A need was identified in the China-MAP project to develop emissions profiles for sulfur dioxide (SO₂) and nitrogen oxides (NO_x) for China for the years 1992/93, 1995, and 2020. Data for 1992/93 and 1995 were needed to drive atmospheric models and produce modeled concentration and deposition data that could be compared with measured data obtained from field studies in China [1]. In addition, the 1995 emission estimates are to be used to drive the sophisticated atmospheric chemistry models that will be used in the China-MAP project to characterize the present-day state of the atmospheric environment. The projections of emissions in 2020 will be used in the same modeling system to assess the potential future development of the atmosphere over China, resulting from the interplay of energy and industrial growth with environmental control policies. For comparison purposes, emissions data for the base year, 1990, and an intermediate year, 2000, are provided.

Five sectors were examined in this project: industry, power, domestic, transportation, and non-commercial (includes biofuels that are collected and burned for energy, such as wood, crop residues, and animal waste). The two sectors that contributed the most SO₂ and NO_x in 1990 were the industrial and power sectors, which were responsible for 50.8% and 28.1% of the SO₂ emissions and 43.6% and 35.5% of the NO_X emissions, respectively. By the year 2000, the industrial sector will be contributing more than one-half of the SO₂ emissions in China (54.5%). The percent share of NO_X emissions will decrease in all sectors over this period except for the transportation sector, which will double its contribution, from 6.6% in 1990 to 13.6% in 2000.

For each of the 27 regions in China (Figure 1), a fixed rate of growth between 1990 and 2000 was assumed for each sector. This allowed the interpolation of values for 1992/93 and 1995 from the

1990 and 2000 values generated by the RAINS-Asia model [2]. The formula for fixed annual growth in this period is:

E₂₀₀₀ = E₁₉₉₀ (1 + r)¹⁰

where E represents the emissions, in Gg, of pollutant and r is the annual rate of growth. By manipulating this function algebraically, we find that:

E₁₉₉₅ = (E₁₉₉₀ * E₂₀₀₀) ^_

Values for 1992/93 were calculated in a similar manner:

E_1992/93 = (E₁₉₉₀ * E₁₉₉₅)^_

For three of the sectors—industry, domestic, and transportation—1992/93 and 1995 values were interpolated by applying this formula. Slightly different methods were used for the power and non-commercial sectors.

The power sector was examined in greater detail. Because RAINS-Asia makes available information about two components of the power sector, small utility generators (< 500 MW) and individual large point sources (LPS, $ 500 MW), it was decided that it would be more accurate to estimate values for individual LPS rather than to interpolate the total power sector values. (This is a more accurate method because we know that the square of the sums is not necessarily equal to the sum of the squares, or (P₁ + P₂ + P₃ + ... + P_N)^_ Ö (P₁ ^_ + P₂ ^_ + P₃ ^_ + ... + P_N ^_ ). Values for 1992/93 and 1995 were interpolated for each LPS as above. The 1992/93 and 1995 values for the total power sector were similarly calculated, then the LPS totals were subtracted to yield values for the small sources. In some cases, however, the LPS was not yet on line in 1990, but is predicted to be in operation by 2000. This presents a problem for the above method, because assuming a fixed rate of growth does not work if the initial value is zero (i.e., let E₁₉₉₀ = 0 Y E₂₀₀₀ = 0 because 0 (1 + r)¹⁰ = 0). For these LPS’s, literature sources [3-6] were consulted to determine when the power plant went on line. If the LPS went on line in 1991, the emissions from this date were used in place of the zero value for 1990 and the years 1992/93 and 1995 were interpolated accordingly. If it was found that the LPS was not yet on line in 1995, it was assigned a zero value for the years of 1992/93 and 1995. Getting the emissions from LPS’s right is important for accurately representing the geographical patterns of emissions, against which monitored deposition is to be compared.

Data for the non-commercial (biofuel) sector are not currently part of the RAINS-Asia model. Data for 1990 were collected for a different project [7] and will be added to future versions of RAINS-Asia. Because only 1990 data are presently available, a different method, extrapolation for future years based on trend data, was developed for this sector. A few literature sources [8,9] have  per capita rates of consumption of non-commercial fuels for several years. Trends are extrapolated from these data for each type of biofuel (wood, crop residue, and animal waste) and are assumed to remain constant through 2000. In each case it was found that the per capita rate of consumption declines over time. However, the rural population (the primary consumers of non-commercial energy) is growing at a faster rate, so total use of non-commercial energy increases slightly over this period. Appropriate conversion factors for each fuel and pollutant are then applied to the energy values projected for 1992/93 and 1995.

