Carbon capturing technology

The impact of CO2 on global warming is well-documented. In order to meet the target of reducing Danish CO2 emissions by 70% by 2030, carbon capture will become an important technology in the years to come. CO2 capture, or carbon capture, includes a range of methods for capturing CO2 directly from combustion processes or from the atmosphere. Captured CO2 is then stored underground or used as an "ingredient" to produce new fuels. 

There is a wide range of carbon capture technologies. Each has its own strengths in different applications.  One of the most commonly used principles is chemical absorption in a scrubber/stripper set-up. This is a well-known process that has been in use in numerous industries for some time, such as in natural gas processing. 

In the scrubber, the exhaust gases are "washed" using a solvent-rich mixture, and CO2 binds to the solvent. Depending on the solvent used, 90% to 99% of the CO2 is removed from the exhaust, and the cleaned gases are released into the atmosphere. Meanwhile, the solvent, now rich in CO2, is pumped to a stripper. There, energy is added (e.g., from steam), and the CO2 is desorbed or "cooked off". The CO2 from the stripper can then be compressed and sent on to be stored or used. 

Different substances may be used as solvents here; amines are among the most commonly used solvents. They may be primary amines, such as monoethanolamine; secondary amines, such as diethanolamine; or specially designed amines patented by various vendors.

The scrubber/stripper process is suitable for large point sources that generate energy, such as power plants. In Denmark, waste processing plants and the extensive network of district heating plants are ideal for this carbon capture method. The exhaust must be cooled before it reaches the scrubber, and exhaust cooling has already been implemented in most Danish waste incineration plants in the form of heat exchangers.

Large amounts of heat are needed to release the CO2 back into the stripper, but this heat can be recovered by heat pumps in the CO2 compression phase at waste incineration plants and fed into the district heating network. In terms of energy, this is almost a net gain for the waste incineration plants, as the reduced electricity production is offset by increased heat production. Moreover, as waste incineration plants produce CO2 with both biogenic and fossil origins, carbon capture in these facilities can result in carbon-negative energy production.