Brazil has long fueled its cars with ethanol brewed from sugarcane, but now the world's first airplane powered by crop has flown over Rio de Janeiro—thanks to genetically engineered microbes.

These living refineries made by U.S. company Amyris convert sugar into hydrocarbon fuel. Azul Brazilian Airlines used the compound, blended with petroleum-derived jet fuel, to power the General Electric engines on an Embraer E195 airliner that propelled the mostly empty passenger jet on a demonstration flight. The microbes can also be used to churn out everything from diesel fuel to chemicals, such as cosmetic oils.

This is not the first bio-jet flight; planes have flown on fuels derived from algal oil to the oil seeds of weedy flower camelina. But it does mark the first flight on jet fuel manufactured by microbes. The demonstration was timed to coincide with this week's Rio+20 global environmental mega-summit. The hope is that bio-jet fuels can one day provide a more environmentally friendly alternative to those made from oil, presuming that the alternative fuel prices can be reduced.