Environmental Impact Evaluation Of Straw Biogas And Straw Gasification Projects Based On LCA

Straw biogas project and straw pyrolytic poly-generation system are environmental-friendly,but pollutants will be caused during the project construction,the crop straw transportation and pretreatment,the products utilization processes.The research on the straw biogas environment performance is a hot topic with the straw biogas industry development of China.Some researchers have been studying on the environmental impact of straw biogas system by the method of LCA.However,the pollutants emission of energy and material during construction unit was seldom considered.This paper started to focus on the environment performance of construction unit of biogas project,which is different from previous studies.The environment performance changes a lot based on the boundary of the system studied.This paper aimed at analyzing the environment impact of each unit and the whole system of straw biogas project and straw pyrolysis project by life cycle assessment.Both the straw biogas system and straw pyrolysis system were divided into construction unit,operation unit and product utilization unit during the inventory analysis.Data of energy coefficient,emission factor,standardization criteria,and weight factor were surveyed from publications and literatures of previous study.The results are as follows:(1)Straw biogas project of Xijie Village can produce biogas 13.6×104 m3/year,the total global environmental impact load of which was 129.94 equivalent/(person a).The environmental impact load of construction unit,operation unit and product utilization unit accounted for 65.62%,32.76%and 1.62%,respectively.The biogas can replace 9.71×104 t/year standard coal,and the total global environmental impact load of coal burning was 262.55 equivalent/(person a).In the view of energy substitution for coal consumption,the environmental impact load of the biogas project system was-132.48 equivalent/(person a).That is to say,the biogas project in this study decreased 50.50%of the environment impact compared to equivalent standard coal burning as household fuel.(2)The total global environmental impact load of the one functional unit of straw pyrolysis system,that is dealing with 1.0×104 tons of crop straw was 172.19 equivalent/(person a).The environmental impact load of construction unit,operation unit and product utilization unit accounted for 16.58%?80.20%and 3.22%respectively.The environmental impact load of steel and PVC pipe consumption accounted 89.42%of the impact in construction unit.And the environmental impact load of electricity consumption accounted for 97.14%of the impact in operation unit.In the view of resource substitution for coal,pesticide and fertilizer,the environmental impact load of the pyrolytic poly-generation system was-498.30 equivalent/(person·a).(3)As an important part of the straw energy utilization system,the construction unit should be considered when evaluating the environmental discharge of the system by the method of life cycle assessment.The environmental impact caused by construction should be incorporated into the system boundary.(4)Straw biogas and straw pyrolytic poly-generation system as clean renewable energy technique can reduce coal consumption and improve the environment quality.It is significant to reduce energy consumption during processing such as coal and electricity,and find low-carbon and use environmentally-friendly building materials in straw biogas system and straw pyrolytic poly-generation system during the construction in the future.