Bentley's efforts to cut the CO2 output of its entire model range by up to 70% are being hampered by fuel retailers.
The company intends to make all its cars compatible with E85 biofuel (85% bio-ethanol and 15% petrol) by 2012, and at the Geneva show it announced that the Continental range GT coupe, GTC convertible and Flying Spur saloon will meet this target with its 2011 model-year cars.
However, though there are 1200 sites in Europe selling E85, only 25 are in the UK - and all of those are at Morrisons supermarket.
Bentley emissions cut by 70%
Dr Ulrich Eichhorn, the company's head of engineering, says that E85 using bio-ethanol from sugar cane can cut the emissions of Bentleys by 70% on a well-to-wheel basis. Most of the CO2 produced by the company's cars is offset by the CO2 absorbed by plants during their growth.
To use the new GTC Supersports revealed at the Geneva motor show as an example, that's the equivalent of a reduction from 385g/km to around 120g/km, which is a similar output for many superminis.
'As with all future mobility, the problem of infrastructure comes up somewhere,' says Eichhorn. 'It is just the same as when unleaded was first introduced. It took 20 years.
'BP has some plans, but fuel retailers are discouraged from putting in new or modified pumps and tanks because they are trying to be very lean and they don't want something that might be used just a few times a week.'
Navigate to your closest E85 retailer
Bentley owners will not be stranded by the shortage of E85 because the cars are flex-fuel, which makes them capable or running on any blend from 100% petrol to 85% bio-ethanol, but the environmental benefits of the company's engineering work are not being felt.
Bentley may programme biofuel sites into future sat-nav systems to help owners track them down, while applications for iPhones or Blackberrys are another possible source of help.
No baby Bentley
It's unlikely there will ever be a small Bentley in the quest for lower CO2, however. 'A luxurious small car would not be a Bentley,' says Eichhorn.
'Our cars have to be the pinnacle of British motoring. Understanding our brand is not just about what we do, but also what we don't do.'