Carbon Capture Technology Relies on High-Performance CO2 Sensors

As the Global South's first Direct Air Capture (DAC) company, Octavia Carbon has commissioned the world's second DAC + geological storage plant. Harnessing Kenya's abundant renewable geothermal energy to capture carbon dioxide from the air for secure storage underground, Octavia has developed a scalable technology that relies on the unique performance characteristics of Vaisala’s CO2 measurement sensors.

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Background

Global efforts to fight climate change seek to lower the levels of greenhouse gases (GHGs) in the atmosphere. This can be achieved by reducing GHG emissions, from industry, buildings and transportation for example, and by removing GHGs from the atmosphere. Carbon capture can be employed in both of these scenarios – capturing CO2 from point-source emissions, and capturing CO2 directly from the air – DAC.

The DAC process requires energy, so for the process to deliver a net reduction in GHGs, it is necessary for the energy supply to be carbon neutral. Here, Kenya has a significant advantage – the Kenyan stretch of the Great Rift Valley offers enormous potential in geothermal energy. Tectonic plate movements around 25 million years ago allowed water to percolate into contact with hot rocks 1–3 km beneath the surface, creating a mix of superheated, high-pressure water and steam, ideal for generating geothermal energy.

Today, around 90% of Kenya’s electricity is generated from renewable energy sources, of which geothermal remains the most significant source. The country’s geothermal power generation plants also create waste heat, and Octavia Carbon’s technology has been designed to utilise this resource. In addition, this underground volcanic geology is ideal for permanent underground CO2 storage.

The success of DAC is heavily dependent on the efficiency with which it is able to remove CO2 from the air. In particular, DAC operators must maximise the difference between the flow of captured CO2 and the CO2 emissions of the capturing process. The accurate measurement of CO2 concentration is therefore critically important.

Octavia Carbon

Founded in 2022 by two innovators, Octavia Carbon now employs over 60 people on its mission to scale DAC technology down the cost curve and up the impact curve. The company’s goal is to provide an effective solution for durable carbon removal, and to act as a catalyst for green industrial growth and climate justice in the Global South.

In September 2025, the Second Africa Climate Summit concluded with a clear call to position Africa not as a victim of climate change, but as a driver of solutions in the global climate economy. Octavia Carbon was established to become one of these solutions.

Octavia offers a number of Carbon Dioxide Removal (CDR) packages enabling individuals and organisations to make philanthropic donations and/or offset their carbon emissions. Organisations participating in carbon trading are also able to purchase CDR Credits directly from Octavia.

After capturing CO2 directly from ambient air, Octavia liquifies the gas and transfers it to a partner for permanent underground geological storage.

CO2 measurement challenge

Conscious of the requirement to develop a DAC process that is as efficient as possible, Octavia’s optimisation team needed to be able to take accurate inline measurements at every stage of the process. In addition, verification of Octavia’s carbon capture process can only be possible with accurate reliable CO2 measurements.

Octavia staff tried and discarded several products from CO2 sensor manufacturers before adopting Vaisala’s. Khamis Mwalwati Muniru, Process Optimisation Lead, explains: "Within my team, we rigorously test materials to assess their CO₂ capture efficiency. This process demands precise CO₂ monitoring across a broad concentration range, spanning from 0–100% vol during CO₂ release phases, and to below 400 ppm during CO₂ capture which necessitates exceptional measurement accuracy."

Khamis found that some sensors were able to measure accurately at some concentrations but not all, and that reliability became an issue. "We need to be able to accurately measure carbon dioxide levels from an ambient concentration of around 430 ppm all the way up to captured CO2 at 99.99%. Vaisala’s were the only sensors capable of delivering the required accuracy across such a wide range."

In addition to measurement accuracy, Khamis’s team also required measurement stability. "Our DAC is essentially a batch process, which means that sensor measurements vary from very low to very high over a short period of time – typically around one hour. We discovered that some of the initial (now discarded) sensors lost accuracy over a single cycle, which had two important consequences. Firstly, we had to conduct frequent laborious, time-consuming recalibrations, and secondly, most importantly, we could not rely on the measurements to identify the point at which the sorbent was fully saturated."

Vaisala’s solution was found to be ideal for carbon capture

Octavia’s process optimisation team evaluated Vaisala’s GMP343 carbon dioxide probe and found it to be ideal. "In addition to a wide range, we also required high accuracy below 400 ppm, which was not possible with most of the sensors that we tried," Khamis explains. "So we were delighted to discover that the GMP343 could achieve this with ±3 ppm accuracy and long-term stability. Happily, this meant that we did not have to recalibrate before every test."

The GMP343 employs Vaisala’s CARBOCAP technology, a silicon-based NDIR single-beam, dual-wavelength sensor with no moving parts. CARBOCAP sensors offer high long-term stability due to a micromechanical FPI filter that provides a reference measurement compensating for changes in light source intensity and optical contamination.

Octavia also employs the Vaisala MGP241, developed specifically for carbon capture processes and capable of reliable measurements in wet and harsh conditions. The MGP241 measures inline with automatic temperature and pressure compensation and offers a range of 0–100 vol-% CO2.

Octavia Carbon’s DAC process

There are three main phases in the process – Adsorption, Desorption and Liquefaction/Injection. Each phase requires energy, but with Kenya’s renewable geothermal energy, Octavia’s processes are low-cost and carbon negative.

In the first phase, ambient air containing around 430 ppm CO2 is pulled into the DAC machine where it passes through a filter containing chemical sorbents. These selectively bind with CO2 until the filter becomes fully saturated.

In the desorption phase, indirect heat under vacuum releases the concentrated CO2, regenerating the filters.

In the final stage, the captured CO2 is compressed and cooled until it liquifies, then transported to geological storage sites where it mineralises into rock over time.

Octavia’s modular DAC process is scalable, with targets of 1,000 tonnes captured annually at the first commercial-scale plant (Project Hummingbird) by 2026, and over one million tonnes annually by 2030.

Summary

Antti Heikkilä, Product Line Manager at Vaisala, says: "We are delighted to be able to help Octavia Carbon with this exciting project. Our unique CO2 probes were developed specifically for challenging applications such as this. However, with 'Taking Every Measure for the Planet' as our Core Purpose, this project is a perfect example of the ways in which Vaisala’s measurement technology is helping to fight climate change."

Khamis adds: "Ultimately, the role of DAC will be dictated by the cost/tonne of CO2 captured. We are fortunate in the Rift Valley to benefit from carbon-free geothermal energy, but the scalability of our technology will depend heavily on process optimisation."

Accurate and reliable CO2 measurements are essential for process optimisation and operational teams alike. Without them, it would be impossible to select and improve sorbent performance or identify the sorbent saturation point. This affects efficiency, cost, energy usage, and the credibility of CDR purchased by Octavia’s customers.