Anaerobic co-digestion of kitchen waste and fruit/vegetable waste: Lab-scale and pilot-scale studies

• Co-digestion of fruit/vegetable waste (FVW) and kitchen waste (KW) were studied.
• FVW to KW ratio of 5:8 was suitable for co-digestion and methane production.
• Two-phase digestion showed better buffer ability to high organic loading rate (OLR).
• Two-phase digestion was more stable as OLR ⩽ 3.0 g (VS) L−1 d−1 in pilot-scale system.
• It was profitable for pilot-scale food waste digestion at OLR of 3.0 g (VS) L−1 d−1.

The anaerobic digestion performances of kitchen waste (KW) and fruit/vegetable waste (FVW) were investigated for establishing engineering digestion system. The study was conducted from lab-scale to pilot-scale, including batch, single-phase and two-phase experiments. The lab-scale experimental results showed that the ratio of FVW to KW at 5:8 presented higher methane productivity (0.725 L CH4/g VS), and thereby was recommended. Two-phase digestion appeared to have higher treatment capacity and better buffer ability for high organic loading rate (OLR) (up to 5.0 g (VS) L−1 d−1), compared with the low OLR of 3.5 g (VS) L−1 d−1 for single-phase system. For two-phase digestion, the pilot-scale system showed similar performances to those of lab-scale one, except slightly lower maximum OLR of 4.5 g (VS) L−1 d−1 was allowed. The pilot-scale system proved to be profitable with a net profit of 10.173 $/ton as higher OLR (⩾3.0 g (VS) L−1 d−1) was used.