Avon and Somerset police has ordered 15 Ford Focus flexi-fuel vehicles in full police livery.
The vehicles are fuelled on bioethanol made from crops such as wheat and sugar beet and plans are in place to produce bioethanol from Somerset wheat.
The force is hoping to reduce emissions by about 70% compared with petrol models.
Nick Rogers, head of transport services for Avon and Somerset police, said: ‘This is a significant step towards reducing global climate change and one which we hope others will follow.
‘The availability of bioethanol in our area makes this a real alternative to using vehicles which can operate only on conventional fossil fuels.’