This chapter is concerned with biotechnological applications involving the use of plants as sources of energy. Plants contain stored carbon captured from light-catalyzed carbon dioxide fixation via photosynthesis. This stored carbon from plants is available in oil and coal deposits that can be used as energy sources known as petrofuels. Living plants or plant residues can be used to generate biofuels such as methane from methane generators, wood fuel from wood chips, and alcohol from plant-based starch or cellulose in fermentation reactions. Topics that illustrate these applications include plant-based biofuels for engines – biodiesel and bioethanol; energy from woodchips (woodchip combustion, gazogen, or wood gasification); and methane (CH₄) or natural gas – methane gas production from landfills, methane gas produced in biodigesters using plant materials as substrate. We discuss the pros and cons of these applications with plant-derived fuels as well as the different types of value-added crops, including algae, that are currently being used to produce biofuels.