title: More value from food waste: Lactic acid and biogas recovery.
abstract: Anaerobic digestion (AD) is one of the traditional technologies for treating organic solid wastes, but its economic benefit is sometimes questioned. To increase the economic feasibility of the treatment process, the aim of this study was to recover not only biogas from food waste but lactic acid (LA) as well. At first, LA fermentation of food waste (FW) was conducted using an indigenous mixed culture. During the operation, temperature was gradually increased from 35 °C to 55 °C, with the highest performance attained at 50 °C. At 50 °C and hydraulic retention time (HRT) of 1.0 d, LA concentration in the broth was 40 kg LA/m(3), corresponding to a yield of 1.6 mol LA/mol hexoseadded. Pyrosequencing results showed that Lactobacillus (97.6% of the total number of sequences) was the predominant species performing LA fermentation of FW. The fermented broth was then centrifuged and LA was extracted from the supernatant by the combined process of nanofiltration and water-splitting electrodialysis. The process could recover highly purified LA by removing 85% of mineral ions such as Na(+), K(+), Mg(2+), and Ca(2+) and 90% of residual carbohydrates. Meanwhile, the solid residue remained after centrifugation was further fermented to biogas by AD. At HRT 40 d (organic loading rate of 7 kg COD/m(3)/d), the highest volumetric biogas production rate of 3.5 m(3)/m(3)/d was achieved with a CH4 yield of 0.25 m(3) CH4/kg COD. The mass flow showed that 47 kg of LA and 54 m(3) of biogas could be recovered by the developed process from 1 ton of FW with COD removal efficiency of 70%. These products have a higher economic value 60 USD/ton FW compared to that of conventional AD (27 USD/ton FW).
authors.affiliation: Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 102 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Republic of Korea; Division of Renewable Energy Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea.
authors.forename: Mi-Sun
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 102 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Republic of Korea; Division of Renewable Energy Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea.
authors.forename: Jeong-Geol
authors.initials: JG
authors.lastname: Na
authors.affiliation: Department of Civil Engineering, Inha University, 100 Inha-ro, Nam-gu, Incheon, Republic of Korea.
authors.forename: Mo-Kwon
authors.initials: MK
authors.lastname: Lee
authors.affiliation: Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Hoyoung
authors.initials: H
authors.lastname: Ryu
authors.affiliation: Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Yong-Keun
authors.initials: YK
authors.lastname: Chang
authors.affiliation: Department of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark, Odense M 5230, Denmark.
authors.forename: Jin M
authors.initials: JM
authors.lastname: Triolo
authors.affiliation: College of Agriculture, Forestry and Natural Resource Management, University of Hawaii at Hilo, 200 W. Kawili Street, Hilo 96720, HI, USA.
authors.forename: Yeo-Myeong
authors.initials: YM
authors.lastname: Yun
authors.affiliation: Department of Civil Engineering, Inha University, 100 Inha-ro, Nam-gu, Incheon, Republic of Korea. Electronic address: dhkim77@inha.ac.kr.
authors.forename: Dong-Hoon
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000693:Anaerobiosis; D056804:Biofuels; D019149:Bioreactors; D005502:Food; D019344:Lactic Acid; D008697:Methane / Q000096:biosynthesis; D062611:Solid Waste
chemical_list: D056804:Biofuels; D062611:Solid Waste; D019344:Lactic Acid; D008697:Methane
keywords: Biogas; Food waste; Lactic acid; Mass flow; Nanofiltration; Water-splitting electrodialysis