Biogas from Manure: How Green?

Pigs in a confined animal feeding operation (CAFO) being raised to market weight. CAFO practices that are already unhealthy for farmed animals will be entrenched by the need to collect enough manure to make energy. Photo by Diane Halverson/AWIOn May 4, Secretary of Agriculture Veneman announced availability of $22.8 million in grant funds to farmers and rural businesses for renewable energy projects, including biomass, wind, geothermal, and solar. Last year, the U.S. Department of Agriculture awarded $21 million to 113 farm energy projects. Thirty involved anaerobic digesters to capture methane (biogas) from confined animal feeding operations (CAFOs) that manage manure as a liquid. Increasingly, biogas production from liquid animal "wastes" is being touted to boost farm incomes, achieve independence from foreign oil, and solve massive environmental problems associated with CAFOs.

While AWI applauds efforts to develop renewable energy sources, we are concerned that subsidizing energy production from liquefied manure artificially creates a demand to continue an extractive and exploitive relationship with animals and nature and perpetuates a form of animal production that has proved detrimental to public health and rural communities.

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In a recent San Francisco Chronicle article a California Energy Commission spokesman estimated that, if all the dairies in California (which subsidizes methane digesters) were hooked into the state's utility grid, they would produce only "100 megawatts or so" of energy. But CAFOs have public costs that exceed their energy potential. CAFOs flush manure from buildings with water, a scarce resource in some regions. Besides methane, anaerobic decomposition of liquefied manure emits other gasses, including hydrogen sulfide, a potent neurotoxin. Hydrogen sulfide from manure pits and inside CAFO buildings has killed animals and people, including three California dairy CAFO workers. Methane is highly explosive and has asphyxiated workers repairing equipment in manure pits. Local governments' health care services and community food shelves too often are forced to "subsidize" CAFOs that hire unskilled workers at wages well below the cost of living.

Commercial biogas production requires skilled and attentive management and top of the line equipment. Most sources indicate that investments in manure digesters are not possible without subsidies. Some contend that manure digesters may never be profitable without them and that equipment life may be little longer than the payback period, necessitating further capital investments. The farmer soon finds himself on an even faster treadmill than the one on which he was running to keep up before. CAFOs' continuous need to expand to pay capital costs has driven industry structure to fewer and larger CAFOs, displacing smaller operators. Additional capital costs of manure energy are likely to exacerbate the trend.

CAFOs house pigs and dairy cattle on solid concrete or slatted floors from which manure is scraped into gutters or flushed into under-floor collection pits. Laying hens live in wire cages through which manure drops onto conveyers and into pits. CAFOs do not provide bedding that would interfere with liquid manure collection and anaerobic digestion. They submit farmed animals to lifetimes of breathing polluted air, without the possibility of performing healthful natural behaviors such as grazing or flapping of wings. Such inhumane practices will be entrenched by CAFOs' need to collect enough manure to produce energy.

Government programs should support farming practices that are inherently sustainable rather than inherently demanding of remediation. A first positive step is to stop liquefying manure. Composting bedding-based manure is safer for people, animals, and the environment than anaerobic digestion. Sustainable farms raise animals in proportion to the land they have for spreading manure. Rather than a "waste," composted manure is a valuable soil amendment needed by crops. Raising animals on pasture contributes to animal health, reduces veterinary expenses and antibiotic use, conserves energy, and helps prevent soil erosion. Requiring low capital investment, sustainable practices keep farmers off the high-tech treadmill and can provide comfortable livings for farm families and better lives for farmed animals.