I think they mean like a gallon of gasoline burned in a car does less environmental damage than the same gallon of gasoline just released into the environment.

Not saying it is or isn't, just how I took it.

He's saying we would never have an oil spill equivalent to the amount of oil that is used because we try very hard not to spill oil. It is expensive and damaging.

If you are asking a hypothetical question comparing the amount of oil in a spill and its damage to the environment vs simply using that oil normally, I think the oil spill wins in a landslide for being the most damaging.