On Making Diesel from Coal Pt. 2
Yesterday we examined how CO2 is created in generation of energy in people and power plants. Today we move on to what can be done with the CO2.
The modern topic of much debate is to figure out how to capture the CO2 generated in coal power plants, sequester it, and put it underground. Trying to convert CO2 to methane (CH4) would require huge amounts of energy; this would be reversing the oxidation (energy-releasing) process into reduction (energy-storing), which makes no sense. The CO2 has to be trapped without reduction (i.e., without turning it back into methane or hydrocarbons), pressurized, and injected into some porous formation below the ground surface.
Every step in the process of segregating, capturing, compressing, transporting and injecting CO2 consumes energy, which means more CO2 is created in each stage.
Kind of reminds you of another inefficient idea: ethanol production, where diesel is used to till and plant and harvest corn, more hydrocarbons are used to make fertilizer, diesel is used to truck the corn to the plant, and natural gas is used to run the plant, and diesel is used to fuel the trains to haul the ethanol to a refinery. Is there a net gain here?
Getting back to the start of the discussion, is there a net gain to capturing and injecting CO2 into underground storage caverns? We need to ask Amoco and other oil companies which produce “sour gas” in western Wyoming, which is part methane, part hydrogen sulfide (toxic) and part CO2, among other things. They do successfully separate these gases into marketable products. The CO2 is now being conveyed by pipeline to old oil fields (“old oil fields” means oil fields where the operators initially recovered maybe 20% of the oil, then injected water and recovered another 10% or 20%), where it is injected into the productive formations. The CO2 mixes with water to form a mild acid, and the pressurized mixture pushes oil out of the sandstone from the injection wells to the recovery wells. The process appears to be economically viable, depending on the price of oil.
So, we could conclude that it is possible to recover the CO2, and economically viable under the right circumstances.