I was having a discussion with sd the other day, and referenced this article here:

https://www.greencarcongress.com/2024/07/20240716-constelliumh2.html

' This casting was performed in a 12-ton furnace following strict internal procedures. Quality monitoring, including the use of Batscan technology, an inclusion detection tool for molten aluminum, was conducted and no quality impact from hydrogen combustion on metal was observed.'

I said that this seemed to show that aluminum production as well as steel could largely be decarbonised by the use of hydrogen, instead of the present coal, NG etc

sd raised the very valid point that this seemed to be about later processing of aluminum, not its initial production.

Now even then, aluminum has a high recycling rate, so hydrogen would be very handy for that.

I have now had a chance to find out a bit more about the initial process of making aluminum from bauxite:

https://www.mckinsey.com/industries/metals-and-mining/our-insights/aluminum-decarbonization-at-a-cost-that-makes-sense

' While the metal itself is sustainable, its production usually is not. Although abundant in the Earth’s soil and rocks, aluminum does not occur in its pure form and has to be extracted from compounds—a complicated process of refining and smelting that requires a large and constant load of electricity. To produce this energy, many countries rely on coal. Globally, about 55 percent of the electricity needed for aluminum smelters comes from coal-fired power plants (with 10 percent from natural-gas plants and 30 percent from hydropower).3 As a result, the aluminum industry is among the highest-emitting sectors in the world, accounting for about 2 percent of global greenhouse-gas (GHG) emissions.4'

And:

' Roughly 80 percent of primary aluminum GHG emissions are generated from smelting, of which 81 percent are associated with the electricity used for electrolysis.6 For aluminum smelters that have opted to supply this energy from their own power plants, as opposed to obtaining energy from the grid, solar or wind generation can be a useful addition. But due to their intermittency, these renewable sources won’t be able to fully power the process.'

And

'More widely applicable alternatives that could reduce nearly all thermal refining emissions are electric boilers powered by either wind or solar,9 hydrogen boilers supplied with green hydrogen, or boilers that employ MVR technology, an energy recovery process that can be used to recycle waste heat.10'

MVR:

'Mechanical Vapor Recompression (MVR) is a proven energy-saving evaporative concentration technology, which reduces evaporation energy use by 90% or more. MVR Thermodynamic Cycle. MVR uses energy recovered from the condensate to create a pure liquid distillate and a concentrated product/waste.'

So it is complex and challenging, and would use a variety of technologies, including hydrogen, but can be done.

The biggest producer of bauxite is Austalia, which also of course has massive renewables resources.

And of course much of the world's iron comes from there, which is currently largely made into steel in China.

Others have argued elsewhere that instead of concentrating on exporting hydrogen, which is tough to do, Australia should simply concentrate on repatriating steel production using their renewably produced hydrogen, an perhaps the same can be done for aluminum production.