Kinetic analysis of the methanization of the byproducts from OFMSW fermentation

Abstract

BACKGROUND During anaerobic digestion of wastes, volatile fatty acid (VFA) production has been studied, but little attention has been paid to alcohols and lactic acid. Thermodynamically, lactic acid and alcohols are better substrates to produce methane than other VFA. This research identified the metabolites produced during the fermentation of the organic fraction of municipal solid waste and studied their methanization in a second stage. Analysis of the methane production curves is provided and explained according to Gibbʼs free energy of acetogenesis and methanogenesis. Based on the Michaelis–Menten model, a kinetic analysis is presented. RESULTS The specific methane production of the identified acids and alcohols are acetic acid, 343 NL/kgCOD; ethanol, 296; methanol, 181; butyric acid, 108; lactic acid, 64. Lactic and butyric acids present a long adaptation phase followed by a fast and short methane production. Acetic acid and ethanol finished the reaction in less than 16 h. The highest methane production rates (Vmax) were for butyric acid, methanol, and ethanol with 2136, 1934, and 1928 NmL L–1, respectively. The best affinity (lowest Km) values were for acetic and lactic acids and ethanol with 1.2, 1.9, and 2.0 gCOD L–1. CONCLUSION Together, acetic acid and ethanol represent 92% of all fermentation products. No endogenous methane production was observed during the methanization from acetic acid and ethanol. The highest specific methane production belongs to acetic acid (98% of the theoretical) and the lowest corresponds to lactic acid. Except for propionic acid, the methanization of the selected substrates follows the Michaelis and Menten model. © 2021 Society of Chemical Industry (SCI).

Effect of carbohydrates on protein hydrolysis in anaerobic digestion

“…Also this can be explained by VFA production, more in particular by the production of propionic acid (Angelidaki et al 1999;Siegert & Banks 2005;Wang et al 2009;Ma et al 2011; Jojoa-Unigarro & González-Martínez 2022). For example, at a Sta/Gel ratio of 5.5 a maximum propionate concentration of 1.73 g COD L À1 was measured (Table S2 in.SI), which exceeds propionate concentrations of 0.7-1.5 g COD L À1 that are reported to inhibit methanogenesis (Wang et al 2009;Ma et al 2011;Jojoa-Unigarro & González-Martínez 2022). This can be explained by the high concentration of propionic acid, which results in an increase of partial hydrogen pressure and subsequent inhibition of the overall acetogenesis and consequently, the hydrogenotrophic methanization ( Jojoa-Unigarro & González-Martínez 2022).…”

Special Issue: biotechnology advances in Latin America

“…They showed that co-digestion of food waste with a small amount of microalgae biomass results in process stability and increasing methane production. Jojoa-Unigarro and González Martínez 20 presented a comprehensive kinetic study of the methane production from the fermentation byproducts of organic fraction of municipal solid wastes. The impact of steam explosion pretreatment on coffee husks was evaluated by Fonseca et al 21 finding significant improvements on methane production from this important residue generated in many regions of Latin America.…”