Rhode Island’s compost law, passed in 2014, requires large institutions such as supermarkets and food makers to divert their organic scrap to a farm, food pantry, compost facility or anaerobic digester, as long as such a facility exists within 15 miles. So far, only a smaller-scale compost facility is operating in Charlestown — Earth Care Farm has been composting food scrap for 40 years. The Compost Plant has proposed a facility in Warren.

In recent years, smaller digesters have been built in Massachusetts that service a single facility, like a Stop & Shop distribution warehouse in Freetown, Mass. In Dartmouth, Mass., a 12-ton-per-day food scrap to biogas anaerobic digestion facility opened in 2014 at the Crapo Hill Landfill. A single digester, or digesters, intended to serve an entire state or region has yet to materialize.

Blue Sphere Corp., an Israeli-based company, is poised to be the first. Planning for its Johnston facility began in 2012. Construction started in 2014. This summer, the facility on Shun Pike began processing liquid waste such as sewage and manure. Solid food waste was added more recently, to build up the proper bacteria level in one of the two 2.5-million-gallon “digester” tanks.

Each tank acts like a giant stomach, breaking down organic material and generating a methane-based biogas that is burned for electricity. That electricity is one of three revenue streams for the facility. The biogas fuels one of two generators with a total capacity of 3.2 megawatts. The power is purchased by National Grid under a 15-year power-purchase deal. The residual organic material is sold as a soil amendment. A tipping fee is charged based on the weight of organic material when it arrives at the plant.

Blue Sphere has contracts to take organic scrap from food manufacturers and hopes to attract more customers in Rhode Island and Massachusetts, such as seafood processors. The plant looks to be operational as Rhode Island’s compost law expands in 2018 to include smaller institutions that produce more than 54 tons of food scrap annually, such as cafeterias and large restaurants. The success of the Johnston operation could inspire other states with compost laws like Massachusetts and Connecticut to follow.

“My sense is there is a wait-and-see attitude on how well [Blue Sphere] does. To see if it’s a successful model. I think this is their test case for the Northeast,“ said Mark Dennen, supervising environmental scientist for the Rhode Island Department of Environmental Management (DEM).

To read the full story, visit https://www.ecori.org/composting/2017/10/2/anaerobic-digester-could-be-model-for-region.