It’s back to school now for most children and for many the start of a new term means one thing – a brand new pencil case. But how green is it?

Pen maker Crayola has been trying to make its plastic marker pens a little greener – by recycling old ones into a fuel.

Schools in the United States and parts of Canada can sign up to the Crayola ColorCycle scheme with a member of staff becoming a Champion to organise collecting and shipping pens to a “marker to energy” conversion factory.

There they are melted down and turned into a “clean-burning fuel”, with 308 markers producing one gallon (roughly four and half litres) of fuel, enough to power a sport utility vehicle or SUV for 15 miles, according to Crayola.

FedEx will pick up the markers from schools and the pen manufacturer says it will pay for all the shipping charges.