Research progress on biochar enhanced anaerobic fermentation technology of organic wastes

Abstract: Anaerobic fermentation is an important technical way to deal with organic wastes in China. However, in the process of treating organic wastes under high load conditions by anaerobic fermentation technology, it is easy to cause anaerobic fermentation operation unstable and the efficiency of organic waste treatment is not high due to the inhibitory substances such as the high concentration of organic acid and ammonia nitrogen. Biochar is a multi-aperture carbonaceous material formed by high-temperature pyrolysis of biomass materials under the anaerobic or anoxic conditions. Biochar has many excellent properties, such as the high specific surface area, good conductivity, mass transfer and heat transfer performance. At the same time, biochar also contains a lot of ash, and the abundant ash contains a lot of elements such as calcium and magnesium, which makes the biochar have good adsorption and ion exchange performance. As an additive for anaerobic fermentation, it can effectively improve the pH value, alkalinity and the acid buffer capacity of the anaerobic fermentation system, and alleviate the inhibition of the excessive production of methane by the volatile fatty acids during the lag period. It can cause the adhesion of microorganisms and had a certain microbial carrier effect. Addition of biochar can effectively solve the problems of the low efficiency of gas production and unstable fermentation in current anaerobic fermentation, and biochar is now widely used in anaerobic fermentation technology research. In recent years, the research status of domestic and foreign showed that biochar could effectively strengthen anaerobic fermentation under certain conditions and improve the treatment efficiency of organic wastes in anaerobic fermentation process. However, for the biochar-enhanced anaerobic fermentation technology approach, there were still no systematic reviewed and reported. In this paper, the chemical composition, surface pore structure, key factors of surface functional groups and important ways of biochar-enhanced anaerobic fermentation technology of biochar materials were systematically analyzed and summarized. Based on the physical and chemical properties of biochar materials, biochar was described. For example, the effects of different types, different particle sizes and different amounts of additive biochar on anaerobic fermentation. And the intensive pathways of anaerobic fermentation technology mainly included: Biochar could effectively improve the buffer capacity of the system, it had a certain microbial carrier function, and it could strengthen the interspecific electron transport of microorganisms. On this basis, the focus of research on anaerobic fermentation technology of organic wastes in the future was proposed. At the same time, it also provided support for the in-depth development of biochar enhanced anaerobic fermentation technology.