CCUS: Basalt, The Rock That Eats Carbon

Two hundred tonnes of CO2 went into the ground near Hellisheidi, Iceland, in 2012,

dissolved in water, pumped into black basalt a few hundred metres down. Within two years, researchers pulled core samples and found 95% of it had turned to stone. Not trapped. Not sealed under a cap rock, waiting for a crack to find it in year eighty. Turned into calcite, magnesite, siderite, solid carbonate minerals sitting in the rock matrix the way limestone sits in a cliff face.

That result, published in 2016, is the reason basalt CO2 storage exists as a category at all.

In the fourteen years since, exactly two places on Earth have run this method at anything beyond laboratory scale. Iceland, where it started and where it is still scaling. And Wallula, Washington, where the Pacific Northwest National Laboratory injected 1,000 tonnes into Columbia River flood basalt in 2012, found 60% of it mineralized within two years, and then shut the project down in 2015.

That is the entire global track record. Two sites. One still running. One that proved the chemistry and stopped.

ONGC has just started building a third.

Gandhar, and the geology nobody else has

The project sits at ONGC’s Gandhar Field in Gujarat, still in feasibility study, envisaging the injection of roughly 100 tonnes of CO2 a day, close to 36,500 tonnes a year at full run rate, into depleted hydrocarbon reservoirs. The CO2 itself would come from petrochemical facilities in Dahej and from ONGC’s own Hazira plant. An Expression of Interest process pulled in leading national and international companies before the project moved into detailed feasibility, covering surface facilities and transport, with a consultant now engaged.

Alongside the pilot, ONGC has built a dedicated CCUS laboratory at the Institute of Reservoir Studies in Ahmedabad, equipped with a Rising Bubble Apparatus for studying CO2 fluid interaction, phase behaviour and displacement efficiency. And it has entered an R&D collaboration with the National Centre of Excellence for CCUS at IIT Bombay, mapping storage potential across saline aquifers and basalt formations in Kutch, Saurashtra and Cambay.

That last detail is the one worth sitting with.

India sits on the Deccan Traps, one of the largest flood basalt provinces on the planet, laid down over roughly 66 million years ago in one of the biggest volcanic events in Earth’s history. Iceland’s basalt, the material CarbFix has spent fourteen years proving out, sits on a much smaller landmass built by an entirely different volcanic process, ongoing seafloor spreading at the Mid Atlantic Ridge. The Deccan Traps were not designed with carbon storage in mind. But geologically, they are a vastly larger canvas than anything Iceland has ever worked with, and almost nobody outside a small circle of Indian and international researchers has connected that fact to the CCUS conversation.

Why basalt matters more than another saline aquifer story is a chemistry question, not a marketing one. Inject CO2 into a conventional saline formation and it sits there as a fluid, physically trapped under an impermeable cap rock. The storage is real, but it is a bet on the cap rock holding, monitored for decades under frameworks like the US EPA’s Subpart RR to prove no leakage. Inject CO2 dissolved in water into reactive basalt instead, and the rock itself supplies the calcium, magnesium and iron ions that bond with the carbon and precipitate as solid mineral. Iceland’s data shows that reaction essentially completing within about two years. Once mineralized, there is no plume to monitor and no cap rock to worry about failing in a century nobody alive today will see.

What it actually costs

Geology decides whether basalt storage is possible. Money decides whether it happens.

Break the cost into its two components, because the industry conflates them constantly and the conflation is where bad headlines come from.

Capture, the process of pulling CO2 out of an industrial flue stream before it reaches the atmosphere, is the expensive part of any CCUS project regardless of what happens to the CO2 afterward. Cost estimates for industrial point source capture run $55 to $112 a tonne, driven by the energy penalty of the capture process itself and the concentration of CO2 in the source stream.

Storage is the cheaper half, and here basalt and conventional geologic storage diverge. The lowest cost, largest capacity conventional storage options, injection into saline formations or depleted reservoirs, run roughly $7 to $30 a tonne. CarbFix’s own disclosed cost for the injection and mineralization process specifically is $17 to $30 a tonne, roughly double a straightforward CO2 injection, because dissolving CO2 in water before injection means pumping several times the fluid volume down the same well. More water, more pumping energy, more wells for the same tonnage.

Add the two halves and a basalt project done properly runs somewhere between $70 and $140 a tonne, all in, before any project specific factors like transport distance or well count are layered on.

