At the start of the Industrial Age the concentration of CO2 in the atmosphere was 280 parts per million (ppm). Now the concentration is over 420 ppm. This increase in CO2 levels was caused by burning fossil fuels — coal, oil, gasoline and natural gas. High concentrations of atmospheric CO2 are the primary cause of global warming.
We need to reduce the CO2 concentration in the atmosphere in order to slow and eventually reverse global warming, Obviously, reducing the use of fossil fuels will slow the buildup of CO2. And natural processes, such as photosynthesis, gradually reduce CO2 concentrations. Unfortunately, we don’t have time to wait for these relatively slow processes. One obvious way to accelerate CO2 removal is to use Direct Air Capture, or DAC.
DAC technology has been used for years to remove CO2 from the waste streams (flue gas) from power plants. The CO2 is absorbed in a liquid or solid media — and is then compressed for use in industrial processes or sequestered in underground wells. But there are two fundamental problems that we need to overcome in order to make DAC practical.
First, it takes a lot of heat to recycle the solid or liquid media in which the CO2 is absorbed. This heat now comes from burning more fossil fuels. So without large-scale renewable sources of heat for the DAC process, the net amount of CO2 removed is small. As a result, DAC deployment is expensive in terms of both capital equipment and thermal energy.
Second, there are limited uses for all the CO2 that would be removed using DAC. By far the biggest current use of this CO2 is for enhanced oil recovery; basically, compressed CO2 is injected into oil and gas wells to force more fossil fuels to the surface. If the CO2 stays underground forever (permanently sequestered), then the net effect on CO2 in the atmosphere is about zero. If the CO2 eventually burps out of these wells we would be increasing the net CO2 concentration in the atmosphere. One step forward and two steps back.
Cost effective and rapid deployment of DAC technology could indeed be a panacea to global warming. However, some people think that going down the DAC path with current technology is more of a Pandora’s Box: if DAC does not scale rapidly and efficiently it could lead to even more CO2 emissions released into the atmosphere. Especially if we continue to burn fossil fuels at the current rate.
As a write this podcast summary the temperature here in San Jose is projected to be over 100 degrees, potentially another record high. We need an “all hands on deck” approach to reduce global warming, and perhaps DAC technology will be a scalable solution. For more about the practical aspects of Direct Air Capture, please tune in to this week’s Energy Show.