l&STAR
fWrng"^
United States
Environmental Protection
Agency
Office of Air and Radiation
Washington, DC 20460
&EPA AgSTAR Digest
EPA-430-F-02-028
Winter 2003
www.epa.gov/agstar
AgSTAR 2002 Highlights 1
Current Status of Farm-scale Digesters 2
State Programs Foster New Farm-scale Digesters 8
Fixed-Film Digesters: A Case Study 10
Comparing Three Swine Waste Management Systems 12
AgSTAR 2002 Highlights
Development of anaerobic digesters
for livestock manure treatment and
energy production has accelerated
at a very fast pace over the past few
years. In the last two years, the
number of operating digesters has
increased by nearly 30 percent.
from 31 to 40. with an additional
seven currently in start-up or under
construction. Most of these
digesters are farm-scale systems;
however, centralized digester appli-
cations for dairy operations are also
emerging. One centralized system
is already operating in California.
and another is being developed in
Oregon. To help support these
activities, the AgSTAR Program is
developing the second edition of
the Industry Directory for On-Farm
Biogas Recovery Systems, which
provides information on system
designers and developers and
equipment manufacturers and dis-
tributors responsible for expanding
the use of digestion technology in
the livestock industry. Look for this
publication on the AgSTAR Web
site (www.epa.gov/agstar).
State anaerobic digest Jon
also play a significant
role in this expansion as they con-
tinue to grow and support digester
projects in a number of innovative
ways. For example, a $10 million
cost-share program for commercial-
ly demonstrated anaerobic digestion
technologies is available to dairy
farms through the California
Energy Commission (CEC). In
addition, the CEC administers a sis-
ter program that provides funding
for the demonstration of emerging
technologies at commercial scale.
The New York State Energy and
Research Development Authority
(NYSERDA) and the Wisconsin
Energy Bureau have similar pro-
grams available to assist livestock
producers in establishing digester
technologies at their farms.
Some states are addressing key
energy policy issues in order to
foster further expansion of biogas
energy technologies. For example,
California and New York have
recently enacted net metering laws
that enable utility customers to use
their own electricity generation to
offset their consumption over
monthly billing periods.
Federal funding opportunities
will also be playing a larger role in
supporting the development of
anaerobic digestion systems. The
Federal Farm Security and
Rural Investment Act of 2002
will provide funding under the
Environmental Quality Incentives
Program (EQIP) and the Renewable
continued on page 2
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2 AgSTAR DIGEST • WINTER 2003
A6STAR 2002 (continued)
Energy Systems sections of the
Energy Title. Potential applicants
are encouraged to visit
www.usda.gov/farmbill or to
contact local USDA officials for
more information on these opportu-
nities. Also, check the AgSTAR
Web site (listed on page 1) for
updates on this important funding
mechanism.
AgSTAR has completed the first of
a series of comparative environ-
mental performance evaluations
to provide the agricultural commu-
nity with key information necessary
to make informed waste manage-
ment selection and upgrade
decisions. A summary of this first
assessment, which compares the
environmental performance of cov-
ered lagoons to open treatment and
storage lagoons for swine manure,
is found on page 12. AgSTAR con-
ducted this evaluation over a
two-year period at commercial
swine farms in North Carolina,
working in conjunction with North
Carolina State University. Other
evaluations are in progress, includ-
ing a collaborative effort with
NYSERDA that compares a con-
ventional dairy separation and
waste storage system to a dairy
plug flow digester with fiber recov-
er}- and liquid storage. These results
are expected to be available
sometime during the winter season.
AgSTAR is also in the initial stages
of a collaboration with the
Wisconsin Biogas Development
Group on a similar evaluation.
A new digester technology
applicable for flush manure han-
dling appears to be ready for
commercial application following
four years of development. Details
about this fixed-film digester, up
and running in Alachua County,
Florida, and developed by Dr. Ann
Wilkie of the University of Florida,
appear on page 10.
Finally, AgSTAR has been busy
updating information about the
current of
in the United States.
