According to senior military figures, by the time a gallon of fuel reaches the frontline in Afghanistan its cost has increased to £250. Add in the cost of escorting those tankers in terms of lives and you have a pretty powerful incentive for the military to cut down its fuel consumption. Top officials in the United States and in the UK are taking this message seriously, investing in research into alternative fuels, portable battlefield power systems and energy reduction strategies.

There's already a company of US Marines operating in Afghanistan with solar powered communications systems whilst back home military chemists are working on fuels from algae. Their ultimate aim is for frontline military bases to produce their own vehicle fuel from on-site tanks of algae, completely eliminating the need for long convoys of fuel tankers. One British company is building enormous fuel-efficient airships that will spend weeks in the air patrolling Afghanistan whilst another builds generators that turn frontline waste into power for military camps.

Could all this military effort be just the tonic that civilian green technology needs? Could the military's cash, expertise and sense of urgency push forward the stagnant technology of solar, wind and alternative fuels? Tom Heap investigates the real eco-warriors in this week's 'Costing the Earth'.

Producer: Alasdair Cross.