In situ volatile fatty acids influence biogas generation from kitchen wastes by anaerobic digestion

• In situ volatile fatty acids influenced biogas generation from kitchen wastes.
• The main component of VFA was acetate as the main inhibitor in anaerobic digestion.
• Aceticlastic methanogenesis was more sensitive to acetate.
• Microbial community changed significantly with the increase of VFA accumulation.

Anaerobic digestion is considered to be an efficient way of disposing kitchen wastes, which can not only reduce waste amounts, but also produce biogas. However, the excessive accumulation of volatile fatty acids (VFA) caused by high organic loads will inhibit anaerobic digestion intensively. Effects of the VFA composition on biogas generation and microbial community are still required for the investigation under various organic loads of kitchen wastes. Our results showed that the maximum specific methane production was 328.3 ml g TS−1, and acetic acid was the main inhibitor in methanogenesis. With the increase of organic load, aceticlastic methanogenesis was more sensitive to acetic acid than hydrogenotrophic methanogenesis. Meanwhile, methanogenic microbial community changed significantly, and few species grew well under excessive organic loads. This study provides an attempt to reveal the mechanism of VFA inhibition in anaerobic digestion of kitchen wastes.