Those are both nonrenewable, use-once resources with fixed (on human timescales) supplies. Metals are different; they're not really consumed, just tied up in m

Those are both nonrenewable, use-once resources with fixed (on human timescales) supplies. Metals are different; they're not really consumed, just tied up in manufactured products during the life of that product. After the product's lifespan, they can be reused. Different calculation entirely.