Reducing Greenhouse Gases!!

We Power The Dairy With Methane From Our Cows

It’s true! 

After a 5-year process, we’re now creating electricity with our methane digester. The digester captures naturally occurring gas from manure and converts it into electricity.  With this new system, we’re generating up to 300,000 kilowatt-hours per year, equivalent to about $40,000 a year!

More importantly, putting a tarp over the manure ponds eliminates the release of methane (a natural byproduct of manure) into the air. According to the 2003 U.S. Department of Energy Report on Greenhouse Gases, agricultural sources, primarily animal waste, account for approximately three percent of greenhouse gas emissions. A dairy cow can generate 120 lbs. of waste each day, totaling  about 40,000 lbs. per year! Solids separated from the waste are composted and reused as fertilizer, providing additional, far-reaching benefits.

The project received a 50 percent grant from the California Energy Commission.  Ours is the first system to take advantage of regulations of “net metering”. Net metering allows Straus to run meters in reverse and also offset other electrical usage from other meters at the farm and the creamery.

This is one more step in creating a self-sufficient dairy that minimizes its environmental impact.

How the Methane Digester Works

Twice a day, the barn is cleaned by flushing with recycled water. Manure is scraped with a tractor toward a holding pond.  The pond is where the processes of decomposition and methane digestion begin.

1. Manure goes through a separator, which separates solids from liquids.
   
2. The liquids are piped into a second, covered pond that uses anaerobic (without oxygen) digestion, a process in which bacteria break down the manure.
   

The byproduct of anaerobic digestion is methane gas. There is sixty percent methane, along with carbon dioxide and a small amount of hydrogen sulfide that is produced.  The tarp that covers the pond captures the gases and they flow to a combustion engine. The methane fuels the engine of the generator. The generator then produces electricity.  Heat created by the combustion engine is also used to heat water for the dairy. This 180-degree water is used for cleaning barns.

Benefits of a methane digester

• Eliminates methane gas - a greenhouse gas that is 21 times more detrimental than carbon dioxide.
• Greatly reduces odors on the farm.
• Fly populations are greatly reduced.
• Separated solids are used as an organic fertilizer on the farm
• Remaining liquids are also applied as an organic fertilizer to the pastures and silage crops.
• The tarp helps to divert rainwater that would otherwise fill the ponds.

Links to the Experts

Allen Dusault
Sustainable Conservation
(415) 977-0380 x303
adusault@suscon.org
Sustainable Conservation promoted the passage of legislation to fund matching grants for the purchase of generator systems and orchestrated the passage of AB 2228 to allow net metering of the electricity. Sustainable Conservation also argued f before the PUC for a better rate structure, winning two decisions, and challenged PG&E on interconnection charges that would create excessive fees for the dairy.