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Novel Approaches to Carbon Management: Separation, Capture, Sequestration, and Conversion to Useful Products - Workshop Report
Deep-sea contained storage of CO2 may also make H2 production from methane clathrates more attractive economically and environmentally. One of several issues surrounding the harvesting of methane clathrates for H2 has been the question of what to do with the CO2. DSCS may offer a solution. A seafloor manufacturing facility could be constructed for methane clathrate processing. The CO2 from this processing facility could be pumped directly to nearby CO2 deep-sea storage containers.
Following are some key arguments that point to the importance of DSCS:
Capacity could be expanded indefinitely. Some 125 containers, as described above, would store 1 km3 or 1 Gt of CO2.
CO2 could be recovered, if desirable, or transferred to another container, if there was danger of leakage.
Ordinary leakages would be comparatively benign.
First estimates of infrastructure development, costs, and time appear to be far less than estimates for sequestering CO2 in traditional subsurface storage formations, given that the volume of CO2 that needs to be sequestered is equal to or greater than the total production capacity of the global petroleum industry. Thus, if used exclusively to meet storage requirements, conventional subsurface storage would require essentially duplicating the existing worldwide petroleum production infrastructure.
There is precedence for this type of storage, as fuel is already stored in large containers in the sea. A considerable body of knowledge and technology already exists for this type of ocean storage.
At this early stage in concept development, operational concepts are needed that consider types of bladders or other containers, their manufacture, deployment, filling, CO2 diffusivity, and longevity. Concepts must include rough order-of-magnitude engineering cost estimates. Ocean floor pipeline considerations must also be included.
Major research areas include the following:
The cost of compressing CO2 and pumping it to the deep-sea bed for disposal in the containers;
Security issues—the total seabed area that would be required to sequester approximately 1 Gt of CO2 for this type of disposal is not large (estimated at 5 km ×5 km×100 m deep) in comparison with deep-sea disposal without containment; limiting the disposal area would enable better surveillance of the area; and
Container protection—the container could be engineered so that it is encapsulated with stronger materials (e.g., cement) to afford it greater protection.