GMP conducts hearing on proposed digester

Facility in works for Dunsmore Rd.

By Elaine Ezerins

Staff Writer

Just
The Facts

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ST. ALBANS TOWN – Green Mountain Power (GMP) met with dairy farmers, town selectboard members and others Tuesday to discuss the potential construction of a digester near the St. Albans Bay.

A digester is a cement holding tank, which paired with a generator can turn cow manure from nearby farms into electricity.

The proposed digester, which would be constructed on nine acres on Dunsmore Road would join three others located on farms in Franklin County, one each in Bakersfield, Berkshire and St. Albans Town.

How it Works

The cow manure is collected in a large cement holding tank called a digester. Inside, the manure sits at 101 degrees Fahrenheit for 21 days.

The methane gas rises to the top two feet or so of the tank. The biogas fuels a modified natural gas engine, which in turn spins an electric generator to create electricity. The electricity goes onto the grid and is distributed to the community.

The byproducts of this process do not go to waste. The remaining manure then goes through a separator, which separates the liquids from the solids.

The liquid portion can be used to fertilize crops for cow feed. The solid material can be recycled as bedding for the cows, instead of using sawdust, which would cost the dairy farmers extra.

This process is repeated indefinitely, because there is a never-ending flow of manure.

Supporters

The St. Albans digester would be part of a larger program called Cow Power, which GMP offers throughout the State of Vermont. For every kilowatt-hour requested by customers, GMP pays the farmer for the electricity as well as a Cow Power charge of four cents for the environmental benefits.

Breweries, colleges, car companies, clothing companies and national parks are all buying into this sustainable energy source.

In a blog post, Woodchuck Hard Cider explained its decision to join Cow Power. “It’s a full circle way of thinking about renewable energy,” it said, on the blog post. “Every part of the process allows the next part to take place.”

“Many businesses, Woodchuck included in its statement, are working to become ‘sustainable’ and ‘green’ and ‘eco-friendly’,” the business wrote. “But sustainability has to be viewed as a moving target.  It’s not something that is ever fully achieved.”

Currently GMP has 13 farms involved in the Cow Power program, each one creating electricity through a digester on their property. Blue Spruce Farm was a pioneer in the program, the first one to test out a digester on its land.

Blue Spruce Farm

Owned by Norman and Mary-Rose Audet, Blue Spruce Farm, of Bridport, is responsible for producing more than 30 million pounds of milk annually, all of which is used to make Cabot Cheese.

Though milk is their main product, the 1300 cows also generate 1,600,000-kilowatt hours of electricity annually and produce bedding.

The electricity goes onto the grid to serve 400 homes, providing a constant source of electricity. By not putting the manure back on their fields right away, the Audets are reducing their green house emissions in an innovative way.

St. Albans Town

David Dunn from GMP explained at the town meeting how the Cow Power process in St. Albans would reach the needs of the community.

GMP wants to use cow manure from three local dairy farms, including Paul Bourbeau and James Bessette farms, and food waste to generate electricity 24 hours a day.

The food waste could come from grocery stores in the area and other places, but it was not specified exactly where in the presentation. The food waste would be made into slurry off site and then brought to an underground reception tank, before combining with the cow manure to be processed in the digester.

After the mixture went through the digester, it would go through two separation systems including dissolved air flotation.

In the liquid portion, the separators would be able to take out up to 80 percent of the phosphorus from the manure, returning to the farms only what was necessary for crop production. This could benefit St. Albans Bay whose water quality has worsened due to excess phosphorus. Agriculture is the largest contributor to this problem in the area at 61 percent, according to the U.S. Environmental Protection Agency.

The liquid portion would be injected directly into the soil for control purposes instead of using traditional manure tankers and spreading techniques.

GMP estimates that there would be a 90 percent reduction of odor in the manure after the digester process. It also anticipates a reduction in greenhouse gas emissions equal to taking 1300 cars off the road.

The trips to bring the manure back and forth would add up to about eight round trips per week. The digester would export 16 deliveries worth of bedding to the Bourbeau and Bessette Farms, creating traffic on local roads, but reducing the amount of bedding purchased from out of state.

GMP would build, own and operate the project on leased property. The design of the digester would come from DVO Anaerobic Digester Systems and only one person would need to check on the operation of the digester during the work week.

GMP is not asking customers to pay extra for the electricity coming from the digester. Its goal is to keep rates steady or even decrease them.

The main concerns from the community during the town meeting were the types of food used in the manure and food waste mixture as well as how exactly the smell from the manure would be reduced.

Future

The digester would reduce the flow of electricity from other sources and someday, it could be it’s own island. If the larger electricity grid went down, the digester could potentially keep part of the town up and running.

The company already filed design and construction plans with the Public Service Board, but questions and concerns from the community can still be worked into the digester’s construction and function.