Fuel is a substance used to produce energy through combustion or nuclear fission. Fossil fuels, such as coal and oil, are formed from the remains of living organisms over millions of years. They are non-renewable resources that will eventually be depleted. Renewable fuels, such as solar and wind power, do not come from fossilized remains and can be replenished.
Fossil fuels are the largest source of energy for humanity. Coal, oil, and natural gas were responsible for 86% of the world’s primary energy consumption in 2010 . These three fossil fuels are combusted to generate electricity, power vehicles , heat homes , and fuel industry . The burning of fossil fuels releases greenhouse gases into the atmosphere , contributing to climate change .
Humans have used wood as a fuel since prehistoric times. It was replaced by coal as our main source of energy in the early Industrial Revolution . Today, wood is mostly used for heating in developed countries while it still accounts for a significant portion of cooking and heating fuel in developing countries. Woodfuel can be renewable if managed properly; however, deforestation is a major concern in many areas where woodfuel is harvested .
Other traditional biomass fuels include animal dung and crop residues . These materials are burned directly or converted into charcoal or briquettes . Biomass has been used as a fuel throughout human history; however, its use has declined in recent centuries with the rise of fossil fuel usage.
Biodiesel is an alternative to petroleum diesel that can be made from plant oils and animal fats. It burns cleaner than petroleum diesel but does not perform as well in cold weather . Biodiesel can be produced from waste oils generated by restaurants ; this reduces environmental pollution and helps reduce dependence on petroleum products .
Ethanol is another biofuel that can be made from plants; it can be blended with gasoline to create gasohol which can power internal combustion engines without modification . Ethanol has a lower octane rating than gasoline so it produces less power per volume ; however, it also reduces tailpipe emissions of carbon monoxide , volatile organic compounds , and particulate matter when compared with gasoline alone .
Hydrogen is sometimes called the “ultimate” renewable energy carrier because it can be produced using renewable sources of electricity (e.g., solar , wind ) to electrolyze water into hydrogen gas which can then be used in Fuel Cell Electric Vehicles (FCEVs) with zero emissions at the tailpipe… provided the hydrogen was produced using renewable sources! FCEVs are similar to battery electric vehicles (BEVs) except they use hydrogen gas instead of batteries to power an electric motor . Hydrogen production currently relies heavily on natural gas but future technologies may enable renewably-produced hydrogen to play a larger role in transportation sector decarbonization efforts..