Contributing more than two-thirds of the warming effect on climate, carbon dioxide (CO₂) remains the most important human-emitted greenhouse gas. Therefore, reducing its concentration in the atmosphere remains pertinent in the fight against climate change.

It is against this backdrop, that Dr. Gift Mehlana, a fellow of the African Research Initiative for Scientific Excellence (ARISE) and Lecturer in the Department of Chemical Sciences at Midlands State University in Zimbabwe, is researching on the conversion of carbon dioxide into methanol and other valuable products.

The ARISE programme is an innovative research and innovation (R&I) initiative implemented by the African Academy of Sciences in partnership with the African Union (AU) and the European Union (EU). ARISE is funded by the EU and co-funded by the Carnegie Corporation of New York.

To achieve this conversion, Dr. Mehlana’s work focuses on improving chemical and biological catalysts that activate carbon dioxide and convert it into chemicals widely used in various industries.

“By immobilizing enzymes within materials like metal-organic frameworks [MOFs], we can enhance the efficiency, stability, and reusability of the system, ensuring that the reaction continues to effectively convert CO₂ into methanol over multiple cycles,” he explained.

“This enzyme-based CO₂ reduction offers a low-energy, environmentally friendly method that helps mitigate climate change while producing useful products, contributing to global greenhouse gas reduction efforts.”

According to Dr. Mehlana, MOFs offer an efficient approach for capturing CO₂ due to their high surface area, tunable pore structures, and strong CO₂ affinity. These porous materials selectively adsorb (hold as a thin film on the outside surface or internal surfaces within the material) CO₂ from the atmosphere, trapping it within their frameworks. They are a promising and energy-efficient solution for sustainable carbon capture and utilization.

His research also focuses on developing modularized units capable of capturing CO₂ directly at the point of source, such as factory chimneys and power plant exhausts. These units, incorporating metal-organic frameworks (MOFs), can selectively adsorb CO₂, providing an efficient method for industrial carbon dioxide capture.

“This aligns with global efforts, such as those led by Omar Yaghi, who has pioneered MOF-based direct air capture technologies for extracting CO₂ from the atmosphere. While direct air capture is essential for long-term climate goals, targeting point-source emissions is a more immediate and scalable solution for reducing industrial carbon footprints,” Dr. Mehlana observed.

He noted that by integrating modular CO₂ capture systems into Zimbabwe’s key emission sites, this research can contribute to sustainable climate action, offering a practical pathway to mitigating greenhouse gas emissions and transitioning toward carbon-neutral industrial processes.

In Zimbabwe, cement plants and coal-fired power stations are significant contributors to CO₂ emissions. The cement industry was recorded to produce about 0.531 million tonnes of CO₂ in 2022 while the energy sector, heavily reliant on coal, emitted about 10 million tonnes in the same year.

Besides Dr. Mehlana’s work, other researchers globally have worked on the conversion of carbon dioxide to methanol using different catalysts. Among them is copper-based catalyst which has been tested under high temperatures and pressures but high energy efficiency and cost remain a challenge.

He notes that electrocatalytic methods have shown promise, with ETH Zurich and Stanford University achieving high selectivity and current efficiency for CO₂ to methanol conversion using electrocatalysts like copper oxide, powered by renewable electricity.

Enzymatic methods, such as those using industrial chemicals like dehydrogenase and methanol dehydrogenase, have been studied at places like UC Berkeley and ETH Zurich, achieving effective CO₂ conversion under mild conditions.

These methods offer advantages like low-energy requirements and high selectivity but face challenges with enzyme stability and reaction rates. While significant progress has been made, Dr. Mehlana notes that further optimization and scalability are needed to improve efficiency and commercial viability.

Besides its contribution to climate change, converting CO₂ to methanol has numerous benefits. Methanol is not only a source of clean energy but industrially, it is a valuable feedstock for producing plastics, formaldehyde, and acetic acid. Additionally, integrating CO₂ conversion with renewable energy sources supports sustainable development by utilizing waste emissions from industries.

Original article written by Sharon Atieno and published in Science Africa