A Massachusetts farmer turns 100 tons of Whole Foods scraps and cow manure a day into power for 1,500 homes

As the holiday season of big meals begins, the amount of food that goes uneaten in the United States is worth a look. The US Department of Agriculture estimates that the food wasted in a year would fill a skyscraper in Chicago about 44 times.

Most of this food ends up in landfills, where it rots and releases methane. Methane is a strong greenhouse gas that adds to climate change. A recent United Nations report by climate experts says up to 10 percent of all human-made greenhouse gas emissions are linked to food waste.

One answer is now being tried in Massachusetts. Dairy farmers there are using food waste to make electricity. The work is done through anaerobic digesters built and run by a company called Vanguard Renewables. These digesters trap the methane and turn it into renewable energy.

From a whole foods store to a dairy farm

The process starts with food that cannot be sold or eaten. Whole Foods is one of the main sources. Its store in Shrewsbury, Massachusetts, has a Grind2Energy system, which is a heavy-duty grinder for leftover food.

Karen Franczyk, sustainability program manager for Whole Foods in the North Atlantic region, explained what goes in. “Everything from bones, we put whole fish in here, to vegetables to dry items like rice or grains,” she said. The machine also takes frying fats and grease.

Whole Foods already gives a lot of its surplus food to food banks. Still, some waste is left, much of it from preparing ready-to-eat food. Just like in a home kitchen, there are onion and carrot peels, rinds, stalks and meat scraps. The grinder turns all of this into a thick liquid. Franczyk called it “liquefied food waste.”

A truck then carries this liquid to an anaerobic digester. Franczyk said it is clearly better than throwing the waste in the trash. The company aims for zero waste and also composts some of its scraps. This system is one more way to reach that goal, she said.

One such digester sits at Bar-Way Farm in Deerfield, Massachusetts, next to a dairy barn. Peter Melnik, a fourth-generation dairy farmer, owns the farm. He receives about 100 tons of waste every day, roughly three tractor-trailer loads. Apart from Whole Foods, the waste comes from a Cabot Creamery nearby, which sends whey, and from a local brewery and a juice plant.

Melnik mixes this waste with manure from his cows. The mixture is heated at about 105 degrees Fahrenheit. As it breaks down, methane rises to the top of a large red tank with a black dome. The gas collects under the dome and is drawn into a motor that runs on methane instead of diesel or petrol. The motor turns a generator.

Power for 1,500 homes and income for the farmer

The generator produces one megawatt of electricity without a break, according to Melnik. The farm uses only about 10 percent of it. The rest goes to the power grid, enough for about 1,500 homes.

The money side matters too, he said. Times are hard for dairy farmers, and the digester has given him a new source of income. Vanguard pays him rent for keeping the digester on his land. The liquid left after the process can be used as fertiliser in his fields. “The digester has been a home run for us,” Melnik said. He added that it has made the farm more sustainable, both for the environment and for its finances.

Vanguard wants to grow. Its chief executive, John Hanselman, said Massachusetts has more than enough food waste to feed its five digesters and many more. A state law helps. It bans businesses and institutions that produce at least one ton of organic waste a week from throwing it away. That gives food businesses a reason to join such programmes.

Hanselman pointed to Europe, where thousands of digesters are in use. He believes the same could be done in every part of the US. The company is now building a digester on a farm in Vermont. The gas from it will be sent by pipe to Middlebury College, helping the college cut its carbon footprint.