Kerosene is a combustible liquid hydrocarbon derived from petroleum. The simple answer to whether it is a fossil fuel is yes. Although kerosene is not found naturally in the ground like crude oil or coal, it is manufactured exclusively from crude oil, which is a fossil fuel. Understanding kerosene requires examining the ancient origins of its source material and the refining processes that create this fuel.
The Nature of Fossil Fuels
Fossil fuels are defined as high-carbon materials formed naturally within the Earth’s crust from the buried remains of prehistoric organisms, such as ancient plants, animals, or microplankton. This conversion occurs through a geological process that takes millions of years under intense heat and pressure. Because this formation operates on a geologic time scale, these fuels are categorized as non-renewable energy resources.
The primary forms of fossil fuels are coal, natural gas, and petroleum, also called crude oil. These substances contain stored energy derived from sunlight captured by the organisms through photosynthesis millions of years ago. Petroleum, the source material for kerosene, forms mainly from the remains of aquatic phytoplankton and zooplankton that settled on the ocean floor and decomposed under anoxic conditions. This geological origin establishes petroleum as the fossil fuel parent material.
Kerosene’s Composition and Identity
Kerosene is a clear or pale yellow liquid composed of a specific mixture of hydrocarbon molecules. Its chemical structure is dominated by branched- and straight-chain alkanes and naphthenes, which are ring-shaped hydrocarbons. These molecules contain between 10 and 16 carbon atoms per molecule, which gives kerosene its characteristic properties.
This molecular size results in a low-viscosity liquid with a relatively high flash point. The flash point is the lowest temperature at which its vapors ignite in the air, typically \(38^\circ\)C (\(100^\circ\)F) or higher. This makes kerosene less volatile and safer to handle than fuels like gasoline. Kerosene is primarily known for its use as jet fuel (aviation-grade kerosene). It also remains a common fuel for domestic heating and lighting, often called paraffin or lamp oil in certain regions.
The Manufacturing Link to Crude Oil
Kerosene’s definitive link to fossil fuels is its production through refining crude oil. Crude oil is a complex mixture of hundreds of hydrocarbon compounds with varying molecular sizes and boiling points. Refiners employ a technique called fractional distillation to separate these components.
This process involves heating crude oil to high temperatures until it vaporizes, then feeding the vapor into a tall distillation column. As the vapor rises, the temperature decreases, and different hydrocarbon fractions cool and condense back into liquid form at specific heights. Lighter molecules, such as gasoline, condense higher up the column, while heavier molecules, like asphalt, condense lower down.
Kerosene is collected as a “middle distillate,” meaning it condenses in the mid-section of the column. It is the fraction that boils and condenses at temperatures ranging from \(150^\circ\)C to \(275^\circ\)C (\(300^\circ\)F to \(525^\circ\)F). This places it on the distillation spectrum between the lighter naphtha and gasoline fractions and the heavier diesel and lubricating oil fractions. Because kerosene is physically separated from crude oil, a proven fossil fuel, it is classified as a fossil fuel derivative.