 I'm Myra Anubi, and this is People Fixing the World from the BBC World Service, where every week we get to find out about new ideas that are changing our world for the better. Now, if there's something that's been clear on this show, it's that human beings can be destructive. Driving, cooking, building, farming, even fishing. Almost everything we do leaves a harmful trail behind us, even when we don't mean to.