Petroleo Brasileiro SA, the only major exporter of ethanol, plans to start exporting the gasoline additive to Japan in 2010, tapping demand in the world’s second-biggest economy.

Brazil’s state-controlled oil company, known as Petrobras, targets annual sales of as much as 6 million kiloliters (37.7 million barrels) of ethanol from 2012, Sillas Oliva Filho, alcohol and oxygenates manager at the company, said in an interview in Tokyo on Thursday.

Brazil wants to increase exports of the biofuel, made from sugarcane, to help the South American nation expand agricultural production and discourage poor farmers from migrating to the cities.

In April 2010, Nippon Oil Corp and Japan’s other petroleum refiners will begin supplying ethanol-blended gasoline at the pump as a way to reduce so-called greenhouse gases blamed for global warming.

‘‘Ethanol will help Japan cut carbon dioxide emissions, and help grow our agricultural business,’’ Filho said.