A Harmful Gases Mitigation Technology Study In Layer Manure Composting Based On Biochar Selection And Modification Chen Wei

Aerobic composting is an effective way to harmless and recycle animal manure. However, the by-products harmful gases such as ammonia（NH₃） and methane（CH₄） emissions had been paied more attention because it can reduce the quality of compost products and increase the greenhouse effect. As a bulking agent in the composting, biochar is an inexpensive and stabilized resource that can reduce gas emission. But different biochars may have different effects on reducing gas emission. No research had been conducted on it. This thesis study the effect of biochar on NH₃ and CH₄ emission in the layer manure composting based on the five different biochars selection and modification, and discuss the mechanism of the biochar on NH₃ and CH₄ emissions. It might provide a theoretical basis on reducing gases emissions in layer manure composting.This study include three parts: first is the effect of different types of biochars on NH₃ and CH₄ emission during layer manure composting; second is the modification of cornstalk biochar; third is the effect of modified biochars on NH₃ and CH₄ emission during layer manure composting. The main result are as follow:（1） The result show that the total NH₃ production significantly decreased（P<0.05）for the treatments with biochars. Among the biochar treatments, cornstalk biochar and woody biochar were the most effective in mitigating NH₃ productions with reduceing the total NH₃ production by 38.50% and 32.87%, respectively. Cornstalk biochar, woody biochar and coir biochar were significantly ruduce the CH₄ emission（P<0.05） with reduceing the total CH₄ emission by 22.17%, 17.72% and 14.31%, respectively. Moreover, adding cornstalk biochar could increase temperature, NO^3--N concentration and decrease p H, NH⁴⁺-N and organic matter conten throughout the composting process. It might be attributed by the higher posity, surface aera and the more surface functional groups of cornstalk biochar.（2） The adsorption capacity for ammonia nitrogen of modified biocahr by 6, 8, 10 mol/L HNO₃（1.43±0.0052 mg/g, 1.42±0.014 mg/g, 1.43±0.0090 mg/g） were significantly higher than 2, 4 mol/L HNO₃（P<0.05）. The adsorption capacity for ammonia nitrogen of modified biocahr by 25% and 30% H₂O₂（1.57±0.010 mg/g, 1.58±0.010 mg/g） were significantly higher than 10%、15%、20% H2O（0.43±0.019 mg/g, 0.85±0.012 mg/g, 1.20±0.0071 mg/g）（P<0.05）. The adsorption capacity for ammonia nitrogen of biocahr modified by 6 mol/L HNO3 and 25 % H₂O₂（mixed modification） can reach 1.56±0.014 mg/g, significantly higher than 6 mol/L HNO₃ modified biochar（P<0.05）. The number of surface functional groups, the surface aera and pore volumes of mixing modified biochar was significantly higher than 25% H₂O₂ or 6 mol/L HNO₃ modified biochar.（3） The results showed that the cornstalk biochar, H₂O₂ modified biochar and mixing modified biochar treatment can reduce the total NH₃ by 23.73%, 15.20% and 41.07%, respectively. The total ammonia emission in mixed modified biochar treatment was significantly lower than other treatments（P<0.05）. Mixed modified biochar treatment also had significantly lower p H and nitrogen loss, higher organic matter degradation rate during layer manure composting. Mixing modified biochar can improve the mean relative abundance of nitrifying bacteria, decrease the mean relative abundance of denitrifying bacteria and methane-producing banteria.In summary, adding mixing modified biochar can reduce ammonia and methane emission by 41.07% and 15.54% during layer manure composting, improve the quality of composts and reduce environmental pollution.