Waste not, want not
Utility co-ownership speeds the payback
on a Wisconsin biogas digester
By Karl Ohm
About five years ago when dairy farmers Gale Gordon and his son, Kyle, built modern, free-stall facilities with a double-14 herringbone milking parlor they included a biogas, or methane, digester. Adding one later for their 900 cows near Nelsonville, Wisconsin would be too costly.
“We saw the biogas digester as a great way to complement the operation since it could generate energy and help save bedding and fertilizer costs,” says Gale. It also improves nutrient management and control of odors and flies.
The digester’s methane powers an 8-cylinder Caterpillar 3408 reciprocating engine that runs an electricity generator. The in-ground, insulated digester, which was designed and built by GHD, Inc., of Chilton, Wis., holds 650,000 gallons and produces about 65 cubic feet per minute (cfm) of methane.
“That’s enough volume for the engine and generator to crank out more than 130 kilowatts (kw) of electricity,” says Gale. “We’re delivering enough electricity on the grid to help provide power to more than 125 homes.”
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Gale and Kyle Gordon (right) stand on their 650,000-gallon plug flow digester. It’s 108 feet long, 65 feet wide and 14 feet deep. Manure flows through it in 18-20 days. |
| Photo: Karl Ohm |
Alliant Energy owns and maintains the engine and generator, which can be nearly a third of a system’s total price. “Essentially, we’re just selling the methane gas to the utility,” says Gale.
The farm is paid 1.5 cents per kilowatt-hour generated and delivered to Alliant’s power transmission system.
Once the manure is digested, the leftover, nutrient-rich effluent is pumped to a lagoon and applied later to cropland to reduce fertilizer costs. The coarse solids in the manure are squeezed out with an expeller screw-type press and used as an excellent and sanitary bedding material in the free-stall barns.
Savings bring quick payback
If you add up all the benefits, Gale says the biogas digester has generated income and energy savings of about $75,000 per year.
“We aimed for a payback period of about six years,” he says. “So far, we seem to be very well on track since our initial outlay was slightly more than $300,000.”
When their project was built in 2001, it received no grants to help offset initial costs. That’s another factor that can affect the payback period.
Today, however, there are more state and federal renewable energy grant and loan opportunities available to livestock producers to help offset some of the costs, especially for the engine and generator equipment.
“When I talk to other dairy producers, I tell them to expect a range of $800 to perhaps $1,000 per cow when calculating a very rough estimate on what a biogas system may cost,” he says.
Bedding cost savings, odor control, better nutrient management and environmental benefits were also very important. About 35 tons of separated solids from the digester are used for bedding each week, saving the dairy $60,000 a year. They also sell some of the solids to area gardeners.
The Gordons’ dairy operation uses about 2,000 acres for corn silage and grain, about 800 acres for alfalfa (on a three- to four-year rotation), and 400 acres for soybeans and other grains.
“The biogas digester also helps in managing the manure and nutrients better,” says Gale. “What it boils down to is that you have a more manageable amount of phosphorus in the effluent for field applications,” explains Gale.
“This liquid fertilizer is either knifed in or broadcasted and then worked into the soil. It’s also broadcasted on growing crops, such as alfalfa and corn. In making those applications, however, we still rely on regular soil testing coupled with cropping maps to avoid nutrient overloading.”
“Most of the organic nitrogen in the manure is converted to ammonia,” says Gale. “When broadcasting, the liquid effluent doesn’t burn the crops, and the nutrient uptake or utilization appears to be real good.”
Gale estimates that the digested manure and effluent have helped trim out-of-pocket fertilizer expenses by about 25%. “In fact, during the past couple of cropping seasons, we actually side-dressed some of the corn with the liquid effluent.”
Dramatic pathogen reduction
Digested manure also helps control fecal forms of bacteria like coliform and streptococcus. Pathogens don’t last long under the anaerobic and high temperature conditions inside the digester and where the hydraulic retention time may be about 18 to 20 days.
Retention refers to the time from when manure first enters the digester and to when it exits the digester.
“This is a tremendous benefit for us in managing manure, says Gale. “It’s remarkable that a biogas digester can kill about 99% of the coliform bacteria. Plus, another added benefit is that we’ve experienced a marked reduction in weed seed germination or viability, such as with velvet leaf, common lambsquarter, and giant foxtail.”
