William Lyons, 10, from Oxford
"The Recyclo"
Features: Plants to absorb carbon dioxide and breath out oxygen
A mast with old carrier bags to catch the wind
A broom to clean the street while moving along
A cabin for children to lie down in, with cushions filled with grass-cuttings
A body made from recycled Coke cans
Headlights powered by a dynamo
Photograph: William Lyons/Guardian
Molly Clark, 9, from Cambridge
"The Cowmobil"
Features: Made from squashed plastic bottles, an ironing board, flower pots, ladders and an old boat
Runs on cow pats - they go down the funnel, land on a conveyer belt and get put in a fire to make fuel
A flashing button that tells you when you are low on cow pats
Old bicycle wheels Photograph: Molly Clark/Guardian
Charlie Gregory-Bird, 6, from Brighton
"The Eco-Plane-Train"
Features: A "hole fixer" to fix the holes in the ozone layer
A cloud collector (it collects rain and drops it on places such as Africa where there might be a drought)
Wind pipes to collect wind to push it along
Propeller to produce electricity
Pedal power
Machine to take away greenhouses gases
Photograph: Charlie Gregory/Guardian
