Capturing CO2 from ambient air - David Keith

Although, the cost of water loss may be managed even in warm, dry conditions if an inexpensive source
of water is nearby. It is not obvious, for instance, why seawater would not work in the system.
3.5.4 Siting
Since CO2 can be captured from anywhere on the globe, air capture systems have enormous siting flexibility.
A large number of factors may be greatly influenced by siting, and will compete for importance when
site decisions must be made. When an optimal site is chosen, the total cost may be pushed significantly
up or down from our estimates. Some important considerations for siting a contactor are:
• Climatic conditions, and availability of water, for reasons discussed above.
• Local construction cost and resources. Construction cost varies by location, and this can have a significant
impact on capital cost. Remote locations may be desirable for many reasons, but necessitate
long transportation distances of, e.g., concrete and steel. If many towers for a large air capture plant
are constructed at once (which is likely), construction may be managed like a large dam project,
where a dedicated cement plant and other production facilities are constructed on site.
• Availability of inexpensive energy. Clearly access to inexpensive carbon-neutral electricity, such as
hydro-power, geothermal, or “stranded” natural gas would improve the economics of the system.
• Proximity to sequestration site. Although CO2 transportation may not be a large component of total
cost, there may be situations where pipeline construction is legally difficult or practically infeasible.
An air capture plant located at a sequestration site would avoid these problems.
• Availability of land. A very large scale deployment of air capture will require a lot of land, and
choosing sites that contested by other uses may be important.
3.5.5 Materials and construction cost
A large portion of contactor cost is initial capital for construction of the structure. Construction costs for
standard cooling towers have increased rapidly in the last several years, as much as doubling since 2000
(Mykyntyn, 2006). Much of this increase is due to high steel and concrete prices. In turn, some of that
increase is due to high global energy prices, and some is probably due to a rapid increase in global demand
for these and other raw materials, driven largely by extraordinary Chinese economic growth. The cost
estimates in this chapter are based on current commodity prices, which one may argue are artificially high.
By the time air capture is actually deployed, world supply may have caught up with demand bringing prices
down. On the other hand, a long-term trend toward higher energy prices or continued global shortage of
concrete and steel could drive the real capital cost up significantly in the future.
47