Carbon Sequestration Potential And Environmental Impacts Of Biochar Based On Life Cycle Assessment

In order to cope with global warming and climate change,how to effectively reduce carbon emissions has become an important issue during the development of all countries around the world.Biomass has attracted wide attention as a kind of renewable and sustainable resource,and especially the conversion of biomass residues into biochar is considered to be an effective way to simultaneously achieve carbon sequestration,waste management and renewable energy production.However,in China,a high volume of crop and forestry residues is produced every year,and their often poorly managed disposal has not only caused waste of resources,but also aggravated the greenhouse effect and environmental pollution.Therefore,Pyrolysis of biomass residues to produce biochar is considered as a promising technology.But there still exists controversy about the carbon sequestration potential and environmental impacts by the application of biochar technology.It is of great practical significance to carry out a comprehensive assessment and research in the context of China.Based on the basic methodology of life cycle assessment(LCA),the whole life cycle process of biochar production and application is analyzed in this paper,and a LCA software,Ga Bi is used to quantify its global warming potential(GWP),abiotic depletion potential(ADP),acidification potential(AP),eutrophication potential(EP),and human toxicity potential(HTP),et al.Meanwhile,the availability of crop and forestry residue resources in China is investigated and statistically analyzed,and the environmental benefits of large-scale implementation of biochar production and application are explained.The main results are as follows:(1)The biochar system has significant carbon sequestration potential.Production of biochar based on 1 t of crop and forestry residues could achieve carbon sequestration of 921.66 and 1213.38 kg CO2e(CO2-equivalent),respectively.The coal-fired generation offsetting has the greatest positive impact on all environmental categories,and the biochar field application mainly contributes to carbon sequestration,thereby mitigating the global warming potential.Due to the great demand for material and energy inputs,slow pyrolysis becomes the process with the greatest negative impact on various environmental categories.(2)Sensitivity analysis of 15 parameters in the biochar system such as electricity consumption in crop residue collection,diesel consumption for crop residue transportation and pyrolysis plant electricity demand shows that biochar yield,carbon or stable carbon content in biochar,bio-oil electricity conversion efficiency are the key parameters which determine the carbon sequestration potential and environmental impacts of the biochar system.In application practice,the optimization of key parameters should be considered first to make the biochar system have a better environmental performance.(3)China’s abundant crop and forestry residue resources can be used as raw material reserves for biochar production.It is estimated that the annual amount of crop and forestry residues available in China is approximately 8.01×108 t.If pyrolysis technology is applied to treat biomass residues across the country,the annual carbon sequestration potential is 7.97×108 t CO2 e,accounting for 7.12% of China ’s net greenhouse gas emissions(111.9 × 108 t CO2e)in 2014.In terms of the resource distribution,more biomass resources are concentrated in the central south and east of China,which has great potential for the application of biochar technology.(4)From a comprehensive perspective,the application of biochar technology in China is environmentally feasible.In addition to small negative impacts on the potential of abiotic depletion and ozone depletion (ODP),biochar implementation from biomass residues in China could positively alleviate the marine aquatic ecotoxicity potential(MAETP),human toxicity potential,and acidification potential,et al.In this paper,through quantitative assessment and research of the potential carbon sequestration capacity and comprehensive environmental impacts of biochar implementation,the carbon sequestration mechanism and environmental performance of the biochar system are revealed,which enriches the theoretical basis of biochar carbon sequestration research field and provides reference and guidance for the application of biochar technology.