Biobased chemicals can help lock up carbon dioxide inside rock, a technology we need to reach net zero.
Here’s how plant-based formulations could boost the carbon storage sector.
A plant-based pathway to net zero
In November 2024, researchers led by Jiajie Wang at Tohoku University, Japan published a paper outlining an exciting new application for biobased chemicals: geological carbon storage.
Biobased chemicals could make rocks better at absorbing and storing carbon dioxide, a key technology in mitigating climate change.
In a vital breakthrough, the researchers also say these chemicals can allow the carbon storage sector to draw on seawater instead of scarcer freshwater – something that has been a barrier to scaling the sector.
Removing carbon from the atmosphere
Carbon storage is any method of slowing climate change by drawing carbon from the air and locking it up in a more stable form.
Many policy pathway models indicate that we need to install a lot more carbon storage than we have in operation today to meet net zero targets.
The technique will likely play a vital role in reducing the climate impacts of industries that are difficult to switch from fossil to renewable energy, such as in cement or certain chemical sectors.
The International Energy Agency estimates that around 107 Gt of carbon dioxide must be permanently locked up through some form of carbon storage mechanism by 2060 in order to meet global climate goals.
If we do not scale carbon storage, the agency said, the energy transition is still possible. However, it will end up costing much more overall. Without it, we would have to make carbon emissions cuts using more expensive and less developed technologies.
The Royal Society agrees on the need for carbon storage expansion, noting that between 300 and 400 new carbon wells connected to underground storage systems would be required by 2050.
Long-term storage is key
In carbon storage, permanence is key. The longer it can prevent greenhouse gases from entering the atmosphere, the more likely it will help us limit climate change.
To be effective, carbon storage needs to keep gases out of the atmosphere for at least several centuries. This is because human activity is already on track to keep heating the planet for another century or longer.
One promising carbon storage method is the geological route. This involves carbon dioxide gas, dissolved in water, into rock. Over time, the carbon gas mineralises. With mineralisation, the storage process is complete: in its solid form, carbon cannot easily break free and re-enter the atmosphere.
Geological carbon storage is described as a ‘permanent’ method of carbon dioxide storage. Although nothing is truly permanent when it comes to geology, it is seen as the most surefire way of keeping carbon out of the atmosphere on the longest possible timescales.
Rock and salt stand in the way of scale-up
There are several methods of achieving geological carbon storage. One of them is to inject carbon-rich fluids into rocks that are naturally reactive with carbon.
The approach is viable in theory and there have been two large-scale pilots showing that it is possible in practice. Yet several things stand in the way of scaling.
Right now, there is not enough economically viable capacity. One reason is that only certain kinds of rocks have the right properties.
Basaltic rocks are particularly well-suited as carbon storage but often even they lack the interconnected pores and permeability to allow large amounts of carbon to be easily pumped in.
Ease of injection is vital to reducing costs and increasing predictability out in the field – non-negotiables for companies seeking return on investment into this nascent tech.
To be suitable for carbon storage, rocks must have a high level of permeability and porosity. This means there are only a limited number of sites in the world where geological carbon storage can be safely and economically carried out.
There have been other resource constraints on geological carbon storage. Injecting carbon dioxide into rocks requires large amounts of water. Yet freshwater is precious on a warming planet and is only set to become scarcer.
Seawater is an abundant alternative but there are major problems with using it in carbon storage applications. Seawater contains a lot of salts and sulfates that can dramatically change the chemical reactions that define the carbon storage process.
The biggest problem is that when dissolved in seawater, carbon can mineralise much quicker than when it is dissolved in freshwater. If the carbon mineralises too quickly it will clog pipes and make injection inefficient.
A two-step biobased solution
To scale carbon storage using seawater, we need a way to ensure that the carbon gas remains a gas while it is being injected into the rock.
Another way is to find a way of altering suboptimal rocks to make them more suitable as carbon stores. By enhancing the physical properties of rock, we could expand the number of sites around the world that would be economical to use as carbon storage.
The Japanese researchers at Tohoku have found a biobased chemical that they say can do both of these things. In their 2024 study, the scientists revealed how an acidic and alkaline version of a single biobased chemical – known as chelating agents -could make geological storage more practical.
The acid and alkaline versions of the chelating agent are meant to be used at different steps in the carbon storage process.
The acidic formulation has a preparatory function – applying it to rocks makes them more suitable for carbon storage. It increases rock porosity and permeability, in other words, makes sure that the rock has enough air pockets inside it to maximise the amount of carbon gas that can get injected inside.
The alkaline chemical, meanwhile, is used in the actual injection step. When added to the carbon-seawater solution being injected into rock, it prevents the premature mineralisation of the carbon.
The alkaline chemical has a dual function. Later on, once the carbon-seawater solution is inside the rock, the alkaline chemical contains ions that encourage the carbon gas to finally mineralise into rock. This mineralisation step ensures that the carbon dioxide cannot leach out into the atmosphere.
Depending on how the alkaline agent is made, producers can fine-tune exactly when the carbon will turn into rock.
Why biobased is better
Synthetic chelating agents exist so why are the biobased ones supposedly better for carbon storage?
The chelating agent that the researchers used in their study is a biobased, biodegradable chemical known as N,N-Bis(carboxymethyl)-L-glutamic acid (GLDA). GLDA can be made acidic or alkaline.
This biobased GLDA has unique features that combine technical performance with sustainability.
First and most importantly, GLDA allows the carbon storage process to draw on seawater instead of freshwater to perform the injection.
This is because GDLA has chemical properties that prevent the technical issues with using seawater in this application
GLDA initially stops the carbon from turning into rock too quickly. This reduces the risk of blocked pipes during injection.
Yet GLDA is also biodegradable in seawater. Over time, the metals and microbes in seawater naturally break down the GLDA until it is no longer able to limit carbon mineralisation.
Once the GLDA is broken down, the carbonin the seawater turns into rock, completing the carbon storage process.
Finally, there is the sustainability advantage of using biobased chemicals. The biobased GLDA the researchers demonstrated is itself a form of carbon storage.
This is because the raw materials used to make it are plants, which lock up carbon from the atmosphere in their cells through photosynthesis. This maximises the sustainability impact of carbon storage tech, since the carbon used to perform the injection process will end up mineralised in rock too.
Another way that biobased GLDA reduces the environmental impact of carbon storage processes is its biodegradability in seawater. This will limit its ecological impacts if it leaks into the environment.
The urgency of scale-up
Carbon storage via injection into basalt is an emergent technology. The earliest large-scale field trial came in 2013 in the Wallula experiment, where carbon was injected into the Columbia River basalts of the US Pacific Northwest.
Seawater-based carbon injection is an even newer innovation. Only one project has managed to inject carbon into basalt using seawater – a pilot project in Iceland conducted by the company Carbfix in 2023.
Yet the sector looks set to balloon in coming decades. There will be growing demand for carbon storage technology as the urgency of cutting greenhouse gases mounts.
The attractiveness of carbon clean-up technologies will only grow if policy to cut emissions at their source continues to lag behind global targets.
Estimates cited by the Royal Society say that there will be a need for between 7 to 8 gigatonnes of storage for carbon dioxide a year by 2050 and cumulative storage of 350-1200 gigatonnes by 2100 to keep temperatures below 1.5 degrees.
The Tohoku University research findings marks the latest milestone in developing basalt-based geological storage, one that shows that biobased materials could have a vital role in expanding the industry.
