Imperial researchers move closer to net-zero by modelling direct air capture

Imperial scientists have modelled the impact of regional climates on the cost and performance of DAC to understand how to utilise the technology.

Removing carbon dioxide (CO₂) directly from the air is challenging but vital for achieving net-zero emissions to mitigate for the volume of CO₂ currently being produced annually. Direct air capture (DAC) is a technology that captures CO₂ directly from the air, rather than from emissions sources such as power plants or factories. The captured CO₂ is then either stored underground or used in other industrial processes.

DAC technology is still in the early stages of development but has the potential to be an important tool in the fight against climate change, as it can remove excess CO₂ from the atmosphere and help reduce global warming.

DAC regional performance is not yet fully understood since its performance depends on regional climate variation, which means that identifying sites where DAC facilities can perform optimally is important from a cost and performance perspective.

In a study published in One Earth, scientists from the Department of Chemical Engineering used high-resolution global weather data from 2016 to 2020, information about the regional cost of capital, and an industrial-scale DAC unit model to predict how a DAC plant can perform in different regions and how that can impact the cost of removing CO2 from the atmosphere in those regions. 

Cold and dry is best - to a point 

Their analysis revealed that regional DAC performance is significantly impacted by daily and seasonal weather variations, emphasising that functionalised amine-based DAC (one of the most common types of DAC) performs better in cold and dry regions. However, regions with extremely cold weather (for example, temperatures below −15°C) most of the year are unsuitable for this process, highlighting the importance of building such facilities in appropriate locations.

“DAC is not cheap a technology and will need public and private investment to accelerate its deployment, so identifying sites where DAC facilities can perform optimally is really important.” Marwan Sendi Department of Chemical Engineering

Using their model, researchers calculated that the approximate cost of removing one ton of CO₂ from the air would be between $320 and $540, assuming an electricity cost of $50 per MWh. For context, the average UK citizen emits 12.7 tonnes CO₂ per year, meaning DAC would cost thousands of dollars per person annually, demonstrating the significant cost associated with DAC to achieve carbon net-zero.

These significant costs highlight the importance of analyses like this. As explained by PhD student and lead author Marwan Sendi: “DAC is not cheap a technology and will need public and private investment to accelerate its deployment, so identifying sites where DAC facilities can perform optimally is really important.”

The next steps

For Marwan and his co-authors, this is just the beginning. Marwan added: “As more materials performance data become available, our results can be updated, and then we will be able to identify the most suitable material for different regions. We are working on coupling the results from this work to energy systems where regional performance variation in energy production can be captured, helping make our results more accurate. We need to develop DAC materials and processes that are adaptive to regional climates. As such, we think everyone involved in the net-zero transitions will benefit from this work. This includes scientists, technology developers, investors, and policymakers.”

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"Geospatial analysis of regional climate impacts to accelerate cost-efficient direct air capture deployment" by Marwan Sendi, Mai Bui, Niall Mac Dowell and Paul Fennell, published 21 October 2022 in One Earth.