That would leave only biofuels as a “sustainable” fuel that could power the current fleet of jet planes. Indeed, a small number of tests have been carried out showing that it is possible to fly planes using biofuels. But can it be done on the large scale needed to get rid of fossil fuels? The first problem is whether biofuels are truly carbon-free. Most likely, the current fuels made from crops are not ; in the sense that they involve extensive use of fossil fuels for their manufacturing. In many cases, however, even the current generation (“1st generation”) of biofuels can provide a significant saving in the use of fossil fuels for the same amount of energy produced. This is the case, in particular, for ethanol produced from sugarcane in Brazil. But there is a more fundamental question is: what would be the consequences of ramping up biofuel production […]