Valorisation of industrial hemp (Cannabis sativa L.) biomass residues through acidogenic fermentation and co-fermentation for volatile fatty acids production

[Display omitted] •Valorisation of hemp biomass residues into VFAs through AF was demonstrated.•An acetic acid percentage of 94% over total VFAs was achieved at alkaline pH.•Under all conditions more than 95.4% of chemical energy was converted to VFAs.•Up to 651 ± 65 mg of HAc per gram of VS were reached from the co-AF of Mix and CW.•HH valorisation could lead to maximum VFA and VFA-derived products revenues. In line with the emerging circular bioeconomy paradigm, the present study investigated the valorisation of abundant hemp biomass residues (HBRs) such as hurds (HH) and a mix of leaves and inflorescences (Mix), and other organic wastes (i.e., cheese whey and grape pomace) through the volatile fatty acid (VFA) production in mono- and co-acidogenic fermentation. The highest VFA yields, measured as acetic acid (HAc) per unit of volatile solids (VS), were obtained with the untreated Mix in mono-fermentation (185 ± 57 mg HAc/g VS) and with the combination of Mix and CW in co-fermentation (651 ± 65 mg HAc/g VS), while the highest HAc percentage reached up to 94% of total VFAs. Finally, a preliminary techno-economic evaluation revealed that the mono-fermentation of alkali pretreated HH could lead to the highest revenues among HBRs, reaching up to 710–1810, 618–1577 and 766–3722 €/ha∙year for the production of HAc, single cell protein and polyhydroxybutyrates, respectively.