Biosolids Renewable Energy Project – Power Generation with Biosolids

Colorado Springs Utilities (Utilities) recently conducted an evaluation on the feasibility of using biosolids as a biofuel for power generation. It focused on the viability of transporting raw primary and secondary solids from the Las Vegas Street Wastewater Treatment Facility (LVSWWTF) to the Martin Drake Power Plant (Drake), using steam from any one of the three natural circulation coal–fired boilers to thermally dry the biosolids, and then beneficially using the dried product as a renewable energy fuel source. LVSWWTF's treatment capacity is rated at 2.8 cubic meters per second (m3/s) for total cold weather flow and 3.2 m3/s for warm weather flow [65 million gallons per day (mgd)/75mgd]. The boilers at Drake are rated at 49 megawatts (MW), 85 MW, and 140 MW.The study demonstrated that the process would be economically and technically viable. Commingling and co-firing the dried biosolids with coal in the Drake facility should have negligible impact on power generation capacity or boiler operation, with minimal risk of slagging or fouling. Odor control, dust control, condensate return, and reliability issues were also determined to be manageable. The energy potential of Utilities' dried biosolids is on the order of 18,600 kilojoule (kJ)/dry kilogram (kg) [8,000 British thermal unit (Btu)/dry pound (lb)], making it equivalent to a sub-bituminous coal. In addition to evaluating the technical and economic feasibility of this process, the team investigated the experiences of power utilities in Europe with co-firing biosolids and coal.