Charcoal and firewood production is one of the major causes of forest destruction and desertification that ultimately lead to water shortages, erosion, and human suffering. I would strongly recommend against lending to people in the charcoal or firewood business. At least in Peru, where I served in the Peace Corps, most of the charcoal was not even used by the poor but rather sold to roasted chicken restaurants for the upper-middle class. While impoverished people do need fuel, improved wood-burning stoves (
http://practicalaction.org/?id=s10_idp_stoves) and solar ovens (
http://www.pathtofreedom.com/pathproject/offthegrid/solaroven.shtml) provide much more sustainable alternatives than charcoal.