The Research On Carbon And Nitrogen Conversion Rate And Greenhouse Gas Emission Reduction Of Organic Waste By Black Soldier Fly

Owing to urban sprawl,economic development,population growth consequently contributing to organic waste generation in huge quantities,resulting in serious shortage situation of the resource and the increasing ecological damage.Therefore,sustainable use of waste,including recycling and valorization,is the current trend in waste management.Treatment of organic wastes by black soldier fly larvae has many potential advantages:the larvae can convert the carbon and nitrogen into biomass,and improve the physical properties of the substrate to reduce the loss of gaseous carbon and nitrogen.In this study,the effects of different conditions on direct greenhouse gas and NH₃ emissions,larval yield and bioconversion of carbon and nitrogen from the organic wastes in black soldier fly composting were investigated.The main research contents and conclusions of this work are as follows:The conversion of carbon,nitrogen and the emissions of greenhouse gas during BSFL bio-treatment of mixtures of pig manure and corncob were explored under different moisture content（45%,55%,65%,75%and 85%）.The results show that the substrate moisture content is a key parameter affecting the larval yield.The total biomass of harvested black soldier fly larvae was 0.62–30.03 g,with about 0.25%–4.68%and 1.03%–12.67%of recycled carbon and nitrogen from substrate at a moisture content from 45%to 85%,respectively.Moreover,with the increasing moisture content of the initial substrate decreases NH₃ volatilization but simultaneously increases CH₄ emissions.Cumulative CO₂,CH₄,NH₃ and N₂O emissions at the different moisture content ranging from 45%to 85%,were 33.51–191.18 g kg^-1,1.04–3831.18 mg kg^-1,0.48–0.86 g kg^-1 and 0.07–0.25 mg kg^-1,respectively.Except for the 85%treatment,the total greenhouse gas emissions of 45–75%treatments were less than 1%of the traditional pig manure composting emissions during the same period.The results show that adjusting the initial moisture content to75%is most suitable for the treatment of pig manure by black soldier fly.The conversion of carbon,nitrogen and the emissions of greenhouse gas during BSFL bio-treatment of mixtures of pig manure and corncob were investigated under different C/N ratios（C/N=15,20,25,25 and 30）.The results indicated that initial raw materials C/N ratios are a crucial parameter affecting the biomass generation of larvae.The total biomass of harvested black soldier fly larvae was 61.71–79.47 g,with about4.17%–6.61%and 17.45%–23.73%of recycled carbon and nitrogen from substrate at a C/N ratios from 15 to 35,respectively.Moreover,C/N ratio significantly affects CH₄and NH₃ emissions during composting.Cumulative CO₂,CH₄,NH₃ and N₂O emissions at the different C/N ratios ranging from 15 to 35,were 107.92–151.68 g kg^-1,0.08–0.77 g kg^-1,0.14–1.17 g kg^-1 and 0.91–1.36 mg kg^-1,respectively.Compared with conventional composting,black soldier fly larvae treatment could reduce the total greenhouse gas emissions by over 85%.Various analyses indicated that C/N ratio of 25 is recommended for the bioconversion of mixtures of pig manure and corncob by black soldier fly.The conversion of carbon,nitrogen and the emissions of greenhouse gases during black soldier fly larvae bio-treatment of food waste were investigated under different p H conditions（p H=3.0,5.0,7.0,9.0 and 11.0）.The results showed that the p H of the raw materials is a pivotal parameter affecting the process.The total biomass of harvested black soldier fly larvae was 21.15–176.22 g,with about 1.95%–13.41%and5.40%–18.93%of recycled carbon and nitrogen from substrate at a p H from 3.0 to11.0,respectively.Furthermore,p H is adversely correlated with CO₂ emissions,but positively with NH₃ emissions.Cumulative CO₂,CH₄,NH₃and N₂O emissions at p H ranging from 3.0 to 11.0 were 88.15–161.11 g kg^-1,0.20–2.62 mg kg^-1,0.15–1.68 g kg^-1and 0.20–1.65 mg kg^-1,respectively.The results indicated that treatment of food waste by black soldier fly could reduce greenhouse gas emissions by over 99%,compared with conventional composting.Therefore,a higher p H value of the substrate can increase the larval output and help the mitigation of greenhouse gas emissions.Overall,optimizing the process parameters of the black soldier fly composting could be beneficial to the recycling of carbon and nitrogen from organic wastes to larvae,increasing the larval yield and reducing greenhouse gas and NH₃ emissions.The results provide theoretical support and data reference for evaluating the sustainability of the black soldier fly composting process in real practice.