Project Development

CommonWealth is the developer, and through a special purpose project subsidiary is the sole owner/operator, of the Greater New Bedford LFG Utilization Project (the LFG Project), a 3.3 MW landfill gas-to-electricity facility located at the Crapo Hill Landfill in Dartmouth, Massachusetts.

The LFG Project generates electricity from combustion of landfill gas in four Caterpillar 3516 LE internal combustion engines. The facility is located on a site adjacent to the landfill and leased from the Greater New Bedford Regional Refuse District, the public entity which owns and operates the landfill.

The gas produced as a result of the decomposition of organic wastes at the landfill is collected from a series of vertical and horizontal extraction wells connected by piping and forming a network that continuously expands to effectively cover the entire volume of the landfill. The gas typically consists of 48% to 55% methane, up to 40% carbon dioxide and less than 1% oxygen, with the balance mostly nitrogen drawn in from ambient air.

Two vacuum blowers connected to the collection network bring the gas from the landfill to the LFG Project, then through a media-based system to remove hydrogen sulfide and a condensate knock-out to remove moisture. The blowers then push the pressurized gas through a radiative cooler and coalescing filter before delivery to the engines for combustion. The engines drive generators rated at 825 KW each. The electricity is delivered to the regional grid through the Eversource 13.2 kV local distribution system. Air emissions are controlled by ensuring efficient combustion, aided by a state-of-the-art air-to-fuel ratio controller on each engine for optimized control of NOx and CO emissions.

The LFG Project was constructed starting in March 2005 and achieved commercial operation in December 2005. A system for removing sulfur from the landfill gas was added in 2016. Development of the project was supported in part by loan programs of the Massachusetts Renewable Energy Trust (now the Massachusetts Clean Energy Center), as well as private investments of debt and equity.

Environmental benefits of the LFG Project include the following:

  • Supports efficient collection of methane gas from the landfill, thereby preventing its emission to the atmosphere. Methane has 28 times more impact on global warming than emission of an equal volume of carbon dioxide.
  • Permanently destroys the methane component of the landfill gas by combustion with an effectiveness that exceeds 99.8 percent.
  • Controls landfill odors by removing the hydrogen sulfide and destroying VOCs and other odorous compounds generated as a component of the landfill gas. Displaces electricity that would otherwise be distributed within the regional power grid that is generated from fossil fuels.
  • Avoids losses and adverse reliability impacts of long-distance transmission of electricity generated from remote sources.