We completed our first update in
late 1999 (AgSTAR Digest, 2000
edition) and the second during
the summer of 2002. A summary
discussion and tables listing all
operating and under-construction
digester systems can be found
below and on pages 3-7.
of
In the past two years, the number of
operating farm-scale digesters has
increased by nearly 30 percent. In
addition, seven additional systems
are currently under construction or
in start-up. Of the 40 operating
digester systems, nine are at swine
farms, 29 are at dairy farms, one is
at caged layer farms, and one is at a
duck farm. Three of these are cen-
tralized systems that provide
manure treatment for surrounding
farms. Tables 1 and 2 provide infor-
mation about each of these digester
systems. In addition, AgSTAR esti-
mates that at least 40 additional
systems are currently in various
stages of planning and should come
on line during the next year or so.
In 35 of the 40 operational systems,
the captured biogas is used to gen-
erate electrical power and heat.
These produce the equivalent of
appoximately 4 MW per year.
The remaining systems flare the
captured gas for odor control and
reduce methane emissions by
Figure 1. U.S. Farm-scale Digesters
about 7.400 tons on a carbon-
equivalent basis. In total, the
operating digesters prevented
nearly 124,000 metric tons of
methane, on a carbon-equivalent
basis, from entering the
atmosphere.
Figure 1 above illustrates the his-
torical trends and the large
increases coinciding with the
AgSTAR Charter Farm Program
from 1997 to 1999 and continued
growth as a result of state programs
that emerged in the following years.
-------
Table 1. Operating U.S. Digesters, October 2002
Location
CA
CA
CA
CA
CA
CA
CA
CO
CT
CT
Digester Type
Mesophilic plug flow,
flexible top
Mesophilic plug flow,
flexible top
Unheated partially
covered lagoon
Thermophilic-mesophilic
complete mix tanks
Mesophilic plug flow,
fixed top
Unheated covered lagoon
Unheated partially covered
lagoon
Mesophilic complete mix,
flexible top
Mesophilic complete mix
Mesophilic plug flow,
flexible cover
Year Animal Type/
Operational Population
1982 Dairy; 400 milkers
2002 Dairy; 650 milkers
1998 Dairy; 200 to 300
cows (includes dry
stock and heifers)
2001 Dairy; 5,000
2002 Dairy; 7,000 milkers,
3,000 other
1 982 Swine; 300 sows farrow-
to-finish
2000 Dairy; 200 milkers,
50 dry
1 999 Swine; 5,000 sow farrow-
to-wean and 1,200 growing
pigs (replacement stock)
1997 Dairy; 600 milkers
1997 Dairy; 200 milkers
Manure Handling
Method
Scrape
Solids separator;
scrape
Flush
Vacuum scrape
Vacuum scrape
Flush
Flush and scrape
Pull plug
Scrape
Scrape
Approximate
Total
Installed
Cost
$200,000
$386,000
$225,000
Not available
$1.8M
$220,000
Not available
$368,000
$450,000
$149,000
Biogas End-use
Electricity and hot water
Electricity and hot water
Flare
Electricity and hot water
Electricity and hot water
Electricity and hot air
Electricity and hot water
Electricity
Electricity
Hot water and flare
Operational
Output
kWhr/hr
40
100
0
200
500
25
25
50
55
0
Methane
Reduction
(MTCQ2E/
year)
1,186
2,965
800
119
296
741
741
1,482
1,631
1,387
FL Unheated fixed film
2000
Dairy; 500 cows
Hydraulic flush $150,000
Hot water and flare
3,467
-------
Table 1. Operating U.S. Digesters, October 2002
Location
IA
IA
IA
IA
IA
IL
IL
IL
MD
Digester Type
Unheated bank-to-bank
covered lagoon
Mesophilic complete mix,
flexible top
Mesophilic plug flow,
fixed top
Mesophilic plug flow,
fixed top
Mesophilic plug flow,
fixed top
Mesophilic bank-to-bank
covered lagoon
Mesophilic plug flow,
flexible top
Mesophilic plug flow,
flexible top
Mesophilic slurry loop tank
Year Animal Type/
Operational Population
1998 Swine; 3,000 nursery pigs
1996 Swine; 5,000 sows
farrow-to-wean
2002 Dairy; 480 cows
2002 Dairy, 800 cows
2002 Dairy; 170 (100 milkers,
20 dry)
1998 Swine; 8,300 finishing hogs
Dairy; 1,400 lactating
