A guide to life-cycle greenhouse gas (GHG) emissions from electric supply technologies

This manuscript reviews and compares the results of recent greenhouse gas (GHG) emission life-cycle analyses. Specific attention is paid to fossil energy technologies, nuclear and renewable energy technologies (RETs), as well as carbon capture and storage (CCS) and energy storage systems. Analysing up- and downstream processes and their associated GHG emissions, which arise upstream and downstream of the power plant (i.e., electricity generation stage), is important; otherwise, the GHG emissions resulting from electricity generation of the various fuel options are underestimated. For fossil fuel technology options upstream GHG emission rates can be up to 25% of the direct emissions from the power plant, whereas for most RETs and nuclear power upstream and downstream GHG emissions can account for way over 90% of cumulative emissions. In economies where carbon is being priced or GHG emissions constrained, this may provide an advantage to technologies with trans-boundary upstream emissions over technologies without significant life-cycle emissions arising outside the legislative boundaries of GHG mitigation policies. It is therefore desirable for GHG emissions under national, regional and international mitigation policies to be accounted for over its entire life-cycle. The results presented here indicate that the most significant GHG avoidance (in absolute terms) can be made from technology substitution. The introduction of advanced fossil fuel technologies can also lead to improvements in life-cycle GHG emissions. Overall, hydro, nuclear and wind energy technologies can produce electricity with the least life-cycle global warming impact.