Two articles on the April 2nd issue of Nature look into some of the physics, chemistry, and geology associated with carbon capture and storage (CCS) as a possible form of greenhouse gas mitigation. The first largely summarizes the results of the second. Each stresses how significant amounts of carbon dioxide (CO2) are already trapped in groundwater in the subsurface environment, suggesting that the artificial addition of more may be safe and effective. Leaks are avoided due to the “presence of sealing, low-permeability rock formations above the targeted layer,” such as those found above natural gas fields. The article considers CO2-rich natural gas fields in North America, China and Europe as natural analogs for future CCS sites. It concludes that relatively little (about 10%) of the CO2 gets incorporated into rocks, from which it is unlikely to escape. Most remains in water, from which future emissions are more possible. It concludes that the hydrogeological characteristics of future CCS sites will need to be carefully considered, bearing in mind that most of the CO2 will apparently end up saturated in water.
None of this provides definitive support for CCS as a mitigation option. Rather, it provides some guidance into the further research necessary to determine if it can be safe and environmentally effective. Notably, this research also gives no consideration to the economics of CCS deployment, nor to the timelines across which it can be achieved. Indeed, these articles could be taken as evidence of the relative infancy of the scientific consideration of subsurface disposal of carbon dioxide, something that governments assuming its near-term commercial viability should note.