Effect Of Modified Biochar On Aerobic Composting Of Chicken Manure And Greenhouse Gas Emission

As a natural new adsorbent,biochar can improve the composting effect and quality.Traditional biochar is difficult to adjust the pore structure and surface physical and chemical characteristics,which has great limitations on the adsorption capacity of biochar.Therefore,modification is an important way to adjust the adsorption capacity of biochar.In this experiment,wheat straw biochar（BC）was modified by three kinds of treatments,namely,sodium silicate modified biochar（SBC）,magnesium hydroxide modified biochar（GBC）and hydrogen peroxide modified biochar（OBC）.The structure characterization of different modified biochar was analyzed,and different modified biochars were used as additives for aerobic composting of chicken manure,and the effects of different modified biochars on the physical and chemical properties of the compost and the emission reduction effect of ammonia and greenhouse gases were explored.The main research results are as follows:（1）Compared with BC,the specific surface area and micropore volume of SBC,GBC and OBC all increased in different degrees,among which the specific surface area and micropore volume of SBC increased the most,increasing 6.25 times and 2.75 times respectively.The vibration peak of hydroxyl association and aromatic structure of three kinds of modified biochars are enhanced.Among them,the peak value of the whole functional group of OBC has little change,but there are still inorganic components in the body.The sharp free hydroxyl stretching vibration peak appears in GBC,and there is almost no absorption peak of aliphatic C-H bond in SBC,and the most stable aromatic structure is formed on the surface.（2）All the physical and chemical properties of the pile meet the national standards（NY-525-2021）.The concentration effect and the increase of available nitrogen,phosphorus and potassium make the total nutrients of each treatment after composting higher than that before composting.Compared with the treatment without biochar（CK）,the total nutrient content of the treatment with biochar increased,and the total nutrient content of SBC treatment was the highest,which was 5.31%,and the nutrient retention effect was the best.The germination index of CK treatment is 101.75%,and that of other treatments is higher than CK treatment,SBC treatment has the highest germination index of 151.15%,which has the best effect on promoting crop growth.（3）Compared with CK treatment,adding biochar to compost can reduce the emission of NH₃,CO₂and CH₄,but the modified biochar has no significant effect on the emission reduction of these three gases compared with the unmodified treatment.According to the characterization analysis,it can be found that the modified treatment caused the pore of biochar to collapse and block.Although the specific surface area and pore volume increased after modification,more powdered carbon and granular carbon were formed on the surface of biochar,which was not conducive to gas adsorption.（4）The cumulative emission of nitrous oxide of CK treatment is significantly higher than that of the other four groups,which is 113.78 g·kg^-1DM.In the treatment of adding biochar,the modified biochar has a significant effect on nitrous oxide emission reduction,among which the cumulative emission of BC is 103.72 g·kg^-1DM,and that of OBC is 28.42 g·kg^-1DM,which is the best.It shows that adding biochar can significantly reduce the emission of nitrous oxide released in compost,and the modified biochar has a better emission reduction effect than the unmodified biochar.This is because the more alkaline modified biochar promotes the release of ammonia gas,thus inhibiting the nitrification reaction and reducing the emission of nitrous oxide.It may also be related to electron transfer inside the heap and various enzymes produced by bacteria.Results show that OBC treatment has a better effect on nitrous oxide emission reduction,and the emission reduction reaches 75.02%and 72.60%compared with CK treatment and BC treatment respectively.