Enhancement of fermentative H2 production with peanut shell as supplementary substrate: Effects of acidification and buffer effect

•VFAs contributed to the acidolysis and organics releasing of peanut shell.•Buffering effect from peanut shell prolonged the fermentation duration.•Co-effect of buffering and acidification on peanut shell enhanced the H2 yield. For bio-H2 fermentation, the progress and H2 yield were significantly affected by culture pH. Our previous research found peanut shell powder (PSP, as supplementary substrate) having a buffer effect on the fermentative time prolongation and H2 yield enhancement. The acid buffer action (ABA), cation exchange capacity (CEC), scanning electron microscope (SEM) and X-ray powder diffraction (XRD) were employed to explore the mechanism and structure changes of PSP. The superior ABA (57.44 ± 0.65 mmol/pH-kg) and CEC (112 ± 2.0 cmol/kg) of PSP, which provided high specific surface area and amorphous content, prolonged the fermentative time. The acidification of volatile fatty acids on PSP was effective to release reducing sugar and enhance hydrogen yield through breaking hemicellulose and amorphous components of cellulose, and enlarging specific surface area. The results indicated that buffer effect and acidification on PSP made positive effects on prolonging fermentation time and enhancing hydrogen yield.