Compost is heating up at Middlebury business
MIDDLEBURY — Folks at the Foster Brothers Farm in Middlebury have been innovators in recycling and green energy for years, whether it be embracing manure-to-energy technology or producing organic manure composts like its popular “Moo Doo.”
So it should come as no surprise that one of the farm’s subsidiaries, Vermont Natural Ag Products, is now looking to harness heat from its composting operation to warm its facilities and generate a new, more potent way to aerate its compost products — and possibly allow the company to dramatically increase production.
“It’s kind of an exciting thing, if it all works out,” said Robert Foster, president of Vermont Natural Ag Products.
The company, launched in 1992, just received a $28,325 federal grant toward a $120,000 pilot project to install new energy efficient equipment that will capture the thermal energy created from its composting materials.
If the equipment yields the hoped-for results, Vermont Natural Ag Products will build a more permanent project that has already received a 20-percent funding commitment from the state of Vermont.
VT Natural Ag Products produces around 45,000 cubic yards of compost each year, which is whisked to organic farmers and gardeners throughout New England and beyond. The process of making the compost from cow manure, chicken litter, and horse bedding in part involves using a giant machine to periodically turn the product to infuse air into the mixture.
“This process here is aerobic and exo-thermic. It gives off heat,” Foster noted. “The temperatures get as high as 170 degrees. So part of the composting process is to raise the temperatures up, kill off a lot of the fungus and pathogens. Then it will stabilize, and then we set it aside for another three or four months and let it re-populate with beneficial organisms — sort of Mother Nature’s process of recycling.”
Foster noted there are around 1 million BTUs per cubic yard of compost material. And there are approximately 35,000 cubic yards on site at the company’s Lower Foote Street headquarters at any one time.
“So the energy potential for this is pretty high,” Foster said. “One of the things that got us thinking about this is when we take one of those (compost) wind rows off and move it to a clear bay, even in February, it will be a month and a half before snow will sit on that. So there’s a lot of heat.”
That’s a lot of heat that Foster and his colleagues reasoned could be doing more good than giving off steam. They contracted with a company called Agri-Labs, which agreed to furnish a box-like structure that will help capture and process the heat from the composting structure.
This pilot project will involve processing two windrows of compost under cover, and two windrows outside, so officials will be able to compare whether conducting the process under cover makes a difference.
“The cover is expensive,” Foster said.
Company officials will draw air through the compost at negative pressure, resulting in that air being heated to around 150-170 degrees, according to Foster.
“It’ll be saturated, so it holds a lot more energy,” Foster said. “We will take it into the box … where it draws the heat out of (the compost).”
Vermont Natural Ag Products will be able to do two main things with the heat.
“We can put it back into the air stream and dry down the compost for some of the professional mixes that can’t be as heavy, or we can use the supplemental heat to heat our bag building, which uses radiant heat in the floor,” Foster said.
The bag building is where roughly 750,000 bags of compost each year are bagged for sale.
It now takes around three months to properly prepare the compost for sale, according to Foster. Using the captured heat in the aeration process could shrink that timeframe by more than half, Foster noted. That means the company would be able to process substantially more compost each year.
“We don’t know how much heat we are going to recover. This is what this is all about. It’s a pilot project,” Foster said.
The pilot process will last six months to a year, according to Foster.
“We don’t know what’s going to happen, but we thought this was a risk worth taking,” Foster said.
The Vermont Natural Ag Products grant was one of 17 loans and grants recently awarded by the U.S. Department of Agriculture. The money is for Vermont businesses transitioning to renewable or energy efficient technologies to cut costs and reduce energy consumption this year.
“Energy costs remain one of the largest expenses for a rural small business,” USDA Rural Development State Director Ted Brady said through a press release. “By providing these businesses with capital, the USDA aims to incentivize small businesses and farms to invest in new technology that not only increases their profitability, but also reduces greenhouse gases, fossil fuel consumption, and increases our nation’s energy independence.”
Reporter John Flowers is at email@example.com.
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