CDR by CO2 storage limited to much lower capacity than thought

[Tom Goreau]

COMMENT: CDR by pumping CO2 into holes in the ground, so popular with the fossil fuel industry, can only be done to the capacity sedimentary rock formations can hold: you can only squeeze so much fizz into the ground before it starts burping back at you! It seems that many proposals to “solve” the CO2 problem by making it vanish forever underground greatly exceed nature’s capacity to hold it!

• efArticle
• Open access

• Published: 03 September 2025

A prudent planetary limit for geologic carbon storage

• Matthew J. Gidden, 
• Siddharth Joshi, 
• John J. Armitage, 
• Alina-Berenice Christ, 
• Miranda Boettcher, 
• Elina Brutschin, 
• Alexandre C. Köberle, 
• Keywan Riahi, 
• Hans Joachim Schellnhuber, 
• Carl-Friedrich Schleussner & 
• Joeri Rogelj 

Nature volume 645, pages124–132 (2025)Cite this article

Abstract

Geologically storing carbon is a key strategy for abating emissions from fossil fuels and durably removing carbon dioxide (CO₂) from the atmosphere^1,2. However, the storage potential is not unlimited^3,4. Here we establish a prudent planetary limit of around 1,460 (1,290–2,710) Gt of CO₂ storage through a risk-based, spatially explicit analysis of carbon storage in sedimentary basins. We show that only stringent near-term gross emissions reductions can lower the risk of breaching this limit before the year 2200. Fully using geologic storage for carbon removal caps the possible global temperature reduction to 0.7 °C (0.35–1.2 °C, including storage estimate and climate response uncertainty). The countries most robust to our risk assessment are current large-scale extractors of fossil resources. Treating carbon storage as a limited intergenerational resource has deep implications for national mitigation strategies and policy and requires making explicit decisions on priorities for storage use.

 

[Bruce Melton -- Austin, Texas]

With all of their scenario-based caveats, it appears that at worst, this is not even an absolute minimum floor with 1.5 or 2 C scenarios.  

This evaluation only looks at sedimentary geology, no ultramafics. They limit storage between 1 and 3 km deep as a very conservative approach to limiting minor seismic activity and surface leakage, where standard industry practice is a minimum of 0.5 km with no depth limit. 

They limit subsea disposal to less than 300 m below the ocean surface, where floating platforms can operate in depths over a mile. The Deep Water Horizon was  in 5,000 feet and large platforms can have over 8o directional bores each.

The 3 km maximum depth for minor offshore seismic activity is moot. Offshore leakage of even the biggest leaks is absorbed in just a few to several hundred feet of water.

Their analysis is heavy on CCS scenarios which have a 50 percent removal penalty versus atmospheric capture, and their maximum rate is only 15 Gt CO2 storage by 2100 as per standard RCP and SSP scenarios.

Their minimum warming analysis of only 0.7 C warming reduction assumes standard 1.5 C (or warmer) scenarios that only address hard to decarbonize sectors and overshoot through 2100. 

The reality of feedback emissions with these year-2100 scenarios cannot be emphasized more they increase natural feedback emissions capture requirement by 500 to 700 Gt CO2. 

Gidden et al., A prudent planetary limit for geologic carbon storage, Nature, September 3, 2025.
https://www.nature.com/articles/s41586-025-09423-y#Sec9

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Bruce Melton PE
Director, Climate Change Now Initiative, 501c3
President, Melton Engineering Services Austin
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