If it's biodegradable, that would help. Only what remains of the tires ends up in landfills/recycled. The rest is a major contributor to microplastics in our oceans. The tires don't just erode into nothing. Those particles (mixed with particles from the road service) become dust that ends up in sewers when it rains, which drain to rivers, which drain to oceans. By the time the tire is used up, we're talking a sizable amount of material. Vulcanized rubber is nasty; it doesn't really break down (that is the whole point of vulcanizing) that easily and is also toxic.