Clean coal for cars has a dirty side

Getting liquid fuels from coal would not reduce carbon emissions, and would likely increase them

Normal 0 false false false MicrosoftInternetExplorer4 If the United States tried to achieve independence from foreign oil by making gasoline from vast reserves of domestic coal, the country would probably end up increasing its carbon emissions, a new study concludes.

Researchers found that in realistic scenarios, the mass production of fuel from coal or natural gas would lead to the emission of more climate-changing greenhouse gases than the current oil-based economy. But even in the most optimistic scenarios, which assumed that breakthroughs in technology could be achieved, coal and gas would not help reduce emissions from transportation, the researchers report in the Oct. 15 Environmental Science & Technology.

“In terms of greenhouse gases, this was dead on arrival, so to speak,” says study coauthor Michael Griffin, an environmental engineer at CarnegieMellonUniversity in Pittsburgh and coauthor of the new study.

The authors have done a “remarkable job in developing robust life cycle analysis tools,” comments chemical engineer Blake Simmons of Sandia National Laboratories in Livermore, Calif. The results show that converting coal or gas “might not be the panacea to our current challenges associated with transportation fuels, especially in terms of negative environmental impact,” Simmons adds.

Both coal and natural gas can be turned into syngas, a mixture of carbon monoxide and hydrogen. Engineers have known for almost a century how to turn syngas into liquids similar to gasoline or diesel fuel — a process Nazi Germany used during World War II to keep its economy going while it was unable to import oil.

Turning coal into syngas and then into liquid fuels could in principle enable the United States to free itself from its dependence on foreign oil, at least as far as transportation fuels are concerned, says study coauthor Paulina Jaramillo. But it would come at a cost, the authors estimated.

The researchers used data from the U.S. Department of Energy, the Environmental Protection Agency and the engineering company Bechtel Corp. to calculate the emissions generated during the production, transportation and consumption of different fuels — the impact of each type of fuel from cradle to grave. This included, for example, estimates of methane — a greenhouse gas — seeping out of coal mines; the energy required to dig out and transport coal; the energy that would go wasted in industrial-scale coal-to-fuel conversion; and the efficiency of internal-combustion engines running on different liquid fuels.

Greenhouse gas emissions could, in some scenarios, almost double if natural gas or domestic coal were to replace foreign oil, the researchers found. But even if all potential ways of reducing emissions were implemented — for example, capturing carbon dioxide that’s a byproduct of syngas conversion — the alternative fuels would not help stem climate change. “This is certainly not a greenhouse-gas reduction technology, no matter what you do,” says Griffin.

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