Energy Content of some Combustibles (in MJ/kg)

Gasoline, which is derived from refining crude oil, contains much more energy (in millions of Joules per kilogram) than coal (almost twice) or wood (three times). Although methane and hydrogen both have higher energy content than gasoline, their gaseous form creates storage difficulties. Furthermore, hydrogen must be synthesized, which requires energy. As a comparison, with a conversion rate of 100%, it would require 100 hours to capture the solar energy equivalent of 1 kg of gasoline on a surface of one square meter.