Effect of biochar in enhancing hydrogen production by mesophilic anaerobic digestion of food wastes: The role of minerals

The role of minerals in biochar in promoting hydrogen (H₂) production by anaerobic digestion of food waste was investigated. The cultures with the addition of biochar, leached biochar, metal sulphate solution and leached biochar combined with metal sulphate solution, respectively, were placed in bench-scale reactors and incubated at incubator at 32 °C. Daily H₂ production and volatile fatty acids (VFAs) were measured and the cumulative H₂ yield (Y_H) and maximum H₂ production rate (R_H) were calculated. The microbial analysis was performed using Illumina MiSeq sequencing. Biochar addition significantly increased the maximum Y_H by 107% and R_H by 54%. However, the addition of leached biochar only increased the maximum Y_H by 39% and R_H by 45% than control. The primary elements in biochars that contribute to H₂ production (Fe, K and Ca) were shown to increase the acetic acid, butyric acid and prevalence of the H₂ producing bacteria Clostridium butyricum.