Thomas Culhane is an urban planner whose German-Egyptian non-governmental organization Solar CITIES trains residents in Cairo’s poorest neighborhoods how to build and install rooftop solar water heaters and other renewable energy, water, and waste management systems. More than 30 solar tanks and 10 kitchen-waste-to-cooking-gas biogas systems now dot the rooftops of Coptic Christian and Islamic neighborhoods as a result of his efforts. As recipients of the first National Geographic Blackstone Innovation Challenge Grant, National Geographic Emerging Explorers Culhane and Katey Walter Anthony are now developing more efficient biogas reactors that use arctic bacterial ecologies to extend their range.