Bioenergy is the most widely used renewable energy worldwide and can be defined as "energy contained in living or recently living biological organisms" (fossil fuels are thus excluded). It can be differentiated into three different types of bioenergy: Biofuel, Biogas, Solid Biomass.

• Biofuels such as ethanol and biodiesel are fuels made from crops such as corn and oil palms respectively.
• Biogas is produced with waste products such as sewage and dung.
• Solid Biomass such as wood has been used since ancient times for cooking and heating purposes – and more recently to generate electricity

Burning biomass releases carbon dioxide. However, plants also take carbon dioxide out of the atmosphere and use it to grow their leaves, flowers, branches, and stems. That same carbon dioxide is returned to the air when the plants are burned.

Many different kinds of biomass, such as wood chips, corn, and some types of garbage, are used to produce electricity. Some types of biomass can be converted into liquid fuels called biofuels that can power cars, trucks, and tractors. Leftover food products like vegetable oils and animal fats can create biodiesel, while corn, sugarcane, and other plants can be fermented to produce ethanol.