Short and medium chain organic acids production from hydrolyzed food waste: technical–economic evaluation and insight into the product's quality.

[Display omitted] • Combined thermal-alkaline hydrolysis favored the food waste acidification into OAs; • Mesophilic environment increased the acidification yield up to 0.87 g COD/g VS; • Caproic acid above 30% COD/COD was reached in mesophilic T under the highest OLR; • Multivariate data analysis showed stability in product's quality under mesophilic T; • An economic income of 4,826,051 €/y is achievable in the food waste value chain. Food waste (FW) was subjected to thermal-alkaline hydrolysis before to be used as source for organic acids (OAs) production under different temperatures and hydraulic regime in long-term acidification process. Mesophilic environment led to the highest acidification yield (0.87 g COD OAs /g VS) with chain-elongation process to caproic acid production (>9.0 g COD cap /L) occurring at lower HRT (2 days). The product's quality, in terms of OAs production and composition, was evaluated through a multivariate approach, which indicated that the mesophilic condition was also appropriate to steadily maintain the requested product's features. The specific gas production (SGP) from the solid-rich acidified residue was 0.47 Nm3/kg VS and, in a full-scale scenario of 150,000 kg FW/d, it can be potentially converted into 24.9 MWh/d as electrical energy. Also, according to the acidification performances, an overall OAs production of 7.2 ton/y has been estimated, generating a yearly economic outcome higher than 4,800,000 €. [ABSTRACT FROM AUTHOR]