Nuclear-Powered Direct Air Capture of CO2

Nuclear-Powered Direct Air Capture of CO2 

Carbon Dioxide Removal (CDR) refers to methods that take carbon dioxide out of the atmosphere and store it safely for the long term. This includes natural approaches like planting trees, as well as engineered technologies that trap and store CO₂ underground or in durable materials. CDR is essential for reaching global climate goals because some emissions, such as those from aviation, industry, and agriculture, are very hard to eliminate. Most climate models that keep global warming below 2 °C rely on using CDR to offset these remaining emissions. However, CDR is not a substitute for reducing emissions; it must be used alongside deep cuts in fossil fuel use (1).  

Direct Air Carbon Capture and Storage (DACCS) is an advanced form of CDR, composed of direct air capture (DAC) of CO₂ and its subsequent storage. Most mature DAC processes use chemical methods to accomplish the selective extraction of CO₂ directly from ambient air. Two dominant approaches exist and can be classified based on the chemical used to capture CO₂: liquid solvent and solid sorbent systems. Both approaches use large air contactors where fans pull in ambient air and CO₂ reacts with the chemical used, effectively pulling carbon out of the air (2).  

One mature liquid solvent approach is Carbon Engineering’s process, which uses a chemical loop with potassium hydroxide (KOH) and calcium compounds to capture and release CO₂ continuously.  process requires high-temperature heat (up to 900 °C), which is needed to break down the carbonate formed in the capture process to release pure CO₂ for subsequent storage (3).  

Meanwhile, Climeworks’ solid sorbent process, now on its Generation 3 iteration, uses newly engineered structured sorbent materials that replace the older packed filter beds. Their system operates at lower temperatures (80 °C to 120 °C). These advanced materials offer greater surface contact with CO₂, allowing the system to capture and release carbon at least twice as fast as before. As a result, each module can now capture more than double the amount of CO₂ compared to earlier designs. The new filters also use 50% less energy and are built to last up to three times longer (4).

Despite recent advancements, capturing CO₂ from the air remains the most expensive form of carbon capture. The concentration of CO₂ in the atmosphere is much lower than in emissions from sources like power plant flue gas or cement factories, making direct air capture highly energy-intensive, requiring significant electricity and/or heat. If this energy is not sourced from low-carbon alternatives, the process risks negate DAC’s climate benefits. 

Nuclear-powered direct air capture offers a compelling solution to large-scale carbon removal. During operation, nuclear power plants produce virtually no greenhouse gas emissions, making them a clean energy source that can significantly minimise the carbon footprint of DAC. Furthermore, nuclear power plants boast exceptionally high-capacity factors, meaning they can operate at maximum power output for extended periods, typically exceeding 92 % of the time. This continuous and stable power supply is essential for the consistent and efficient operation of energy-intensive DAC facilities.

Small Modular Reactors (SMRs) represent a significant advancement in nuclear technology, offering a flexible and scalable approach to power generation that is particularly well-suited for integration with DAC (5). Compared to traditional large-scale nuclear power plants, SMRs are smaller in size (typically producing up to 300 MW), allowing for modular construction and deployment.

This modularity offers several advantages for DAC integration. SMRs can be deployed in locations closer to DAC facilities, potentially reducing the costs associated with long-distance electricity transmission. Their smaller footprint also makes them suitable for co-location with industrial facilities or near geological storage sites, further optimising the overall carbon capture and storage process. 

For example, certain SMR designs can readily provide the low-temperature heat needed for solid sorbent DAC, enhancing the overall energy efficiency of the integrated system. For example, Finland’s LDR-50 (6) is a district-heating SMR producing water at ~80 °C to 100 °C, closely matching the ~100 °C required by solid-sorbent DAC. A recent study suggests coupling DAC to an SMR can boost the utilisation of thermal energy from 32 % in an electricity-producing SMR to 76-85 % in an SMR-DAC system (7).  

In terms of cost, recent analysis suggests that DAC operators would need to pay existing nuclear power plants approximately $30–80 per tonne of CO₂ Vcaptured, or $150–400 per tonne of CO₂ captured for new nuclear plants, to make nuclear energy economically viable in least-cost electricity markets that lack carbon pricing or subsidies for nuclear power (8). 

DAC in the SANE Project

A solid sorbent-based DAC process is integrated into the LDR-50 Lite model using APROS. APROS is a comprehensive software for modelling and dynamic simulation of power plants, energy systems, and industrial processes. The objective is to evaluate the performance of a combined DAC process and the LDR-50 reactor, focusing on the utilisation of nuclear heat for DAC, as well as the DAC system’s productivity and specific energy requirements. The overall aim is to integrate DAC technology with nuclear systems, ensuring safety and efficiency.