A novel cascade biorefinery approach to transform food waste into valuable chemicals and biogas through thermal pretreatment integration

Abstract

A novel biorefinery platform integrating thermal pretreatment and solid-liquid separation unit is here proposed to fully exploit food waste (FW) potential for production of valuable chemicals and energy through semi-continuous anaerobic bioconversion. The liquid fraction deriving from raw or pretreated FW, was fermented into volatile fatty acids (VFAs, from acetic to caproic acid) while the residual fraction was converted into biomethane. Thermal pretreatment effectively extracted a portion of the macromolecular organics, especially starch, to the liquid phase, promoting acidogenic fermentation and chain elongation pathways (0.43 gVFA g^-1VS_fed and 0.58 gVFA g^-1VS_fed with raw and pretreated extract, respectively). In parallel, anaerobic digestion of solid residue in 10 L reactors showed process stability and higher conversion rate for the pretreated residue (0.31 against 0.26 Nm³CH₄ kg^-1VS_fed). The mass-transfer balance coupled with the economic assessment, calculated in terms of direct gross added value, indicated promising revenues by integrating the thermal upstream treatment.

Keywords: Anaerobic digestion; Food waste; Mass transfer balance; Thermal hydrolysis; Volatile fatty acids.