I think it falls into the same category as 'not at all sustainable' and maybe vegan. But I have a backpack who's outer skin is made from recycled bicycle inner-

I think it falls into the same category as 'not at all sustainable' and maybe vegan. But I have a backpack who's outer skin is made from recycled bicycle inner-tubes sewn together to make a watertight surface. After years it's worn almost like leather, though I suspect eventually it will break down into a powder like an old rubber band. It start off as shiny but eventually developed minute scratches and turned quite matte and more plyable. It does not, of course, have that earthy leather smell and will forever smell somewhat of rubber inner-tubes. Sadly it seems like they no longer make the backpack I own but here is an example (https://www.alchemygoods.com/collections/upcycled-backpacks-and-messengers/products/brooklyn-backpack https://www.alchemygoods.com/collections/upcycled-backpacks-...)