Biofuels are an energy source that comes from burning certain kinds of plants. Sunlight is essential for plant growth and we can burn the plants to get energy to warm our houses, produce electricity, or supplement gasoline. When specific plants like corn (pictured left) is burned, it is converted into ethanol, which can be added to gasoline to power our cars. Biofuels are renewable because we can grow more plants easily. They are potential energy because the energy is stored in the plants. Potential energy is energy that is being stored. Biofuels are chemical energy because it is stored in chemical bonds in the plants. Biofuels are useful because they are renewable. They also can come from many places. The downside is that they can pollute when you burn the plants and that some production of biofuels can use up plants that might be needed for food.
This diagram shows an example of a biofuels energy transformation. First, the Sun (radiant energy) causes plants to grow, such as a tree. Then, the tree (chemical energy) gets burnt (thermal energy). Next, the steam from the fire turns a turbine (mechanical energy). The turbine spins which transforms mechanical energy to electrical energy. The electricity comes to us in power lines. We use this electrical energy to do everyday things at our homes like using a hair dryer (thermal energy). That is an example of an energy transformation with biofuels as its source.