Tad Patzek of the University of Texas at Austin and Gregory Croft of The University of California, Berkeley, decided to find out. They contend that the stated coal reserves published by governments have a significant political component. They say, "The proved reserve numbers are the source of the myth of a 200-400 years supply of coal worldwide at the rate of production of roughly 6.5 billion tonnes per year."
So they used historical production data fitted to Hubbert curves, which predict the total amount that can be extracted from a mining resource based on past rates of extraction. They also looked at the world's coal reserves in terms of the quality of the deposits--the amount of energy produced per tonne by burning it. They say they wanted "to inject some geophysics into the debate."
They found that the peak of energy production (and CO2 emission) from coal may have nearly been reached.
Their work is reported in the journal Energy. The abstract and citation is here. (Unfortunately the full article is behind a $35.95 pay wall, unless you subscribe to Energy. You don't, do you? Hardly anybody does. This is called "secret science". Fortunately the paper is available in PDF here.) From the abstract:
We develop a base-case scenario for global coal production based on the physical multi-cycle Hubbert analysis of historical production data. ... The resulting base-case is significantly below 36 of the 40 carbon emission scenarios from the IPCC. The global peak of coal production from existing coalfields is predicted to occur close to the year 2011. The peak coal production rate is 160 EJ/y, and the peak carbon emissions from coal burning are 4.0 Gt C (15 Gt CO2) per year. After 2011, the production rates of coal and CO2 decline, reaching 1990 levels by the year 2037, and reaching 50% of the peak value in the year 2047. It is unlikely that future mines will reverse the trend predicted in this BAU scenario.Translation: "Our statistical analysis suggests that peak coal is upon us, and that the use of coal to generate energy will decline in the future, even if more mines are dug."
A summary of their findings:
- Both global coal production and CO2 from burning coal will peak in 2011.
- CO2 from coal will decrease by half by 2050.
Very Different NumbersThis contradicts coal industry and even government agency forecasts. The U.S. Energy Information Administration shows continuous increase in energy from coal (almost entirely in Non-OECD Asia) in their projections to 2035. (See International Energy Outlook 2010 - Highlights. The full report is available in PDF here.)
Patzek and Croft compare their prediction of coal consumption over time with 40 IPCC scenarios developed to model future coal use and emissions. They assert, "Most of the IPCC scenarios seem to have little to do with reality predicted by the actual coal production data. In the year 2100, the physical Earth will not be producing 5-7 times more than at the peak in 2011. ... The real problem 40 years from 2009 will be an insufficient supply of fossil energy, not its overabundance, as the IPCC economists would have it."
Could newly discovered coal fields or new mining technology prevent the decline in coal production? The authors think not. "Gradual improvements in recovery percentage should fall within the base-case; only a technology that allows access to a new population of coal seams should create a new fundamental Hubbert cycle, such as in unconventional natural gas recovery in the U.S." Such technology breakthroughs are always possible. They also point out that some new fields are remote, or have environmental or water-availability issues that may hinder their ability to change the overall picture.
ImplicationsBarring such revolutionary technological breakthroughs, want does this analysis mean for the future of energy, and in particular for atmospheric CO2 concentrations?
They point out that lower-energy coals will become increasingly uneconomic. Coal has a significant transportation cost, which would be a higher proportion of the cost of using low-energy coal.
As coal production declines, while global energy demand continues to increase, the authors suggest that there will be an increasing emphasis on more efficient coal-to-energy technologies, such as "to gradually replace the existing electrical power generation blocks with the new ultra supercritical steam blocks (steam temperatures of 620-700 °C, and pressures of 220-250 bars), whose electrical efficiency is close to 50%, compared with the ~35% efficiency currently realized. This replacement might ultimately lower current CO2emissions from coal-fired power stations by 15/35 ≈ 40% for the same amount of electricity." They think increasing coal-fired generating capacity, as opposed to efficiency, would be a dumb idea given the future decline of coal supply.
They also say "Scarce coal will make it difficult to justify the energy penalty of CCS [carbon capture and storage at coal plants]." They feel there are cheaper and quicker ways to sequester carbon than by coal-fired carbon extraction and compression systems.
They add, "Cap-and-trade policies for carbon dioxide emissions will not be effective if the cap is set near peak emission levels, and may allow the natural decline of coal production to effectively subsidize a lack of effort on the part of energy industry."
The Phase-Out of CoalAlthough the authors of this report do not say so, reduced supply of coal will drive up its price. As we try to extract more and more energy from coal we will deplete the easy-to-get-at and high-quality deposits, and have to turn to more expensive and less-energy-dense sources. Thus the production of energy from coal combustion will become more expensive. The coal itself will be more costly, and more will have to be burned to generate the same amount of power.
This will make competing sources of energy such as wind more competitive. Already Europe is projected to substantially increase its share of energy from wind, with a corresponding decrease in the share from coal.
Coal miners and coal companies have considerable political clout, which has minimized restrictions on coal use to control greenhouse gas emissions. But they can do little about the cost of coal. In the end the switch from coal to gas, nuclear and renewables may be driven more by the decline in supply of coal and its increasing cost than by national emissions-control strategies.
National Geographic has a good article about this research report.
The image is Figure 2 from Patzek and Croft, A global coal production forecast with multi-Hubbert cycle analysis, Energy, Volume 35, Issue 8, August 2010, Pages 3109-3122 at http://dx.doi.org/10.1016/j.energy.2010.02.009
copyright 2010 Elsevier Ltd. All of the quoted content is also copyright Elsevier. Used under Fair Use standards.