Petroleum, natural gas, coal and other materials used to produce energy

A fuel is any material that can be made to react with other substances so that it releases energy as heat energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy such as nuclear energy (via nuclear fission and nuclear fusion).

Articles

Reports of Peak Oil's Death Are Somewhat Premature, by Kevin Carson, 22 Jul 2013
Examines shale oil and tar sand oil vis-à-vis the state policies that allow extraction to be profitable
"These new sources of oil all have very low energy returns on energy investment. It takes a lot of energy to get just a little more net usable energy at the end of the process. That means it's only profitable when it's heavily subsidized by taxpayers, extracted from stolen land at government expense. And even then, the total increase in net energy output doesn't equal the oil produced by all those legacy fields in places like Saudi Arabia and Texas that are near exhaustion."

The introductory paragraph uses material from the Wikipedia article "Fuel" as of 29 Oct 2018, which is released under the Creative Commons Attribution-Share-Alike License 3.0.