Evaluation of chlorophyll and anti-oxidative components harvested from the anaerobic digestion of fruit and vegetable waste

•Two-phase anaerobic sludge blanket filter system is built with packed concentric column for increasing sludge retention time (SRT) during treatment of fruit and vegetable waste (FVW).•A suitable SRT is manifested crucial for feeding homogenate of FVW in batch operation without circulation of sludge.•Pigments and related antioxidants were present in the suspension solid gradually accumulated in the digester.•Recycle of fruit and vegetable resources concerning pigments and anti-oxidative compounds is proposed.

Two-phase up-flow sludge blanket filter (TUBF) digestion process of fruit and vegetable waste homogenate generated anaerobic sludge with concentrated pigments and reducing compounds. In the 5–50 L scale-up daily batch and semi-batch operations, the organic loading rate attained was over 6 kg COD/m3.day. A comparative study indicated that Minox polyethylene ring packing was critical for optimization of anaerobic digestion. The biogas production in terms of the volatile fatty acid pattern with a C2–C6 level of 600 mg/L through liquefaction and acidification (LA) maintained the alkalinity over 3500 mg/L and stabilized the pH of the LA phase at 5.2–6.8 according to the loading status. In the semi-batch operation of 50 L, pigments gradually condensed in the sludge layer were concentrated by a factor of at least ten fold, and a high level of reducing activity was retained by the chlorophyll and anti-oxidative components.