reusability is mainly done for cost instead of environment, but you need to launch a lot to re-cup the costs, and esa is not a commercial org like spacex.
I do think the ESA rockets use a more eco friendly fuel then others, that is probably more important then some metal on the seabed.
I do think the ESA rockets use a more eco friendly fuel then others, that is probably more important then some metal on the seabed.