Finally I have seen an article (on the BBC) about a subject that I have been talking about for years! Seaweed made into cardboard and invasive fish into pet food….. Spain would be a perfect place to do this kind of thing. (Carp in the Ebro and elsewhere, Introduced crayfish etc etc etc. Even many invasive plants could be harvested and composted). Right up to their erradication if needed as humans are pretty good at that!