Indoor Air Pollution in China: Analysis of Global Warming Contributions and Exposure to Particles

Abstract

About 60% of the Chinese population lives in rural areas, where biomass and coal are the main sources of energy for cooking and heating. Indoor air pollution from household fuel burning is a major health concern, responsible for at least 420,000 premature deaths annually in China alone. However, less is known about the emissions of greenhouse compounds from the household sector. Therefore, this work aims to quantify the global warming contribution (GWC) from main household fuels in rural China. Global warming potentials (GWPs) are used to compare the impact of different greenhouse compounds (GHCs) relative to CO2. This is combined with emission data from Zhang et al. (2000), to estimate the total GWC in CO2 equivalents from household fuel combustion stratified by main fuel categories. The key factors affecting GWC are the GHCs included in the calculations, whether the biomass fuels are harvested renewably or not and choice of time horizon. There are large differences in GWC between different fuel categories, with estimates for a 20 year time horizon ranging from 130 g CO2 equivalents per MJ delivered energy for gas to 1560 g CO2 equivalents / MJ for coal, when all GHCs are taken into account. However, the uncertainty for GWC is large, with standard deviations in the range of 5-30% for different fuel categories due to both high variation in the emission data and uncertainty associated with the GWP values. On average, CO2 is the compound that contributes most to total global warming, followed by black carbon and carbon monoxide. Organic carbon has the largest cooling effect, while the contribution from sulfate is negligible. To be able to consider potential co-benefits in terms of health improvements by switching to cleaner fuels, the GWC results were compared to population exposure to respirable particles, stratified by fuel groups. The results show that gas is the most preferable fuel, both when it comes to global warming contribution and public health. The picture is more complicated when it comes to choosing between coal and biomass, where a fuel switch to biomass increased the exposure while most likely cut the GWC. However, only 3 fuel categories were included in the exposure estimate. In reality many more options exist, including improved stoves. Further work should investigate this as well as aim to reduce the uncertainty by obtaining less variable data.