Operational and biochemical aspects of co-digestion (co-AD) from sugarcane vinasse, filter cake and deacetylation liquor

Abstract

This work performed co-AD from the vinasse and filter cake (from 1G ethanol production) and deacetylation liquor (from the pre-treatment of sugarcane straw for 2G ethanol production) in a semi-Continuous Stirred Tank Reactor (s-CSTR) aiming to provide optimum operational parameters for continuous CH4 production. Using filter cake as co-substrate may allow the reactor to operate throughout the year, as it is available in the sugarcane off-season, unlike vinasse. A comparison was made from the microbial community of the seed sludge and the reactor sludge when CH4 production stabilized. Lactate, butyrate and propionate fermentation routes were denoted at the start-up of the s-CSTR, characterizing the acidogenic phase: the Oxidation-Reduction Potential (ORP) values ranged from -800 to -100 mV. Once the methanogenesis was initiated, alkalizing addition was no longer needed as its demand by the microrganisms was supplied by the alkali-characteriscs of the deacetylation liquor. The gradual increase of the applied Organic Load Rates (OLR) allowed stabilization of the methanogenesis from 3.20 gVS L-1 day-1: the highest CH4 yield (230 NmLCH4 gSV-1) and average organic matter removal efficiency (83% {+/-} 13) was achieved at ORL of 4.16 gVS L-1day-1. The microbial community changed along the reactor operation, presenting different metabolic routes mainly due to the used lignocellulosic substrates. Bacteria from the syntrophic acetate oxidation (SAO) process coupled to hydrogenotrophic methanogenesis were predominant ([~] 2% Methanoculleus) during the CH4 production stability. The overall results are useful as preliminary drivers in terms of visualizing the co-AD process in a sugarcane biorefinery integrated to scale. KeypoitnsIntegration of 1G2G sugarcane ethanol biorefinery from co-digestion of its residues Biogas production from vinasse, filter cake and deacetylation liquor in a semi-CSTR Lignicellulosic substrates affected the biochemical routes and microbial community Biomol confirmed the stablismenht of thermophilic community from mesophilic sludge