TECHNOLOGY FOR AVOIDING CO_2 EMISSIONS

摘要

The Intergovernmental Panel on Climate Change (IPCC) has indicated that global reductions in greenhouse gas emissions of around 60% may be needed in order to stabilise atmospheric concentrations at a level which avoids dangerous changes in climate. This implies that deep reductions in emissions will be needed from major energy using plant and these measures will need to be widely applicable. Technologies for reducing CO_2 emissions from energy systems fall into 3 categories: 1. reducing energy use, e.g. by improving efficiency 2. replacing high-carbon fuels by low-carbon fuels or no-carbon fuels 3. sequestering the CO_2 arising from fossil fuel combustion Improving energy efficiency is cost-effective in many places today. It is expected this could achieve emission reductions of at least 20% but, on its own, this will be insufficient to avoid damaging climate change. Switching from high carbon fuels, such as coal, to low carbon fuels, such as gas, can reduce emissions by 50% but application will depend on the availability of gas supplies. Deeper reductions could be achieved by switching to renewable sources of energy, or to nuclear power. Renewable sources can deliver low cost energy in the right circumstances but the extent of their application will be limited by factors such as availability of land and public acceptability. Application of nuclear power is also likely to be restricted by such considerations. As fossil fuels supply nearly 90% of the world's primary energy, a rapid switch away from them could be disruptive to the world's economy. In the past few years it has been recognised that CO_2 sequestration could substantially reduce emissions from fossil fuels. One form of sequestration is the enhancement of natural sinks for carbon, such as by afforestation. However, such measures will be limited in their global capacity. Another form of sequestration, capture and storage of CO_2, potentially, has wide applicability. It could be used in power generation, oil refining and other major energy using industries, as well as in the manufacture of hydrogen, if that becomes accepted as a transport fuel. An overview will be presented of the cost and potential of CO_2 capture and storage.