Amy Smith, who has a master's degree in mechanical engineering and teaches at MIT, isn't interested in building faster computers or bigger jetliners. She's thinking about how to cook dinner in a Haitian slum. Smith and her students have developed a way to turn this plentiful (and otherwise useless) material into clean-burning charcoal by carbonizing it in a covered oil drum. Smith, a practitioner of humanitarian engineering, wants to solve everyday problems for rural families in the developing world: where to find clean water, how to preserve vegetables for market, how to do laundry without electricity or plumbing. Smith's inventions include a hammer mill for grinding grain into floura task African women usually do by hand and a portable kit to test drinking water for contaminating bacteria. Smith, who was awarded a Macarthur Fellowship in 2004, runs MIT's IDEAS Competition, for which teams of student engineers design projects to make life easier in the developing world.