Post-combustion has drawn by far the most research interest owing to its lower cost and relative ease to retrofit existing plants, but only accommodates absorption capture methods. Pre-combustion methods, on the other hand, can accommodate any of the capture methods because of the easier separation of CO2 from their gas streams and their flexibilities. Publication trends for most capture methods show patterns generally consistent with the overall publication trends (Figure ), with numbers of publications per year growing from 2000 to the early or mid-2010s and then leveling off or decreasing.