Carbon capture and mineralisation pilots in the Middle East

44.01 named their company after the mass of the molecule that is central to their business: Carbon Dioxide. They use CO₂ captured from indus­try or the atmosphere and dissolve it in water to create a carbonated in­jection fluid, a kind of sparkling wa­ter. The fluid is injected deep under­ground, where it dissolves minerals within mafic or ultramafic rock. This creates an ion-rich fluid that spreads through the existing fracture network while the captured CO₂ reacts and mineralises to carbonate.

Carbon capture and mineralisation (CCM) mimics the natural process of silicate rock weathering. It entails the conversion of CO₂ to carbonate minerals via fluid-rock reactions. The process is an accelerated version of surface weathering due to elevated subsurface temperatures and an increased CO₂ concentration. During the carbonation process, atoms of magnesium and calcium in olivine and pyroxene combine with CO₂ to form secondary carbonate minerals such as magnesite and calcite, permanently locking CO₂ in the subsurface.

44.01 first trialled this concept in Oman; they injected CO₂ captured at an ammonia plant into peridotite at 100 to 400 m depth. Monitoring the composi­tion of the injected solution demonstrat­ed that 88 % of the CO₂ was mineralised as carbonate within 45 days of injection.

Of course, this raises the question of whether the newly precipitated min­erals will clog up fluid pathways, thus preventing further injection. Interest­ingly, because carbonation of peridotite results in a volume increase, this could conveniently cause fracturing or so called ‘reaction-driven cracking’. This process increases permeability and leads to the exposure of fresh reaction surfac­es, enhancing further mineralisation.

However, it is yet to be seen which process, precipitation or cracking, will dominate during injection on an industrial scale. It does seem likely that additional permeability enhancement, such as fracking, will be needed to accommodate injection rates.

A second test site is located in Fu­jairah. During the initial stage, direct air-captured CO₂ was mixed with sea­water and injected into peridotite. This resulted in the mineralisation of ap­proximately 10 t of CO₂. Now 44.01 has teamed up with its first industrial customer, Holcim, with the plan to inject CO₂ captured from cement pro­duction. 44.01 has started injecting at a rate of 5 t/day and hopes to increase to 20 t/day. The borehole has an estimated CO₂ capacity of 25,000 t/year.

The Fujairah project will generate essential data on techno-economics, injection performance and long-term storage validation, insights that will guide 44.01’s future commercial-scale projects.