Renewable energy is energy that is generated from natural processes that are continuously replenished. This includes sunlight, geothermal heat, wind, tides, water, and various forms of biomass. This energy cannot be exhausted and is constantly renewed.
Alternative energy is a term used for an energy source that is an alternative to using fossil fuels. Generally, it indicates energies that are non-traditional and have low environmental impact. The term alternative is used to contrast with fossil fuels according to some sources. By most definitions alternative energy doesn't harm the environment, a distinction which separates it from renewable energy which may or may not have significant environmental impact.
What is Biomass?
Biomass, is a renewable organic matter, and can include biological material derived from living, or recently living organisms, such as wood, waste, and alcohol fuels.
Wood energy is derived both from harvested wood as a fuel and from wood waste products. Waste energy can be generated from municipal waste, manufacturing waste, and landfill gas. Biomass alcohol fuel, or ethanol, is derived almost exclusively from corn.
What is Biodiesel?
Biodiesel is fuel made from plant oils that can be used in diesel engines. They are typically made of renewable organic raw materials such as soybean or rapeseed oils, animal fats, waste vegetable oils or microalgae oils.