A couple of years ago I came across Tjeerd Veenhoven's palm leather[0][1]. It is probably not quite as super-durable as pure leather, but still quite incredible given how simple it is to produce (basically, soak a palm leaf husk in a water/glycerine solution for a few days), and given that it is mainly made from what used to be waste materials.

Sadly it seems the products based on it did take off enough for it to become a thing (especially since he seemed to be doing his best to also ensure the local economy of the places where this material would be produced would benefit from it). The project got turned into a foundation that tries to support a local economy and design community, so who knows, it might make a comeback in a few years[2].

More recently Veenhoven has been developing pigments from discarded tulip flower heads[3], and fabrics based on algae[4].

[0] http://www.tjeerdveenhoven.com/portfolio_page/palm-leather/

[1] https://www.youtube.com/watch?v=Xo7Zfw8eLso

[2] http://www.tjeerdveenhoven.com/portfolio_page/wishful-doing-...

[3] http://www.tjeerdveenhoven.com/portfolio_page/tulip-pigments...

[4] http://www.tjeerdveenhoven.com/portfolio_page/algaefabrics/