What Every Householder Should Know

do not use on aluminum warning from washing soda package

According to the CBC, a Canadian has patented a method for extracting hydrogen from aluminium. While this patent has some extra specifics to deal with managing the reaction, it’s not that far removed from the old home science trick of dissolving aluminium foil in washing soda. Indeed, every box of washing soda I’ve used has come with the warning message above.

It takes a lot of energy to form aluminium from its various ores. According to an Alcan report, it takes over 15.5 kWh/kg to do this — that’s over 55 MJ of power per kg of metal. Smelting aluminium can also be massively polluting. I’ve heard tell that the smelting plant near Fort William used to turn the surrounding hillsides yellow from the fluorine emssions.

I haven’t done the sums properly on how much hydrogen a kilogram of aluminium will produce when reacted with caustic soda, but it’s probably going to be less energy than it took to form the metal. You’d also have to deal with disposal of alumina sludge at the end of the reaction, which is mostly harmless but bulky. There’s also a huge amount of heat evolved by the exothermic reaction, and thereby not turned into useful chemical energy. It’s a similar reaction those caustic soda/magnesium metal chip drain cleaning powders, and you know how hot they make the drainpipes.

This patent seems typical of many of the methods that are being thought up in our mad dash to a hydrogen economy; uneconomic, inefficient and ill-advised. But you can’t criticize it publically, ‘cos everything going to be running on hydrogen soon, isn’t it?

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