ADVANCED DIGESTION TECHNOLOGIES IMPLEMENTATION AT INLAND EMPIRE UTILITIES AGENCY AND ENHANCED BIOGAS GENERATION

Biogas generation from waste solids digestion process and use of the biogas in co-generation is one of the promising renewable energy sources, since the biogas contains significant quantities of methane. Existing literature indicates that by implementing co-digestion of biosolids and food waste, it is possible to achieve even higher biogas production. The biogas can then be used in co-generation systems, such as the microturbines, improving the feasibility of renewable energy generation. Anaerobic digestion technology alternatives that can be used to facilitate co-digestion at existing biosolids treatment and handling facilities were evaluated. The evaluated technologies included: (1) single phase mesophilic and thermophilic digestion; (2) two phase acid-gas phase digestion; (3) three phase digestion. The results of the evaluation that included an extensive literature review revealed that some of these digestion technologies (e.g., acid-gas phase digestion) had the potential to meet VS reduction levels achieved with single mesophilic operation at lower HRTs, thus to open capacity for co-digestion implementation. IEUA staff has been experimenting with different anaerobic digestion technologies since 1998. Supplemented with the RP-1 digestion and dewatering operation and performance data, the anaerobic digestion technology evaluation revealed that the mesophilic-mesophilic acid-gas digestion can be a suitable technology to provide sufficient capacity and operational benefits.