Dairy; 2,000 lactating
1994 Dairy; 120 lactating,
70 heifers
Manure Handling
Method
Pull plug
Pull plug
Scrape
Scrape
Scrape
Pull plug
Scrape
Scrape
Scrape
Approximate
Total
Installed
Cost
$15,000
$500,000
$348,000
$450,000
$200,000
$140,000
$1.2M
$875,000
$500,000
Biogas End-use
Flare
Electricity
Electricity and heat
Electricity and
hot water
Hot water
Hot water and flare
Electricity
Electricity
Flare
Operational
Output
kWhr/hr
0
50
80
100
0
0
360
246
0
Methane
Reduction
(MTC02E/
year)
1,738
1,482
2,372
2,965
1,179
2,380
10,673
7,293
1,317
Ml Plug flow
1981 Dairy; 730 milkers
Scrape
$150,000
Electricity
5,061
-------
Table 1. Operating U.S. Digesters, October 2002
Location
MN
MS
NC
NY
NY
NY
NY
NY
PA
PA
PA
Digester Type
Mesophilic plug flow,
flexible top
Unheated bank-to-bank
covered lagoon
Unheated bank-to-bank
covered lagoon
Mesophilic plug flow,
flexible top
Mesophilic complete
mix tank
Mesophilic complete mix,
flexible top
Mesophilic plug flow,
flexible top
Mesophilic, fixed film tank
Mesophilic slurry loop,
fixed top
Mesophilic plug flow,
flexible top
Mesophilic complete mix
Year
Operational
1999
1998
1997
1998
1985
2001
2001
2001
1983
1985
1985
Animal Type/
Population
Dairy; 850 milkers
Swine; 145 pigs
Swine; 4,000 sows
farrow-to-wean
Dairy; 500 to 550
Dairy; 295 milkers
Dairy; 560 milkers, 40 dry
Dairy; 850 milkers, 100 dry
Dairy; 100 milkers
Dairy; 250 milkers
Swine; 4,000
Swine; 1 ,000 sows
farrow-to-finish
Manure Handling
Method
Scrape
Recycle flush
Pull plug and
gravity flow
Scrape
Scrape
Scrape and gravity flow
Continuous scrape
Gutter flush with liquid
solids separation
Scrape
Scrape
Scrape
Approximate
Total
Installed
Cost
$355,000
$27,000
$290,000
$295,700
$500,000
$350,000
$400,000
Not available
$80,000
$225,000
$325,000
Biogas End-use
Electricity and hot water
Flare
Electricity and hot water
Electricity and hot water
Electricity and hot water
Electricity and hot water
Hot water
Hot water
Electricity and hot water
Electricity and hot water;
flare
Electricity and hot water
Operational
Output
kWhr/hr
130
0
41
44
25
130
0
0
45
130
33
Methane
Reduction
(MTC02E/
year)
3,854
84
2,317
3,640
2,045
3,854
1,779
693
1,334
3,854
1,666
-------
Table 1. Operating U.S. Digesters, October 2002
Location Digester Type
PA Mesophilic plug flow,
slurry loop, fixed top
Year Animal Type/
Operational Population
1983
Manure Handling
Method
Chicken; 350,000 layers Scrape
Approximate
Total
Installed
Cost
$125,000
Biogas End-use
Methane
Operational Reduction
Output (MTC02E/
kWhr/hr year)
Electricity and hot water 150
4,447
PA Mesophilic slurry loop,
fixed top
1979,1981, Dairy; 2,300 milkers
1984 (three
digesters)
Scrape
$225,000 each Electricity and hot water 350
10,376
VT Mesophilic plug flow,
flexible top
1982
Dairy; 340 milkers
Scrape
$300,000 Electricity and hot water 28
(steam)
2,357
Mesophilic plug flow,
flexible top
2002
Dairy; 900 cows
Scrape
$425,000
Electricity and hot water 125
3,706
Mesophilic complete mix,
fixed top
1988
Ducks; 300,000
Scrape
$500,000
Digester heat and
electricity
180
5,336
Mesophilic two-stage
mixed, fixed top
2002
Dairy; 600 milkers
Scrape
$550,000 Digester and dairy heat,
electricity, and hot water
135
4,002
Mesophilic two-stage
mixed, fixed top
2002
Dairy; 750 cows
Recycle flush
$487,500
Electricity, heat, and
hot water
160
4,743
Mesophilic two-stage
mixed, fixed top
2002
Dairy; 2,800 milkers
Scrape
$1.4M
Digester heat, dairy heat 425
solids drying, electricity,
hot water, and flare
12,600
-------
Table 2. Digesters Under Construction and in Start-up, October 2002
Digester
Location Type
Animal Type
and
Population
Manure
Handling
Method Estimated Installed Cost
Mesophilic two-stage mixed, fixed top Dairy; 3,500 cows
Scrape
$1.75M
Biogas End-use
Digester heat, solids drying, dairy heat,
electricity, hot water, and flare
Mesophilic plug flow, flexible top
