Engineering and microbial characteristics of innovative lab and pilot continuous dry anaerobic co-digestion system fed with cow dung and corn straw.

ABSTRACT

Dry anaerobic digestion (dry-AD) allows high-solid digestion; however, dry-AD application is limited because it is prone to blockage and intermediate inhibition. Here, we reported innovative continuous dry co-digestion systems at both lab and pilot scales. The effects of digestate recirculation ratio, dry mass ratio of cow dung to corn straw (CDCS), and TS content on the digestion performance were investigated. The effects of the three factors were ranked as follows TS content > CDCS > digestate recirculation ratio. The daily biogas production rate reached 0.386 NL/d/g VS with the optimal parameter combination, which was determined to be TS content of 30%, a substrate ratio of 13, and a digestate recirculation ratio of 40%. In addition, increasing the CDCS and TS content increased digestate viscosity, which inhibited biogas production; however, increased abundance of Proteiniphilum and acetoclastic methanogens facilitated biogas production. This study provides empirical support for further application of dry-AD.