Efficient methane fermentation from the waste of a novel straw alkali-heat pretreatment-butyric acid fermentation process

<b>ABSTRACT</b>The butyric acid biorefinery technology for straw is highly significant for environmental protection and the restructuring of the energy system. However, this process produces waste from alkali-heat pretreatment (PW) and butyric acid fermentation (FW). In this study, the feasibility of methane fermentation from the wastes was confirmed, with the methane production from PW and FW of 351.1 ± 11.8 and 741.5 ± 14.2 mLCH₄/gVS, respectively. The initial pH and <i>V</i>_FW/<i>V</i>_PW of methane fermentation using the mixed waste of PW and FW were optimized at 7.5 and 1.8, respectively. The methane fermentation using the mixed waste was also verified by operating two anaerobic digesters in sequencing batch mode. At the <i>V</i>_FW/<i>V</i>_PW of 0.25 (actual ratio), methane production was 301.20 mLCH₄/gVS with the waste load of 0.64 kgVS/m³/d. When the <i>V</i>_FW/<i>V</i>_PW was 1.8 (optimal ratio), methane production reached 396.45 mLCH₄/gVS at the waste load of 1.20 kgVS/m³/d. This study facilitates the comprehensive utilization of all components within rice straw.