Resource Limits, Conversion Efficiency and Climate Change

There are two commonly-used approaches to modeling the future supply of mineral resources. One is to estimate reserves and compare the result to extraction rates, and the other is to project from historical time series of extraction rates. Perceptions of abundant oil supplies in the Middle East and abundant coal supplies in the United States are based on the former approach. In both of these cases, an approach based on historical production series results in a much smaller resource estimate than aggregate reserve numbers. Because the U.S. holds very large coal reserves, synthesizing liquid hydrocarbons from coal has been suggested as an alternative fuel supply. This conclusion is not supported by published coal production data, which show that U.S. anthracite and bituminous coal are already past their production peak. This result contradicts estimates based on aggregated reserve numbers. Because increasing coal consumption is the leading source of growth in carbon emissions, this result has major implications for climate change models, most of which assume steadily increasing emissions.