If the world continues to follow a business as usual energy path, current projections of increased energy demand threaten a massive disruption of the global biosphere, as fossil fuels consumption is the primary cause of global warming. Climate change is a direct threat to sustainable development itself, especially in developing countries that are most vulnerable to its impacts. Within this context, the potential role of renewable energy (RE) is twofold: cutting greenhouse gas (GHG) emissions in the industrialized world and expanding energy supply to the world's poor while curbing the increase of GHG emissions from developing countries. In fact, an adequate supply of RE is an important key to sustainable economic, environmental, and social development for many countries. The country of Brazil is reviewed as a particularly illustrative example of this point, thanks to the large-scale use of hydropower and sugarcane products (ethanol and bagasse) and to a huge RE potential yet to be tapped.