CHASING THE DRAGON'S TAIL; LIFE CYCLE CARBON ANALYSIS APPLIED TO CO_2 SEQUESTRATION

摘要

A huge variety of methods have been proposed for reducing emissions of greenhouse gases, ranging from energy-efficiency measures for emissions avoidance, to the sequestration of combustion-derived CO_2 in deep oceans or spent oilfields. We have investigated the use of various tools for comparing the effectiveness of different methods, illustrated by examples in this paper. Of these, the technique of Life Cycle Carbon Analysis (LCCA) should be developed as an effective tool for the comparison of options for the reduction of greenhouse gas emissions, for the introduction of energy-efficient processes, and for the utilisation of renewables in power generation or liquid fuel production. Comparisons may be made in terms of carbon payback time per tonne of 'carbon' invested; or of the lifetime cost per tonne of CO_2 foregone or sequestered. Examples are given of coal-fired power generation with CO_2 removal and sequestration, domestic energy-saving equipment and small-scale renewable energy installations. These enable some generic conclusions to be drawn about the current state of technologies for ghg reduction/sequestration; and also lead to target costings per tonne of CO_2 equivalent avoided. These costings indicate that, with current technology, investments in the containment of HFCs, in CH_4 leakage reduction, and in straightforward measures for energy efficiency and energy conservation, are all far more cost-effective than CO_2 capture technologies. In particular, cost-effective and carbon-effective reductions in emissions of non-CO_2 ghgs are far more readily achievable than CO_2 reduction measures, both economically and in engineering terms. LCCA demonstrates that policies that address the impact of these releases will show the most immediate and tangible benefits.