Tables 1 and 2 show the SO₂ and NO_x emissions by sector for each of the 27 regions in China (Figure 1). For the industrial, power, domestic, and transportation sectors, the years 1990 and 2000 represent data extracted from the RAINS-Asia model. The emissions values for the years 1992/93 and 1995 are derived using the methodology described above. Table 3 lists each LPS in China, by region, name, and location (longitude and latitude). SO₂ and NO_x emissions are presented for each LPS, with values for the years 1990 and 2000 taken from the RAINS-Asia model. Emissions values for the years 1992/93 and 1995 are interpolated as explained above. Figures 2 and 3 illustrate the total SO₂ and NO_x emissions in China by sector and year.

In order to calculate SO₂ and NO_x emissions for China in 2020 (Table 4), it is necessary to determine both energy consumption levels and emission rates. For both SO₂ and NO_x the RAINS-Asia "Base" (BAS) energy path was used. This pathway assumes a "business-as-usual" scenario that is partially based on forecasts made by government planning agencies. Chinese energy consumption is predicted to continue along current trends in energy policy, assuming no strong promotion of energy efficiency measures or reduction of acidifying emissions through fuel substitution [2].

SO₂ emissions are calculated using the BAS energy data and the Advanced Control Technologies control scenario (ACT). The ACT scenario assumes that only the most cost-effective measures will be adopted in Asia by 2020. These controls are sector-specific. Industrial and power generation controls include flue-gas desulfurization on all new power plants and large industrial boilers. The use of low-sulfur fuels is also included in this scenario, with the industrial sector using 100% low-sulfur liquid fuels and 50% low-sulfur coal. The domestic sector is predicted to be using low-sulfur commercial fuels in 100% of its consumption. Under the ACT scenario, 2020 SO₂ emissions are projected to be 30.3 mt. This result is nearly a 50% decrease in Chinese SO₂ emissions compared to the "No Further Controls" scenario (NFC), at 60.1 mt-SO ₂ [10]. Because China is presently enacting laws to require SO₂ emission controls in certain regions of high emissions, and because the influx of advanced technology is already occurring at demonstration plants, we believe the ACT scenario is a better reflection of likely practices in China in 2020 than is the NFC scenario.

Individual emissions from LPS’s for 2020 are not included here, but can be found in the RAINS-Asia model [2]. Regional estimates of the share of power sector emissions due to LPS’s are made by running the model twice for each region, once selecting "Total Regional Emissions" and again, selecting "Total minus LPS" (used as "Small-Power"). The "Small-Power" portion is then subtracted from the regional totals to yield estimated LPS emissions. This means that LPS emissions in 2020 are estimated using regional-average sulfur contents, rather than sulfur contents of the actual coals burned in 1990.

In order to estimate 2020 non-commercial SO₂ and NO_x emissions, it is necessary first to project consumption of biofuels. Usage trends per capita for several years [8,9] were gathered as previously described. Because it is believed that biofuels will eventually be phased out and replaced by more efficient fossil fuels, it is assumed that by 2020 the per capita rate will be falling more quickly than it is currently. The 2020 per capita rate is multiplied by the projected population of China in 2020 and the SO₂ and NO_x emission factors (assumed to be the same as in 1990) and allocated to the appropriate regions.

NO_x emissions are also projected using the "Base" energy path. However, unlike SO₂, it is assumed that no additional NO_x emission controls will be implemented by 2020 [11,12]. It is believed that NO_x emissions controls will be too expensive for Chinese implementation by 2020; thus, NO_x emissions are expected to rise rapidly in a pattern closely correlated to energy growth.

Total Chinese SO₂ emissions in 2020 are projected to be 30.3 mt (Table 4), with the majority (75%) of SO₂ coming from the Industrial-Combustion sector (22.8 mt). NO_x emissions in 2020 are projected to be 33.0 mt. The transportation sector is expected to contribute about one-third of the NO_x emissions (10.8 mt), though there is a more even distribution among sectors for NO_x than for SO₂.

Sulfur Emissions

NOx Emissions

Acknowledgments

The authors are grateful to The World Bank for permission to use Figure 1. This work was funded by the National Aeronautics and Space Administration as part of the China-MAP program.

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