Biomass is a renewable fuel source that can be used efficiently to produce both heat and power. It is derived from recently living organisms such as wood wastes, sawdust and combustible agricultural wastes. Biomass fuels provide about 3 percent of the energy used in the U.S. and they are an environmentally friendly fuel source thanks to minimal greenhouse gas emissions, especially as compared to traditional, petroleum-based fuel sources. (Source: EPA, Photo: Flickr)