The problem with regular diesel fuel is that it emits a lot of carbon and other nasty byproducts. But now there are clean diesel vehicles and biodiesel, a low carbon fuel refined from used vegetable oils and animal fats, that can be used in diesel vehicles without any modification to the vehicle's engine.
There is a lot of uncertainty out there with alternative fuel vehicles but buying a diesel vehicle right now covers all your bases. You can meet more stringent mileage requirements imposed by the EPA with regular diesel fuel which in itself lessens global warming impacts because you go further with less fuel and you can run your clean diesel engine effortlessly with B5 biodiesel (that is 5 % biodiesel added to regular diesel fuel) cutting carbon emissions even more.
What is so special about clean diesel? Clean diesel vehicles have special emission control technology that lowers the nitrous oxide and sulphur emissions; using biodiesel fuel lessens carbon emissions even more. Buying a clean diesel vehicle gets phenomenal mileage on its own and you can use B5 biodiesel (higher blends are usable however, most of the manufacturers will not cover warranties if you use higher blends). Any fuel you choose is good for the environment and you sacrifice nothing in performance.