Scale-up and economic assessment of volatile fatty acids production from food waste

The high potential of food waste (FW) as a substrate in the anaerobic digestion (AD) raises the dilemma between producing added value bioproducts such as volatile fatty acids (VFA) or biomethane. This work assessed the scale-up of producing VFA from FW. At lab-scale (5 L), pH 7 and organic loading rate (OLR) of 10 g COD/L/d were selected as the best conditions, obtaining a VFA yield of 36.6 % g COD-VFA/g COD substrate and a rate of 3.9 g COD-VFA/L/d. Afterwards, a semi-industrial pilot plant (1.5 m3) was operated under these conditions, showing VFA production indicators in line with those of lab scale, with acetic acid as main VFA (50 % mass basis), followed by propionic and butyric (20 % each). The economic comparative between the production of VFA and biomethane concluded that revenues from VFA production (22.9 €/t FW) are considerably higher than those from biomethane (11.7 €/t FW). [Display omitted] •Scale-up of VFA production process with food waste (FW) from lab to pilot scale was assessed.•Best operating conditions for VFA production were identified at laboratory scale.•pH 7 and OLR 10 g COD/L/d were the optimum for maximising VFA yield and rate.•Pilot plant operation reported comparable results to those at lab scale.•Net profit of VFA is higher than that of biomethane (22.9 vs 11.7 €/t FW).