In Situ Biogas Upgrading and Fertilizer Recovery in Anaerobic Digestion from Laminaria Hydrothermal Carbonization Process Water by Fe-Modified Hydrochar
2020
Wang, Fengbo | Wang, Jing | Han, Ying | Lu, Jingping | Zan, Shuaijun | Du, Miaomiao
Hydrothermal carbonization (HTC) combined with anaerobic digestion (AD) is a cost-effective process to simultaneously treat biomass wastes for hydrochar production, energy recovery, and wastewater treatment. However, low fermentation efficiency and high carbon dioxide content in biogas are tricky problems of this process. This study developed a novel strategy based on Fe-modified hydrochar (Fe-HC) for in situ biogas upgrading and fertilizer recovery by AD of macroalgae Laminaria HTC process water. The daily yield and proportion of methane in biogas in the Fe-HC added reactor were 216.6 ± 13.1 mL/g CODfₑd and 90.3 ± 1.3%, respectively. The conductive Fe-HC increased relative abundances of Trichococcus and hydrogenotrophic methanogens (Methanosarcina and Methanobacterium) and promoted the electron transport system activity, heme c content in extracellular polymeric substances, and sludge granulation. These results implied the Fe-HC-promoted biogas upgrading might be ascribed to the enhancement of H₂-mediated interspecies electron transfer, potential direct interspecies electron transfer, and trace FeCO₃ precipitation. The effluent from the Fe-HC supplemented reactor was rich in nutrients, including K⁺, I–, gibberellin (GA₃), etc., but low in human potential pathogenic bacteria and heavy metal content, indicating it had excellent potential as a fertilizer. This study provides an ecofriendly and sustainable strategy for energy and fertilizer recovery from macroalgae wastes.
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