Dairy; 3,000 milkers
Scrape
Not available
Electricity
NY
NY
Mesophilic
Mesophilic
plug flow,
plug flow,
fixed top
fixed top
Dairy;
Dairy;
1 , 1 00 cows
1,000 milkers,
200 dry
Scrape
Scrape
$650,
$900,
,000
,000
Electricity and hot water
Electricity, hot air, and hot
water
OR
OR
Mesophilic complete mix, fixed top
Dairy; 325 milkers
Scrape
Not available
Electricity
Mesophilic plug flow, flexible top
Dairy; 4,000 cows
Scrape
Not available
Electricity
Thermophilic complete mix, fixed top Dairy; 1,425 milkers
Scrape
Not available
Electricity
-------
8 AgSTAR DIGEST • WINTER 2003
lew
A number of state programs
provide support for biogas energy
recover}' systems. These programs
are helping to advance biogas
digester technologies and energy
applications, meet local energy-
needs, and enhance environmental
protection. This article profiles sev-
eral of these programs and some of
the projects that they are support-
ing. It also provides information on
how farmers, local governments,
and other entities can take advan-
tage of these programs. Be sure to
check the AgSTAR Web site
(www.epa.gov/agstar) for updates
on other state program opportuni-
ties that are emerging to expand the
use of digestion technologies.
The New York Energy
Research Dewelopment
Authority supports
energy analysis, research and devel-
opment, and energy efficiency
programs. NYSERDA offers fund-
ing through periodic competitive
solicitations and interest rate reduc-
tions for renewable power sources.
NYSERDA also sponsors annual
conferences to discuss current proj-
ects and upcoming funding
opportunities. NYSERDA has con-
tracted with more than 20
agricultural projects designed to use
manure for biogas energy or con-
vert it to marketable compost. One
of these projects was recently rec-
ognized as an AgSTAR Partner
Farm. Some examples of biogas
energy projects NYSERDA has
supported are listed below:
» Mat link Dairy Farm. A demon-
stration project at Matlink Dairy
Farm in Clymer, Chautauqua
County, produces biogas from a
complete mix anaerobic digester.
This system is unique in that it
utilizes a mixture of scrape dairy
manure and food processing
wastes for digestion, producing
about 130 kW of electrical power
and flaring excess gas. The total
installed cost of the digester sys-
Ted Mathews (center) of Matlink
Dairy Farm, recognized as an
AgSTAR Partner Farm, with Ann
Kurtis, Seneca Trail RC&D Council
(left) and Joseph DelVecchio, State
Conservationist, USDA/NRCS (right).
tern is $623,000, including solids
separation. Factoring in the use
of separated solids for bedding,
electricity cost savings, electrici-
ty sales to the local utility,
revenues for treating food pro-
cessing wastes, and costs of
operation and maintenance, the
farm is projected to realize annu-
al net benefits of about
$175,000. To use the excess bio-
gas to improve farm profitability,
the farm is now constructing a
dryer to produce value-added
animal feed from higher quality
food process wastes. NYSERDA
provided $200,000 for the con-
struction and testing of the
digester and an additional
$250,000 for the demonstration
of the food waste dryer. Matlink
Dairy Farm, owned by Ted
Mathews, is the second New
York dairy farm to be recognized
as an AgSTAR Partner Farm.
Dairy Development
International, LLC. NYSERDA
is providing $200,000 for a
demonstration project at an 850-
cow facility in Little York,
Cortland County. The project is
hosted by Dairy Development
International, LLC and is co-
funded by NYSERDA and the
F*A*R*M*E Institute, which is
headquartered in Homer, New-
York. The system was started up
in 2001 and is currently using
biogas in a boiler to heat the
digester. Excess biogas is com-
busted for odor control and
greenhouse gas reduction in a
flare. The digester produces
enough biogas to generate the
equivalent of about 500,000
kWh of electricity per year.
