Co-production of biohydrogen and biomethane from food waste and paper waste via recirculated two-phase anaerobic digestion process: Bioenergy yields and metabolic distribution

To achieve the co-production of H₂ and CH₄, co-digestion of food waste (FW) and paper waste (PW) was performed on the recirculated two-phase anaerobic digestion (R-TPAD). The PW content in the feedstock increased from 0% to 20%, 40% and 50% (in total solids) with FW as the rest. The results showed that bioH₂ and bioCH₄ were simultaneously and stably produced in the long-term operation. With the increasing PW content, the removal efficiency of volatile solids decreased slightly from 84.9% to 78.4%; the bioH₂ yields increased from 50 to 79 NL-H₂/kg-VS_fed while the bioCH₄ yields decreased from 426 to 329 NL-CH₄/kg-VS_fed. With the fixed amount of FW, adding PW could significantly increase the total bioenergy yields. The relative abundance showed that the key H₂-producing bacteria, Caproiciproducens and Thermoanaerobacterium, increased after PW addition. The microbial distribution suggests that the H₂-producers were recirculated to the first stage after proliferating in the second stage.