Forget the traditional meat- or cheese-filled pasteles sold by street vendors here. These days, walking the streets of Rio de Janeiro could make you hungry for fries.

From January through June of 2002, up to 25% of the city's military police and electric utility vehicles are scheduled to run on a mixture of used cooking oil, alcohol and diesel fuel.

Engineering students at the Federal University of Rio de Janeiro, funded by money from the Brazilian Ministry of Science and Technology, along with Petrobrás, the state oil company, are performing scientific road tests in Brazilian climatic conditions. The federal government requires this before final legal approval can be granted for use of the fuel.

Utilizing 25,000 liters/month of used frying oil donated by McDonald's (normally sold to soap manufacturers), the vehicles are slated to log as many as 80,000 kilometers before the end of the test, which has received approval from Ibama, the federal environmental protection agency.

Interest in the alternative fuel has heated up in the past year. At least one tractor manufacturer has announced it has biodiesel-ready engines, with special fuel injectors that can cut emissions from 11 to 53%.

In addition, a company called Ecomat, described as the first biodiesel company in the country, has developed a soybean oil additive. It claims that the additive can cut pollutants by 50% when mixed with alcohol and used in diesel fuel. Last June, the president of the Brazilian Vegetable Oil Industry Association met with President Fernando Henrique Cardoso to discuss development of a government program to encourage production of biodiesel.

Why all the interest? First and foremost, Brazil has always been an alternative fuel leader. It's a national security issue in a developing country that, according to one estimate, imports 100,000 barrels of diesel fuel daily at a cost of $2 billion annually.

Brazil is so eager to avoid petroleum dependence that the country aggressively encouraged development of a program to switch many cars to using 100% alcohol in reaction to the energy crisis of the 1970s. Interestingly, many of the experiments in this country, which produces more sugarcane than any other, involve a dash of alcohol in the vegetable oil and diesel mix.

A big test in the southern Brazilian city of Curitiba, where urban buses logged 400,000 kilometers since 1997, and where a liquid biofuels conference was held a year later, helped spur interest in the product. However, it was an interest that was already there. Sixteen years ago, the heavy earth-moving equipment used in the construction of South America's largest airport, Guarulhos, in São Paulo, used vegetable oil fuel.

Recently, a number of factors have made biodiesel an interesting proposition. For one, soy complex prices have dropped, making soy-based biodiesel a relatively less-expensive alternative. Meanwhile, the Brazilians aren't limited to just soy when considering what crops they can stuff into a fuel tank. Palm oil, babassu and castor beans all can make biodiesel — not to mention used fast-food oil.