Food Digesters and Compost Sites Open for Business

By TIM FAULKNER/ecoRI News staff

This 96,000-gallon tank in Dartmouth can process up to 30,000 gallons of organic waste daily. (Tim Faulkner/ecoRI News)

This 96,000-gallon tank in Dartmouth can process up to 30,000 gallons of organic waste daily. (Tim Faulkner/ecoRI News)

DARTMOUTH, Mass. — Think of it as a giant stomach. That’s how a builder described one of the first in a wave of new food digesters being built to process organic waste in Massachusetts and Rhode Island.

The structure, at the edge of the New Bedford/Dartmouth regional landfill — also known as the Crapo Hill Landfill — is a pilot facility with space to expand if demand grows. Initially, the anaerobic digester will take in 3,000 gallons of organic waste daily, a tiny sum compared to the massive volume of organic material that that is buried, burned or pumped into waterways through wastewater treatment facilities. According to the Environmental Protection Agency (EPA), about 25 percent of all waste in landfills is food and other organic material.

This “bioenergy" digester is unique because it accepts food, as well as sludge from wastewater treatment plants and a category of waste called FOG (fats, oils and grease). Through a closed 96,000-gallon tank, the organic material is converted into a fuel and a low-nutrient liquid "digestate" for use on the landfill.

For now, the organic material arrives in a tanker truck. The material is pumped into one of three underground grinder/chopper tanks and then flows into the 96,000-gallon digester. The gases are drawn off and burned to provide about 75 kilowatts of power to an existing methane power plant that runs on gases from the landfill.  

The liquid digestate has three uses. Since most of the smelly gases are burned off, the digestate can displace water used as a spray on top of the landfill to control debris. It can be mixed with leaf and yard waste to increase decomposition, and, lastly, the digestate can be injected into the landfill to increase decomposition and thus create additional gas for fueling the power plant. In all, the increase in biogas is expected to add some 300 kilowatts of power generation on top of the 2.7-megawatt energy capacity at the biogas power plant.

The reduction in waste and the increase in decomposition is expected to help increase the life of the regional landfill by 10 years. Prior to the project, the landfill was nearing the end of its 20-year life expectancy.

The $1.5 million cost for the project was funded through private investments and state and federal grants. The facility has the capacity to accept up to 30,000 pounds of organic material daily.

During the Oct. 7 dedication, EPA Region 1 Administrator Curt Spalding said New England is ahead of the rest of the country in addressing food scrap. “It’s one of the things we need to change in America," he said.

The Massachusetts ban on commercial organic waste took effect Oct. 1. The state aims to shrink its waste stream by 30 percent by 2020 and 80 percent by 2050. The ban requires any entity that discards at least a ton of organic material weekly to donate or repurpose any useable food. Any remaining food scrap must go to a composting facility or animal-feed operations, or shipped to an anaerobic digestion facility. The ban applies to about 1,700 businesses and institutions, such as supermarkets, large restaurants, colleges and universities, hotels, convention centers, hospitals, nursing homes, and food service and food processing businesses.

Organic waste bans also are in place in Connecticut and Vermont. Rhode Island’s ban takes effect in 2016.

Organics processing facilities are going on-line regionally as new laws prohibiting organics in the waste stream go into effect.

A Stop & Shop warehousein Freetown is breaking ground on an anaerobic composting facility.

Food composting sites recently opened or will open soon in Wrentham, Waltham, Lowell, Hadley and Gardner.

Supermarket food digesters with electric generation are planned for Fall River and Millbury.

Seafood scrap and other organic material will be converted to electricity and fertilizer at a proposed anaerobic digester in North Kingstown, R.I.