A bonus: curbing greenhouse gas
The digester also mitigates methane that is a potent greenhouse gas with 21 times the heat-trapping capacity of carbon dioxide. The reduction in methane emissions, on a carbon dioxide equivalent basis, has been estimated at about 3 tons per cow/year.
Electricity generated from biogas also reduces carbon dioxide emissions by displacing fossil fuels that otherwise would be used to produce power.
“In the near future, we plan to aggregate our carbon credits with other biogas digester operations and sell them on the Chicago Climate Exchange (CCX),” says Gale. “We plan to explore these details with the CCX, which fully administers this unique program.”
“Biogas digesters are definitely beginning to usher dairy farming into a value-added and dynamic marketplace,” says Gale. “There’s no question in my mind that this technology will tremendously benefit our industry in the years ahead by generating new revenue streams and producing great environmental benefits. It already has on our farm.”
Learn more
The AgSTAR Program, a joint EPA, USDA and Dept. of Energy project. Website includes info on state and U.S. grants.
www.epa.gov/agstar
| MAIN DIGESTER TYPES |
Anaerobic digestion is decomposition of organic matter by anaerobic bacteria that live without oxygen. They can be found in pond and swamp bottoms. |
Reprinted from Successful Farming®.
© Copyright 2006 Meredith Corporation. All rights reserved.
Michigan State Univ. leverages public, private funds
for farm waste-to-energy project
EAST LANSING, Mich. — State and foundation grants exceeding $3 million will assist Michigan State University (MSU) researchers in developing technology for smaller farms to turn animal waste into usable heat, electricity and other valuable products.
MSU’s planned Anaerobic Digestion Research and Education Center will consolidate new and existing programs in a planned 3,280-square-foot building south of campus, at MSU’s expanding farm animal and environmental research complex.
Researchers aim to develop and commercialize turn-key digester/microturbine modules for affordable waste-to-power systems for small and mid-sized farms.
“The initiating of the center completes our vision for a continuum of research capabilities from theoretical calculations, laboratory-scale, bench-scale, pilot-scale and farm-scale anaerobic digestion research," said Steven Safferman, the center’s director and an associate professor in the Department of Biosystems and Agricultural Engineering.
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MSU researcher Steven Safferman with an anaerobic digester of the sort his team hopes to mate with power generators to produce power from animal waste. |
| Photo: G.L. Kohuth / MSU |
A two-year, $1.5 million Michigan Public Service Commission research grant “recognizes MSU’s strong capacity to address the critical issues of sustainability of animal agriculture and the need for renewable energy and economic development in Michigan,” department chairperson Ajit Srivastava said.
An additional three-year grant totaling $1.5 million from a private southeastern Michigan foundation to build the facility and fund new programs “is an excellent example of how universities and foundations can work together to address critical issues of society such as food, environment and energy,” Srivastava added. The foundation prefers to remain anonymous.
Farm waste management is a growing issue due to concerns over food contamination, pollutant runoff, odor and, most recently, greenhouse gas emissions. Petrochemical cost spikes, meanwhile, have added to farmers’ costs for fertilizer and fuel.
The MSU ADRE Center will develop ways to efficiently convert manure liquid into methane for heat and electricity while extracting fiber for soil enrichment or ethanol manufacture and water for irrigation. Other valuable output could include animal feed and algae, which can be processed into biofuels.
Anaerobic digestion is not a new concept, and has been applied in recent years by some large dairy farms to generate power. Development of scalable, modular systems could allow smaller farms, those with fewer than 500 head of cattle, to convert waste into valuable resources.
Despite the loss of two-thirds of U.S. dairies since 1988, such smaller operations still account for 53 percent of the 71,510 remaining and 48 percent of U.S. milk production, according to the U.S. Department of Agriculture.
“The enhanced revenues and reduced pollution from the proposed system will significantly improve the quality of life and health of residents in rural communities and turn an environmental and economic liability into a public and private asset,” said project lead investigator Wei Liao, an assistant professor of biosystems and agricultural engineering.
“It is our hope that success at this level will lead to extensive applications of similar technology throughout Michigan and the nation.”
| A large-scale anaerobic digester at the Scenic View Dairy in Fennville, Michigan. |  |
| Photo: Biosystems and Agricultural Eng. |
The ADRE Center is also expected to conduct contract testing of related equipment and processes to help support itself, and to house a recently created farm energy auditing program that could conduct digester/power system feasibility studies for dairy clients. It is slated for completion by mid- to late 2009.
