Sequential bioethanol and methane production from municipal solid waste: An integrated biorefinery strategy towards cost-effectiveness

Abstract

The organic fraction of municipal waste (OFMW), source-sorted (SS-OFMW) and non-sorted (NS-OFMW), was used as raw material for the sequential production of bioethanol and biogas. Non-isothermal and simultaneous saccharification and fermentation (NSSF) resulted in maximum ethanol concentrations of 51 g/L and 26 g/L for SS-OFMW and NS-OFMW samples, showing overall process yields of up to 80 % and 59 %, respectively, even without subjecting substrate to hydrothermal pretreatment. Subsequently, the solid residues resulting from the fermentation were further subjected to anaerobic digestion (AD), showing a methanogenic potential of 384 ± 6 mL CH4/g of volatile solids (VSin) and 322 ± 3 mL CH4/g VSin, respectively. These methane yields were similar or even higher to those obtained when using non-fermented OFMW substrates (SS-OFMW: 380 ± 18 mL CH4/g VSin and NS-OFMW: 239 ± 4 mL CH4/g VSin), highlighting NSSF as a beneficial step to enhance methane yields during AD. Overall, bioconversion of OFMW would benefit from coupling bioethanol and biogas production since the biogas produced might be further employed as bioenergy source to compensate operational costs.