About 1,000 German companies are based in São Paulo. Currently, the number of "green" firms is growing: companies like the wind generator manufacturer Wobben and the Nickol company, which cleans up contaminated industrial grounds. São Paulo has 20 million residents and is one of the world's most important industrial sites. But the concentration of manufacturing here entails environmental problems. And that means opportunity for "green" German companies. Report by Edgar A. Jochems.