A National Survey of Biogas Use at Wastewater Treatment Plants in the United States: The Results

Recognizing the economic and environmental value of renewable energy and resource recovery projects to wastewater treatment plants (WWTPs) and others in the wastewater industry, the Water Environment Federation (WEF) provided seed funding for collection of biogas data that would be used to populate a consensus-driven, publicly-available database.The project team was diverse and comprised of non-profit organizations, communications outlets, consulting engineers, and vendors. A team of approximately 20 wastewater industry experts from these organizations were involved in compiling data, state-by-state, using an online survey and unique online collection database.Initially the database was populated from U.S. EPA data sources (e.g., DMR reports, Clean Watershed Needs Survey) and data collected by Insinkerator and others (that were graciously contributed by them to the project). The data were then verified by cross checking the database, validating with knowledgeable people in certain regions (such as the federal and state biosolids coordinators), and contacting individual facilities.An interactive online database (www.biogasdata.org) was created to present the data collected. The database illuminates: 1) existing anaerobic digestion (AD) systems at U.S. WWTPs and 2) the current uses of, and potential future opportunities for using, the biogas produced by these facilities.The key findings of this study are:A total of 5,127 WWTPs are included in the current (September 2012) database. Most of them are over 1 million gallons per day (MGD).The solids from at least 1,238 WWTPs are confirmed to be processed via AD.The states of HI (41%), WA (36%), and CA (27%) have the highest percentages of WWTPs that send their solids to AD.It is estimated that 1,054 WWTPs beneficially use the biogas they produce (85% of the 1238 facilities sending solids to AD)Facilities with AD use biogas in the following ways (from most common to less common): digester heating (an estimated 77% of AD facilities use gas in this way), building heating (43%), power generation (26%), driving process machinery (12%), and pipeline injection (2%).270 WWTPs were confirmed to be generating electricity from biogas.Those WWTPs generating electricity use the following technologies (from most common to less common): internal combustion (IC) engines (76%), microturbines (12%), combustion turbines (7%), and fuel cells (5%).An estimated 1,148 WWTPs (or approximately 93%) with AD operate them at mesophilic temperatures. An estimated 40 WWTPs (or approximately 4%) operate digesters at themophilic temperatures. Approximately 34 WWTPs (or approximately 3%) operate digesters at both temperature ranges.An estimated 216 WWTPs (approximately 17%) import organic waste to co-digest with their wastewater solids.The data reported here are best current estimates based on data collected by this study as of September, 2012. Interest in anaerobic digestion is expanding rapidly, and changes are occurring throughout the country. It is hoped that, with additional funding and support, these data will be maintained, updated, further refined, and expanded. In the meantime, the initial, “Phase 1” data reported here are available for perusal at a new, online database open to anyone: www.biogasdata.org.