American CO2 emissions have plummeted thanks to natural gas and energy emissions from coal have not been this low since the early 1980s, but a decades long war against energy science meant nuclear power - a truly viable emissions-free source - was scuttled and that meant more coal plants starting in the early 1990s, which meant more CO2.

There are environmental complaints that CO2 is not dropping worldwide because America simply 'exports' its CO2 emissions now. Anti-business policies ran manufacturing out of this country and sent those jobs to Asia, they say, but in the case of coal, exporting coal might be a good thing. Exporting emissions was, of course, the intent of cap-and-trade, which was never approved in the United States; the idea was that businesses would be rewarded for lower emissions.

Exporting coal accomplishes that without hefty government profiteering, and it's even beneficial when transportation is factored in, because Asian plants are modern and more efficient. A new paper in Environmental Science&Technology finds that emissions could drop 21 percent. And if we then scuttle older coal plants and replace them with natural gas, it might be even more.

"Despite the large amount of emissions produced by shipping the coal such a long distance, our analysis shows that the total emissions would drop because of the superior energy efficiency of South Korea's newer coal-fired power plants," said Dalia Patiño-Echeverri, assistant professor of energy systems and public policy at Duke. If imported U.S. coal were to replace natural gas or nuclear generation in Korea, the emissions produced per unit of electricity generated would increase, Patiño-Echeverri said, but it would be unlikely, since coal would still be cheaper.

It would also solve a political problem. The president is now anti-coal along with being anti-nuclear, anti-gas and anti-oil, so Democrats have to be nervous that the administration has declared war on so many union jobs. In the United States, union members tend to vote Democrat. If coal declines, they would be in the position of having to subsidize jobs in an industry they helped kill.  But if coal companies can instead take advantage of a growing export market, jobs are protected while emissions cuts still happen. Due to natural gas uptake domestically and demand from Asia, U.S. coal exports to Asian countries have tripled since 2009. 

To conduct their analysis, the authors performed lifecycle air-emissions and economic assessments of two scenarios: a business-as-usual scenario in which the coal continues to be burned domestically for power generation at power plants in the U.S. Northwest after they have been retrofitted to meet EPA emissions standards, and an export scenario in which the coal is shipped to South Korea. For the export scenario, they focused on the Morrow Pacific Project being planned in Oregon by Ambre Energy. Under the project, Ambre would ship 8.8 million tons of Powder River Basin coal each year to Asian markets using rails, river barges and ocean vessels. 

In the export scenario, emissions of "equivalent carbon dioxide" -- a scientific measure of the coal emissions' total global warming potential over a 100-year period -- dropped 21 percent.

Other harmful emissions, including sulfur dioxide, nitrogen oxide and particulate matter, dropped similarly.

"In addition to these benefits, our analysis shows that the export scenario would generate more than $25 billion in direct and indirect economic activity in the United States," Patiño-Echeverri said. "It would also directly or indirectly create nearly $6 billion in total employee compensation, $742 million in new tax revenues, and roughly $4.7 billion in profits for all sectors involved."

Promising though these results are, "it's too early to give the export scenario an unequivocal green light," she said.

Further studies are needed to assess the export scenario's full environmental impacts, including water use, land use, the loss or degradation of vital fish and wildlife habitats, and risks associated with extraction and wastewater disposal of U.S. shale gas deposits. And there's still some fine tuning to do on the economic end.

Patiño-Echeverri said the team's projections are limited in precision due to the fact that the Morrow Pacific Project is in a permitting stage, and many of its operational and financial details are still unknown. As more specific information about the project is released, calculations can be updated to present a clearer picture of the impacts the project may have on the U.S. energy system and global environmental conditions.

"It's important to note that this is just one scenario. The export of coal to different markets, under different conditions, might yield very different results," Patiño-Echeverri said. "Our work does not provide a carte blanche for all energy export projects, but it does give us a framework for comparing their impacts and making smarter economic and environmental policy decisions."