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.

AN Mather CChem MRSC
Leicestershire, UK

Editor’s note: Thanks also go to several other readers who calculated much lower estimates of lithium mining’s power consumption than stated in the article.

Update 5 September 2023: The article has now been corrected

In the balance

Alzheimer’s is a terrible disease and we are desperate for effective treatments. The recent study on Donanemab engendered great excitement in the media even before the clinical results were published. It is in Lilly’s commercial interest to engender this excitement to put pressure on regulatory authorities for approval.

It was therefore refreshing to read Phillip Broadwith’s more considered response. As he said, the published clinical data shows that Donanemab only slows down the progression by a few months, in many on average by as little as three months, after which time the rate of cognitive decline is the same as in the placebo group. To me that confirms that there is another, as yet unidentified, cause of cognitive decline that continues in the absence of amyloid in the brain.

Donanemab and the other antibodies are not cures, nor do they reverse any loss of cognitive ability. It is also worth noting that the studies were carried out in a carefully selected group of patients and it is almost certain that a positron emission tomography (PET) study would be a requirement before starting antibody therapy. Currently there are only 69 PET scanners in England, Wales and Northern Ireland, mainly used to detect cancer. Therefore, there is not only the cost of the drug and treatment, and the incidence of side effects to consider, but also the cost of providing sufficient PET scanners to identify the dementia patients most likely to respond to the antibody. The approximate capital cost for a scanner and cyclotron facility is in the region of around £6 million each. A tricky problem for The National Institute for Health and Care Excellence (Nice).

Frank King FRSC
Hertfordshire, UK

The nature of geology

Philip Ball is right to debate the question of the nature of life and, therefore, its habitable zone. However, he is not quite right to say that there is no known geological source of phosphine. Schreibersite, for example, an iron/nickel phosphide mineral, is said to be common in iron–nickel meteorites. Although weathering to phosphate is its most likely fate on Earth, the liberation of phosphine on sulfuric acid-rich Venus is credible. It is unlikely to persist, however, as it will eventually abstract oxygen from sulfuric acid, giving rise to a variety of less volatile sulfur and phosphorus oxyacid species. If Ball can extend the definition of extra-terrestrial life then, surely, we can do the same for extra-terrestrial geology!

Dave Smith MRSC CChem
Alnwick, UK

Food, not fuel…

The July issue of Chemistry World has a good article on the development of ammonia manufacture using less energy than the standard 100-year-old process. This is commendable for providing less expensive fertiliser for food for underfed millions. However, it is not in any way a good idea to replace methane as an energy source. Ammonia is manufactured, not collected from nature. It is also more toxic and corrosive than methane.

Methane is readily available from the Earth. It makes little sense to use it and other organic materials (fossil fuels) to power factories to produce a manufactured fuel which does not produce more energy that it takes to make it. Until we get sustainable efficient energy sources, please use reason and use ammonia for feeding people and methane for energy to enable the economy. It is a fool’s choice to allow methane to sit idle or escape to the environment while we use ammonia for energy rather than food production. People cannot metabolise methane but they can metabolise the foods grown with ammonia fertiliser.

Richard Lamoureux MRSC
Via email

… And drink

After a very good and helpful response to my band keratopathy letter, I have another plea for help. This is for a more commercial project idea and relates to ‘depriving the angels of their share’ (the evaporative loss of alcohol) and the accelerated ageing of raw whisky in bonded storage. Both are long sought-after prizes of whisky producers.

Ten years ago I realised that I possibly had an inventive answer to these long sought-after goals. My reasoning was based on sound chemical, economic and technology considerations. This led me to try and engage interest within the Scottish whisky community. I was given a polite hearing but nothing came of my overtures. IP protection issues preclude me explaining more.

As far as I can tell my idea has never been tried. If anyone is curious to know more please get in touch with me through the good offices of the Royal Society of Chemistry.

Nevin Stewart FRSC
Guildford, Surrey