Biomass

Biomass: "Biomass fuels are a renewable resource because they can be replaced fairly quickly (within a human lifetime) without permanently depleting Earth's natural resources. By comparison, fossil fuels such as petroleum and coal, require millions of years of natural processes to be produced. Therefore, drilling for petroleum is considered a nonrenewable process as it depletes Earth's resources for thousands of generations.

Wood
Wood was once the main energy resource used during the early history of the United States, but now it plays only a small role in meeting the nation's energy needs (3%). Still, in certain parts of the country, including Wisconsin, wood provides people with a cheap and plentiful source of energy for heating. About 20 percent of U.S. homes get some heat from burning wood, while about four percent use it as their primary fuel."