July 28, 2016

This Pilot Has Taken Off

Amy Barad, Program Director

It’s always great to hear about a “pilot” project that not only proves out its hypotheses, but exceeds expectations and lays the groundwork for a full-scale facility.  That’s been the case for the pilot anaerobic digester, developed by Massachusetts-based CRMC Bioenergy, LLC at the Greater New Bedford Regional Refuse District’s Crapo Hill landfill in Dartmouth, Mass.

Anaerobic digesters are oxygen-free vessels where organic materials – in this case, about 3,000 to 5,000 gallons of  food waste daily – are broken down by microorganisms into biogas and digestate, a nutrient-rich liquid. At CRMC Bioenergy, the biogas is blended with landfill gas and fed to on-site generators that make electricity. The digestate is used to spur biological activity in the adjacent landfill, helping it to produce more gas to be fed to these electric generators.  

Operating since late 2014 the pilot project has provided valuable information, including the availability of appropriate inputs to the digester, how much useful biogas could be produced, and the compatibility of digester operations with ongoing landfill operations. The digester has been a success on all counts.  In particular, it is producing more biogas (and of higher quality) than anticipated, resulting in greater electricity generation: at over 70% methane, the biogas from the pilot-scale digester is responsible for about 187,000 kilowatt-hours per month – enough to power about 295 average Massachusetts homes.  As a result, CRMC is planning a ten-fold expansion of digestion capacity, the installation of another generator, and new equipment that will allow it to process a wider variety of feed materials.  The expanded facility will help regional producers of food waste comply with the statewide ban on the disposal of large quantities of food waste, while substantially increasing the generation of renewable energy.  

The company is also exploring two ancillary projects that would use excess generator heat to make fertilizer from the digestate and to enable year-round growing in a greenhouse.