Vermont Environmental Consortium

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BRATTLEBORO REFORMER

#43, January 27, 2008
New Uses for the World's Smallest Livestock
by
Daniel Hecht

One astonishing fact of mankind’s relationship with our fellow creatures is that the first livings things we domesticated were not dogs, horses, cats, or cattle. We probably tamed and husbanded much smaller domestic livestock thousands of years earlier: micro-organisms.

We use them in innumerable ways. Bacteria and yeasts allow us to make yogurt, cheese, beer, wine, bread, soy sauce, and many more foods. Nowadays, they’re also being selectively bred and raised to produce energy, such as the various types of bacteria that perform biodigestion for methane generation or ethanol fermentation.

Josh Nelson of Pawlet is an advocate of another common use of micro-organisms: composting. As he says, “Composting has been around forever – it’s an established, viable technology.” But while many farms, homes, and businesses compost to provide a soil enrichment, what excites Josh is its use as an energy source.

Decomposition generates heat – your compost bin steams in winter due to the metabolic activity of millions of organisms as they eat, excrete, and respire. In the farm context, composting manure produces water vapor that ranges from 131 to 149 degrees. Why not use that heat?

“When I tell people about this, they say ‘Sounds like a great idea,’” Josh exclaims. “And I say, ‘It’s not an idea! It’s a reality, it’s in use, and it works!”

He should know, having worked in related fields for decades. After earning degrees in Livestock Husbandry and International Agriculture at Ohio State, he went on to get a master’s degree at the School for International Training in Brattleboro. He spent his early professional life in El Salvador and Guatemala, mainly working to breed high-producing dairy cows suited to that tropical climate. He’s been back in Vermont for eight years, operating a small grass-fed sheep and goat outfit near Pawlet – and advocating for compost energy.

He’s now director of U.S. operations for Agrilab Technologies, a Canadian firm with a proprietary process for recovering the heat generated by composting. He first read about it in an industry journal, then contacted Brian Jerose, who was installing an Agrilab system at Diamond Hill Custom Heifers, in Sheldon.

At Diamond Hill, Terry and Joanne Magnan raise about 2,000 milk calves and heifers; like other farmers, they were facing both rising energy costs and tighter manure management regulations. The Agrilab process provided a solution to both.

The Diamond Hill system encloses the compost windrows – long, narrow heaps of the stuff – in a barn built for the purpose. Manure and cattle bedding are mixed with chopped hay and straw to provide the proper balance of carbon, nitrogen, and moisture. When the mixture is laid in windrows, a huge herd of the world’s smallest domestic livestock goes to work.

Fans draw air down through the windrows to pipes in the floor. From there, the compost-heated steam travels to a heat exchanger that warms water in a bulk tank. The tank water can then be circulated as needed, such as to heat-radiating pipes in barn or residence floors.

The trick is to produce net energy gain – the fans consume electricity – so the system requires high efficiency and good insulation. In the past, fine tuning such technology would have been hard, but today computers permit continuous monitoring and adjustment. The Diamond Hill computer monitors 35 points in the tank, pipes, windrows, and floor, then analyzes the data so that equipment settings can be optimized.

Josh especially likes the system because it makes maximum use of every resource. Farmers can save money on energy bills by using the heat; they can also sell the composted manure or, with a little more processing, use its cellulosic components as livestock bedding, avoiding another major expense. Fluids extracted from the manure can be sprayed on fields, soaking in and maintaining soil fertility without polluting nearby streams.

Building or retrofitting a composting barn is the most expensive part of the arrangement; the additional cost of installing the heat-gathering and heat-exchanging system is relatively small. Josh believes this method of extracting energy from manure is more cost-effective than anaerobic digestion. “We’re capturing one million BTUs per ton of material!” he says. Since constructing a compost heating system costs much less than a digester, Josh suggests it might be better to spend the same amount of money building 10 of these systems on 10 farms rather than one biodgester on one farm.

And, in fact, the two can be complimentary. Farmers might choose to set up both, using the compost to warm the biodigester, cranking out heat, electricity, and valuable co-products.

It’s refreshing to suddenly recognize new value in things we’ve long taken for granted – like the steam from the compost bin – and to see ancient technologies converge with high tech. Certainly, our oldest, smallest livestock have an important role in Vermont’s farming and energy future.

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Daniel Hecht is a novelist and executive director of Vermont Environmental Consortium. For more information on any Green Grapevine topic, contact vec@norwich.edu.

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