More value from food waste: Lactic acid and biogas recovery. (1st June 2016)

• Record Type: Journal Article
• Authors: Kim, Mi-Sun; Na, Jeong-Geol; Lee, Mo-Kwon; Ryu, Hoyoung; Chang, Yong-Keun; Triolo, Jin M.; Yun, Yeo-Myeong; Kim, Dong-Hoon
• Is Part Of: Water research. Volume 96(2016)
• Page Start: 208
• Page End: 216
• Publication Date: 2016-06-01
• Subjects: Food waste -- Lactic acid -- Biogas -- Nanofiltration -- Water-splitting electrodialysis -- Mass flow; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2016.03.064
• Languages: English
• ISSNs: 0043-1354

Abstract

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). Graphical abstract: Highlights: Recovery of both lactic acid (LA) and biogas from food waste (FW). The first-step reaction was LA fermentation using indigenous mixed culture. LA extraction from the broth by nanofiltration and water-splitting electrodialysis. LA-fermented solid residue was fermented to biogas by anaerobic digestion. Recovery of 47 kg LA and 54 m 3 biogas (60 USD/ton FW) from 1 ton FW.