Renewable resources include biomass energy (such as ethanol), hydropower, geothermal power, wind energy, and solar energy. Biomass refers to organic material from plants or animals. This includes wood, sewage, and ethanol (which comes from corn or other plants). Renewable energy is energy that is collected from renewable resources that are naturally replenished on a human timescale. It includes sources such as sunlight, wind, rain, tides, waves, and geothermal heat.