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How does pre-combustion carbon capture work with coal gasification?

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coal utilization Cross-regenerative coke oven. (A) Cross section, showing the alternating arrangement of flue walls and ovens; (B) longitudinal section, showing (left) a series of combustion flues in a single flue wall and (right) part of a long, slotlike oven.

Pre-combustion carbon capture is a method of removing carbon dioxide (CO₂) from fuel before it is burned. When applied to coal, the process relies on coal gasification, which involves partially oxidizing the coal using steam and a mixture of oxygen and air under high pressure.1

This process converts the coal into a synthesis gas, or syngas, primarily composed of hydrogen, carbon monoxide, and methane. Through additional processing, this syngas is transformed into a mixture rich in hydrogen gas and CO₂.1

Pre-combustion capture is considered more efficient than post-combustion methods because the gas feedstock contains a significantly higher concentration of CO₂—often between 15 and 50 percent—making it easier to separate. Furthermore, this process allows for the production of usable by-products, such as hydrogen. While effective, the infrastructure required for gasification is often more expensive to install than the initial construction of a standard coal-fired power plant. Once captured, the CO₂ can be compressed into a liquid state for transport, storage, or industrial reuse.12