title: Enhancing anaerobic digestion of high-pressure extruded food waste by inoculum optimization.
abstract: The inoculation for extruded food waste anaerobic digestion (AD) was optimized to improve methane (CH4) yield. The inoculum of acclimated anaerobic sludge resulted in high biodegradability, producing CH4 yields from 580 mLCH4 g(-1)·VSadded to 605 mLCH4 g(-1)·VSadded, with corresponding BDCH4 ranging from 90% to 94%. We also investigated inoculum to substrate ratios (ISRs). With regards to digested slurry as inoculum, we found that a decrease in ISR improved CH4 yield, while a lower ISR prolonged the lag time of the initial AD stage due to lipid inhibition caused by excessive food waste. These results demonstrate that minimal inocula are required to start the AD system for high-pressure extruded food waste because it is easily biodegraded. High ammonia concentration had a negative effect on CH4 production (i.e., when free ammonia nitrogen [FAN] increased from 20 to 30 mg L(-1) to 120-140 mg L(-1), the CH4 yield decreased by 25%), suggesting that FAN was a significant inhibitor in CH4 yield reduction. In terms of CH4 yield and lag time of the AD process, the optimal inoculation of digested slurry for the extruded food waste had an ISR of 0.33 with CH4 yield of 505 mLCH4 g(-1)VSadded, which was 20% higher than what was found for higher ISR controls of 2, 1 and 0.5.
authors.affiliation: Key Laboratory for Solid Waste Management and Environment Safety, Ministry of Education of China, School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address: kongx13@mails.tsinghua.edu.cn.
authors.forename: Xin
authors.initials: X
authors.lastname: Kong
authors.affiliation: Key Laboratory for Solid Waste Management and Environment Safety, Ministry of Education of China, School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address: xsylvia1024win@foxmail.com.
authors.forename: Shuang
authors.initials: S
authors.lastname: Xu
authors.affiliation: Key Laboratory for Solid Waste Management and Environment Safety, Ministry of Education of China, School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address: jgliu@tsinghua.edu.cn.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Liu
authors.affiliation: Shenzhen Environmental Microbial Application and Risk Control Key Laboratory, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China. Electronic address: li.huan@sz.tsinghua.edu.cn.
authors.forename: Huan
authors.initials: H
authors.lastname: Li
authors.affiliation: BESG Environmental Engineering Co., Ltd., Beijing Environment Sanitation Engineering Group Co., Ltd., Beijing, 100101, China. Electronic address: zhaoke@besgrd.com.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhao
authors.affiliation: BESG Environmental Engineering Co., Ltd., Beijing Environment Sanitation Engineering Group Co., Ltd., Beijing, 100101, China.
authors.forename: Liang
authors.initials: L
authors.lastname: He
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D002681:China; D005502:Food; D019649:Food Industry; D005735:Garbage; D007220:Industrial Waste / Q000032:analysis*; D008697:Methane / Q000032:analysis; D008962:Models, Theoretical; D011312:Pressure; D012722:Sewage / Q000382:microbiology*
chemical_list: D007220:Industrial Waste; D012722:Sewage; D008697:Methane
keywords: Anaerobic digestion; Food waste; Inhibition; Inoculation; Methane