A worker shows a sample of biodiesel made from castor beans at a biodiesel refinery in Iraquara, 310 miles (500 km) west of the Bahia state capital, Salvador March 31, 2008. Investors, including many foreigners, have flocked to Brazil's hinterland with its enormous farm potential and some of the world's lowest costs to produce biofuels. Picture taken March 31, 2008. REUTERS/Jamil Bittar (BRAZIL)