Coal resources are the largest known primary energy resource. Supplies will last for centuries, even if use grows at a moderate rate. Reserves are widely distributed in politically stable areas. The many uses of coal, from electrical power generation to the production of gaseous or liquid fuels and the use as petrochemical feedstock, make it likely that this versatile hydrocarbon will remain a major raw material for the foreseeable future.
The mining and especially the use of coal will become more complicated and hence the energy produced more expensive. Coal mining, coal transportation, and coal burning have been subjected to ever more stringent regulations. This trend toward tighter regulations will continue. A major environmental factor that will affect the future of coal is the growing concern about global warming. While technologies such as CO2 capture and sequestration are being researched, restrictions on CO2 releases will add significantly to the cost of producing energy, in particular electricity, from coal.
Predictions for the near future suggest a modest, steady increase in coal production. The main competition in the next few decades will be from natural gas. Natural gas reserves have risen steadily over the past 30 years, in parallel with the increased demand and use, and hence the increased interest in exploration for gas. Natural gas is preferred because it is richer in hydrogen, poorer in carbon, and hence the combustion products contain more steam rather than CO2. If, in the somewhat more distant future, the predictions of a reduction in supply of natural gas and oil were to come through—and for over a century such predictions have proved ‘‘premature’’— coal might once again become the dominant fossil fuel. The rise in demand for electric power seems likely to continue in most of the world to reach reasonable living standards and in the developed world for such needs as electric and fuel cell-driven vehicles and continued growth in computers and electronics in general.
To make coal acceptable in the future, steps need to be taken at all phases of the coal life cycle, from production through end use. A major focus in the production cycle is minimizing methane release associated with mining. Methane (CH4) is a greenhouse gas. It also is a main cause of coal mine explosions. Great strides have been made in capturing methane prior to and during mining. In gassy seams, it now is collected as a fuel. In less gassy seams, especially in less technologically sophisticated mines, it remains uneconomical and impractical to control methane releases. Extensive research is in progress to reduce methane releases caused by coal mining.
Other environmental problems associated with mining coal include acid mine drainage, burning of abandoned mines and waste piles, subsidence, spoil pile stability issues, and mine site restoration and reclamation. Technological remedies exist, but their implementation may need societal decisions for regulatory requirements.
Coal preparation is critical for improving environmental acceptability of coal. Super clean coal preparation is feasible. Technically, virtually any impurity can be removed from coal, including mercury, which has drawn a great deal of attention over the last few years. Coal transportation, particularly in ocean going vessels, has modest environmental impacts, certainly compared to oil.
Coal users carry the heaviest burden to assure that coal remains an acceptable fuel. Enormous progress has been made in reducing sulfur and nitrogen oxide emissions. Capturing and sequestering CO2 will pose a major challenge to the producers of electric power.
More efficient coal utilization contributes to the reduction in power plant emissions. Modern power plants run at efficiencies of about 37%. During the 1990s, power plants have come on stream that run at over 40%. It is likely that 50% can be achieved by 2010. Increasing efficiency from 37 to 50% reduces by one-third the coal burned to generate electricity and reduces by one-third gas (and other) emissions.
Coal has been attacked for environmental reasons for over seven centuries. With ups and downs, its use has grown over those seven centuries because of its desirable characteristics: low cost, wide availability, ease of transport and use. It will be interesting to see whether it can maintain its position as a major energy source for another seven centuries or whether more desirable alternatives will indeed be developed.