Addison County Is Now Home To The Largest Anaerobic Digester In The Northeast. So How Does It Work?

An image showing a large red building with two domes on top and a sign reading Goodrich Farm

Elodie Reed
Goodrich Family Farm hosted a celebration Wednesday for its new anaerobic digester, the largest in the Northeast. The system creates biogas from organic materials like food waste and cow manure, which is then turned into natural gas.

Goodrich Family Farm in Salisbury is now home to the largest anaerobic digester in the Northeast. Several dozen people, including Gov. Phil Scott, gathered at the dairy farm Wednesday to celebrate.

So how exactly does the digester work?

An image showing black and white dairy cows

Elodie Reed
Goodrich Family Farm’s dairy cows (and their poop) are an essential part of the anaerobic digester process.

The digester has the capacity to turn more than 180 tons of food waste, and 100 tons of cow manure, into biogas in a single day.

Unlike traditional natural gas, it isn’t a fossil fuel extracted from the ground, but from existing organic materials.

In this case, it’s from things like wastewater and spoiled food from Cabot and Ben & Jerry’s, and then the cow poop from the farm.

All that goes into this holding tank:

An image showing a metal door in the ground, with cloudy grey skies in the background

Elodie Reed
This tank built into the hillside at Goodrich Family Farm can hold up to 400,000 gallons of organic waste.

According to John Hanselman, the CEO of Vanguard Renewables (the waste-to-energy company partnering with the farm), these materials then go into this “2 million-gallon Instapot,” where they’re heated to 105 degrees.

Microbes in the manure eat the waste and excrete biogas.

That raw biogas is converted to natural gas in this station:

An image showing a grey pipe with a sticker on it that says natural gas

Elodie Reed
This chemical station helps convert raw biogas into natural gas that can then be fed into Vermont Gas’ system.

It uses high pressure to break apart and isolate the methane molecules, aka natural gas, that then enter the Vermont Gas system.

Middlebury College plans to purchase a little more than half of the gas created by the anaerobic digester to replace its current use of traditional natural gas. The school expects this to fall into place sometime in 2022.

Then there’s the byproducts. Once the gas is extracted from the organic waste, that liquid is prepped to become fertilizer for the farm. It goes through this dissolved air flotation (DAF) system that removes phosphorous to reduce pollution in Otter Creek and Lake Champlain.

The phosphorous is pressed, dried and made into cakes, which can be sold to places like nurseries.

An image showing a room with a tank and machinery

Elodie Reed
This phosphorous removal system is one of the first in the country according to Vanguard Renewables CEO John Hanselman.

Prior to the farm’s manure ever going to the digester holding tank, it’s separated out into liquid and solids. The solids are dried out and made into bedding for the cows.

An image of someone holding brown material in their hands

Elodie Reed
Some of the dry cow bedding that’s been created from their manure.

According to Goodrich co-owner Danielle Goodrich-Gingras, the digester is good for business: “This project didn’t really change how many more cows we were taking on. It just allowed us to, you know, add income without having to add more milk. It definitely diversifies some income for us.”

For context: Goodrich Family Farm is one of just under 600 conventional dairies left in Vermont, down from nearly 1,000 in 2021.