Quest With Me: Anaerobic Digester

I took a couple of my Vital Communities colleagues on a field trip to the Anaerobic Digester at Vermont Technical College in Randolph a few weeks ago. We checked off a stop on the Super Quest and got the grand tour of the amazing structure while we were there.

 Your first question is probably the same as mine was: what on Earth is an anaerobic digester?? I’ll leave this description to the experts:

Anaerobic digestion (AD) is a natural biological process used by ruminant animals like cattle, goats and sheep to extract energy from food. Our AD facility will use the same natural biological process that occurs in the four stomachs of a cow.  While cows use feed to produce milk, meat and more cows, our facility will use dairy manure and food ‘residuals’ to produce electricity and heat for Green Mountain Power and the campus. Like a cow, this anaerobic digestion facility will produce manure-like material that will allow us to recycle nutrients from food residuals into crop fertilizer. (Source:

This incredible process harnesses energy from the methane in manure to power our homes, businesses, and schools. It also generates quite a bit of heat along the way, which VTC pumps into their classroom buildings in the winter. What’s left at the end of the process can be used as fertilizer.


Zyla shows Phil the digestion tanks


Zyla gave us a fantastic tour of the Digester buildings as trucks continuously came and went with their loads. After the trucks drop off “meals” for the digester, they also pick up liquid fertilizer to take back to the farms.


A peek into the genset

After the tanks digest the manure, the gases are piped to the generating engine (genset), where they are combusted to generate electricity and heat. At full capacity, the digester can generate about 2.8 million kilowatt hours of electricity per year.


Nancy checks out the solids that are reused after digestion as cow bedding or as fertilizer

After digestion, the solids separator does exactly what you’d expect: it separates the remainder of the slurry into solids and liquids. The solids can be used as cow bedding, fertilizer, or to create a compost. The liquids are spread onto the fields as fertilizer or are pumped into a holding pond.

The team at the Anaerobic Digester offers full tours to the public on the second Thursday of the month, from 2 pm to 7 pm.  If you want to go on the full tour before the end of Questing season, mark your calendar for Thursday, September 11 or Thursday, October 9. You don’t have to go on a tour to complete the Quest, but I highly recommend it! This map of the VTC campus will help you find your way.

If you can’t make it to one of the tours, the VTC website also has a great “geeky” explanation of how the digester works, complete with a diagram of Big Bertha to help you figure out what you’re looking at while you’re there.

And if you haven’t registered your team for the Super Quest yet, now is the time! You’ll be entered to win the “Almost as Grand” Prize just for registering. Once you complete your quest, you’ll also be entered for the Grand Prize! As always, thanks to Farm-Way for generously sponsoring this year’s Super Quest.