Final answer:
The slow process of producing gas from coal seams after extracting large volumes of water is due to the geological and physical properties of coal, including its solid state and the naturally present water that must be removed.
Step-by-step explanation:
The production of gas from coal seams is a slow process primarily due to the historical formation of coal and the physical characteristics of coal itself. Over millions of years, plant materials were buried under sediment and subjected to geological forces, becoming coal through a process of carbonization. During coal gasification, the extraction of gas typically starts only after a large quantity of water, which is naturally present in the coal seam, has been pumped out. Coal is a solid and does not flow like liquids or gas, requiring considerable physical effort to mine and significant volumes of water to be brought out before gas production can commence.When discussing coal versus other fossil fuels, coal produces more CO2 per gram during combustion. Compared to substances like natural gas, the hydrogen content in coal does not contribute to energy generation in a way that would avoid CO2 emissions. Furthermore, technological and economical factors also play a role, as methods for coal gasification and liquefaction are not as economical unless oil and natural gas prices are high. The decline in demand for coal, due to the rise of cheaper and cleaner natural gas, has also impacted how coal is mined and used. As such, only after the extensive process of dewatering can coal gasification efficiently take place, contributing to the longer time frames required to produce gas from coal seams.