New inventory of black carbon emissions from China finds 2007 levels higher than previously reported
|BC emission map of China at 0.1° × 0.1° for year 2007. East and West China are separated by a dashed line from Qiqihar, Yinchuan, to Kunming. Major emission areas are marked. Credit: ACS, Wang et al. Click to enlarge.|
A new black carbon (BC) emissions inventory from China found BC emissions levels in 2007 of 1,957 Gg BC—higher than reported in earlier studies. The inventory also forecasts that BC emissions in China in 2050 will be 920–2,183 Gg/yr under various scenarios, with the industrial and transportation sectors standing to benefit the most from technological improvements. The paper by researchers from Peking University and Environment Canada appears in the ACS journal Environmental Science & Technology.
Black carbon is released into the atmosphere via incomplete combustion of carbonaceous fuel and is of major concern because of the impact on climate systems. BC emissions from Asia have been identified as a major cause of changing monsoon, the occurrence of the atmospheric brown cloud, and the retreat of Tibetan glaciers, in addition to impacting global temperature rise. (Earlier post.) Asia contributes more than half of global anthropogenic BC emissions and China is the largest emitter, according to the researchers.
|Comparison of relative contributions from various sources to total BC emissions between China and other countries/regions including India, North America, and Africa. Credit: ACS, Wang et al. Click to enlarge.|
To develop the new inventory, the team included 22 BC emission sources including both anthropogenic and natural sources (savanna and forest fires), and used emission factor values (EFBC), references, and the detailed data sources for coke production, open-fire agricultural waste burning, and wildfires.
For the remaining sources, the following fuel consumption data were used: national data from the United Nations Statistics Division (1949−1970); national data from the International Energy Agency (IEA) (1971− 1979); provincial data from the China Energy Statistics Yearbook (CESY) (1980−2007); and predicted national data from the National Long-term Development Plan (NLDP) (2008−2050).
In addition, predicted oil consumption for use in motor vehicles between 2008 and 2050 were used to develop the inventory. County-level fuel consumption in 2007 was derived for 2,373 counties using a set of provincial data-based regression models.
By comparing fuel consumption data (1980−2007) from IEA and CESY provincial statistics, it was found that IEA statistics underestimated coal consumption in the residential and industrial sectors from 1988 to 2007, petroleum consumption by motor vehicles from 2003 to 2007, and coke production from 1980 to 1996, because the fuel produced or consumed by local units has not been taken into account.
The IEA statistics are based on national statistics from the Energy Research Institute, which are provided by key state energy producers. As a result, the use of coal from small local mines is included in the provincial statistics, but not in the national statistics. Similarly, consumption of oil by a large number of non-state-owned small refineries before 2003 was counted only in the provincial statistics, but not by the national statistics. In addition, a large number of small-scaled beehive coke ovens operating in the 1990s were missed in the national statistics.
As a result, the total energy consumption based on provincial data in CESY were higher than that in IEA statistics with a relative difference of 14.6−39.6%. The possible underestimation of national emission statistics has been corroborated by NOx emission trends based on the energy statistics and observed by the satellite images. Considering the information presented here, provincial fuel consumption data provided by CESY for 1980−2007 were used in this study.—Wang et al.
For the 1,957 Gg (median, 1238−3077 Gg as R50) of BC emissions in 2007, the team found that 988, 646, 50.7, 188, and 77.7 Gg were from residential, industry, power plants, transportation, and outdoor biomass burning, respectively. The larger inventory than reported in other studies was largely due to the updated EFBC for residential fuels, industrial activities, and motor vehicles, as well as the inclusion of biomass burning sources and a noncompliance rate of control technologies in the new inventory, the authors said.
BC emissions from motor vehicles were primarily from diesel engines (85%). Generally, the source distribution pattern of BC in China was similar to that in India, but very different from those in African countries, where wildfires dominate the emission totals, or those in developed countries, where motor vehicles contribute to more than half of the total emissions.—Wang et al.
To predict anthropogenic BC emissions to 2050, the researchers used various scenarios. Among their findings:
BC emissions in China in 2050 would be 2,183, 1,663, 1,338, and 920 Gg/yr in baseline-high, low-carbon-high, baseline, and low-carbon scenarios, respectively.
Under the baseline-high scenario, the total BC emissions in China would increase to a peak of 2,273 Gg/yr (1,376−3,719 as R50) in 2041 due to the increase of BC emissions from motor vehicles (by a factor of 3.6), off-road diesel machineries (by a factor of 3.1), coal combustions in industrial boilers and power plants (by a factor of 1.8), brick production (by a factor of 1.6), and coke production (by a factor of 2.4). These increases result directly from greater fuel consumption.
If either the low-carbon strategy (low-carbon-high scenario) or technology improvement (baseline scenario) were implemented alone, total BC emissions in China would be reduced by 92 or 29 Gg/yr in 2010, 394 or 583 Gg/yr in 2020, 476 or 583 Gg/yr in 2030, 519 or 765 Gg/yr in 2040, and 520 or 845 Gg/yr in 2050, respectively.
If the low-carbon strategy and technology improvement were implemented together (low-carbon scenario), the mitigated emissions would reach totals of 158, 988, and 1,263 Gg/yr in 2010, 2030, and 2050, respectively. Mitigation measures would be most effective for industry and transportation, two sectors for which the effects of technology improvement are significant.
The researchers cautioned that future predictions are associated with high uncertainty, because of the uneven pace of technology development as well as the potential for emerging technologies to a fast decrease in EFs over a short period of time in the future. A good example is the diesel particulate filter used on motor vehicles, which can result in a rapid reduction of associated emissions over a short period of time if widely implemented.
Rong Wang, Shu Tao, Wentao Wang, Junfeng Liu, Huizhong Shen, Guofeng Shen, Bin Wang, Xiaopeng Liu, Wei Li, Ye Huang, Yanyan Zhang, Yan Lu, Han Chen, Yuanchen Chen, Chen Wang, Dan Zhu, Xilong Wang, Bengang Li, Wenxin Liu, and Jianmin Ma (2012) Black Carbon Emissions in China from 1949 to 2050. Environmental Science & Technology doi: 10.1021/es3003684