Get used to it. You’re going to hear a lot in the next few years about processes that are renewable and about methodologies that are sustainable. We all need to understand the difference. If we don’t those who want us to confuse them will be able to do so easily.
A process is renewable if you can do it more than once. For example, mining coal or drilling for oil is not renewable, but growing corn for ethanol is renewable. You can grow a crop, harvest it, and then grow another crop in the same place. All things being equal, it’s better for a process to be renewable than to be non-renewable. So far, so good.
A process that’s renewable, however, is not necessarily sustainable. To be sustainable, it must be something you can keep doing, not just year after year, but decade upon decade, generation upon generation, century upon century. It must not require nonrenewable fossil fuels, it must not deplete supplies of fresh water or topsoil, and it must leave stocks of fish and other wildlife at least as rich and as varied as they were when the process started.Here’s an explanation of what it takes to be sustainable.
So growing corn for ethanol, for example, while renewable, is not sustainable because it (a) requires fossil fuel inputs for traction, irrigation, fertilizer, insecticide, and pesticide and (b) depletes topsoil. A garden in your back yard, on the other hand, could be sustainable if you could keep doing it for centuries without depleting your soil or requiring external inputs.
Expect to hear many companies and governments use the word “renewable,” knowing many people will hear it as “sustainable.” They are intentionally misleading you. Expect many more to use “sustainable” when the process they describe is merely “renewable.” They’re just lying.