Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions

Abstract

Carbon capture and storage (CCS) provides a solution towards decarbonization of the 21global economy. The success of this solution depends on the ability to safely and 22 2 permanently store CO 2 . This study demonstrates for the first time the permanent 23 disposal of CO 2 as environmentally benign carbonate minerals in basaltic rocks. We 24 find that over 95% of the CO 2 injected into the CarbFix site in Iceland was mineralized 25 to carbonate minerals in less than two years. This result contrasts with the common 26 view that the immobilization of CO 2 as carbonate minerals within geologic reservoirs 27 takes several hundreds to thousands of years. Our results, therefore, demonstrate 28 that the safe long-term storage of anthropogenic CO 2 emissions through 29 mineralization can be far faster than previously postulated. 30 31The success of geologic CO 2 storage depends on its long-term security and public 32 acceptance in addition to regulatory, policy, and economical factors (1). CO 2 and brine 33 leakage through a confining system above the storage reservoir or through abandoned 34 wells is considered as one of the major challenges associated with geologic CO 2 storage 35 [e.g. (2, 3, 4)]. Leakage rates into the atmosphere of ≤0.1% are required to ensure 36 effective climate change mitigation [e.g. (5, 6)]. To avoid CO 2 leakage, caprock integrity 37 needs to be evaluated and monitored (7). Leakage risk is further enhanced by induced 38 seismicity, which may open fluid flow pathways in the caprock (8). Mineral 39 carbonatization (i.e. the conversion of CO 2 to carbonate minerals) via CO 2 -fluid-rock 40 reactions in the reservoir minimizes the risk of leakage and thus facilitates long-term 41 and safe carbon storage and public acceptance (9). The potential for carbonatization is, 42 however, limited in conventional CO 2 storage reservoirs such as deep saline aquifers, 43 and depleted oil and gas reservoirs in sedimentary basins due to the lack of calcium, 44 3 magnesium and iron rich silicate minerals required to form carbonate minerals (10, 11). 45An alternative is to inject CO 2 into basaltic rocks, which contain up to 25% by weight of 46 calcium, magnesium and iron. Basaltic rocks are highly reactive, and one of the most 47 common rock types on Earth, covering ~10% of continental surface area and most of the 48 ocean floor [e.g. (12, 13)]. 49 50The CarbFix pilot project was designed to promote and verify in situ CO 2 mineralization 51 in basaltic rocks for the permanent disposal of anthropogenic CO 2 emissions (14). Two 52 injection tests were performed at the CarbFix injection site near the Hellisheidi 53 geothermal power plant: Phase I: 175 tons of pure CO 2 from January to March 2012, and 54Phase II: 73 tons of a CO 2 -H 2 S gas mixture in June to August 2012, of which 55 tons were 55 CO 2 . Note that H 2 S is not only a major constituent of geothermal gases but also of CO 2 -56 rich sour gas. Since the cost of CCS is dominated by capture and gas separation, the 57 overall cost could be lowered substan...

Frictional Instabilities and Carbonation of Basalts Triggered by Injection of Pressurized H2O‐ and CO2‐ Rich Fluids

“…The presence of newly formed dolomite grains at the end of our friction experiments supports the great effectiveness of mineral carbonation in basalts interacting with H 2 O + CO 2 mixtures (e.g., Aradóttir et al, 2012; Matter et al, 2016). However, in our experiments and compared to natural conditions, dolomite precipitation was possibly fostered by both rapid temperature rise (up to 600–800°C) and grain comminution associated to the main fault frictional instability and simulated seismic slip.…”

A 2018 Horizon Scan of Emerging Issues for Global Conservation and Biological Diversity

“…Researchers in Iceland have developed a method by which CO 2 is dissolved in water before being injected into basaltic rocks for storage [53]. Injections of pure CO 2 and of a CO 2 -H 2 S (hydrogen sulfide) mixture, along with carbon-14 and other tracers, were monitored for almost 2 years.…”

A step function density profile model for the convective stability of CO $$_2$$ 2 geological sequestration

“…Geological CO 2 sequestration has been found to be one of the most effective short-term solutions to alleviate CO 2 greenhouse effects. Some innovative strategies have recently been proposed that reduce the risk of the carbon dioxide leaking back into the atmosphere [4]. From a modeling standpoint, one of the key objectives is to quantify the mechanisms and time scales associated with the possible migration of CO 2 back into man's environment.…”