Integrated Assessment Of The Environmental And Economic Effects Of "Coal-to-gas Conversion" Project In Rural Areas Of Northern China

The problem of air pollution in the north of China is quite serious,especially in winter.The bulk coal used by rural residents for heating is one of the main sources of atmospheric pollutants.In order to reduce the emission of atmospheric pollutants in the heating season,the Chinese government has issued a policy of "coal-to-gas" which utilize natural gas instead of bulk coal as heating fuel in winter.Coal-to-gas project will cover more than 1.8 billion m2 floor area and affect more than 12 million heat users.The household wall-mounted gas boiler adopted after coal-to-gas has the advantages of higher combustion efficiency and less pollutant emissions.After the implementation of the coal-to-gas policy,the energy consumption structure of the whole rural areas in northern China will undergo tremendous changes,which will also have a significant impact on the living standards of residents.Using natural gas for winter heating has certain environmental benefits,while the problems of insufficient gas source and high cost have also aroused many doubts.Beijing,Tianjin,Hebei and the surrounding areas are selected as the objective areas in this research.Energy usage of rural households in one year is defined as the function unit.The method of life cycle assessment and life cycle cost are combined to quantify the environmental impact and economic cost of five scenarios before and after coal-to-gas.Based on the results of quantitative analysis of environmental impact,the key environmental impact categories and the key elements before and after "coal-to-gas" are identified.Combined with the research results and the actual situation of rural areas in the target areas,suggestions for the optimization of "coal-to-gas" heating and the implementation of clean heating in rural areas are made from the aspect of natural gas resources,insulation measures of rural houses,the thermal efficiency of natural gas and other winter heating measures.According to ReCiPe midpoint(H)model,before the implementation of coal-to-gas in the objective rural areas,the environment impact of rural household energy usage mainly focused on climate change,freshwater eutrophication,human toxicity,particulate matter formation,freshwater toxicity and marine toxicity,and the key element is the bulk coal for winter heating.The key environmental impact types after coal-to-gas are freshwater eutrophication,human toxicity,fossil depletion,freshwater toxicity and marine toxicity,and the key elements for environmental impact and economic cost are natural gas for heating and household electricity consumption.The overall environmental impact of annual household energy consumption in rural areas has been reduced by about 50%,and coal-to-gas for winter heating has achieved better environmental benefits.It is found that after the implementation coal to gas,the annual economic cost of energy consumption of rural households in the objective areas has increased by about 80%through life cycle cost analysis,which has brought a heavy burden to the lives of rural residents.As for the problem of insufficient gas source after coal-to-gas in rural areas,the scheme of using biomass straw gasification to produce natural gas was put forward.This scheme can meet one third of the rural natural gas demand in Beijing,Tianjin,Hebei and the surrounding areas,and effectively supplement the shortage of heating gas supply.In order to further optimize the energy usage of rural households after the implementation of coal-to-gas project,using condensing gas wall mounted gas boiler and adding insulation measures to rural houses are proposed.The two measures can further reduce the environmental impact of rural household energy usage by 7.5%and 14.3%after demonstration.In addition,other rural heating methods,such as air source heat pump,biomass briquette fuel,solar,briquette and multi-energy complementary,have certain utilization prospects in rural clean heating.This study will provide theoretical and data support for rural clean heating,implementation of coal-to-gas project and the control of air pollution.