This article was originally published in The Link, Q3, 2023.
Energy demand will double in the next 50 to 70 years, requiring considerable leaps in clean, reliable, and affordable energy. There is a menu of opportunities to decarbonize. Let’s look at one: Carbon Capture and Underground Storage, or CCUS.
Why do we need CCUS?
A simple analogy follows: think of our atmosphere as a bathtub and the water as CO2. Our atmosphere is becoming an overfilled bathtub; to keep the bathtub from overflowing, we must turn down the tap and remove the plug. That’s where Carbon Capture Utilization and Storage (CCUS) comes into the energy sustainability picture. Carbon Capture Utilization and Storage prevent CO2 from entering the atmosphere, essentially like a dripping tab instead of a tap that is open all the way. Carbon removal takes out existing CO2 in the atmosphere. Carbon removal and Carbon capture work together to reduce overall levels of CO2.
There are four key steps in the CCUS value chain, each with varying complexity.
First, you need a source of CO2, which can be the atmosphere or a smokestack. There are many sources of CO2, such as coal-fired power plants, gas-fired plants, cement facilities, ethanol facilities, and ammonia facilities. Some are more complex than others. The primary driving economic factor is the relative concentration of CO2 and purity of the stream.
High-purity sources include Blue hydrogen or ethanol. Low-purity sources include cement and power generation. The high-pressure, high-purity point sources are the best candidates for CCUS. (Carbon in CCUS)
Next, you need a CO2 capture technology. On one extreme, there is a simple capture, for instance, an ethanol facility with a flue gas concentration of about 95% CO2. In this case, capture is pretty straightforward: dehydration to eliminate water and compression before you can move the CO2. Moving to more complex capture, we look at point source, i.e., a coal-fired power plant that is typically 5-10% CO2 concentration by volume (along with other sets of criteria pollutants that are regulated). In these cases, capture is accomplished via three primary technologies:
- Absorption (solvents absorb CO2 into a liquid stream)
- Adsorption (molecules of CO2 being adsorbed on the sorbent surface)
- Cryogenic Membranes
Of these, chemical absorption is the most common and mature. (Capture in CCUS).
Once you capture the carbon, there are two options: utilization or storage. Two different value chains, but both require compression and transportation. The predominant pathway is via pipeline; we have a network of pipelines built throughout the United States, and we know how to move gas. Capital is the complication here; capital to build the quantity of CO2 pipeline that will be required. Other options for transportation include shipping and trucking. Both shipping and trucking have significant limitations.
Last, we have storage and utilization. These are two archetypes: carbon capture and storage (CCS) and carbon capture and utilization (CCU). Storage is straightforward; CO2 is sequestered for thousands of years. On the use pathway, however, there are many uses of CO2. CO2 for EOR, which drives incremental oil production in conventional reservoirs, has been used for decades and is justifiably economical.
Other use cases include beverages and CO2-enriched cement, where CO2 is bound to the cement and plastic. Scalability and impact vary.
These are the four steps in the value chain. Further innovation is required in the capture and utilization technology, capital is needed for the transportation, and lots of monitoring verification and reporting is required in the sequestration.
Three complications exist: Physical, Economic, & Regulatory.
- Physical: the source-sink link. We need to link an industrial point source with a geological location. Pipeline construction expense will depend on the distance between the source and the sink.
- Economic: the bulk of the cost structure is in the capture. The capture expense is based on a function of concentration. Whereas CCS has only costs (taking CO2 off an industrial point source and sequestering), without revenue opportunity other than regulatory incentives, CCU, on the other hand, provides a value in use such as EOR or cement. However, techno-economic immaturity is one of the reasons it has yet to scale so far.
- Regulation: As we all know, building a pipeline is tricky; we need lots of cooperation, from right-of-way to permitting. For CO2 injection and storage, we need to ensure sequestration is safe and permanent, which requires monitoring, verification, and reporting.
Consider taking SGA’s Carbon Capture class to learn more:
SGA’s Fundamentals of Carbon Capture and Utilization Storage (CCUS) course has 100% positive scoring and feedback from registrants who have participated in the course’s learning experience.
A previous registrant stated, “This was a great learning experience, with a lot of detailed information, most of which I had not heard before.”
–Suzanne Ogle, APR, IRC, CAE, CSR-P President and CEO
Want to continue your introduction to carbon capture? Join our Fundamentals of Carbon Capture & Underground Storage, a virtual, instructor-led session on Monday, February 19, 2024.