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)