The diagram shows how the carbon now in coal moved over millions of years. Arrow X shows the carbon leaving the air. Burning coal in a power station adds ca...
Question 1 Report
The diagram shows how the carbon now in coal moved over millions of years. Arrow X shows the carbon leaving the air. Burning coal in a power station adds carbon dioxide to the atmosphere. The carbon in this coal was originally removed from the air by
Answer Details
Coal formed from ancient plants that had removed carbon dioxide from the air by photosynthesis, fixing the carbon into their tissues; that carbon stayed locked in the fuel until now. So the carbon released by burning the coal was originally taken from the air by photosynthesis in those ancient plants. Nitrogen fixation belongs to a different cycle, ancient animals respired carbon out rather than removing it, and combustion adds carbon dioxide rather than removing it. Photosynthesis is the only process that takes carbon dioxide out of the air.
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