title: Biomethane recovery from Egeria densa in a microbial electrolysis cell-assisted anaerobic system: Performance and stability assessment.
abstract: Renewable energy recovery from submerged aquatic plants such as Egeria densa (E. densa) via continuous anaerobic digestion (AD) represents a bottleneck because of process instability. Here, a single-chamber membrane-free microbial electrolysis cell (MEC) equipped with a pair of Ti/RuO2 mesh electrodes (i.e. the combined MEC-AD system) was implemented at different applied voltages (0-1.0 V) to evaluate the potential effects of bioelectrochemical stimulation on methane production and process stability of E. densa fermentation. The application of MEC effectively stabilized E. densa fermentation and upgraded overall process performance, especially solid matters removal. E. densa AD process was operated steadily throughout bioelectrochemical process without any signs of imbalance. The solubilization-removal of solid matters and methane conversion efficiency gradually increased with increasing applied voltage, with an average methane yield of approximately 248.2 ± 21.0 mL L(-1) d(-1) at 1.0 V. Whereas, the stability of the process became worse immediately once the external power was removed, with weaken solid matters removal along with methane output, evidencing the favorable and indispensable role in maintaining process stability. The stabilizing effect was further quantitatively demonstrated by statistical analysis using standard deviation (SD), coefficient of variance (CV) and box-plots. The syntrophic and win-win interactions between fermenting bacteria and electroactive bacteria might have contributed to the improved process stability and bioenergy recovery.
authors: Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan. Electronic address: zhenguangyin@163.com.
authors: Guangyin
authors: G
authors: Zhen
authors: Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan.
authors: Takuro
authors: T
authors: Kobayashi
authors: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi, 980-8579, Japan.
authors: Xueqin
authors: X
authors: Lu
authors: Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan.
authors: Gopalakrishnan
authors: G
authors: Kumar
authors: Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan; School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address: joexu@nies.go.jp.
authors: Kaiqin
authors: K
authors: Xu
mesh_terms: D001419:Bacteria; D001674:Bioelectric Energy Sources; D019149:Bioreactors / Q000382:microbiology*; D004566:Electrodes; D004572:Electrolysis; D005285:Fermentation; D008697:Methane / Q000032:analysis / Q000096:biosynthesis*; D064028:Tracheophyta / Q000378:metabolism*
chemical_list: D008697:Methane
keywords: Egeria densa; Electromethanogenesis; Methane; Microbial electrolysis cell (MEC); Renewable energy