Biomethane potential and physicochemical characterization of cassava vinasse from ethanol distillery

Abstract

In this study, the biochemical methane potential (BMP), biodegradability index (BI), competitiveness index (CI), physicochemical properties and elemental compositions of cassava vinasse (CV) obtained from an ethanol distillery were investigated using experimental as well as instrumental analyses. Results showed that at room temperature of 28 ​°C, the CV was very watery with a specific gravity of 1.03. The relatively high Chemical Oxygen Demand, COD (62000–736500 ​mg/l) and Biochemical Oxygen Demand, BOD (21620–25000 ​mg/l); acidic pH (4.2–4.8) and cyanuric acid content (386–450 ​mg/l), emphasized its potential as a pollutant when discharged directly on land and water. A volatile solids content, VS (71580–72250 ​mg/l) and brix (5.9% sucrose) respectively indicate the presence of biodegradable organic matter and residual sugars in addition to many macro and micro-nutrients. At standard temperature and pressure (STP), BMP was experimentally determined to be 247.10 Nml/gVS which shows that the CV is a bioenergy resource. The results of BI and CI determination indicated that 82% of organic matter in CV is biodegradable and with a CI value above 10, there will be no competition between the methanogens and the sulphate-reducing bacteria (SRB) if the CV is subjected to anaerobic digestion (AD). This work improved existing knowledge and provided information for distillery operators and environmental regulators on alternative utilization and treatment routes for CV.