By Sharon Atieno
Responsible for over sixty-six percent of the heating impact on our climate, carbon dioxide (CO₂) continues to be the primary greenhouse gas emitted by humans. Consequently, decreasing its levels in the atmosphere remains crucial in combating global warming.
Against this background, Dr. Gift Mehlala, who is both a fellow of the African Research Initiative for Scientific Excellence (ARISE) and a lecturer in the Department of Chemical Sciences at Midlands State University in Zimbabwe, is investigating the process of converting carbon dioxide into methanol as well as other useful substances.
The ARISE programme ARISE is a pioneering R&I program led by the African Academy of Sciences in collaboration with the African Union and the European Union. This initiative receives funding from the EU and additional support from the Carnegie Corporation of New York.
Dr. Mehlana's research aims at transforming chemical and biological catalysts to enhance their ability to process carbon dioxide, converting it into commonly utilized industrial chemicals.
"By confining enzymes inside materials such as metal-organic frameworks [MOFs], we can boost the efficiency, stability, and recyclability of the process, guaranteeing that the reaction consistently transforms CO₂ into methanol through several cycles," he clarified.
This approach uses enzymes to reduce CO₂ with minimal energy consumption and environmental impact. It aids in combating climate change and generates valuable outputs, thus supporting worldwide initiatives aimed at decreasing greenhouse gases.
Dr. Mehlana asserts that MOFs provide a highly effective method for extracting CO₂ because of their extensive surface areas, adjustable pore designs, and robust attraction to CO₂ molecules. As porous substances, they specifically bind CO₂ from the air, retaining it inside their structure. This makes them a valuable and energy-saving option for eco-friendly carbon extraction and usage.
His work additionally concentrates on creating modular systems designed to extract CO₂ right from where it originates, like factory smokestacks and power station emissions. These modules use metal-organic frameworks (MOFs) which efficiently bind with CO₂, offering a selective approach for capturing industrial carbon dioxide.
"This is consistent with worldwide initiatives, including those spearheaded by Omar Yaghi, who has developed groundbreaking MOF-based technology for directly capturing CO₂ from the air. Although direct air capture plays a crucial role in achieving long-term climate objectives, focusing on point-source emissions offers a quicker and more feasible approach to decrease industrial carbon footprints," noted Dr. Mehlana.
He pointed out that incorporating modular CO₂ capture systems at Zimbabwe’s major emission sources could significantly aid in achieving sustainable climate goals. This approach provides a feasible method for reducing greenhouse gases and moving towards industries with zero net carbon emissions.
In Zimbabwe, both cement factories and coal-powered electrical plants significantly contribute to CO₂ emissions. In 2022, the cement sector produced approximately 0.531 million tonnes of CO₂. Meanwhile, the energy domain, which largely depends on coal, released around 10 million tonnes during that period.
In addition to Dr. Mehlana’s research, numerous scholars around the world have explored the transformation of carbon dioxide into methanol with various catalysts. One such catalyst involves copper, which has been examined under conditions involving elevated temperature and pressure. However, achieving high energy efficiency and managing costs continue to pose significant challenges.
He points out that electrocatalytic techniques have demonstrated potential, with researchers from ETH Zurich and Stanford University attaining high selectivity and current efficiency in converting CO₂ to methanol through the use of electrocatalysts such as copper oxide, driven by sustainable electrical sources.
Methods involving enzymes, including the use of industrial substances like dehydrogenase and methanol dehydrogenase, have been explored at institutions such as UC Berkeley and ETH Zurich. These studies have successfully facilitated efficient CO₂ conversion under moderate conditions.
These techniques provide benefits such as minimal energy consumption and high specificity yet struggle with enzyme durability and speed of reactions. Despite considerable advancements, Dr. Mehlana points out that additional refinement and expansion are necessary to boost effectiveness and ensure economic feasibility.
In addition to its role in climate change, transforming CO₂ into methanol offers several advantages. Methanol serves as both a clean energy resource and an essential raw material in industry for making plastics, formaldehyde, and acetic acid. Moreover, combining CO₂ conversion processes with renewable energy fosters sustainability by leveraging industrial exhaust gases effectively.
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