Make no mistake about it: super exotic cars are not environmentally friendly. Combined with upcoming emissions standards in the US and EU (China will be next, I guarantee it), automakers are currently racing towards the best electric/hybrid/fuel combination that will allow the greatest mileage and best performance.
Koenigsegg has built an interesting possible solution, its CCXR. Introduced in 2007, it can be fueled by either standard octane petrol or E85 or E100 ethanol fuel.