Everything from crops left in the field to weedy trees, from animal waste to humans’ garbage, can be recycled and transformed into usable energy. Biomass is a very broad term covering a wide variety of materials that can be used as energy resources. Since the sun’s energy is absorbed by all living things; humans, animals, and especially plants, a lot of materials we see as leftovers are storehouses of energy. For example, a tree uses photosynthesis to store energy in its leaves and trunk. The tree is biomass. The tree can be burned to release the energy in the form of heat. Learn more with this video from the Explore More: The Future of Energy series.