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Life cycle sustainability assessment in the energy sector 157

As mentioned before, renewables tend to require more metal resources
per unit electricity generated when compared to fossil fuels. Consequently,
depletion of elements increases greatly from 22t Sb eq./year in 2009 to
298–1430t by 2070 (see Fig. 5.13). This highlights the critical importance
of reuse, recycling and implementation of circular economy principles in
general over the coming years.

3.2.5 Case study conclusions
Robustly evaluating a complex LCSA can be very challenging. In such
cases, multicriteria decision analysis can be an extremely useful tool, as dis-
cussed in Section 2.5. However, a simpler approach is a summed rank anal-
ysis. It should be stressed that this is a simplistic analysis that ignores both
the distribution of results for individual indicators and the importance of
the issues addressed by each indicator: each indicator is given equal weight
within its group.
It is relatively straightforward to rank each subscenario against each
sustainability indicator in the year 2070 and sum their ranks to obtain
a single score; the lower the score, the better the option. To avoid bias
resulting from the different number of indicators in the techno-
economic, environmental, and social dimensions, the analysis should
be hierarchical: summed ranks should first be created for each dimension
and then the overall ranking estimated based on the summed ranks for the
three dimensions.
When such an analysis is performed, the baseline 2009 electricity mix is
preferable from the techno-economic perspective with a score of 37, fol-
lowed by 100%-2 which has an equal share of nuclear and renewables,
with 39. The renewable-intensive 100%-1 and CCS-intensive 65%-1 have
the joint worst score of 47 for techno-economic performance. In terms of
environmental impacts, 100%-2 has the best score of 21, followed by 80%
with 25. The 2009 mix and 100%-1 are the worst ranked options. However,
100%-1 appears to be the best option from the social perspective, followed
by 100%-2, with the 2009 mix being the worst.
Overall, the ranking suggests that all 2070 electricity mixes are superior
to the 2009 mix with the exception of 65%-1 which scores the same. The
best option, within the limitations of this simplified ranking approach, is
100%-2 (score of 5), followed by 80% (9). Thus it appears that aggressive
decarbonization using a mix of nuclear power and renewables is likely to
be the preferred route.