Synthetic fuel the fuel, and the fuel is less dense than conventional jet fuel allowing aircraft to fly further on the same load of fuel. The "cleanness" of these FT synthetic fuels is further demonstrated by the fact that they are sufficiently non-toxic and environmentally benign as to be considered biodegradable. This owes primarily to the near-absence of sulfur and extremely low level of aromatics present in the fuel. One concern commonly raised about the development of synthetic fuels plants is sustainability. Fundamentally, transitioning from oil to coal or natural gas for transportation fuels production is a transition from one inherently depletable
Ethanol fuel by country and a recent payment receipt will in most cases suffice to prevent fines if customs check tank contents. (Authorities are aware of high taxation on fuels and cross-border fuel refilling is a well-known practice.) Sweden is the leading country in Europe regarding the use of ethanol as fuel, though it has to import most of the ethanol. All Swedish gas stations are required by an act of parliament to offer at least one alternative fuel, and every fifth car in Stockholm now drives at least partially on alternative fuels, mostly ethanol. The number of bioethanol stations in Europe is highest