NYSERDA is also providing
additional funding to conduct
evaluations of the biogas quality,
alternative gas cleaning methods,
the potential for microturbine
applications, and the benefits,
costs, and performance of the
overall system. The cost of these
studies will be shared by the
New York State Electric and Gas
Corporation, Cornell University,
and EPA's Environmental
Technology Verification
Program.
Noblehurst Farms. NYSERDA is
contributing $250,000 to a proj-
ect in Linwood, Livingston
Count}', to construct and operate
an anaerobic digestion system at
a 1,100-cow farm. This collabo-
ration with Noblehurst Farms.
Inc. will produce almost 1 mil-
lion kWh of electricity annually.
Part of the funding will be used
to evaluate the potential use of
the digester as a centralized sys-
tem to commercially treat
livestock wastes from other
farms.
-------
AgSTAR DIGEST • WINTER 2003 9
« Town of Perry. In 2001.
NYSERDA provided funding to
conduct a feasibility study with
the Town of Pern' for a central
digester to serve four farms.
This study evaluated the cost of
implementing one or more bio-
gas digesters to treat manure
from 3,000 dairy cows. The proj-
ect would recover enough biogas
to generate more than 2 million
kWh of electricity per year. The
farmers determined that a central
digester would involve more
manure trucking than desirable
but that costs could be saved by
selecting and constructing a
common digester technology to
be built on each of three farms.
NYSERDA supplied $50,000 to
support the project, to match
costs met by the Town of Perry,
Cornell Cooperative Extension,
and the participating farms.
Building on data developed by
the feasibility study, the Town of
Pern,7 and the three farms sub-
mitted a successful proposal for
constructing three combined heat
and power generator systems
using biogas generated on these
three farms. This selected pro-
posal requested approximately
$800,000 through NYSERDA's
Combined Heat and Power
Program.
Information about NYSERDA's
competitive solicitations for manure
management systems can be found
atwww.nyserda.org/funding.htnil.
or by contacting Tom Ficsingcr at
(518) 862-1090 extension 3218 or
via e-mail at twf@nyserda.org.
The California Energy
Commission administers the $9.64
million Dairy Power Production
program. The Western United
Resource Development (WURD)
Corporation is the contractor for
this program. The program's goals
are to:
• Help the development of biogas
energy projects using commer-
cial anaerobic digestion
technologies at California
dairies.
* Help California dairies meet
energy demands and offset the
purchase of electricity demands.
* Provide environmental benefits
by reducing potential air and
water pollutants associated with
the processing of animal wastes.
Project funding is awarded through
two vehicles: a buy down grant and
an incentive grant. The buydown
grant covers a maximum of up to
50 percent of the capital costs of
the system based on estimated ener-
gy production, not to exceed $2,000
per installed kW, whichever is less.
The incentive grant is based on 5.7
cents per kWh of electricity gener-
ated by the dairy biogas system.
paid out over a maximum of five
years.
An advisory group screens applica-
tions (modeled after the AgSTAR
Program's Charter Farm initiative
during the late 1990s), and then a
due diligence review of pre-
screened applications is completed.
Finally, the advisory group reviews
the comments from the due dili-
gence review and decides which
projects to approve. The core advi-
sory group consists of
representatives from the CEC,
WURD, the AgSTAR Program,
California Department of Food and
Agriculture, Sustainable
Conservation, State Water Resource
Control Board, and the University
of California at Davis. Ten projects
have been approved, totaling more
than $6.8 million in project costs.
The total electricity generation
capacity from the 10 approved proj-
ects is expected to be at 1.7 MW,
over 12.6 million kWli per year of
energy delivery. The approved
projects are planned to be opera-
tional by the end of 2003. For
more information on the Dairy
Power Production Program.
please contact Zhiqin Zhang at
(916) 654-4063 or via email at
zzhang@energy.state.ca.us.
Additional information about the
Dairy Power Production program is
available at www.energy.ca.gov/
pier/renew/anaerobic/anaerobic.html
or www.wurdco.com.
