Ever hear of "going green"? It's the same idea - a sex toy that is in some way environmentally friendly.
A green toy could be rechargeable, reducing the number of batteries being thrown away. It could be made of easily renewable materials, like wood (which is also biodegradable). Or it could be made of materials that will last a long, long time, like steel, glass, and pure silicone - that way they toy won't need to be replaced every so often.