The Energy Blog – by Andy Silber

This should never happen

On April 12th a lagoon holding cow manure failed, causing a spill of millions of gallons of waste into the Snohomish River. In the annals of industrial accidents this is pretty low on the horrific scale. But the tragedy is that the lagoon that failed should not have been there in the first place. Our attention is grabbed by failure and size, not by the slow, steady release of pollution that these lagoons routinely emit. As the manure breaks down methane, a powerful greenhouse gas, slowly rises, along with other noxious gases. In addition E Coli and other pathogens collect and are spread in fields when the manure is used as fertilizer.

This might be acceptable if it was a difficult problem to solve. But the opposite is true. Anaerobic digesters for dairy cow waste is a fully-realized commercial technology. In the digester the manure is eaten by bacteria in an oxygen-free environment and methane is created.  The gas is captured and can be used to power a generator, while the waste heat can be used to warm a barn or greenhouse or other farm uses. The manure in the digester is heated to a higher temperature than it would be in a lagoon, which kills off most of the pathogens like E coli. The benefits are many:

  • Improved air quality
  • Reduced greenhouse-gas emissions
  • Renewable electricity
  • Co-generation of heat for the dairy
  • Removed or greatly reduced risk of spills
  • High-quality bedding for the dairy cows
  • High quality fertilizer for the fields growing the feed for the dairy cows

A small percentage of dairy farms do have digesters, but most don’t. If they are so great, why doesn’t every dairy farm have one? This is a classic example of a market failure:

  • The farmer doesn’t pay for the reduced air quality, so he has no economic incentive to improve it.
  • The farmer doesn’t pay for the greenhouse-gas emissions, so he has no economic incentive to reduce them.
  • These projects are capital intensive and fall outside the expertise of the farmer, so the farmer doesn’t bother.

Though these projects do generate electricity and useful heat, the value of those products alone don’t generate enough revenue to make these projects happen. By selling renewable energy credits (RECs) and carbon offsets some projects do happen, but most dairy farms still use open lagoons to hold their waste. Since dairy farming is already a financially risky proposition, legislatures are loath to require digesters and the farmers are unwilling to invest in these projects themselves.

Even broad policy measures like Washington State’s I-937 and other renewable energy portfolio standards aren’t very effective in encouraging digesters. Utilities aren’t very interested in these projects because they are small (typically less than 1 MWatt or equivalent to less than one utility scale wind turbine) and more expensive than electricity generated at a large wind farm.  Also, these renewable standards still don’t capture all the value these projects have. Grants like those from the Department of Agriculture and the Recovery Act (Federal Stimulus) do help these projects happen, but not very quickly. A requirement for the largest dairy farms and Concentrated Animal Feeding Operations to install digesters would go a long way to bringing this technology into the mainstream, but I don’t expect to see that happen any time soon.