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，碳捕获与封存（CCS）是唯一能够使主要工业脱碳的技术，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将是重要的。尽管迫切需要CCS，但由于担心注入地下储存的二氧化碳可能会泄漏到地面，全球推广工作一直进展缓慢。CCS的安全性和公众购买取决于二氧化碳的长期安全储存。大多数现有的CCS项目将二氧化碳注入沉积盆地，这依赖于盖层密封来防止二氧化碳泄漏，并且需要昂贵的监测来确保安全储存。相反，将二氧化碳注入合适的活性玄武岩中，可以导致二氧化碳快速反应成新的稳定矿物，有效地将二氧化碳转化为石头，永久地将其锁住。适合二氧化碳矿化的活性岩石几乎占地球的三分之二，构成了大部分的海底和约10%的大陆。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，印度的德干暗色岩）。据报道，30-40亿吨二氧化碳，相当于2012年所有人为排放的二氧化碳，已经被锁定在冰岛地热系统的矿物中。扩大这些估计意味着，玄武岩中的二氧化碳矿化提供了比地球上所有化石燃料燃烧所排放的碳多10到100倍的安全储存。然而，尽管有巨大的潜力，真正的存储资源尚不清楚，因为该技术迄今仍局限于实验室和小体积的现场实验。唯一的工业规模的例子是冰岛Hellisheidi地热田的CarbFix项目。该项目自2012年开始运营，通过在水中鼓泡捕获二氧化碳和H2S，将产生的充满气体的水注入地下玄武岩，释放矿物离子，诱导碳酸盐和硫化物矿物沉淀。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，这给在哪里可以发生以及在不同地点可以矿化多少二氧化碳带来了不确定性。这是因为快速的碳酸盐矿物沉淀会迅速堵塞现有空间，限制锁住二氧化碳的能力。然而，现场和实验室观察表明，新沉淀的矿物可以破坏岩石，增加岩石中的流体流动，使降水继续进行。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射线成像和新型现场尺度固有二氧化碳指纹识别工具，确定孔隙尺度过程如何控制工业规模的二氧化碳矿化，从而解决这一关键知识缺口。这将通过与世界领先的二氧化碳矿化测试公司CarbFix的合作直接促进。该项目将为二氧化碳矿化提供无与伦比的现场尺度的孔隙理解，并为优化工业规模的二氧化碳矿化提供一个基于证据的框架，并改进全球对二氧化碳矿化地点和数量的估计。这将降低全球储存估算的风险，并有助于该过程的商业推广，使该技术能够为限制气候变化迫切需要的二氧化碳减排做出贡献。

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.