Volatile fatty acid production from food waste: The effect of retention time and lipid content

Abstract

The bioconversion of food waste to renewable products has an important role in alleviating the environmental burden of food wastage. This study evaluates the effect of solids retention time (1.5, 4, and 7 days) and lipid content (up to 30 % DS) on the solid's destruction efficiency and VFA yield from food waste fermentation. Although SRT below 4 days and lipid content beyond 20 % reduced the solids destruction efficiency (SRT -12 %, lipids -13 %), the VFA yield improved (SRT 0.36 to 0.48 g COD_VFA/TCOD_FED; lipids 0.17 to 0.39 g COD_VFA/TCOD_FED). This appeared to be a mechanism of improved acidification which doubled to 0.77 gCOD_VFA/g SCOD at 1.5-day SRT. The introduction of easily degradable organics in waste oils and methanogen inhibition by LCFAs were likely causes of process instability when lipids >20 %. Further research is needed considering the COD fractionation of the feed to maximize recoverable products on a commercial scale.

Keywords: Anaerobic digestion; Food waste; Lipid content; Retention time; Volatile fatty acids.