Many hail it as the fuel of the future. But in Brazil, ethanol is part of the here and now. The country has pioneered use of this alternative way to power motor vehicles, so much so that today around 80 percent of new cars sold in Brazil can run on ethanol as well as petrol. Tax incentives have boosted the appeal of these so-called "flex-fuel" cars, making them an attractive option for the Brazilian motorist.
It is three decades since Brazil's energy revolution began. Keen to reduce its dependence on expensive Middle Eastern petrol in the wake of the 1970s oil crisis, the country started transforming sugar cane into the clear liquid called ethanol that motorists can pump into their cars. Supporters praise its green credentials.
Biofuels are seen as an ideal way to reduce emissions of greenhouse gases believed to contribute to climate change. But critics complain that planting crops to produce fuel wastes land and water resources that could otherwise be used to grow food. They also claim that the Amazon rainforest is under threat from increasingly lucrative sugar cane plantations. Brazil and the United States combined produce around 70 per cent of the World's ethanol, although in the US the biofuel is mainly made from corn.
Last month the two nations agreed to co-operate in promoting ethanol. Both hailed the environmental and economic importance of their agreement. The deal makes the biofuel a commodity on the international market, in what some see as an attempt by the United States and Brazil to counterbalance the all-powerful OPEC cartel of oil-producing nations.