W5.1 Waste to energy
Generate additional energy from waste products (e.g., woody biomass and sewage) in Thurston County.
Woody biomass –
The Evergreen State College did an extended study assessing the feasibility of converting the campus heating system from natural gas to a woody biomass gasification plant. (There was a great deal of passionate, though not always well informed, political opposition to it and to Simpson’s contemporaneous proposal for a quite different biomass incinerator project in Shelton.) The study included an extensive consultant’s report on the availability of fuel, and the final report’s major concern regarded the predictable quantity and reliability of an FSC-certified fuel supply, and noted that although there would be a carbon benefit to switching from natural gas to forest slash for fuel, actual carbon neutrality would require purposeful afforestation of otherwise unused land.
Dry anaerobic digestion –
The Anaerobic Digestion Technical Advisory Group, made up of a number of county organizations, commissioned the WSU Energy office to evaluate and report on a potential dry anaerobic South County Community Digester in 2016.
According to the Center for Sustainable Infrastructure’s recent report, “From Waste Management to Clean Materials”, anaerobic biodigestion could produce up to 26 billion cubic feet of RNG a year from biomass sources in the state, 10% of state gas use, and thermal gasification could double that.
There are dry anaerobic composters in operation in Monterey, in South San Francisco, and in San Jose. (This big project was covered in 2011 and in 2014 in BioCycle.) The Surrey, BC Biofuel Facility processes 120,000 tons of Vancouver’s organic wastes each year, producing enough Renewable Natural Gas to power 8,500 cars, as well as 45,000 metric tons of compost. 40,000 tons of Sacramento’s food waste is anaerobically digested each year, producing gas to fuel the waste collection fleet.
BioFerm Energy Systems has done a number of projects in Europe, as well as one for the University of Wisconsin’s Oshkosh campus that digests food waste and one for municipal waste in Edmonton. JC-Biomethane’s plant in Junction City, Oregon digests commercial food waste, but has encountered ongoing problems.
King County did an anaerobic digestion feasibility study in 2017. (In 2013, the Thurston Conservation District also did a report on using an anaerobic digester to manage the 11 tons a day of dog waste in the County.)
Impact BioEnergy, in Auburn, makes microdigesters for on-site generation of energy from food waste and similar organic materials, offsetting trucking to distant facilities. (They have bigger systems under development, and just received a $550,000 grant from the Department of Commerce to develop a systematic, community-scale food waste biocycling plant on Vashon Island. It’s intended to “eliminate the need to ship out food waste materials and bring in amendments like compost and fertilizer. Food waste will be converted to energy for heat, power and alternative fuel vehicles, liquid organic fertilizer and sequestered CO2 used in agriculture and horticulture.”)
WSU’s Center for Sustaining Agriculture and Natural Resources has an ongoing research program on anaerobic digesters and a website with resources, though it’s primarily concerned with dairy digesters.
Codigestion –
Gresham, Oregon’s wastewater treatment plant codigests fat, oil and grease along with the wastewater to increase its methane production. It now produces more energy than it uses, and expects to payback the investments in seven years. The East Bay Municipal Utility District Treatment Plant now codigests 20 to 40 tons a day of restaurant food scraps, and is planning to scale that up. (The EPA did a report on six wastewater facilities doing this with food waste, and a webinar about a couple of codigestion projects and the Oshkosh dry anaerobic digester.)