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Comment on "Environmental implications of United States coal exports: a comparative life cycle assessment of future power system scenarios".

Exports: A Comparative Life Cycle Assessment of Future Power System Scenarios” A recent article in this journal by Bohnengel, PatiñoEcheverri, and Bergerson (BEB) provided a life-cycle materials flow analysis of alternative uses of U.S. thermal coal. Unfortunately, just as economists err when they ignored physical reality in their economic theorizing, this article has ignored economic reality in developing what it labels its “scenarios.” This weakens significantly the insights that that analysis can provide about environmental impacts, especially the projection of greenhouse gas (GHG) emissions. The headline-grabbing result reported by BEB was that “...the environmental impacts of shipping PRB coal to Asia are significant...[and] could lead to a greenhouse gas reduction of 21%...” (p.9908). In fact, the Duke University press release announcing the article headlined exactly this result. (DukeNews, 8/19/2014) Other news stories about this BEB article also chose to headline that reported result. What BEB actually analyzed were two different uses of Powder River Basin (PRB) coal: Burning it in two older American coal-fired electric generators that are already planned for retirement or conversion to natural gas and burning that PRB coal in two newer, higherefficiency, coal-fired generators in South Korea. Life cycle air emissions from these two alternatives were compared to see what the joint impact of these changes in the use of PRB coal would have on net emissions of various pollutants. BEB found that when the impacts of these two changes in the use of PRB coal were combined, total emissions of most pollutants, including GHG, were reduced. The source of this projected aggregate decline in emissions was a combination of some partially offsetting factors in the U.S. and South Korea. The shift from using coal at the U.S. generators to using natural gas to generate the equivalent amounts of electricity reduced GHG and other coal combustion emissions because natural gas has only about half of the GHG emissions of coal and lower levels of most other pollutants per MWH generated. That is why those coal-fired generators have been scheduled for retirement. In addition, because the two U.S. generators were older, less efficient, and dirtier than the newer South Korean coal-fired generators, there would be less carbon (and most other pollutants) emitted per MWH generated in the South Korean plants than if the same coal had been burned at the specified U.S. generators. These reductions in pollutants from the electric generators were projected by BEB to substantially offset the air pollutants from shipping the PRB coal to South Korea by trains, barges, and ocean-going ships. The economic flaw in this analysis is the assumption that the two different uses of PRB coal were somehow causally linked. If these two alternative uses of PRB coal are not linked economically or in some other causal manner, then combining them does not represent an actual real world “scenario.” In order to ship PRB coal to South Korea to generate electricity there, it is not necessary to shut down coal-fired generators in the U.S. and serve the same load with gas-fueled generators. The PRB coal fields are capable of meeting both U.S. domestic and export demand at a relatively low mine-mouth cost. Similarly, the retirement of coal-fired electric generators across the U.S. and the replacement of their generation with naturalgas-fueled generators are not necessarily tied in any way to whatever the demand for coal is in Asian markets. Assuming that the fueling decisions for electric generators in the U.S. and in South Korea are linked would require some specific economic assumptions. No such economic assumptions are stated and justified with empirical evidence by BEB. One such assumption might be that the amount of economically feasible PRB coal is limited to about what is currently being annually mined. If that were true, new export markets could be served by PRB coal only if some current U.S. domestic users of that coal reduced their consumption of it. Whether the alternative to current use of PRB coal in the U.S. would be natural gas or some other source of coal would have to be determined in the analysis. If there is additional annual production capacity in the PRB or it could be created relatively cheaply, no displacement of current uses of PRB coal would be necessary in order for new PRB coal exports to proceed. Historical experience in the PRB coal fields and geologic analysis do not support an assumption that the PRB coal reserves are at the economic limit of what they can produce. PRB coal production increased dramatically over the last three decades, rising from about 100 million tons in 1983 to almost 500 million tons in 2008. During that same time the average real price of PRB coal at the mine mouth fell by almost 50%. (We are using U.S. subbituminous coal to approximate PRB coal production and price. Since 2000 PRB coal has made up about 90% of U.S. subbituminous coal production.) U.S. government estimates of how mining costs in the PRB would rise with increased annual production show only modest increases in costs for significant additional expansion in annual production in the PRB. These PRB cost curves come from EPA’s Integrated Planning Model v.4.10 that was designed to project regional coal production and use in the U.S. In addition, PRB coal production has declined significantly since 2008, making available previously developed coal production capacity: PRB production peaked at 496 million tons in 2008 and had declined to 419 million tons by 2012. If sales of PRB coal to Asia do not require a decline in the combustion of coal in the U.S, e.g. by the replacement of U.S. coal-fired generators with natural-gas-fueled generators, then the projected reductions in coal combustion products due to the switch from coal to natural gas in the U.S. are not linked to the export of coal to Asia. In that case there is no basis for BEB’s claim in the article that U.S coal exports may significantly reduce GHG emissions.