"Agricultural operations are extensive energy users. Most can reduce their energy use, sometimes even resulting in increased production, by adopting new high-efficiency technologies,” said MSU professor Truman Surbrook, who is managing director of the Michigan Agricultural Electric Council.
“Advances in this field are occurring at such a rapid pace that it is hard for producers to keep up without the assistance of highly trained personnel such as Michigan's certified farm energy auditors.”
The farm energy audit program is supported by a two-year, $250,000 grant, also from the private foundation. MSU will contribute another $230,000 toward the cost of managing and operating the ADRE Center.
For more detail on the MSU ADRE facility, its funding and background on anaerobic digestion, click to: www.egr.msu.edu/age/. The Department of Biosystems and Agricultural Engineering is affiliated with the MSU College of Agriculture and Natural Resources and College of Engineering.
Contact: Steven Safferman, Biosystems and Agricultural Engineering, Office: (517) 432-0812, safferma@msu.edu; or Ajit Srivastava, Biosystems and Agricultural Engineering, Office: (517) 353-7268, srivasta@msu.edu
Harnessing manure's value
with methane gas digesters
Research and better system designs lead to renewed interest
in converting manure into energy and more useful fertilizer
By Karl Ohm
In the near future, agriculture appears poised to becoming a significant, if not major, energy producer that could usher in a more sustainable type economy, according to key researchers at the U.S. Department of Energy's National Renewable Energy Laboratory in Golden, Colorado.
New research with enzymes at Cornell University, for example, shows promise in making it much more economical to convert biomass, such as corn stover and other plant materials, into fuel.
For livestock farmers, advancements in molecular biology and bacteriology have also begun to rekindle interest in converting manure into methane or biogas that can power electric generators.
Refinements are also being made in the design of the methane gas digesters and related equipment used to process and transform this valuable resource into value-added products.
Manure can be transformed into biogas through "anaerobic digestion," says Lut Raskin, University of Illinois civil and environmental engineer. This is nothing new. However, anaerobic digesters have come a long way since the 1970s, and U of I researchers have embarked on new research that aims to refine the process even further.
Producing biogas
In the anaerobic digestion process, bacteria break down organic matter very quickly in an oxygen-free environment. Unlike a lagoon, it is a closed system, so methane is contained and is, therefore, a usable fuel.
The system also seals in odorous gases or vapors. The ability to reduce odors is another reason why methane gas digesters are being seriously looked at today by farmers whose operations are near populated areas.
What's more, the fertilizer produced with an anaerobic digester is very stable and degrades slowly over time. And if Raskin and fellow researchers are successful, a digester will also be able to extract phosphorus from manure, allowing it to be used or sold separately.
The Anaerobic Sequencing Batch Reactor (ASBR), developed at Iowa State University, is a new digester that shows great promise for efficient and reliable processing of manure. Its biggest advantage over previous designs is its size, says Raskin. It is small, but can be used at the same loading rates as larger systems.
Hypothetically, if all the manure produced annually in Iowa from 20 million head of swine were processed through ASBR, the result would be a methane value of $40 million. At current market prices, the nitrogen in Iowa's swine manure would translate to about $60 million in fertilizer.
While these numbers are impressive, says Raskin, it is unlikely that pork producers or dairy farmers will invest in an anaerobic digester unless they are sure that it is reliable and affordable. An on-farm cost-benefit analysis of ASBR is on-going.
Raskin's team, partially funded by the Illinois Council on Food and Agricultural Research, aims to build on the promise of this technology by further reducing ASBR's operating costs and increasing the value of its products.
For example, separating out the phosphorus in manure provides environmental and economic advantages. Typically, farmers apply manure to ensure sufficient nitrogen for the crops. But in the process of applying enough manure to provide adequate nitrogen levels, they may over-apply phosphorus.
If nitrogen and phosphorus can be measured separately, this problem can be avoided.
Also, phosphorus extracted from manure can be sold to industry. Mining of phosphorus is becoming increasingly difficult and supply is limited. So industry and government efforts to recover phosphorus have recently begun to intensify, says Raskin. Animal manure is high in this nutrient and is a cheap resource.
One way to reduce the cost of a digester is to reduce its start-up time. It takes months for bacteria to multiply to the point where the anaerobic digester is up and running. If the start-up time is during colder seasons, a heater may be required.
By trying different sources of bacteria in the digester, Raskin says he hopes to find the fastest start-up route. With a quick start-up time, methane will be produced sooner, lowering operating costs in the first few months, and maybe even lowering the initial investment, if a heater is not necessary.
