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Using a bottom-up type global energy model, this article explores in detail the potential role of coal over the 21st century and focuses on the prospects for coal gasification-based conversion technologies with CO2 capture and sequestration (CCS) under the CO2 stabilization target of 550 ppm. The results show that even in the CO2-constrained world, coal can remain one of the important primary energy sources throughout the century on the condition that the resulting CO2 is properly captured and sequestered. Coal's competitiveness in such a world would increase with the introduction of CCS, but decrease with the leak rate for CO2 stored underground. For the optimal coal use, a common trend toward producing convenient and clean final energy carriers via gasification is observed. Under the CO2 constraint, coal is increasingly converted via gasification with CCS into electricity and hydrogen, thereby providing CO2-neutral energy carriers and facilitating CO2 capture, which helps China and India develop in a sustainable manner. These findings prove to be robust with respect to the costs of gasification-based conversion technologies and CCS. It is suggested that the establishment of reliable CCS technologies and low-cost gasification-based conversion technologies and their transfer to developing regions would raise the value of coal and provide energy security benefits under the CO2 constraint. However, it is also indicated that large-scale introduction of coal with CCS into leaky reservoirs would cause large CO2 emissions from leaks over the very long term.

This paper presents global scenarios of sulphur dioxide (SO2), nitrogen oxides (NOx), and particulate matter (PM) emissions from road transport through to 2050, taking into account the potential impacts of: (1) the timing of air pollutant emission regulation implementation in developing countries; (2) global CO2 mitigation policy implementation; and (3) vehicle cost assumptions, on study results. This is done by using a global energy system model treating the transport sector in detail. The major conclusions are the following. First, as long as non-developed countries adopt the same vehicle emission standards as in developed countries within a 30-year lag, global emissions of SO2, NOx, and PM from road vehicles decrease substantially over time. Second, light-duty vehicles and heavy-duty trucks make a large and increasing contribution to future global emissions of SO2, NOx, and PM from road vehicles. Third, the timing of air pollutant emission regulation implementation in developing countries has a large impact on future global emissions of SO2, NOx, and PM from road vehicles, whereas there is a possibility that global CO2 mitigation policy implementation has a comparatively small impact on them.

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