A fuel cell operates using hydrogen and oxygen, but these elements are not classified as biofuels. Biofuels are derived directly from biomass, such as ethanol from corn or vegetable oils from plants. Natural gas, primarily methane, is typically categorized as a fossil fuel due to its formation over millions of years from decomposed organic matter. However, methane can also be produced from the decomposition of organic waste, such as in landfills or from animal manure, which may qualify it as a biofuel in those contexts. Hydrogen can be produced from natural gas or through electrolysis of water, making it a hybrid fuel rather than a biofuel.