THE CITY OF SAN JOSE BIOMASS WASTE TO ENERGY EVALUATION

Sustainable management of wastewater treatment plant biosolids and other biomass wastes remains a challenge for wastewater utilities and other municipal agencies across North America. Traditional beneficial use practices such as composting and agricultural land application are becoming increasingly more difficult because of rising costs, regulatory uncertainty and public opposition. With a growing awareness of climate change issues, and greater emphasis on energy consumption, utilizing renewable fuels such as biosolids for energy applications is increasing in importance.The City of San José, CA already utilizes a biomass-to-energy process at the San José/Santa Clara Water Pollution Control Plant (WPCP) through anaerobic digestion of plant primary and secondary sludge to produce digester gas. The WPCP presently satisfies approximately 27 percent of its energy needs by combusting digester gas and nearby landfill gases to generate mechanical and electrical energy.In order to meet the treatment plant's increasing energy demand, meet sustainability goals, and combat rising energy costs and disposal issues, the City embarked on a study to evaluate the potential of using digested biosolids and other readily available biomass to produce electricity. The study investigated availability of biomass resources for conversion to usable fuel, screened biomass-to-energy technologies, conducted a technical and economic assessment of viable biomass-to-energy technologies, and evaluated the environmental impacts of these alternatives.