Letters: September 2023

Extracting estimates

I have just read the interesting article on lithium extraction. The article makes the claim that crushing rocks for lithium mining uses an estimated 5% of global power consumption. If true this would seriously impact on our ability to use lithium battery technology to reduce fossil fuel use. However, estimates I found suggest that the world mining industry uses between 3.5–11% of the world’s energy in total (the range is probably because of differences in what was included as well as different approximations made).

Now most mining is carried out for coal (8 billion tonnes/year), iron ore (2.5 billion tonnes/year), copper (around 2 billion tonnes/year) and gold (around 1 billion tonnes/year – much of which requires fine grinding and sometimes pressure oxidation of concentrates which is very energy intensive), as well as aggregates for construction that probably require less demanding processing.

By contrast, the total amount of lithium ore is unlikely to exceed 20 million tonnes of hard rock (1–2% lithium oxide) requiring crushing and processing, plus additional amounts of salt deposits that are probably less energy intensive to process even though the grades are lower (0.1%), since fine grinding of hard rock is not required.

Some of these figures are necessarily approximate. However, because of the small proportion of total mining actually carried out for lithium mining it seems unlikely that a significant proportion of world energy use is devoted to lithium extraction. This is fortunate if we are to make significant reductions in greenhouse gas production using lithium battery technology.