Prince Charles has reduced his motoring emissions by running his 38-year-old Aston Martin, a 21st birthday present from the Queen, on fuel made entirely from surplus English wine.
The eco-friendly prince's Jaguars, Audi and Range Rovers have also been converted to run on 100% biodiesel made from used cooking oil.
The annual report of the Prince of Wales and Duchess of Cornwall said: "When their Royal Highnesses are travelling in the UK the aim is to reduce emissions through greater use of cars, trains, and turbo-prop aircraft.
"In accepting and arranging engagements more consideration is being given to reducing travel distances."
The prince's office said greater use of green energy and fewer plane and car journeys helped Charles cut the amount of carbon dioxide he produced by 18% to 2 795 metric tons.
Charles has promised to reduce his emissions of greenhouse gases by 25% between 2007 and 2012.