Calcium-doped carbon fabrication for improving bioH2 and bioCH4 production

Abstract

Carbon-based materials have been well demonstrated to significantly improve biohydrogen (bioH2) and biomethane (bioCH4) production. However, the use of the same material for two-phase anaerobic digestion requires further investigation. In this study, three calcium-doped magnetic biochars (Ca-MBCs) with Fe2+ (0.01, 0.05 and 0.1 mol/L) and calcium lignosulphonate (CL) were prepared to promote H2 and CH4 yields. Material characterization revealed that the specific surface area was significantly increased and Fe ions were successfully attached to the BCs. All three Ca -MBCs can effectively raise H2 yield, especially Ca-MBC2 (0.05 mol/L Fe2+), and the highest H2 yield of 1050 mL was obtained. Under optimal conditions, the cumulative H2 (37 °C, pH 6.0) and CH4 yields (37 °C, pH 7.0) were 948 mL and 1599 mL, respectively, which were 64.9% and 40.8% higher than those of the control group. Ca-MBC2 promoted the activity of butyric acid fermentative bacteria at the H2 evolution phase, raising the relative abundance of Clostridium; At the methanogenisis phase, the content of coenzyme F420 was increased, and Ca-MBC2 could change the methanogens dominant strain, strengthen the dominant strain position of Methanolinea, and raise the relative abundances of H2- and acetic acid-trophic strains of Methanoregula, Methanosaeta, and Methanosarcina.