**5.2 Coal**

Coal produces 48% of electricity in the United States (Energy Information Administration [EIA], 2011a) and approximately 42% in the world (EIA, 2011b, Table 66) Many utilities promote coal-burning as a low-cost alternative, but recent studies suggest that the often quoted 200 years of coal supply, both globally and in the US, is a serious overestimate.

Heinberg (2009) reviewed several available investigations and concluded that exhaustion of high quality coal reserves and infrastructure limitations on development and marketing of

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drinking water prompted a Congressional mandate to the Environmental Protection Agency (EPA) to study the issue. Preliminary results are due in 2012 and a final report in 2014 (EPA, 2011, p. *x*). Fracking has been widely used for production of coalbed methane in the western U.S. and the potential energy resource is exceedingly valuable, so that the practice will

Second, questions have surfaced concerning the magnitude and potential cost of shale gas production, as reviewed by Hughes (2011a). Evidence exists that shale gas wells deplete rapidly, so that the ulimtate resource is smaller than conventional projections (Figure 10). Morever, the technology-intensive drilling process (even apart from environmental concerns) requires elevated prices to be profitable—higher than present prices and higher than EIA projections for a decade or more. Consequently, either shale gas resources will prove to be smaller than early optimistic estimates or prices will rise so that shale gas can

Finally, doubt has arisen over the life-cycle carbon emissions of shale gas, particularly compared to coal, and therefore over the potential of natural gas to reduce emissions by displacing coal and thus to serve as bridge fuel in a transition to a renewable energy economy. Hone (2011) reviews this issue and Hughes (2011a) also compares two discordant shale gas-coal comparison studies. Shale gas probably would reduce total emissions, especially as best-practices evolve to minimize fugitive emissions (methane, the principal component of natural gas has roughly 20 times the heat-trapping effect as CO2), but perhaps

Fig. 10. Shale gas drilling rates (blue) and production (red)(Hughes 2011a). Solid lines represent historical data. Red dashed line and blue dotted line represent Hughes'

continue in most countries, possibly under greater regulatory scrutiny.

profitably accommodate growing demand.

alternatives to EIA projections.

not by the 50% projected by the most optimistic estimates.

lower quality resources will advance the timing of Peak Coal into the relatively near future (one to two decades, not one to two centuries). Independently, Rutledge (2011) has analyzed the patterns of coal development and concluded that actual developed reserves typically are about ¼ of the early reserve estimates of the geological resource. He concludes that the world will consume 90% of producible coal by 2070. Although he refrains from discussing peak production, his analysis again points to a time no more than a few decades into the future. Patzek & Croft (2010) project a peak already in 2011, with a production decline to 50% of the peak by 2037.

Glustrom (2009) provides a bottom-up analysis of coal reserves, focusing primarily on the western United States. Analyzing the production potential of individual mines, especially in the Powder River Basin of Wyoming and Montana, which accounts for about 40% of U.S. coal production, she finds that extant surface mines on the basin perimieter have 10-20 year production horizons. Expanding production by development of new surface mines faces regulatory and infrastructure obstacles; mining of deeper deposits faces these, as well as additional energetic and economic costs. She does not analyze the coal resources of other countries in detail, but citing Rutledge and one of the same studies as Heinberg, she infers that the issue is global. Although the existence of vast coal resources is clear, the energetic and economic viability of production from lower and lower quality formations in less and less accessible places renders increasing rates of production problematical.

Consequently, expanded reliance on coal-powered electricity to meet agricultural needs faces economic challenges. These challenges apply also to post-farm components of the food system, implying an overall rise in household food expenditures, especially in developed countries where these components account for a much larger share of food system energy.
