Biogas Technology: ‘Cow Power’ Catching On In The U.S.

by Bruce Dorminey, via Renewable Energy World

For years, third world ranchers have been using methane from manure to run electrical generators down on the farm. This clean-burning biogas is not only a good local fuel in countries with little or no infrastructure, now even countries like the U.S. are reaping energy from this foul-smelling source.

Some 80 percent of the estimated 160 biogas energy projects in the U.S. are currently installed on dairy farms, which then combust the gas to generate electricity.  The combined installed capacity of all dairy farm projects is nearly 60 MW.

It’s a complicated process. First the farms have to facilitate both the production and collection of biogas in anaerobic digesters.  These are processing systems that allow methanogenic bacteria to feed on the manure’s natural acids in a very oxygen-depleted environment.  In turn, the bacteria both generate methane-rich biogas and reduce the manure’s foul odor by as much as 90 percent.

After collection from storage systems such as covered lagoons — akin to large swimming pools very nearly brimming with manure — this gas is usually piped to an electrical power generator.

Although a large portion of the U.S.’ biogas energy projects are found in New York, Pennsylvania, Vermont, and Wisconsin, they represent only a fraction of the estimated 8,000 farms out there that could support some method of biogas energy production.  By some estimates, the total electrical capacity of all these farms could range as high as 1,600 MW.  That’s about 10 percent of the U.S.’ current electricity needs.

To date, Vermont has been a standout.  Since 2002, Central Vermont Public Service, the state’s largest utility, has delivered over 47 million kWh of local “Cow Power” to some 3 percent of its 160,000 customers.

Dave Dunn, an animal scientist with the Vermont utility, says that while its cow power customers are mostly homeowners, they also have 200 non-residential customers, from a gas station to a brewery to Green Mountain College in Poultney.  The college now gets about half of its monthly electricity (100,000 kWh) from the utility’s biogas energy program.

Dunn says the 10 farms that currently are part of the cow power program have a total estimated capacity of 3.5 MW.  All of this energy is fed back into the electrical grid.  On average, Dunn says a 1,000 cow dairy has a capacity of some 250 kW.  That’s enough cow power to provide the electrical energy for as many as 250 Vermont homes. As a result, biogas power now makes up 10 percent of the utility’s current energy mix.

“This is really last year’s solar energy and a way to store solar [carbon] energy in crops that a cow doesn’t fully utilize and is excreted and turned into biogas,” said Dunn.  “We’re using about a fifth of all cow manure in Vermont.”

But the program is still not a panacea for the farmer.  After grants, the farm still has to pay for more than half the cost of an average $2 million dollar digester project, which would usually be amortized over a 10-year period.  However, gross income from biogas energy for a 1000-head farm averages only $300,000 a year, about 7.5 percent of a dairy’s total gross revenue.  Given that the life expectancy of a given system runs only about 20 years, biogas energy installation is not without financial risk.

“Because dairy farming profits vary quite drastically with the price of milk, it’s hard for farms to invest in something other than their primary business,” said Dunn.  “Becoming an energy producer is not typically what farms think about doing.”

Barring conversion to electricity, another likely scenario for biogas energy production involves cleaning the gas to meet commercial standards and pumping it into a nearby natural gas pipeline.

A project underway in western Wisconsin is trying to do just that.  Agri-Waste Energy, Inc. Of St. Paul, Minnesota, has already successfully demonstrated delivery of biogas from an Emerald, Wisconsin dairy into an existing natural gas pipeline.

The next step is installation of two separate digesters on farms in western Wisconsin.  Bob Zwald, co-owner of Bomaz farms in Hammond, will allow Agri-Waste Energy to build and own a digester on his 1000 cow dairy.  From there, the gas would be extracted and sent through a pipeline before being directed into a commercial natural gas network.

“Now our manure is stored in a clay-lined pit and injected into the soil as fertilizer,” said Zwald.  “Agri-Waste Energy would pay us a stipend for extracting the biogas and afterwards we would still be able to use the manure.”

The Agri-Waste project, expected to cost several million dollars, may see fruition next year, when it is expected to begin producing an estimated 1000 dekatherms of methane gas daily.

Even while agricultural manure holds promise, there may be even more biogas energy potential from food waste than manure.

Dunn says that ice cream, yogurt, cheese, waste milk and anything else that has a sugar, starch or fat component all have great biogas energy potential.

“In the U.S., what’s yet to move forward with [biogas energy] is leftover consumer waste,” said Dunn, “stuff from cafeterias, restaurants and grocery stores; the old doughnuts, the leftover steak and mash potatoes on somebody’s plate.”

But that could also be changing.  Since 2011, the University of Wisconsin at Oshkosh has been operating a $3.5 million digester that uses a combination of agricultural waste, yard waste, supermarket waste — even waste from the campus food court.  When the digester goes into full production in April, it should process some 8,000 tons of organics annually providing as much as 10 percent of the university’s electricity needs.

