Aluminium is the third most abundant element (after oxygen and silicon).
It’s everywhere in earth’s crust. But to separate it from oxygen requires as much energy as it produces when burned. And there’s always additional overhead. It would be a clean fuel if that’s what this article is driving at, but how clean is the energy source used to extract it? The pollution just gets bumped up to another level.
Needs electrical process to extract from oxide-—expensive!