Preparation Of Biochar From Anaerobically Digested Food Waste And Its Potential Use In Phosphorus/Chlorpyrifos Adsorption And Soil Amendment

With increasing global economic development and urban populations,food waste is largely produced by the ever-growing demand from hotels,canteens,hypermarkets and companies Significant pollution in the environment has been caused by the excessive discharge of huge amounts of food waste.Traditional disposal methods include landfilling,incineration and composting.However,huge financial costs are required in order to dispose of food waste without negatively affecting the environment.Anaerobic digestion has been found effective than traditional disposal methods.However,biogas residue（BR）produced during the anaerobic digestion of food waste may remain a burden.It is necessary to find an effective strategy for the safe disposal of biogas residue.In this study,biogas residue which collected from food waste biogas production in Pudong New Area of Shanghai was pyrolyzed to biochar（BRB）in a laboratory scale reactor at a broad temperature range from 400 to 900 ^oC.The physical and chemical properties of biochar such as pyrolysis yield,volatile matter,fixed carbon content,ash and moisture,electrical conductivity,pH,elemental composition,mineral fraction X-ray（XRF）,surface properties surface area(S_BET),SEM-EDS and FT-IR were thoroughly studied.The properties that are required for soil amendment application and adsorption of phosphorus/chlorpyrifos were also examined.The results showed that the individual parameter values were related to biochar pyrolysis temperature.With pyrolysis temperature increased from 400^o C to 900^oC,the biochar pyrolysis yield decreased from 70.35to 43.65%,ash content decreased from 39.55 to 13.36%,volatile matter decreased from 40.67to 20.68%,moisture increased from 0.12 to 0.60%,fixed carbon deceased from 58.43%,to19.18%pH increased from 9.19 to 12.52,electrical conductivity（EC）increased from 2.23 to11.50 mScm^-1,the carbon content decreased from 19.81 to 7.07%,hydrogen decreased from1.51 to 0.63%,nitrogen decreased from 1.41 to 0.14%,silver increased from 0.99 to 1.57%,and oxygen decreased from 21.73 to 4.92%.The ratio of（C/H）,（C/N）,（C/O）,（O+N+S）/C and（O+N）/C were determined.The surface area and pore volume was raised with the increasing of biochar pyrolysis temperature.As biochar pyrolysis temperature increased from400℃to 900℃,the equilibrium adsorption concentration of biochar to phosphorus（P）increased from 23.04 mg?g^-1 to 70.90 mg?g^-1.The kinetics of P adsorption on BRB could be described by the pseudo second order equation.The P adsorption capacity of BRB900 was12.28 mg?g^-1.The results from phosphorus and chlorpyrifos adsorption indicate a pronounced effect of pyrolysis temperature on the adsorption of biochar.The amount of chlorpyrifos adsorption increased from 38.36 mg·g^-1 for BRB400 to 39.18 mg·g^-1 for BRB900.The pot experiments showed that the biochar derived from food waste is beneficial for cabbage growth.Overall,turning the solid residues under the anaerobic digestion of food waste for biogas production into biochar shows promise as a mean to solve the problems and also creating new markets for food waste biogas residues.