Buildings · Analysis

The farm that sells gas: inside the Salisbury digester

A Vermont dairy farm turns manure and food scraps into pipeline gas for Middlebury College. Here is how the digester works, why the college signed for two decades, and what the deal does and does not do for the climate.

Flat geometric illustration of a Vermont dairy farm with a red barn, a large cylindrical digester tank, and cows in the pasture — An original illustration made for this publication.

BY THE CLEAN ENERGY VERMONT EDITORS · FILED NOVEMBER 2, 2026 · 6 MIN READ

How manure becomes pipeline gas

Drive Route 7 south of Middlebury in November, past the stripped cornfields and the first hard frost on the Salisbury flats, and you pass a dairy farm that now does something most Vermont farms do not: it sells gas. Not the kind you pump at the Maplefields, but pipeline gas, cooked out of cow manure and food scraps and piped a few miles to heat a college.

A Vermont Gas Systems customer in Chittenden or Addison County may already have a sliver of this in the meter. The utility blends a small amount of renewable natural gas (pipeline gas made from decaying organic matter rather than drilled from the ground) into the same distribution system that carries conventional gas, so your furnace cannot tell the difference and neither can you.

The mechanics, start to finish

Begin in the barn. Manure and off-farm food waste go into a sealed, heated tank called a digester, where bacteria break them down without oxygen over roughly three weeks and give off biogas, a raw mix that is a bit more than half methane with carbon dioxide and traces of other gases. The Goodrich Farm project in Salisbury, operated by Vanguard Renewables, is built around this at dairy scale, taking manure from one of Addison County's larger herds plus food scraps trucked in from around the region.

Raw biogas is not pipeline gas. A cleanup skid strips out the carbon dioxide, water, and sulfur until what is left is almost pure methane, the same molecule as conventional natural gas, now called renewable natural gas. That upgraded gas is compressed and pushed into a Vermont Gas Systems pipeline built to reach the farm, which is the part that makes this project unusual, and we will come back to it.

The 20-year signature, and the math behind it

Middlebury College agreed to buy the output under a contract reported at about 20 years. For the project, that signature is the whole ballgame: a digester, a gas-cleanup system, and a dedicated pipeline cost real money up front, and no lender funds that against a buyer who might leave in three years. A two-decade offtake agreement turns a risky farm experiment into something a bank will finance.

For the college, the trade is a local, lower-carbon fuel to displace the fuel oil and conventional gas it burns in its central heating plant, bought at a price it can plan around for two decades. Renewable natural gas usually costs more per unit of heat than the drilled kind, so this is not a way to save money. It is a way to buy down emissions and support a neighbor's farm, with the premium carried by an institution that chose to pay it rather than spread across every ratepayer.

The interconnection quirk

Most Vermont farm digesters you have heard of make electricity, burning biogas in an engine and selling the power to the grid, often through the state's standard-offer program (a set price the utility pays small renewable projects). Goodrich does not do that. It skips the electric grid entirely and injects gas into the gas distribution system, a different kind of interconnection with a different regulator and a different set of problems.

That choice has a logic. Burning biogas in an engine wastes a lot of the energy as heat, while upgrading it to pipeline gas keeps more of it usable and sends it straight to a heating load. The catch is that you need a gas pipeline within reach of the farm and a buyer at the other end, which is why this model fits a handful of sites near the Vermont Gas Systems network and does not scale to every hill farm with a manure pit.

Worth watching this month

1. Watch the Vermont Public Utility Commission case files for filings implementing Act 179, the 2024 renewable energy standard, which mostly governs electricity but sets the policy backdrop for every farm energy project.

2. Watch Vermont Gas Systems rate and tariff filings for how the cost of renewable natural gas is recovered, since that determines whether the premium stays with voluntary buyers or reaches general ratepayers.

3. Watch the EPA AgSTAR project database, updated periodically, for whether new Vermont digesters come online or stall, a routine data release that is the clearest public count of who is actually building.

4. Watch Middlebury College sustainability reporting for how much of its heating load the Salisbury gas actually covers in a given year, which has been less than the whole and tends to vary.

5. Watch the Public Utility Commission standard-offer announcements, usually seasonal, for whether electricity-making digesters still pencil out, since that is the road Goodrich did not take.

Common questions

Will renewable natural gas lower my heating bill?

Probably not. It generally costs more per unit of heat than conventional gas, and the extra is usually carried by the buyer who chose it, like the college, rather than passed to everyone.

Is this gas carbon-free?

No. Burning it still releases carbon dioxide, so the real benefit is capturing methane from manure and food waste that would otherwise leak into the air, where methane is a far stronger warming gas. The climate case rests mostly on that capture, not on the combustion.

Could my family farm do this?

Most likely not. The numbers tend to work only for larger herds with a steady manure supply, nearby food waste, and a gas pipeline or power line close enough to reach, which describes very few Vermont sites.

Does this count toward Vermont's 100% renewable electricity goal?

Mostly no. Act 179 governs electricity, and this is a heating-gas project, so it lives in a different policy box even though both are part of the state's broader energy transition.

Sources of record

Vermont Public Utility Commission: State regulator; case files and orders on renewable energy standard implementation and the standard-offer program (.gov).
Vermont Department of Public Service: State energy agency; renewable energy and Act 179 policy context (.gov).
EPA AgSTAR: Federal program tracking livestock anaerobic digesters, with a national project database (.gov).
Vermont Gas Systems: The utility operating the pipeline; renewable natural gas program pages and rate filings.
Vanguard Renewables: Developer and operator of the Goodrich Farm digester in Salisbury; project description.
Middlebury College sustainability: The offtaker's energy goals and reporting on the Salisbury gas supply.

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