How is oil shale different from coal?

Oil shale and coal are distinct types of organic-rich sedimentary deposits with different compositions and formation processes.

• Composition: Oil shale is a mudrock containing solid organic matter primarily in the form of kerogen, which is a waxy mixture of hydrocarbon compounds. It contains no naturally occurring liquid oil or significant bitumen. In contrast, coal is a combustible rock formed through the process of coalification, which transforms plant matter into various ranks such as lignite, bituminous coal, and anthracite.123
• Extraction: To obtain liquid petroleum products from oil shale, the rock must undergo pyrolysis—heating it to temperatures above 300 °C in the absence of oxygen. Coal is typically burned directly as a fuel source or processed for other industrial uses.43
• Economic Context: Extracting oil from shale is generally more costly and energy-intensive than extracting equivalent quantities of coal, crude oil, or natural gas, often requiring significant water consumption and resulting in higher carbon dioxide emissions.1