Enabling CO2 mineralisation through pore to field-scale tracking of carbonate precipitation: INCLUSION

政府间气候变化专门委员会（IPCC）和国际能源署（IEA）都指出，碳捕获和储存（CCS）是唯一能够使主要行业脱碳的技术，特别是高排放的水泥，钢铁和石化行业。这些行业是就业和经济增长的主要来源，在我们不断发展的社会中仍然很重要。尽管对CCS的需求迫切，但由于担心注入地下储存的CO2可能泄漏到地表，全球推广一直很缓慢。CCS的安全性和公众接受度取决于二氧化碳的长期安全储存。大多数现有的CCS项目将CO2注入沉积盆地，这依赖于盖岩密封来防止CO2泄漏，并需要昂贵的监测来确保安全储存。相比之下，将二氧化碳注入到合适的反应性玄武岩中，可以使二氧化碳迅速反应成新的稳定矿物，有效地将二氧化碳变成石头，将其永久锁定。适合二氧化碳矿化的反应性岩石几乎占地球的三分之二，形成大部分海底和大约10%的大陆陆地。这包括位于向大气释放最多二氧化碳的国家附近的几个巨大的洪水玄武岩（例如，美国的哥伦比亚河玄武岩，印度的德干圈闭）。据指出，冰岛地热系统中的矿物已经封存了30-40 GtCO 2，相当于2012年排放的所有人为CO2。这些估计的规模扩大意味着，玄武岩中的CO2矿化提供了安全的碳储存，其碳含量是地球上所有化石燃料燃烧所排放的碳的10至100倍。然而，尽管有巨大的潜力，但真正的存储资源尚不清楚，因为该技术迄今仍限于实验室和小批量现场实验。唯一具有工业规模的例子是冰岛Hellisheidi地热田的CarbFix项目。该项目自2012年开始运行，通过将二氧化碳和硫化氢鼓泡入水中，将产生的含气水注入地下玄武岩，释放矿物离子并诱导碳酸盐和硫化物矿物沉淀，从而捕获二氧化碳和硫化氢。二氧化碳矿化过程依赖于活性矿物表面的持续暴露，因此依赖于通过活性岩石的流体流动的维持。目前对可矿化的二氧化碳量的估计没有考虑到在一个地点注入二氧化碳多长时间是经济的，这就造成了在哪里注入二氧化碳以及在不同地点可以矿化多少二氧化碳的不确定性。这是因为快速的碳酸盐矿物沉淀可能会迅速堵塞现有空间，限制锁定二氧化碳的能力。然而，现场和实验室的观察表明，新沉淀的矿物可以打破岩石，增加通过它们的流体流动，使降水能够继续。这些过程如何竞争和平衡目前尚不确定，这是限制工业规模矿化项目投资的关键问题。该项目将通过集成微尺度碳酸盐矿物分析、最先进的岩心尺度4D X射线成像和新的现场尺度固有CO2指纹工具，确定孔隙尺度过程如何控制工业规模CO2矿化，从而解决这一关键知识缺口。该项目将通过与全球领先的CO2矿化测试CarbFix的合作直接促进这一目标的实现。该项目将提供对CO2矿化的无与伦比的孔隙到油田规模的理解，并为优化工业规模的CO2矿化和完善全球对CO2矿化地点和矿化量的估计提供基于证据的框架。这将降低全球储存估计的风险，并有助于该过程的商业推广，使该技术能够有助于限制气候变化所迫切需要的二氧化碳减排。

The Intergovernmental Panel on Climate Change (IPCC) and International Energy Agency (IEA) both cite that carbon capture and storage (CCS) is the only technology capable of decarbonising major industry, particularly the high emitting cement, steel and petrochemical sectors. These industries are major sources of employment and economic growth that will remain important in our evolving societies.Despite the urgent need for CCS, global rollout has been slow, held back by concerns that CO2 injected underground for storage may leak to the surface. The safety and public buy-in for CCS depends on secure long-term storage of CO2. The majority of existing CCS projects inject CO2 into sedimentary basins, which depend on a cap rock seal to prevent CO2 leakage and require costly monitoring to assure secure storage. In contrast, injection of CO2 into suitable, reactive basaltic rocks, can result in rapid reaction of the CO2 into new stable minerals, effectively turning the CO2 to stone, locking it away for good.Suitable reactive rocks for CO2 mineralisation comprise almost two-thirds of the Earth, forming most ocean floor and some ten percent of continental landmasses. This includes several vast flood basalts located near to the countries that release the most CO2 to the atmosphere (e.g. Columbia River Basalts, USA, Deccan Traps, India). It is cited that 30-40 GtCO2, equal to all man-made CO2 emitted in 2012, is already locked-up in minerals within Icelandic geothermal systems.Scale up of these estimates implies that CO2 mineralisation in basaltic rocks offers secure storage for 10 to 100 times more carbon than will be emitted through combustion of all fossil fuels remaining on Earth. However, despite this vast potential, the true storage resource is not yet known, as the technique has so far remained limited to lab and small volume field experiments. The only industrial-scale example are the CarbFix projects, at the Hellisheidi geothermal field in Iceland. This project, operating since 2012, captures CO2 and H2S by bubbling them through water, injecting the resulting gas-charged water into subsurface basalts, liberating mineral ions and inducing precipitation of carbonate and sulphide minerals.The CO2 mineralisation process relies on the continued exposure of reactive mineral surfaces and hence on the maintenance of fluid flow through the reactive rocks. Current estimates of the amount of CO2 that can be mineralised do not take into account how long CO2 injection at a site can be economical, posing uncertainty as to where it can take place and on how much CO2 can be mineralised at different locations. This is because rapid carbonate mineral precipitation could quickly clog up existing space, limiting the capacity for locking away CO2. However, field and laboratory observations show that the newly precipitated minerals can break the rocks and increase fluid flow through them, enabling precipitation to continue. How these processes compete and balance is uncertain at present, which is a critical issue that limits investment in industrial scale mineralisation projects.This project will address this key knowledge gap by determining how pore scale processes control industrial scale CO2 mineralisation through integration of micro-scale carbonate mineral analysis, state-of-the-art core scale 4D x-ray imaging and novel field-scale inherent CO2 fingerprinting tools. This will be directly facilitated by collaboration with CarbFix, the world's leading CO2 mineralisation tests.The project will provide unrivalled pore to field scale understanding of CO2 mineralisation and produce an evidence-based framework for optimising industrial-scale CO2 mineralisation and refining global estimates of where and how much CO2 can be mineralised. This will de-risk global storage estimates and aid commercial rollout of the process, enabling the technique to contribute to the CO2 emissions reduction urgently required to limit climate change.