In addition, the CEC's Public
Interest Energy Research (PIER)
Program supports development of
innovative energy sendees and
products. The program awards up
to $62.5 million annually to indi-
viduals, businesses, utilities, and
public or private research institu-
tions for projects that benefit
electricity ratepayers. The PIER
Program provides funding for
renewable technology research
development and demonstration
projects that convert waste to ener-
gy. In April 2002, the PIER
Program released a biogas-targeted
solicitation to support advanced
research and demonstration projects
using anaerobic digestion. The goal
of the solicitation is to utilize
renewable resources from solid
wastes, including animal wastes
and biosolids generated from other
waste streams, for environmental
and economic benefits using
advanced technologies in
California. A total of $5 million
is available for the selected
projects. For more information
on the PIER Program, please
contact George Simons at
(916) 654-4659 or via email at
gsiinons@energy.state.ca.us, or
visit the Program's Web site at
www.energy.ca.gov/pier/index.html.
continued on page JO
-------
10 AgSTAR DIGEST • WINTER 2003
New
Farm-Scale (continued)
The Wisconsin Diwision of
Energy administers the Wisconsin
Focus on Renewable Energy
Program through a third-party non-
profit consortium, the Wisconsin
Renewable Energy Network. The
program offers information, educa-
tion, training, and technical and
financial assistance to Wisconsin
electric utility customers.
Government, utilities, the energy
efficiency industry, and the public
are partnered in this alliance to pro-
mote the use of renewable energy,
including biomass.
Installation grants, based on the
amount of renewable energy pro-
duced, are available through the
Renewable Energy Program.
Commercially available renewable
electric and thermal projects, such
as systems that cogenerate electrici-
ty and heat from anaerobic
digestion of organic waste, are eli-
gible for funding through this
program. These systems can be
sited at agricultural, commercial,
industrial, institutional, or residen-
tial customer locations. Marketing,
demonstration, and research grants
are also available for customer-
sited renewable energy businesses,
technologies, and projects.
For more information on Wisconsin
Focus on Energy's Renewable
Energy Program, please contact
Don Wichert at the Wisconsin
Division of Energy at (608) 266-
7312 or visit the Program's Web
site at www.focusonenergy.com.
A Case
The Dairy Research Unit (DRU) at
the University of Florida's Institute
of Food and Agricultural Sciences
is home to a new "fixed-film"
anaerobic digester. This innovative
system stabilizes wastewater,
retains valuable fertilizer nutrients,
and produces energy by turning
waste into biogas. It can also
reduce the offensive odors associat-
ed with dairy manure by as much
as 90 percent. After four years in
development, this new digester is
up and running in Hague, Alachua
County, Florida, and is poised for
commercial deployment.
Dr. Ann Wilkie, an environmental
microbiologist and associate profes-
sor with the Soil and Water Science
department at the University of
Florida. Gainesville, designed the
digester to treat dilute waste from
Florida dairies. The Florida Energy-
Office was the project's primary
sponsor, and the digester serves as
a model for the Florida dairy indus-
try. The digester is a key
component of the waste manage-
ment system at the 500-milking
cow DRU.
The fixed-film anaerobic digester
consists of a 100,000-gallon tank
filled with plastic media. The media
supports a thin layer of anaerobic
bacteria called biofilm (hence the
term "fixed-film"). As the waste-
water passes through the
media-filled digester, the attached
and suspended anaerobic biomass
convert both soluble and particulate
organic matter in the wastewater to
biogas—a combination of methane
and carbon dioxide. The unit is
operating at a three-day hydraulic
retention time at ambient tempera-
ture. (For North Central Florida.
this corresponds to an average
operating temperature of 68 degrees
F in winter and 86 degrees F in
summer.)
According to Wilkie. the partial
decomposition of organic matter by
anaerobic microorganisms is the
main reason that livestock manure
smells. Because it is a completely
closed system, the fixed-film
digester allows more complete
anaerobic digestion of the odorous
materials found in manure to less
offensive compounds and mini-
mizes gaseous emissions to the
atmosphere. "Bacteria in the
digester convert organic matter in
the animal waste into methane and
carbon dioxide. At the same time,
the microbes convert materials that
cause odor into nonoffensive com-
pounds, so when the processed
wastewater leaves the digester, it
can be applied to the land without
the problem of nuisance odor," says
Wilkie. "In previous designs, bacte-
ria flowed into a digester with the
animal waste and then back out
again. We retain the bacteria inside
our system on the plastic media.