As Becky Larson, a bio-waste engineer at the University of Wisconsin in Madison points out:  “We’re at the cusp of finding a way to make these biogas energy systems profitable,” noting that she expects the biogas market to be pushed along by the continuing emphasis on sustainability; high costs of competing energies; and concern over reduction of greenhouse gas emissions.

This piece was originally published at Renewable Energy World and was re-printed with permission.

16 Responses to Biogas Technology: ‘Cow Power’ Catching On In The U.S.

  1. joyce says:

    I’m glad you are addressing this. It is an overlooked resource that is a “win-win-win” on many fronts. Not only can it generate electricity, but the fiber can be processed into a peat substitute or used as livestock bedding, the natural gas can be refined and used for transportation fuel, and waste heat can heat greenhouses or barns. One of the nicest outcomes of the process is that the manure, that would normally either be composted releasing ghg’s, or spread on the ground releasing ghg’s or lie in lagoons waiting for the next flood to pollute the water, can be contained. Emissions can be scrubbed to minimilize pollution, and lagoons are not as full.
    In our county we have several digesters, and the local university has developed a methane refinery to ready the methane for fuel. There is a fuel pump at one digester in anticipation for commuter busses, that have been converted to natural gas, to be able to fuel up. There is talk of connecting to the natural gas pipeline.

    Several cities in Sweden have developed an almost “closed loop” energy, running everything on biodigesters. I’ve seen some cool videos showing this.

    It has amazed me that “energy experts” hardly ever put this in the mix when they talk about future scenerios.

  2. Leif says:

    “By some estimates, the total electrical capacity of all these farms could range as high as 1,600 MW. That’s about 10 percent of the U.S.’ current electricity needs.”

    That would represent a significant income stream into the pockets of struggling farmers and farm communities and out of the pockets of the Ecocidal Fossil Barons. Talk about making a silk purse out of a sows ear. Or effluent…

  3. dan p says:

    1600 MW is nothing to sneeze at but it’s about the electricity of one large nuclear reactor, and nowhere near 10% of the total US electricity usage (460 GW). More like 0.3%

  4. Calamity Jean says:

    I’m interested in making biogas to use it as cooking and engine fuel. I’m looking for links on adapting an internal combustion engine to burn biogas. Any suggestions will be gratefully received.

  5. Leif says:

    One large Nuke Reactor puts the profits into the hands of the fat cat developer and the liability onto the backs of the people. Green tech puts the profits into the hands of “We the People.” Starts to heal Earth’s life support systems, and lets the fat cats lose a little weight. That is the difference dan p! Today my Solar PV will pay me ~ $10.

  6. Mulga Mumblebrain says:

    But, Leif, you’ve forgotten all that lovely depleted uranium that can be turned into weapons to be used in the eternal struggle for ‘Feedom’ and ‘Demo-crazy’.

  7. Mulga Mumblebrain says:

    The Chinese have taken to using ‘night-soil’ to produce bio-gas, as well as animal effluent. Human excrement is another resource now existing as a waste problem. Composting toilets produce quite safe compost for use in maintaining soil fertility.

  8. Christopher S. Johnson says:

    So do I understand correctly that CO2 is the emission from burning the gas, but that is better than what the manure would emit if left on it’s own, which is methane, a much worse ghg? Even so, is this whole process really neutral? Is there no net increase in atmospheric CO2 for this present day carbon cycle, at the end of the day?

  9. joyce says:

    I asked the same questions to a scientist working on such issues here–and received a very thorough and comprehensive answer that’s way too long to post. I’ll forward it via e-mail if you want me to.

  10. Mark E says:


    10% of electric production sounds great, until you start factoring in:

    * fossil fuel based fertilizers to replenish soils that are depleted to grow grain for those cows to eat

    * fossil fuel burning to produce grain for those cows to eat

    I’m all for biogas, but it should never be ballyhooed without pointing the bigger finger at the real issue: we don’t need petro-cows in the first place.

  11. Leif says:

    It is an ill wind indeed that blows no one some good.

  12. Dr.A.Jagadeesh says:

    Yes. Cattle rich areas can go in for Biogas. In Denmark there is a law that animal dung cannot be put in open fields during winter as it won’t be decomposed quickly. Hence they construct big tanks and generate biogas for power as well as heating.

    Getting huge quantities of animal dung is difficult . Thanks to nature many plants yield biogas. Water Hyacinth(Eichhornia Crassipes), Opuntia,Agave etc. produce biogas. By mixing about 20 percent animal dung and the rest plant material from the above yields huge quantities of Biogas. For example in Andhra Pradesh,India there is a KOLLERU LAKE where water hyacinth is available in about 200 square kilometers area for nearly 9 months. Biogas on a massive scale can be generated from this. Also Opuntia is a care free growth plant which can be effectively utilised in biogas production along with animal dung.

