Estimating geological CO2 storage security to deliver on climate mitigation

Abstract

Carbon capture and storage (CCS) can help nations meet their Paris CO2 reduction commitments cost-effectively. However, lack of confidence in geologic CO2 storage security remains a barrier to CCS implementation. Here we present a numerical program that calculates CO2 storage security and leakage to the atmosphere over 10,000 years. This combines quantitative estimates of geological subsurface CO2 retention, and of surface CO2 leakage. We calculate that realistically well-regulated storage in regions with moderate well densities has a 50% probability that leakage remains below 0.0008% per year, with over 98% of the injected CO2 retained in the subsurface over 10,000 years. An unrealistic scenario, where CO2 storage is inadequately regulated, estimates that more than 78% will be retained over 10,000 years. Our modelling results suggest that geological storage of CO2 can be a secure climate change mitigation option, but we note that long-term behaviour of CO2 in the subsurface remains a key uncertainty.

An Overview of the Status and Challenges of CO2 Storage in Minerals and Geological Formations

“…In groundwater, the presence or an increase of CO 2 can be deduced from reaction products (Hovorka et al, 2006;Jenkins et al, 2012;Romanak et al, 2012;Yang et al, 2013;Anderson et al, 2017), from analyses of pressurized samples representative of the subsurface conditions (Freifeld et al, 2005), and from tracers that help track waters containing dissolved CO 2 (Kharaka et al, 2009;Ringrose et al, 2009;Würdemann et al, 2010;Matter et al, 2011). Probabilistic modeling of risks associated with leakage suggest that 98% of the CO 2 will be retained in 10,000 years (Choi et al, 2013;Alcalde et al, 2018;Rogelj et al, 2018). An increase in CO 2 in aquifers may mobilize lead and arsenic contained in rocks (Zheng et al, 2009) creating an environmental hazard if drinking water sources are affected.…”

Evaluating climate geoengineering proposals in the context of the Paris Agreement temperature goals

“…CO 2 removal methods require adequate storage reservoirs, either directly for CO 2 or for other forms of carbon (e.g., biomass, minerals and consumer products). A variety of reservoirs are possible, either quasi-permanent, confidently isolating CO 2 from the atmosphere over long timescales (e.g., >10,000 years 178 ), or temporary, where a non-negligible amount of the removed CO 2 might return to the atmosphere within decades to centuries 179 . The achievability for nearly all reservoirs is qualitatively estimated (see Figure below) to be relatively high for small amounts (e.g., <1 Gt(CO 2 )), but challenging for larger amounts (e.g., >1000 Gt(CO 2 )), with considerable research needed, e.g., into ecological and economic implications, and development of adequate infrastructures for extensive deployment.…”

Pyrolysis shaker reactor for the production of biochar

“…Biochar is produced by heating a biomass feedstock in the absence of oxygen. Examples of biochar applications include carbon sequestration, [1] soil amendment, [2][3][4] activated carbon for water [5][6][7] or gas purification, [8,9] biocoke fuel source for metallurgical applications, [10][11][12] filler for composite/polymer materials [13,14] or concrete, [15] and electrode material for batteries and supercapacitors. [16,17] Industrial pyrolysis reactors for the production of biochar from biomass can be classified according to how quickly the biomass particles are heated.…”