Optimizing dry anaerobic digestion at pilot scale for start-up strategy and long-term operation: Organic loading rate, temperature and co-digestion

Abstract

Dry anaerobic digestion (AD) with high total solid content might upgrade conventional wet AD by enhancing digestion and reducing liquid digestate generation, which was not so popular due to lack of adequate knowledge and perceived operational complexity. In this study long term (447 days) pilot scale investigation was performed for various feedstocks including pig manure, corn straw and sludge. It was found dry method was more suitable for reactor start-up than wet method with relieved inhibition. Volatile fatty acid (VFA)/alkalinity (0.1 ~ 0.4) was effective as dry AD system stability indicator. Organic loading rate of 4.8 kg/(m3·d) and temperature of 48 °C was optimized. Co-digestion achieved better volatile solid removal and system stability. Both hydrogenotrophic and acetoclastic methanogens stably existed in rector while hydrogenotrophic obtained higher abundance. This research contributed to understanding of reactor start-up, system stability indicator and optimized operational conditions (organic loading rate and temperature) during dry AD process.