by the time the first trees are harvested, and the investors see their returns, stefan prostler will be almost as old as his father is now. you can find a full interview with leo prostler at our website, dw.de/globalideas. still, there are challenges where every minute counts. a key one is access to clean drinking water. some 800 million people are still living without it. boiling water is the only fast and effective way to kill germs. but the people who need that most, often lack resources. a plumber from scotland had a striking idea which manages to make the most of what is available. it's called a "jompy" and it's inventor is a true global brain. see for yourself. >> as in many of the world's poorer regions, clean drinking water is a rare and precious commodity in uganda. according to the world health organization, diseases related to contaminated water account for almost 8% of all deaths in africa. we're in the kabale district in the remote south of the country, where an invention designed to purify contaminated water is now being tested. a simple solution to a serious problem. >>