    Using spineless cacti as an energy crop offers serious perspectives to countries prone to drought and relying on imports for their energy consumption. Under a mediterranean climate, Opuntia can easily be cultivated under rain fed conditions without any supplementary irrigation, whereas maize cannot be cultivated without it.

    Spineless cacti have a high water use efficiency, they can be grown with limited water on marginal lands, creating a valuable source of biomass on degraded land in semi-arid regions. Opuntia ficus indica inermis respond very strongly to fertilization and irrigation. 100 tons of fresh biomass (12 t DM) /ha/year can be harvested with 300 mm of rainfall. 500 tons of fresh biomass/ha/year is obtained in Santiago de Chile and in the North East of Brazil where it is harvested just one year after planting under intensive cultivation.

    Under the same irrigated and fertilized intensive culture Opuntia can yield around 120,000 kWh/ha/year, which is twice as much as maize under a mediterranean climate. 4000 m3 of natural gas equivalent can be produced per hectare per year under rainfed conditions with an annual rainfall of 300-350 mm.

    In view of multiple uses of cactus, a cactus crop may prove a boon for the rehabilitation of degraded sites including wastelands. The low cost of establishing and producing the crop, as well as its tolerance to drought, make cactus imminently suited to becoming a viable future industry in India. The Thar desert in Rajasthan, Rann of Kutch in Gujarat, southwestern parts of Haryana, Bundelkhand, and other similar rainfed areas prone to severe drought would be very productive. Since cactus has good potential for the arid and semiarid India, it would be helpful if we could produce a research and development plan involving people having similar interests to import and exchange Opuntia germplasm. To start with, a centre for germplasm collection and its maintenance should be identified. Possibilities must be explored for international collaboration involving people from those countries where the crop is commercially cultivated and has already become a part of their dietary requirements. Also, there is a need for a coordinated effort within the country to promote cactus and its linking with the already existing international network on cactus as advocated by Gurbachan Singh Assistant Director General(Agro) of ICAR,New Delhi, India.

    Dr.A.Jagadeesh Nellore(AP),India

  13. This is an old and well proven technology. I visited such an installation back in the mid 1980s at a cow farm up in the Napa Valley, and there was a lot of discussion about such installations in the 1970s.

    It is true that burning the methane to produce CO2 is better than just having the methane escape, but also don’t forget that the methane you produce is displacing natural gas, so biogas plants, whether at sewage treatment plants or at cow farms are a negative net emissions resource (and a negative net cost resource). The sewage plants and cow farms that are not using this technology are really missing out.

    For a detailed potential estimate see
    Cow power: the energy and emissions benefits of converting manure to biogas
    Amanda D Cuéllar and Michael E Webber

    And yes, the estimate that 1600 MW could supply 10% of us electricity needs is incorrect. Total installed capacity in the US is about 1000 GW (or 1,000,000 MW) so there’s no way 1600 MW could generate 10% of all electricity in the US.

  14. Leif says:

    Any way you cut it, effluent is effluent. Should we be eating less meat? Of course. Should we be growing Bio gas stock in and of itself? No. However people could do a lot better with our waste stream as well. Better to reclaim energy that would otherwise pollute the environment even more or better yet return a profit, supply job and establish enhancement for life support systems as we learn to get better.

  15. Christopher S. Johnson says:

    Thank you. I just think it’s paramount to know if this is neutral or not, even in the opening paragraph of a story about it.

    I’ll email you.

  16. Mark E says:

    Lief, no offense meant here….I blast Bambi. And I love to sink my teeth into Bambi, with the juice on my chin. So this isn’t about cute animal vegetarianism. This is about the ruthless reality of global warming.

    So no offense meant when I say if we apply your logic, then by figuring out how to harness 2nd hand smoke, we can just give lip service to getting people to quit!

    “Better to reclaim energy that would otherwise pollute the environment even more or better yet return a profit” is an eloguent explanation as to why casinos give free meals to gambling addicts.

    You can only envision these beef/dairy operations as turning a “profit” if you do not expect them to pay for environmental services or make monetary restitution for their real social and environmental costs.

    I like helping family farmers with hay-munching cows, but that quaint notion has given way to the corporate farmers growing petro-cows, nearly all of whom will go belly up no matter what, given the warming in the pipeline and and NCAR’s projected A1B drought conditions>

    Biogas is great, in the right context but these massive petro-cow operations are absurdly unsustainable. From an ecological point of view, the only rational beef/dairy mitigation strategy starts with massive reduction in consumption.

    Will this hurt producers? No. It will change the timing of their fate, but not fate itself. It is unreasonable to think they can survive NCAR’s drought predictions. They aren’t my enemy, but they just can’t last at -6 PSDI. (What can?)

    A rational society would deal with this reality, and seek the most bang for buck in both mitigation AND adaptation by teaching the population how to eat vegetarian ASAP.

    Of course, we lack evidence that society is rational, so never mind. You wanna supersize that?