An early pioneer
Fairgrove Farms, a 650-plus cow dairy operation based near Sturgis, Michigan was one of the early pioneers in methane gas digestion. In 1981, John Pueschel and his brother, David, constructed a plug-flow digester system for about $150,000 that holds 120,000 gallons of manure.
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John Pueschel (shown here), and his brother, David, dairy farmers from Sturgis, Michigan, were early pioneers in using a biogas digester system. They installed one back in 1981. |
| Photo: Karl Ohm |
Manure is scraped twice daily from the free-stall barns into a below grade pit that transfers the manure into a underground V-shaped concrete tank. Designed by Perennial Energy, of Iowa, and modified by the Pueschel brothers, a plug-flow digester essentially allows fresh manure to come in one end while older digested manure is slowly pushed out the opposite end of the tank.
The methane is used to power an engine to produce electricity which has been saving, on the average, the farm $4,000 to $5,000 monthly in energy costs. John says that the payback for the system was about four to five years. The big pluses of the system have been electricity cost savings, reduced odors and fly problems from manure and better fertilizer value, according to John.
Once fully digested, the manure effluent is transferred via a pipeline to a centrifuge where it is separated into solid and liquid fractions.
Solids reclaimed have a sawdust-like consistency and is used as an odor-free stall bedding material. John says the material has helped reduced mastitis when compared to conventional bedding materials. John also estimates that the dairy has reduced bedding expenses by as much as $3,000 monthly.
The liquid effluent flows by gravity into a storage lagoon and is spread directly on fields as fertilizer, using a boom system for better coverage. The liquid fertilizer is usually applied at rates up to 5,000 gallons per acre, which offsets the need for 100 lbs. of nitrogen, 25 lbs. of phosphate, and 100 lbs. of potassium. John estimates a savings of $25 to $30 per acre in fertilizer costs.
An integrated approach
Taking an integrated approach to the production of renewable energy has been the focus of PRIME Technologies, LLC, of South Dakota. It recently received $402,500 from the Value-Added Ag Subfund to study the feasibility of combining a beef feedlot, ethanol plant, anaerobic digesters and feed processing into one operation.
"Combining these four operations is a completely new concept," says Ron Wheeler, commissioner, Governor's Office of Economic Development. "People have combined feedlots with ethanol plants, but adding the other two elements gives it a whole new dimension."
The proposed facility would sit on 320 acres in southern Sully County. The integrated, environmentally sound, complex would include four distinct operations.
- The first would be a weather-protected 25,000 head custom beef feedlot.
- The second would be a grain handling and processing center for approximately 8 million bushels of local grain annually. The third would be a 15 million gallon per year ethanol unit with wet feed recovery system.
- And the last operation would be an anaerobic digestion unit to treat all animal waste for odor control. It would also capture methane to be used as a heat source for ethanol production and produce biofertilizers.
"This project is a good opportunity for our beef and corn producers in that is allows them to capture almost 100 percent of the value to their products," says Larry Gabriel, South Dakota Secretary of Agriculture. "A major goal of the Governor's Office of Economic Development is to enhance value-added agricultural opportunities in South Dakota. This project would certainly do that," Wheeler says.
According to Wheeler, capital investment on the project would be nearly $40 million. The project would use approximately 8 million bushels of corn and feed 65,000 - 75,000 head of local feeder cattle yearly. "Additionally, producers could see an increase of 10 to 20 cents a bushel in corn prices. Local tax revenues would increase and up to 50 new jobs could be created," Wheeler says.
The PRIME Technologies project is the largest project to be funded by the Agricultural Subfund. "As the awareness of this fund grows, we are seeing more and bigger projects being presented," Wheeler says. "We are pleased with the results to date and are optimistic this fund will continue to benefit South Dakota agricultural producers."
| AgSTAR Program is resource on methane gas digesters |
In 1993, the U.S. Environmental Protection Agency (EPA), along with the U.S. Department of Agriculture(USDA) and U.S. Department of Energy (DOE) launched the AgSTAR Program designed to promote cost-effective and efficient methods to reduce methane emissions from manure management. EPA AgSTAR Program |
Editor's Note: This dairy operation in southern Michigan was one of the first in the country to install a biogas digester system. This story was first published by in late December 2000. I'm republishing this story to recognize the early pioneers in biogas digester systems.