Fig. 3From: Enhancing methane production from food waste fermentate using biochar: the added value of electrochemical testing in pre-selecting the most effective type of biocharTime course of total VFAs (a), n-butyrate and i-butyrate (b), propionate (c) and acetate (d) concentration (mgCOD/L) in bottles supplemented with conductive particles, with non-conductive sand, and in unamended controls, during the 2nd feeding cycle. Error bars represent the standard deviation of two replicate bottlesBack to article page