SPECIAL ISSUE: INNOVATIVE GLOBAL SOLUTIONS FOR BIOENERGY PRODUCTION Comparative Life Cycle and Technoeconomic Assessment for Energy Recovery from Dilute Wastewater Deborah L. Sills, * Valerie L. Wade, and Thomas D. DiStefano Department of Civil and Environmental Engineering, Bucknell University, Lewisburg, Pennsylvania. Received: March 24, 2016 Accepted in revised form: June 21, 2016 Abstract Anaerobic treatment offers a sustainable alternative to aerobic treatment by recovering energy from wastewater. Anaerobic treatment, however, is challenged by reduced performance at lower temperatures and dissolved methane in the effluent, which represents a loss in recoverable energy and a potent greenhouse gas emission. Long-term operation of a bench-scale anaerobic baffled reactor (ABR) at 15–20°C, with domestic wastewater, provided data to evaluate life cycle environmental and economic performances of mainstream anaerobic treatment. Performance of the ABR was compared to a conceptual design of treatment with trickling filter+anaerobic digestion (TF+AD). The ABR and TF were modeled as example low-cost anaerobic and aerobic treatments, respectively, because these technologies may be more easily implemented (compared to membrane systems and activated sludge) in devel- oping countries. This type of comprehensive study, not conducted previously for the ABR, is imperative for selecting appropriate technologies as we determine how to bring sanitation to billions who are unserved. The ABR recovered approximately six times more energy from low-strength wastewater than TF+AD and resulted in significantly more beneficial life cycle impacts for ecosystem quality and human health. Furthermore, techno- economic analysis showed that the ABR has a life cycle cost that is about 40% lower than TF+AD. Dissolved methane in the effluent of the ABR, however, resulted in a harmful impact on climate change, whereas TF+AD resulted in approximately neutral impacts on climate change. A combined ABR+TF assembly, which was assumed to oxidize residual organics and dissolved methane, resulted in beneficial environmental impacts for four en- vironmental categories. Advancements in synergistic technologies that remove or recover dissolved methane in anaerobic effluent would allow implementation of the ABR without increasing climate change impacts. Key words: anaerobic processes; energy use and resources; life cycle assessment Introduction I n 2010, *80% of the world’s wastewater was untreated (Tauseef et al., 2013), and this poses a significant threat to human health and the environment. A majority of populations that lack proper sanitation reside in the developing world where implementation of conventional wastewater treatment (e.g., activated sludge) is hindered by high costs and the lack of reliable electricity. Approximately 1.5 billion people liv- ing in urban centers discharge wastewater through collection systems with no treatment (Baum et al., 2013). Furthermore, although >50% of households in the upper middle-income countries (e.g., India) are connected to sewers, over 85% of this sewage is not treated (Baum et al., 2013). Central India and Pakistan represent regions that are served by sewers, but lack wastewater treatment with average wastewater tempera- tures as low as 15°C (Sato et al., 2006; Shahzad et al., 2015). In addition, developing countries that implement conventional wastewater treatment allocate almost half of their municipal budgets to water management ( James et al., 2002). In response to these challenges, the U.N. Sustainable Development Goals 6 and 7 aim ‘‘to achieve adequate and equitable access to sani- tation; to improve water quality by reducing pollution, halving the proportion of untreated wastewater; and to provide access to affordable and sustainable energy’’ (United Nations General Assembly, 2015). Low-cost wastewater treatment technolo- gies that recover energy at relatively low temperatures and do not rely on grid electricity may help reach these sustainable development targets. Electricity requirements for aeration in conventional acti- vated sludge treatment of domestic wastewater contributes to high costs and subsequent greenhouse gas emissions. Con- sidering the significant electricity demand, carbon footprint, and biosolids production (Smith et al., 2014), the export of activated sludge technology to developing countries should be carefully evaluated. By contrast, anaerobic treatment requires no aeration and produces methane that can be converted to *Corresponding author: Department of Civil and Environmental Engineering, Bucknell University, Lewisburg, PA 17837. Phone: +1 607 277 5609; Fax: +1 577 570 3415; E-mail: deborah.sills@ bucknell.edu ENVIRONMENTAL ENGINEERING SCIENCE Volume 00, Number 00, 2016 ª Mary Ann Liebert, Inc. DOI: 10.1089/ees.2016.0153 1