Basics of DACCM Like direct air capture with pore space storage (DACPS), direct air capture with carbon mineralization storage (DACCM, pronounced dăk-c-m) involves capturing CO2 gas from the atmosphere, compressing the CO2 gas to a semi-liquid state, and then injecting it underground for long-term storage.
similar
igneous rock, in contrast to sedimentary rock such as sandstone, a common injection target in DACPS.
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Basalt lava flow deposits exposed in canyon wall in central Oregon (USA), showing horizontal layering and vertical cooling joints and fractures. For scale, trees are about 10 meters tall. Credit In DACCM, carbon and oxygen in the injected CO2 chemically react with calcium in the basalt to form calcium carbonate (CaCO3), limestone. So, in DACCM, the CO2 is converted to solid rock for long-term storage, in contrast to DACPS which stores CO2 as a semi-liquid fluid physically trapped in the pore spaces of rock.
DACCM is restricted to geographic areas where basalt lava flows or similar igneous rocks have been deposited. In contrast, DACPS is restricted to areas underlain by sedimentary rocks (sandstone or limestone, which commonly are oil and gas producing areas).
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DACCM has six basic steps (note that steps 1 through 4 are the same as for DACPS):
Extract CO2 gas from the atmosphere in a plant where fans blow air through an air contactor and CO2 molecules attach to either a liquid solvent or a solid sorbent (the two main types of DAC plants).
Release the CO2 from the solvent or sorbent using heat and/or water. The solvent/sorbent is reused.
Liquify extracted CO2 by compressing.
Transport the liquified CO2 via pipeline to underground injection wells.
Inject the CO2 deep (>800 meters) into the ground into a basalt layer or similar igneous rock. Basalt is dense and it must have enough fractures or joints in it to allow the the invasion of the injected CO2 . Also, the injection layer must be overlain by relatively impermeable rock for preventing upward flow of the buoyant CO2 toward the land surface.
Following the path of least resistance underneath the less permeable layer, the injected CO2 flows laterally, outward from the injection well, fingering through fractures and joints in the basalt, reacting with the basalt along the flowpath to form limestone.
Relationship of DACCM and DACPS to DACCS
DACCS (direct air capture with carbon sequestration) is the traditional, widely used expression for both carbon mineralization storage and pore space storage.2 leakage potential and storage durability, and understanding the commercial development DACCS and DACCM as CDR methods.
Role of DACCM in CDR, and its criticism
DACCM, as one of the two types of DACCS, is viewed by many as a tool that is necessary for the world to reach net zero during the transition from fossil fuels to energy sources that have low or zero greenhouse gas emissions.
alternative to DACPS in geographic areas where sedimentary rocks are lacking, but basalt or similar rocks are present.
criticized for the potential to prolong the use of fossil fuels and the potential for hindering the scale-up of low emissions energy sources such as solar.
criticism of many carbon dioxide removal projects is that in society's pursuit of net zero emissons, it would be more energy- and cost-efficient to replace fossil fuels very soon with renewable energy sources such as solar and wind, than to continue burning fossil fuels and developing complex systems such as DACCS for capturing and storing the resulting CO2 emissions.
Deployment status
The only large-scale
DAC plant that stores CO2 underground relying on carbon mineralization (DACCM) is Climeworks' Mammoth Project in Iceland. Mammoth began operation in May 2024, with annual capture capacity of 36,000-tons of CO2 . As of early 2025, Mammoth is the largest DACCS plant in the world.
. . performed in 2009 by the U.S. Department of Energy, the Wallula Project, located in the western U.S. state of Washington where about 1,000 tons of purchased CO2 were injected into basalt.
view table ). Also, some of the DAC projects listed in the CDR.fyi database could possibly use carbon mineralization for storage (see CDR.fyi, search on DACCS ). These projects have pre-sold carbon credits for future delivery to buyers who are trying to meet their companies' net zero goals by the year 2050 — a deadline consistent with many national net-zero goals. Investors and government incentives in the form of grants or tax credits help drive many of projects.
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Environmental impacts
Injecting CO2 underground can cause earthquakes
if injected with a high enough pressure to fracture rock underground. Semi-liquid CO2 stored underground can leak to the land surface through an injection well or an old oil or gas well in the storage area if CO2 degrades the steel well casing. CO2 can also leak
to the land surface if, prior to carbon mineralization, a flow pathway through a topseal layer of rock is dissolved by carbonic acid that is created when CO2 dissolves in groundwater.
2 that has been converted to solid limestone underground has no risk of leakage
from storage.
Energy use and carbon negative status
DACCM has the same energy requirements as DACPS for capturing and compressing one ton of CO2 , an estimated 2.17 MWh/tCO2 , dropping to 1.44 MWh/tCO2 by year 2050.
2 equates to the annual energy use of 96,000 homes (assuming each home uses an average of 3.0MWh of energy annually).life-cycle
assessment of a project is necessary for verifying the project will be carbon negative.
Cost per ton of CO2 captured
Like DACPS, DACCM costs include the costs of: CO2 capture, compression, transport, underground storage, and monitoring. The total cost of removing and storing one ton of CO2 using DACCS (either DACPS or DACCM) in 2020 was estimated to be between approximately €175 to €400 per ton of CO2 removed ($204 - $467 USD). This cost has been projected to drop to roughly the €100 to €250 range ($117 - $292 USD) by the year 2050 due to gains from economy of scale and technology advances.
Monitoring, reporting, and verification (MRV)
The number of tons of CO2 removed from the atmosphere and stored in a DACCM project can be measured
using a flow meter at the injection wellhead.2 from the underground reservoir. Monitoring methods include monitoring wells, seismic mapping of the underground CO2 plume, and CO2 gas detectors installed in soil or on the land surface. Government regulations typically require an approved monitoring plan prior to approving a permit for a CO2 injection well.2 removed in a carbon mineralization storage project. Puro Earth has certified carbon credits created by the Climeworks' Orca carbon mineralization project in Iceland.
CO2 storage durability
CO2 stored in a geological formation (including a DACCM project) is considered to be virtually permanent (at least 10,000 years).
Long-term global CDR potential
DACCM, as well as the other
geologic methods of CDR, are referred to as "novel" (new, unproven) methods of CDR — compared to conventional, proven CDR methods (e.g., biochar, bioenergy with carbon
capture and storage, afforestation).
described for the year 2050 in which the novel methods annually supply about 2 gtCO2 of the total annual 10 gtCO2 of CDR that will be needed then in order to limit global warming to 2o C above pre-industrial levels (circa year 1850).2 per year) of the annual 2 gtCO2 , then 500 DACCM plants each with 1 million gtCO2 annual removal capacity will be needed.
