Pre-Combustion Capture

Pre-combustion capture removes carbon from the fuel before it burns, by reforming a hydrocarbon into syngas (hydrogen and CO) and shifting the CO with steam to CO2 plus more hydrogen, then separating the CO2 at high partial pressure. The remaining hydrogen burns carbon-free. The high-pressure, concentrated CO2 stream is cheaper to separate than dilute post-combustion exhaust, but the reformer and shift reactor add plant and cost. In shipping it is mostly a route to onboard or bunkered hydrogen rather than a retrofit for existing diesel engines, where post-combustion capture fits better.