When we bring in fresh wastewater.
an army of bacteria are already at
work."
Because the University of Florida's
digester retains a large amount of
fixed biofilm on the plastic media,
the digester can treat dilute waste-
water in two to six days. This
retention time is much shorter than
that of other anaerobic digesters,
which retain wastewater for as long
as 25 days. Anaerobic lagoons, a
commonly used manure manage-
ment system, can take even longer,
depending on process water volume
for a complete treatment cycle.
The shorter hydraulic retention
time means that, by design (after
liquid solids separation), fixed-film
digesters have a much smaller
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AgSTAR DIGEST • WINTER 2003 11
microbial pathogens harmful to ani-
mal health, providing cleaner water
for recycling back through the free-
stall flush system. At the DRU,
biogas from Wilkie's system is used
directly to heat water for the milk-
ing parlor, providing an immediate
payback in savings on propane fuel
costs. Future plans include power-
ing space heaters in the parlor
during the winter months.
The fixed-film digester is simple to
operate and easy to maintain.
"There are no moving parts inside
the tank." says Wilkie. "The system
is continuously fed and it does not
need daily attention.'' According to
Wilkie, anaerobic digestion under
controlled conditions offers produc-
ers a holistic solution that allows
them to coexist with their neighbors
without limiting the enterprise. The
system can be easily integrated into
any livestock operation (dairy or
swine) that uses a flush-type
manure handling system.
For further information on the
fixed-film digester, contact:
Dr. Ann Wilkie
Soil and Water Science Department
University of Florida
P.O. Box 110960
Gainesville, FL 32611-0960
Phone:(352)392-8699
E-m ai 1: ac wilkic(a)m ail. if as. ufl. edu
Biogas flare burns at the University of Florida's fixed-film anaerobic digester.
footprint than conventional plug-
flow, complete-mix, and covered
lagoon digesters—an important fac-
tor where land availability is
limited.
The fixed-film anaerobic digester
offers other benefits, including
energy generation, greenhouse
gas reduction, and retention of
important fertilizer nutrients (i.e.,
nitrogen, potassium, phosphate) in
the wastewater effluent. The organ-
ically bound nutrients are
mineralized to soluble form s in the
digester, which transforms them
into a more predictable fertilizer
product. The digestion process
also kills weed seeds and reduces
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12 AgSTAR DIGEST • WINTER 2003
(The following article is excerpted
from. "Covered Anaerobic Lagoon
Systems for Swine Waste Treatment:
Concepts and Performances on an
AgSTAR Charter Farm in North
Carolina, " K.F. Roos andJ.A.
Martin, Jr., Conference
Proceedings, Water Environment
Federation, March 2002.)
AgSTAR recently completed the
first in a series of evaluations to
quantify the environmental per-
formance of conventional waste
management and anaerobic digester
systems used in commercial swine
and dairy production facilities. The
overall objective of this effort is to
develop a better understanding of:
« The potential of individual sys-
tem components and
combinations of these compo-
nents to reduce the impacts of
swine and dairy wastes on envi-
ronmental quality.
* The relationships between design
and operating parameters and the
performance of the biological
and physical/chemical processes
involved.
A clear understanding of these
issues is essential for the planning
and design of these waste manage-
ment systems. This information can
also facilitate the identification of
specific processes or combinations
of processes that will effectively
address air and water quality con-
cerns. Figure 2 shows the
standardized methodology used in
these comparative evaluations.
This evaluation focused on swine
waste management systems in
North Carolina. A covered anaero-
bic lagoon (see Figure 3 on page
13) was compared to a convention-
al anaerobic lagoon in which the
treatment and storage functions are
combined. This study also evaluat-
ed a third system, a minimally
aerated single cell lagoon with
u
T
Figure 2. Standardized Methodology Used for AgSTAR Comparative Evaluations
ozone injection. Because this sys-
tem performed about the same as a
conventional lagoon, it is not dis-
cussed further in this article.
Table 3 summarizes the charac-
teristics of these farms and systems.
Table 4 summarizes the costs and
revenues of the covered anaerobic
lagoon.
