A solar-powered oven made from cardboard is the 50,000-pound winner of a contest to find the world's greenest invention.
The invention bagged the FT Climate Change Challenge crown after beating 300 other creations, including a food additive, which stops cows passing wind.
Kenya-based entrepreneur Jon B°hmer a Norwegian, set up Kyoto Energy with his Kenyan wife Neema, and has used his own money to fund the project.
The oven - which costs just 3.50 pounds to make - can slowly cook casseroles, boil water and bake bread.
It is made from two boxes, one inside the other with an acrylic cover, which lets the sun's power in and traps it.
Black paint on the inner box and silver foil on the outer help concentrate the heat while a layer of straw or newspaper between the two provides insulation.
B°hmer hopes that the oven would put an end to the use of firewood to cook in developing countries.
"We're saving lives and saving trees. I doubt if there is any other technology that can make so much impact for so little money," Sky News quoted B°hmer as saying.
He plans to use the prize money to conduct mass trials in 10 countries, including South Africa, India and Indonesia and gather data to back an application for carbon credits.