Ways to reduce carbon dioxide emissions
While the U.S. Global Change Research Program monitors the effect of twentieth century technology on our environment and climate (see separate story, this issue), twentieth century technology has not completely distanced itself from its environmental consequences. Cognizant that carbon dioxide emissions from fossil fuel combustion pose the prospect of unprecedented rates of increase in global warming, much recent industrial research has focused on altering fossil fuels so that we can continue to enjoy their benefits without having to worry about their consequences.
According to Bette Hileman's article, "Fossil Fuels in a Greenhouse World," in the 18 August 1997 issue of Chemical and Engineering News, carbon dioxide emissions from the use of fossil fuels can be controlled by a combination of 1) decarbonizing the fuel, 2) sequestering the carbon (as carbon dioxide), and 3) using the remaining hydrogen in hydrogen fuel cells. Hileman points out the natural gas (mostly methane) is already being decarbonized to make hydrogen fuel and that the Dakota Gasification Company has contracted to separate carbon dioxide from gasified coal. The carbon dioxide by-product of decarbonized natural gas has been pumped into fossil fuel wells to enhance recovery, into deep saline aquifers under the Norwegian seabed (where there is allegdly room for 280 billion tons of carbon, 47 times the present annual emission rate in carbon dioxide). The Norwegian carbon dioxide also originates as a 9% admixture in natural gas deposits and as a 71% admixture in natural gas deposits north of Borneo. Because carbon dioxide is a supercritical fluid with a density almost that of water at hydrostatic pressure below 2600 feet and denser than sea water below 11,500 feet, another projected repository for sequestered carbon dioxide is the deep ocean floor.
The key to making this three-part program to reduce carbon dioxide emissions has been recent improvements in proton-exchange membrane fuel cells, which run at low temperatures, have high power densities, and fit easily into vehicles. Still to be decided is whether to transmit natural gas via existing pipelines and decarbonize it locally or to decarbonize natural gas centrally and transmit hydrogen through newly-built pipelines.
The more traditional approach to reducing carbon dioxide emissions has been to use our fossil fuels more efficiently, and these efforts continue as well. As Hileman reported in "Industry Considers CO2 Reduction Methods" in the 30 June 1997 issue of Chemical and Engineering News, a conference organized by the International Climate Change Partnership promoted substitution of biological processes in materials production, the development of lower temperature chemical processes (largely through new catalysts), increased efficiency in current chemical processes, reduced use of chemical processes (e.g., through use of lower octane gasoline), more energy efficient equipment, and taxes (for emitting carbon dioxide) or tax credits (for not emitting it).
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