Nobody pays that cost voluntarily. It gets paid because a policy puts a price on not paying it.

In the United States, the 45Q tax credit pays $85 a tonne for industrial capture paired with permanent geologic storage, rising to $180 a tonne for direct air capture. That single number, an $85 floor under every tonne stored, is what triggered the wave of US CCS investment that produced ExxonMobil’s Houston hub proposal, Chevron’s Gulf Coast projects and a dozen others now moving through permitting. $85 sits comfortably inside the $70 to $140 cost range above. The credit does not just help the economics. In a reasonable project, it can cover most or all of the gap.

India’s own carbon price, under the Carbon Credit Trading Scheme now moving toward compliance trading, is estimated around $15 a tonne.

Fifteen dollars against a project that costs seventy to a hundred and forty. That is not a subsidy gap. That is a different order of magnitude.

Delhi’s answer, so far, is not a per tonne credit modeled on 45Q. It is a ₹19,700 crore (about $207M) CCUS scheme cleared by the Expenditure Finance Committee and moving toward Cabinet approval, structured as viability gap funding rather than an ongoing production credit, targeting 7 million tonnes a year of national capture capacity across power, steel, cement, refineries and chemicals. Viability gap funding covers a shortfall on a project by project basis, front loaded, finite. A per tonne credit like 45Q pays out for as long as the plant runs, scaling automatically with volume. They are structurally different instruments solving the same problem from opposite directions, and which one actually gets India to gigatonne scale storage is an open question nobody, in India or anywhere else running a similar scheme, has fully answered yet.

ONGC’s Gandhar pilot has disclosed no cost per tonne. It is not expected to. The project is still pre investment decision, and a feasibility study is not where unit economics get finalized. That absence is not a gap in the reporting. It is an accurate reflection of where the project actually stands.

Stress test

None of the above survives contact with three questions.

First, water. CarbFix’s process uses roughly 25 tonnes of water per tonne of CO2 injected, because the CO2 has to be fully dissolved before it goes downhole. Iceland has no shortage of fresh water. Gujarat, where Gandhar sits, does. Any basalt project scaled beyond a pilot in Kutch, Saurashtra or Cambay runs directly into a water allocation question that Iceland’s version of this technology never had to answer.

Second, scale. Gandhar’s roughly 36,500 tonnes a year is a rounding error against the global picture. ExxonMobil alone currently runs about 9 million tonnes a year of CO2 capture capacity, with 5.5 million tonnes in signed customer commitments and a Houston hub concept targeting 50 million tonnes a year by 2030. The gap between Gandhar and ExxonMobil’s current baseline, not its 2030 target, is roughly 250 times. A pilot is supposed to be small. But the honest reading is that India’s CCS effort is not competing with the majors’ programs yet. It is several steps behind the starting line those programs are already running from.

Third, sequencing risk. CarbFix took from 2007, when it was founded, to 2012, when it ran its first pilot injection, to 2016, when peer reviewed results confirmed the mineralization rate, to a scheme now targeting 3 million tonnes a year by 2032 through its Coda terminal. That is roughly two decades from founding to meaningful scale, in a country with essentially unlimited cheap geothermal power to run the process and no domestic water stress. Wallula ran the same chemistry, got a positive result, and still shut down after the funding ran out in 2015, because a positive pilot result and a durable revenue model are two different things. Gandhar is earlier in that timeline than either of those projects was at the equivalent stage, without yet having Iceland’s energy cost advantage or a domestic carbon price anywhere close to what the chemistry requires.

The actual question

Every piece of coverage on ONGC’s carbon capture work so far has been written as a sustainability story, a checkbox next to Net Zero 2070. That framing misses what is actually interesting here.

India has geology that almost nobody else on Earth has tested at this method, at a scale Iceland could never offer, sitting directly underneath some of ONGC’s own operating fields. That is a real, rare technical asset. What India does not yet have is a price on carbon that comes anywhere close to what basalt storage, or any geologic storage, actually costs to run. The United States built an entire CCS investment cycle on an $85 number. India is currently working with $15, backstopped by a viability gap scheme that has not yet reached Cabinet approval.

The world spent fourteen years proving basalt can hold carbon forever. India’s task now is smaller in scope and harder in practice: proving someone is willing to pay for it before the geology stops being the interesting part of the story.