I was reading about an environmental project where soft plastics were melted by villages in the sub India continent to make bricks and those used to make houses! (web site of Doingyourbit) Wow. I read the details and they mentioned using a "solar grill" designed by a Danish (woman) engineer to make the bricks. I have never heard of such a thing and today when googling the net I read more about this idea. I want one!
(picture from a UK supplier web site, not promoting them and there are others available in the world).
Pity they are still fairly expensive, large, and don't work as well in UK - but can you just imagine if someone improved this thinking and gave us fuel free cooking!!!
Our frugal community would all be customers!