Table 5 summarizes the environ-
mental performance of the covered
anaerobic lagoon system. AgSTAR
based this performance characteri-
zation on results of analyses of
influent and effluent samples
collected semimonthly over a
12-month period beginning in May
1999. In this evaluation, more than
Table 3. Characteristics of Study Facilities
96 percent of the total solids.
volatile solids, chemical oxygen
demand, total phosphorus, and
orthophosphate phosphorus and
more than 92 percent of the total
Kjeldahl nitrogen (TKN), organic
nitrogen, and ammonia nitrogen
entering the system was accounted
for in the material balances that
were developed.
When compared to conventional
anaerobic lagoon, covered anaero-
bic lagoons demonstrated the
following additional environmental
benefits:
* Reduced pathogen densities (1 to
1.5 log reductions, 3.5 log total
reduction), including reductions
System
1
2
3
Waste Stabilization System
Covered anaerobic lagoon
followed by an effluent
storage pond
Minimally aerated single cell
lagoon with ozone injection
Conventional anaerobic
lagoon
Swine Operation
Size/Type
4,240-head farrow-to-wean
5,400-head finishing
8,100-head finishing
Estimated
Capacity (m3)
26,000 (lagoon)
52,000 (pond)*
27,500 (lagoon)
33,000 (lagoon)
This pond was originally used as a combined anaerobic stabilization and storage lagoon. It is over-
sized for its current application (storage only).
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AgSTAR DIGEST • WINTER 2003 13
Table 4. Cost and Benefits of
Covered Anaerobic Lagoon
(Moser and Roos, 1997)
Manure transfer pipe $3,500
Excavation
Digester cover
Gas/hot water piping
Gas pump, meter
Engine-generator
Boiler and hot water use
Engine-generator building
Engineering
otal Cost
$57,400
$39,300
$4,600
$3,200
$87,540
$7,600
$8,200
Heat loop, farm labor, $21,134
electrical
$232,474
$25,000
$257,474
Figure 3. Schematic of Covered Anaerobic Lagoon System Investigated in Study
Annual Electricity Production $35,000/yr
Value of propane offset $11,000/yr
otal $48,000/yr
in Salmonella and other indicator
organisms.
Land requirement reductions of
at least 50 percent, on a nitrogen
application rate basis, for dispos-
al of effluent withdrawals.
* Atmospheric methane emission
reductions of approximately
10 million cubic feet/year.
Methane is a potent greenhouse
gas.
All other values for conventional
anaerobic lagoons were comparable
to those shown in Table 5.
The results of this study demon-
strate that covered anaerobic
lagoons can reliably provide excel-
lent odor control and, through
anaerobic stabilization, can sub-
stantially reduce the water and air
pollution potential of swine wastes.
As shown in Table 4, the study
results also demonstrate that the
initial investment can pay for itself
within a five- to six-year period
when biogas is combusted for ener-
gy production. A complete
evaluation report will be made
available on the AgSTAR Web site
(www.epa.gov/agstar).
Table 5. Summary of Covered Lagoon and Storage Pond Performance (Martin, 2002)
Parameters
measured
Total solids
Total volatile solids
COD
TKN
Organic nitrogen
Ammonia nitrogen
Total phosphorus
Orthophosphate phosphorus
Net loads,
kg/day
1,667
1,194
2,813
217
94
127
57
27
Covered lagoon
reductions, kg/day
1,502
1,139
2,729
81
79
5
47
18
Covered lagoon
reductions, %
90,1%
95,4%
97,0%
37,3%
84,0%
3.9%
82,5%
66,7%
Storage pond
reductions, kg/day
129
44
79
138
16
122
9
7
Overall
reductions, %
97.8%
99.1%
99.8%
100%*
100%*
100%*
98.2%
92.2%
* This is an overestimate as indicated by the closure errors in the mass balances of less than eight percent for TKN, organic nitrogen, and ammonia nitrogen.
-------
Information
All AgSTAR Program
information is available
through the
and Web site
(www.epa.gov/agstar).
You can download fact sheets,
brochures, and other informa-
tional materials from the Web
site, or call the Hotline to
request hard copies, The Web
site also has direct links to
related industry, vendor, and
utility sites, as well as an
online directory of technology
providers, including
consultants, developers, and
manufacturers and distributors
of covers, tanks, and engines.
For
or the an at:
EPA
1200 Ave., NW
DC
of to EST)
www.epa.goM/aistar
STAR
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