Effects Of Plant-derived Biochar And Its Magnetic Modification On Methane Production In Anaerobic Digestion

The improvement of efficiency and stability is the key problem faced by anaerobic digester treating organic waste.Biochar has great potential in improving the efficiency and stability of anaerobic digestion?AD?.However,the engineering application of biochar in AD still faces some challenges:On the one hand,since the characteristics of biochars derived from different materials may be significantly different,how to choose high-efficiency biochar in AD?On the other hand,how to strengthen the effect of biochar and prevent the loss of biochar and microorganisms colonized on it during the operation of anaerobic digester?In this study,we investigated the effects of biochar derived from different plant materials on the AD of glucose using an methane potential test system,and identified the key characteristics of biochar in AD.Combined with molecular biological techniques and network analysis,we preliminary explored the microbial mechanism for biochar affecting the efficiency of AD.Then we investigated the effect of magnetically modified biochar on the AD of kitchen waste hydrolysate.And the potential mechanisms for the improvement of AD with magnetic biochar was studied from the perspective of microbial community and spatial distribution of microorganisms.The main conclusions are as follows:?1?The specific surface area?SSA??p<0.05,r=0.89?and electron donating capacity?EDC??p<0.05,r=0.83?of biochar was the key characteristic for the enhancement of methane production rate of AD.And 0.5%?w/w?of woody biochar addition can result in 10.18?15.35%increasement of cumulative methane production?p<0.05?,while herbal biochars has no significant effect on it.?2?The SSA and EDC of biochar is benefit for the growth of Enterococcus?p<0.05,r?0.83?,which is helpful for the increasement of the daily methane production rate during the key stage of AD?p<0.01,r=0.93?.Woody biochar can enhance the interaction between Methanosarcina and unidentified-WS6-?Dojkabacteria??p<0.05,r>0.6?,promote the conversion from CO₂ to CH₄,and increase the cumulative methane production.?3?Magnetization modification can significantly improve the SSA,electrical conductivity,and electron accepting capacity of biochar?p<0.05?.Magnetic biochar can significantly increase the cumulative methane production and the maximum methane production rate by 11.69%and 4.95%,respectively?p<0.05?.The SSA of biochar was still the key characteristic of?magnetic?biochar for the enhancement of AD in the system with AD as the main process?p<0.05,r>0.99?.?4?Large amount?25.30%?of methanogens can be fixed and recovered by magnetic biochar,indicating that the strategy of stabilizing and enhancing the AD efficiency by recovering magnetic biochar is feasible.Moreover,microorganisms involved in hydrolysis,acidification,acetation,and methanization,such as Clostridiaceae,Porphyromonadaceae,and OTU in Bacteroidales,can be selected enriched on magnetic biochar.It can improve the efficiency of mass and electron transfer between microorganisms,and significantly improve the efficiency of AD?p<0.05?.This research provide a new strategy for improving the efficiency and stability of anaerobic digester treating organic waste,and it is helpful for the application of biochar in AD.