Effects Of Different Biochar On Anaerobic Digestion Of Food Waste And Analysis Of Economic Benefits

With the development of society while people’s living standards have improved food waste has become increasingly serious.If the food waste（FW）disposal method is improper it will become a potential source of hazards affecting food safety and ecological safety.FW is rich in organic matter and anaerobic digestion（AD）is the inevitable trend of resource treatment and utilization of FW.However,AD of FW has problems such as easy acidification and low gas production efficiency.As a new mediating material,biochar has the characteristics of large specific surface area（SSA）special pore structure abundant surface functional groups and cheap and easy to obtain.These all provide the possibility to promote the stability of food waste in the anaerobic fermentation process and improve the efficiency of gas production.In this study wheat stalks（WS）and discarded apple branches（AB）were used as raw materials to prepare biochar.Different types of biochar were prepared and characterized under different pyrolysis temperatures and different KOH modified concentrations and then different types of biochar were added in the AD of FW to characterize the impact of biochar on the AD of FW through factors such as daily gas production methane production process parameters VFA composition and microbial community structure and to explore its mechanism of action.Finally,by comparing and analyzing the gas production benefits and economic benefits of various types of biochar for the AD of FW the paper provides theoretical basis and support for the selection of biochar types and the practicability of biochar in the AD of FW.The main conclusions include:（1）The pyrolysis temperature and KOH modification affect the properties of biochar together.As the pyrolysis temperature increases the yield of biochar also increases.KOH modification increases the ash content of biochar thereby increasing the yield.The p H value of biochar increases with the increase of the concentration of the modified solution.In wheat straw biochar（WSB）the average p H value of 2 mol L^-1 modified biochar was1.71 higher than that of unmodified biochar;in waste apple branch biochar（ABB）the average p H value of 2 mol L^-1 modified biochar was1.57 higher than that of unmodified biochar.Among WSB WS650-1 has the highest specific surface area of 47.91 m² g^-1.2 mol L^-1 modified biochar has a lower SSA than 1 mol L^-1 modified biochar and the surface structure is more complex;Among ABB the SSA of biochar with a pyrolysis temperature of650℃increased sharply and the SSA of AB650 AB650-1 and AB650-2 were 168.39186.17 and 392.20 m² g^-1 respectively.The modified solution makes the surface of biochar not smooth and increases the number of micropores.The FTIR of WSB and ABB showed that KOH modification introduced more functional groups on the surface of the biochar.（2）Different WSB significantly improved the gas production efficiency of AD of FW.The cumulative gas production is increased by 17.39%-45.16%compared with CK and the cumulative methane production is increased by 14.86%-68.43%compared with CK.WS650-2 has the best effect.WSB increases the p H value during the AD of FW stabilizes the content of ammonia nitrogen（AN）.In addition,the activities of key enzymes（acetokinase and coenzyme F420）during anaerobic digestion were increased,thus the degradation rate of acetic acid was increased.In terms of microbial communities,wheat straw biochar is enriched in Firmicutes and Methanosarcina at the same time mediating direct interspecific electron transfer（DIET）between the two communities.（3）Different ABB have significantly improved the gas production efficiency of AD of WS.The cumulative gas production is 19.98%-43.70%higher than that of CK and the cumulative methane production is 38.17%-64.87%higher than that of CK.AB450-2 has the best effect.ABB increases the p H value during the AD of FW stabilizes the content of AN,increased the activity of coenzyme F420,and promotes the degradation of acetic acid and butyric acid.In terms of microbial community,the ABB enriched Bacteroidetes,Synergistetes and Methanosarcina simultaneously,and mediated DIET between the three communities.（4）Among the WSB WS650-2 has the highest gas production economic benefit with an annual net income of 310.56 yuan/year which is 45.5 yuan/year higher than that of CK;AB450-2 in the ABB has the highest gas production economic benefit and annual net income It is 357.13 yuan/year which is 61.11 yuan/year higher than CK.These two 2 mol L^-1 modified biochars have significant advantages in anaerobic fermentation of food waste and are suitable and recommended for actual production.WS450-1 WS550-1 WS550-2WS650-1 AB650-1 and the economic benefit of AB650-2 is lower than that of no biochar so it is not recommended to be used in actual production.