GC: n

CT: There are three major forms of fossil fuels: coal, oil and natural gas. All three were formed many hundreds of millions of years ago before the time of the dinosaurs – hence the name fossil fuels. The age they were formed is called the Carboniferous Period. It was part of the Paleozoic Era. “Carboniferous” gets its name from carbon, the basic element in coal and other fossil fuels.
The Carboniferous Period occurred from about 360 to 286 million years ago. At the time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants, similar to the picture above. The water and seas were filled with algae – the green stuff that forms on a stagnant pool of water. Algae is actually millions of very small plants.

S: http://www.energyquest.ca.gov/story/chapter08.html (last access: 22 February 2015)

N: 1. fossil (n): 1610s, “any thing dug up;” 1650s (adj.) “obtained by digging” (of coal, salt, etc.), from French fossile (16c.), from Latin fossilis “dug up,” from fossus, past participle of fodere “to dig,” from PIE root bhedh- “to dig, pierce.”
Restricted noun sense of “geological remains of a plant or animal” is from 1736 (the adjective in the sense “pertaining to fossils” is from 1660s); slang meaning “old person” first recorded 1859. Fossil fuel (1833) preserves the earlier, broader sense.
fuel (n): c.1200, feuel, feul “fuel, material for burning,” also figurative, from Old French foaille “fuel for heating,” from Medieval Latin legal term focalia “right to demand material for making fire, right of cutting fuel,” from classical Latin focalia “brushwood for fuel,” from neuter plural of Latin focalis “pertaining to a hearth,” from focus “hearth, fireplace” (see focus (n.)). Figurative use from 1570s. Of food, as fuel for the body, 1876. As “combustible liquid for an internal combustion engine” from 1886. A French derivative is fouailler “woodyard.” Fuel-oil is from 1882.
2. Organic fuel formed from the remains of plants or animals within or beneath the earth’s crust …
3. Examples are peat, coal, petroleum (crude oil) and natural gas, and related materials such as tar sands and oil shales.
4. Note that coal, oil and natural gas are primary energy sources which are extracted from the earth (fossil fuels). Natural uranium is also a primary energy source extracted from the earth but does not come from the decomposition of organisms (mineral fuel).
5. fossil fuel: term often used in the plural as a collective term.
6. fossil fuel: term used at the Office of Energy Efficiency, Natural Resources Canada, and extracted from its 2001 Annual Report.

S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=fossil+fuel&searchmode=none (last access: 22 February 2015). 2, 3, 4, 5 & 6. TERMIUM PLUS (last access: 22 February 2015).

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CR: blue hydrogen, carbon , carbon monoxide, coal, fuel, natural gas, petroleum, hydrocarbon.