2. Produce Large Amount of Energy: Fossil fuels are easily combustible. Most combustion engines need to be powered with little amount of fuel to and they can produce large amount of energy. Fossil fuels have been serving us for centuries. It is considered as a portable form of energy. Industrial revolution has popularized the usage of fossil fuel in the entire planet. All machines, devices, vehicles depend on the fossil fuels, may it be coal, petroleum or natural gas. Sustainable fuel sources like solar, wind or geothermal have complex process to harness energy from them.