The Brazilian government is promoting the use of biodiesel produced from soya beans to reduce its dependence on fossil fuels.
But, says Giulio Volpi in this article, clearing large areas of Amazonian rainforest to grow soybeans is too high an environmental price for this policy to be sustainable.
He says the deforestation caused by soybean farming in Brazil means the biodiesel has "virtually no advantage" over fossil fuels, in terms of the greenhouse gas emissions generated by each form of fuel.
Deforestation is responsible for 80 per cent of Brazil's carbon dioxide emissions.
Volpi's article responds to another, by Brazil's president Luiz Inácio 'Lula' da Silva, promoting the country's efforts to reduce its dependence on fossil fuels.
Volpi argues policymakers should only promote biofuels whose overall environmental effect is positive.
To achieve this, he calls for a certification scheme to assess each biofuel according to environmental and social criteria.