Anaerobic Digesters

by: Kaitlyn Gisler

British Columbia farmers are using their livestock manure and off-farm organic wastes (like your lawn clippings) to produce renewable, clean energy for everyone’s use. This may sound like the idiom ‘making silk out of a sow’s ear,’ and although it’s pretty close, it isn’t the pig’s ear that is producing the power.

Matt Dickson of the BC Agricultural Research Development Corporation is the program manager of the Renewable Agri-energy Initiative. In 2007 they launched the Anaerobic Digester Initiative Advisory Committee (ADIAC) for British Columbia farmers:

“The idea…was we had several farmers interested in building a digester but not really knowing who to talk to about the regulations…and policy,” says Dickson of ADIAC, “so we decided to form a group and tried to pull together someone from each of the associations and organizations that the farmer would need to speak with.”

ADIAC hasn’t been meeting for a little over three years but Dickson says all the information is up online and he is only an email or phone call away.

How anaerobic digestion works is by using naturally occurring bacteria to breakdown carbon rich material, like manure, in a sealed oxygen-free environment. This air-tight facility means odours are reduced by a whopping 99% because if the facility smells, biogas is being lost, and consequently, money. The resulting biogas from the decomposition is a carbon neutral gas composed of 55-75% methane and 25-45% carbon dioxide, as explained on the BC Farm Biogas website. The captured biogas is then fed into a boiler to make heat, or can power a generator to produce electricity. It can also be modified further into biomethane—a renewable substitute for natural gas.

Digestate, the only by-product of an anaerobic digester, comes in two forms: liquid (fertilizer) or solids (bedding for animals). Farmers spread the fertilizer onto their fields with the viability of weed seeds reduced by 70%. The solids also save farmers thousands of dollars in bedding costs.

The biggest challenge for digesters in B.C all boils down to “straight and pure economics.” Dickson notes Ontario and Germany as world leaders currently using this technology. Their success comes from the fact that farmers are reimbursed for the costs to produce the energy. Dickson says the numbers have recently changed, but in Ontario farmers were getting paid 16 to 25 cents a kilowatt-hour and in Germany prices vary from 24 to 26 euro cents. In comparison, the going rate in B.C is approximately 8 cents per kilowatt hour.

Dickson’s formula for figuring out the approximate cost for a digestion system is as follows:

“It is very rough but a rule of thumb is [to take] the energy production capacity [of the digester] and multiply that by 5,000 dollars. Systems can range from one million to what-do-you-want depending on its size and all the bells and whistles.”

What motivates people to participate in buying digested energy? It takes some faith and foresight. Digested energy, or Cowpower—as the program is called—cannot be separated from the regular power grid, so customers are paying more with no guarantee they are using captured biogas to light and heat their homes. What they are doing is funding the future of on-farm anaerobic digesters.

And Dickson is setting goals:

[blockquote style=”1″]Our goal for Cowpower is to support fifty digesters on fifty farms. If you want local sustainability, local agriculture, clean water, clean air and reduced greenhouse gas emissions you have to support it, and one way is through the Cowpower program.[/blockquote]