Lifecycle Environmental Evaluation of Exploitation and CO₂ Sequestration of Coal

Masayuki Sagisaka, Research Centre for Life Cycle Assessment, N ational Institute of Advanced Industrial Science and Technology (AIST)

Coal is expected as one of the main energy sources for long period in future because of abundant deposit. However, relatively high CO₂ emission is supposed as one of the large barriers for wider utilisation of coal. Because, we cannot avoid CO₂ emission by combustion, we should find possibility of the emission reduction before and after the combustion stage. The author applied Life Cycle Assessment (LCA) methodology for evaluation of greenhouse gas (GHG) emission for exploitation of coal and CO₂ sequestration into coal seams in Japan.

In the production of coal, more than 100kg of CO₂ equivalent GHG has been released by the extraction of 1 ton of coal in 1980s, but because of inefficient mine closures, the GHG emission recently became less than 50kg. Results of the LCA show significant source of the emission and they suggest the possibility of further emission reduction.

For the CO₂ sequestration by coal seams, lifecycle GHG emission by enhanced coal bed methane recovery (ECBMR) system was analysed including CO₂ separation and recovered methane usage. The results suggest that ECBMR system can contribute for the reduction of CO₂ emission compared with simple electric power generation by coal. And the possibility to realise this system was also suggested by its rough cash flow analysis.

LCA can be used for finding the possibility to reduce environmental burden of coal usage to be a match for other energies.