But fossil fuels bear fingerprints of their origins. The various characteristics of coal, oil, and natural gas depend on the organisms that went into them and what happened to their tissues over time. It depends on where they lived, how they died, where their remains ended up, and what kinds of temperature and pressure they experienced. The dead matter carries the chemical imprint of its history—altered and jumbled in various ways—for millions of years. After we dig it up, we spend a lot of effort stripping the evidence of this story away, refining the complex hydrocarbons into uniform fuels.
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