As the century draws to its close, the dark reaches of the world have shifted from the West to the East.
An ambitious analysis of global sulfur emissions estimates spanning two centuries shows that the United States, Europe and the former Soviet Union have stabilized their emissions over the past 20 years, while mainland China's sulfur emissions have soared. China now leads the world in the dubious distinction of most sulfur emissions produced in a country.
Coal consumption overwhelmingly accounted for the highest contributions to sulfur emissions worldwide. Other activities taken into account in the analysis were metal smelting and oil consumption.
The data were gathered and analyzed by Rudolf B. Husar, Ph.D., professor of mechanical engineering and director of the Center for Air Pollution Impact, Trends and Analysis (CAPITA), the world's largest private library of air pollution statistics, at Washington University in St. Louis. He published the analysis in the 1999 fall issue of Atmospheric Environment. Co-authors are Janja D. Husar, Ph.D., research associate in CAPITA, and Allen S. Lefohn, Ph.D., of A.S.L. and Associates in Helena, Mont. The Department of Energy funded part of the research.
"Fuel consumption is the key piece of data," Husar says. "And it is relatively easy to get because most countries have kept track of their consumption." Husar and his colleagues relied on a vast network to get their fuel and metal smelting data. Nineteenth-century data were found in literature and in occasional obscure publications. The 20th- century data were mostly based on League of Nations -- later United Nations -- publications, mineral yearbooks of the U.S. Bureau of Mines, and Her Majesty's Stationary Office in London. The researchers also used fuel consumption data from 1950 to 1990, which previously had been compiled by the U.S. Department of Energy, Oak Ridge National Laboratory. In all, estimates were derived for 234 countries.
The researchers estimated yearly emissions per country based on net fuel production -- production plus imports minus exports. Sulfur content and sulfur retention information based on the individual country's activities also figured into the estimates.
"The stabilizing U.S. and Soviet Union sulfur emissions have occurred in part by switches in the United States from high- to low-sulfur coals and tighter environmental controls," says Husar. "In the former Soviet Union, there has been a greater reliance on natural gas, which is abundant in Russia.
"In the United States, alternative fuels such as natural gas and nuclear power have made an impact. In both countries, but particularly the United States, the shift from a smokestack economy to a service-oriented economy also has made a difference, as have the use of scrubbers and desulfurization techniques in coal-driven power plants.
"As for China, it is an immense country with a growing population, and their coal reserves are massive and predominantly soft coal, which is the dirtier kind. China is in the midst of a booming industrialization process. It makes economic sense for them to burn coal because it is so abundant. We've begun to see more acid rain complaints in Indochina, Japan and Korea, mostly from Chinese sulfur emissions. So, in the broad sense, as we begin a new century, that big problem of the '70s and '80s has now shifted more toward the East."
The United States, the former Soviet Union and China have been the world's major super powers over the past 50 years and they easily lead the world in sulfur production, accounting for 53 percent of global sulfur emissions during the latter part of the study. The European community was next, followed by Japan. Husar's time frame was 1850-1990, encompassing the Industrial Revolution, two world wars and complex economical and policy changes of the latter part of the century. The study is the only sulfur emissions study to examine annual sulfur emissions by each country through a long time span. Husar says that global fuel consumption over the past 50 years actually has gone up, yet emissions have stabilized in most parts of the world because of cleaner fuels and cleaner consumption methods.
"One of the reasons that emissions haven't really gone up exponentially over the past 100 years in the United States is because of the fact that now perhaps two-thirds of the energy is supplied by relatively clean fuels," he says. "Also, particularly in the past 40 years or so, pollution controls have reduced the amount of emissions released into the atmosphere. If not for cleaner fuels and emissions controls, the amount of sulfur emissions today would easily be three or four times what they are now."
Husar estimates that global sulfur emissions in 1850 were 1.2 million metric tons, just 1.7 percent of his 1990 estimate of 71.5 million metric tons. Beginning in 1913, there was a leveling off and then a decline during World War I. The early years of the Great Depression saw a marked decrease in emissions, but that soon changed with World War II. There was a continuous increase in the post-war years, with a drop in 1981-83, corresponding to declining oil demand during the global recession.
Since 1970, U.S. emissions show a general decline. No coincidence, according to Husar, who notes the passage of the Clean Air Act in 1977 and the subsequent Clean Air Act of 1990, which requires that all power plants not exceed a certain amount of emissions.
As the 1990s began, the United States and Canada were emitting a combined estimated 15 million metric tons of sulfur, compared with approximately 22 million metric tons by China.
"The data clearly show that while North American and in some cases, European, emissions have been leveling off, rapid increases are occurring in China," Husar says.
Sulfur emissions are the prime ingredient in the creation of acid rain. While the United States and Canada contested each other over acid rain in the 1980s, it's not the villain that it was then largely because of less acidic, cleaner skies in the Western hemisphere. The clouds now loom over the East. "The same cycle that characterized the industrial areas of North America and Europe in the '70s and '80s is well under way in Asia now, particularly mainland China," Husar points out. "The Asian countries realize something must be done to control acid rain, and they are beginning to address the problem. Acid rain does not depart the world with the end of the century. It's just gone somewhere else now."
Materials provided by Washington University In St. Louis. Note: Content may be edited for style and length.
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