The lagoon will be an irregular shape to meet set back requirements within an approximately 600’ x
300’ footprint with a depth of 10’ feet. The maximum liquid level will be approximately 8’ to allow for
adequate freeboard. The lagoon will have a ramp for easy access in and out for lagoon cleanouts and will
have a permanent pumping station for filling tanker trucks that will transport the material to nearby farm
fields. Markers will be present to clearly identify how much material is in the lagoon and how much
storage capacity remains.
Alternative Design Elements
CHP
As an alternative, the financial model also explores replacing the gas upgrade and CNG fueling station with
a combined heat and power system (CHP) to produce electricity and heat. The biogas produced in the
digester will be piped to a 333kW microturbine unit. Gas conditioning equipment is included prior to the
microturbine to pressurize the gas, remove moisture, H2S and siloxanes. The byproduct of the
microturbine is heat, which is collected from the jacket cooling water and from the exhaust. This waste
heat is used in a heat loop to provide for both the digester and Class A heating needs.
Under this alternative food waste and FOG would be accepted in addition to biosolids and septic waste.
Figure 9: Biofilter for Odor Control
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Table 26: Capital Cost Estimate‐Alternate Microturbine Design
Description Millions
Design $0.7
General Conditions $0.7
Total Cost of Work $4.4
Design‐Builder Fee $0.4
Construction Engineering Support $0.1
Commissioning $0.1
Bonding $0.1
Contingency $0.7
Interconnection Cost $0.2
Total Price Cost $7.4
Cost of Work Detail Millions
Digester $0.71
Process Piping $0.17
Operations Building $0.43
Sitework $0.19
Solids & Liquids Receiving $0.47
Microturbine $1.00
Class A $0.36
Lagoon $0.30
Electric $0.35
Feedstock Tank $0.16
Heating $0.18
Miscellaneous $0.08
Total $4.40
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VI. Project Economics
Financial Model
Using the variables as described above, quasar compiled a financial model for the proposed project. This
models all revenue sources including tip fee revenues and biogas sales as well as all operational costs
including plant staffing and maintenance, and effluent management costs. A yearly snapshot of the
project economics can be seen in the table below. The full model can be found in the appendix.
Table 27: Yearly Project Financials
Annual Financial Summary
No Contributions With Contributions ($225K/yr)
RNG Electric RNG Electric
Tip Fees $ 460,599 $ 549,904 $ 460,599 $ 549,904
Energy Revenue $ 338,263 $ 65,898 $ 338,263 $ 65,898
Municipality Contributions $ ‐ $ ‐ $ 225,000 $ 225,000
Total Revenue $798,861 $615,803 $1,023,861 $840,803
Effluent Management ‐$218,701 ‐$259,033 ‐$218,701 ‐$259,033
Facility O&M ‐$285,750 ‐$285,750 ‐$285,750 ‐$285,750
Facility Utility Expense ‐$142,539 ‐$8,234 ‐$142,539 ‐$8,234
Total Expenses ‐$646,990 ‐$553,017 ‐$646,990 ‐$553,017
EBITDA $151,871 $62,785 $376,871 $287,785
Interest Expense ‐$259,492 ‐$252,179 ‐$259,492 ‐$252,179
Earnings after Interest ‐$107,621 ‐$189,393 $117,379 $35,607
Facility Cost $7,588,667 $7,224,787 $7,588,667 $7,224,787
Utility Interconnect Cost $0 $150,000 $0 $150,000
Total CAPEX $7,588,667 $7,374,787 $7,588,667 $7,374,787
Simple Payback (Years) 50 117 20 26
The results of the financial model are not promising if the digester is to be considered on the revenue and
expenses associated with the digester operations alone. The estimated simple payback period is 50 to 117
years, depending on the gas use. Private sector funding sources would not view this as a finically viable
project and even with attractive low interest loan terms the project cannot support its interest payments.
The project suffers from being small scale due to a lack of available material in the surrounding rural area.
The material that can be secured commands only a modest tip fee value. Furthermore, there is not a large
market for the resulting energy produced from the digester. With the CNG option a good portion of the
gas is flared and the intricacies of the RFS program provide a disincentive to accept food waste. With the
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CHP option there is limited value to the electric. Finally‐there is not an ideal effluent management
solution, therefore there is an added cost of constructing a lagoon, the challenge of securing sufficient
acreage for land application and a near requirement to produce Class A material.
Community Benefits
Not captured in the project financial model for the digester are the cost savings that participating
municipalities could receive from sending their biosolids to the regional digester. Given the digester
operation’s preference for non stabilized biosolids, facilities that are aerobically or anaerobically
digesting could take their existing systems offline, saving significant utility consumption and avoiding
future maintenance and repair costs. Furthermore, the cities would recognize savings on their sludge
management expenses by avoiding the landfill and potentially having lower costs of disposal than
running their own land application programs. Three cities that were particularly eager to make efforts to
realize these savings were the City of Athens, the City of Jackson and the City of Marietta. Estimated
savings for each City can be seen in the table below.
Table 28: Estimated Annual Municipal Savings
Category Athens Jackson Marietta Total
Electric Savings $ 90,720 $ 120,000 $ 90,720 $ 301,440
Disposal Savings $ 27,000 $ ‐ $ ‐ $ 27,000
Maintenance Savings $ 10,000 $ 15,000 $ 10,000 $ 35,000
Total $ 127,720 $ 135,000 $ 100,720 $ 363,440
If these cities and others can be convinced to make capital contributions towards the project, then the
project may become more economically feasible. For example if participating communities that are
recognizing additional economic benefits made annual payments to the digester owner from their
operational savings in the cumulative amount of $225,000 per year then the project simple payback
would improve to 20 and 26 years for each option and may become economically feasible. Any
additional revenue collected from partnering municipalities will only improve the project financials.
VII. Project Ownership and Financing Options
Project Ownership
There are several potential entities that could become the ultimate owners and operators of the
digester facility, including:
o SOPEC
o AHRC
o Athens County
o City of Athens
The ultimate owner of the facility may impact the type of funding and low cost financing that the project
would be eligible for given that SOPEC and AHRC are non‐profits and the City of Athens and Athens
County are municipalities.
