Use of sugar cane-based ethanol as a substitute for gasoline is among the cheapest and easiest ways to reduce greenhouse gas emissions, according to a Brazilian study published on Wednesday.

Cane ethanol provides about eight times the energy used to produce it and adoption of new cane plant varieties and processes could increase its efficiency further.

The study looked only at the future production of cane over pastures or as a replacement for other crops -- not over native forests.

Most new cars in Brazil can run on ethanol alone and the biofuel's environmental benefits are redoubled by burning its bagasse byproduct in thermoelectric plants powering mills and sometimes even feeding into the grid.

As ethanol is already competitive with gasoline at current oil prices, the additional cost (in adopting ethanol) is zero, said Isaias Macedo, from the Interdisciplinary Center of Energy Planning at the University of Campinas, one of the study's authors.

And the possibility of producing ethanol in several countries makes it especially attractive, Macedo added.

Brazil is the world's largest producer of cane-based ethanol. The United States is the No. 1 ethanol maker but its fuel is made from corn whose energy output is roughly equal to that used to produce it.

Ethanol's gradual replacement of gasoline since the introduction of flex-fuel cars in early 2003 and the blending of 20 to 25 percent of ethanol in all gasoline sold in Brazil, combined with the co-generation of energy through the burning of bagasse at mills, has slashed greenhouse gas emissions.

In 2006 alone, the drop in emissions by the transport and energy sectors was 22 percent of what they would be if the country's cars were burning gasoline, according to the study.

Still, Brazil remains one of the top emitters of greenhouse gases due to destruction of its massive Amazon rain forest. Trees release carbon dioxide into the atmosphere when they're felled or burned.

Considering Brazil's total emissions unrelated to deforestation, ethanol helped reduce overall emissions by 10 percent that same year, according to the study which also involved researchers at the University of Sao Paulo.

Considering fuel production and emission-cutting targets set by Brazil in its 2008's climate change plan, ethanol could reduce emission levels in the transport and energy sector by 43 percent in 2020 and 18 percent for all emissions excluding deforestation.

Brazil is seeking to play a leading role in talks in Copenhagen in December aimed at agreeing a new climate treaty to replace the Kyoto Protocol when it expires in 2012.

The ethanol industry does not want Brazil's poor ranking for total emissions to tarnish its environmental credentials. It has been fighting to show the world how cane is the most energy-efficient raw material for ethanol.

About 90 percent of Brazil's sugar cane is produced in the center-south region, which includes Pantanal wetlands. But the main producing areas are about 2,000 km (1,250 miles) from the Amazon forest. The rest in the north/northeast of the country.

Macedo said that, based on an estimated cost of $100 per tonne of CO2 avoided in 2020 or 2030, it would be possible to attribute to ethanol an additional value of 20 U.S. cents per liter.
When you decide to use ethanol, this is how much you'll avoid paying for another option, the researcher said.

(Editing by Peter Murphy; Editing by David Gregorio)

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