Greenhouse gases, abatement and control: the role of coal, IEACR/39

Author(s): Irene M Smith, Kelly Thambimuthu

Ref: IEACR/39
ISBN: 92-9029-192-3
Published Date: 01/06/1991
No. of Tables: 18
No. of Figures: 56
No. of Pages: 86

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Various concepts for assessing the relative importance of greenhouse gas emissions are discussed. Emission factors (gC/MJ) need to include all greenhouse gas emissions and energy losses throughout the cycle in order to compare the fuels. The most important greenhouse gas overall is CO2 and it is the most important gas from coal utilisation. Trends in regional emissions of CO2 are compared briefly and related to head of population, gross domestic product and energy use sectors. Coal provides about 28% of commercially traded world energy supply, half of this is in power generation. In 1988, CO2 emissions from coal use amounted to 2.4 GtC/y out of a total of 6.5-8.5 GtC/y, the range depending on estimates for emissions from deforestation and land use. The increased concentration of CO2 in the atmosphere resulting from coal use accounts for 16-21% of the enhanced greenhouse effect, that is the part of the global greenhouse effect which is due to human activities. Making an allowance for the longer term effect of emissions over a hundred years, increase the relative contribution of coal to 17-23%. In addition, there is a small contribution from other gases emitted by coal use, but this cannot be quantified at present. The overall contribution from coal use is likely to be in the order of 20%. The scope for emission reductions (abatement) by continued improvements in the efficiency of coal use is assessed within the context of existing and emerging power generation technologies, including the use of blending fuels and cogeneration or combined heat and power. Various combinations of these options can achieve a 20% or more reduction in CO2 emissions. However, the time frame will depend on the speed with which such options can be implemented. Post combustion control of CO2 emissions by flue gas separation and disposal is considered to be a less promising option owing to the high cost and energy penalty of most methods. The use of CO2 for the synthesis of fuels and chemicals by natural biological processes appears to be the most practical and economic, both in terms of cost and energy. They are not, however, likely to remove CO2 on the scale required to stabilise its concentration in the atmosphere. It is concluded that there is no firm basis for evaluation the effect of reducing emissions on their global warming potential. However, abatement technologies aimed at improving conversion efficiency or reducing energy consumption will reduce emissions whilst having their own commercial justification in a `no regrets' policy. By contrast, control technologies usually add to costs and to energy consumption. They are therefore inherently less attractive than abatement options.

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