On the selectmen’s advisory Solid Waste Committee, there is an occasional attempt to revive discussion of Anaerobic Digestion. That term refers to the process of accelerating and controlling the natural process of digesting organic materials in the absence of oxygen.
To clarify further, the stomach does this all the time, although control is not always complete. In the British television series All Creatures Great and Small, there was an episode in which one of the vets was trying to relieve a bloated cow. Just as he succeeded, a nearby helper lit a cigarette. The resulting methane explosion blew both men into a nearby pasture.
In controlled situations, large quantities of organic matter are moved through a series of sealed tanks in which temperatures are gradually raised, methane is drawn off, and the remaining solids, with high nitrogen content, are packaged and sold to nurseries and farmers for soil enrichment.
I recently read an article about a dairy farm in Vermont with 385 milk cows. Things went well until the price of milk dropped and the operation started to lose money. The owner installed a big anaerobic digestion system and, thanks to an active market for soil conditioner, started to make a handsome profit. At the same time, they burn the methane in a boiler-plus-generator to provide much of the farm’s electricity.
An article in the current issue of Sierra magazine, titled “On the Moove,” expands on the subject. At Western Washington University, Professor Eric Leonhardt and his students have built a hybrid car that gets the equivalent of 94 miles to the gallon, using a biofuel made from cow manure, at a projected cost of $2.50 per gallon.
With the help of a grant from the Department of Energy, Leonhardt’s team built a mini-refinery at a dairy farm near Bellingham. There, they scrub the gases coming off of the manure, extracting the methane that is its major component.
To quote the professor: “It is a huge net winner for the environment. Not only are we removing a major source of methane emissions, which are 23 times as potent as carbon dioxide as a greenhouse gas, but we are also displacing fossil fuels by using biogas in hybrid vehicles.”
The team can produce the equivalent of 100,000 gallons of gas from the dairy’s 667 cows.
Although the article does not describe the added benefit of using the solid residue for soil conditioner, that important byproduct provides added income for the production facility, plus soils that are rejuvenated without use of petroleum derivatives.
I can’t resist this one: If your family had two cars, each traveling 15,000 miles a year at 30 miles per gallon, you would use 1,000 gallons, the output of just less than seven cows.
To offset your greenhouse gas emissions, donate seven cows to the Vermont dairy farm, claim a charitable tax credit from the IRS, claim a Renewable Energy Credit from MassCEC and feel good all year.
On another subject, Fred Krupp, president of the Environmental Defense Fund, reports that wind now employs more people than the coal industry. This lends support to a recent statement by Larry Summers, President Obama’s economic advisor, that the key to economic recovery is to remake the energy sector.