This episode of The Green Interview features Mohamed Hage, who is turning the flat rooftops of Montreal's industrial buildings into fertile farms that feed thousands-and he's making a profit in the process. Hage, a self-described "technology geek" turned urban farmer, explains the genesis and genius of Lufa Farms in this Green Interview. After seven years, Hage and a small group of colleagues have created two rooftop greenhouse farms in Montreal and plan a third for Boston. The farms grow over 100 varieties of vegetables and herbs, and they feed about 5,000 people. Perhaps most remarkably, Lufa Farms is pesticide-free and uses about half the energy of conventional greenhouses. The farms rely on an army of carefully chosen insects to perform their pest management, and they conserve water and preserve precious nutrients by recycling rainwater. It's an urban success story that could provide a template for revolutionizing food production, blending old-style farming techniques with sophisticated software to create local, sustainable agriculture right in the middle of the city.