Comparison of Life Cycle Costs at Operating Cogeneration and RNG Facilities

An increasing number of water resource recovery facilities (WRRFs) are considering options for beneficial use of biogas due to an increasing focus, both internally and externally, on resource recovery and sustainability. Conversion of biogas to electricity (through cogeneration) and to renewable natural gas (RNG) (for pipeline injection or vehicle fueling) are often considered side by side as alternatives that can produce revenue and reduce the greenhouse gas footprint of WRRFs. While there are a large number of WRRFs across the country that have operated cogeneration systems over the last decades, operating costs can vary significantly depending upon the technology selected, condition of the raw biogas, and age of the system. In addition, while the technology used to convert biogas to RNG is established, pipeline injection and vehicle fueling projects remain relatively few and far between in the U.S. These unknowns make it difficult to quantify O&M costs for utilities considering a biogas utilization project. This complicates the evaluations of these systems, since long-term operating and maintenance (O&M) costs are a significant factor in selection of a recommended alternative.