Catalysis: a key to greenhouse gas emission reduction?

By Pradeep Murthy, PhD candidate at University of Sydney

Given the excess carbon dioxide (CO₂) resulting from excessive fossil fuel consumption, urgent mitigation is necessary.

The global CO₂ concentration has surged at a rapid rate of 1.5 to 3 parts per million (ppm) annually between 2006 and 2023, leading to climate induced disasters like ice caps melting, bushfires, and storms. The United Nations aims to reduce 15-32 GtCO₂-e (gigatonnes of CO₂ equivalent emissions) of global emissions by 2030, while the Australian Government targets a contribution of 900 MtCO₂-e. While ambitious, these goals can be achieved through technological advancements and greener practices.

Efforts to capture and store CO₂, as seen with companies such as Climeworks in Switzerland are expensive and pose risks. A more profitable approach is to not just capture, but also convert CO₂ into valuable fuels and chemicals like methane, carbon monoxide, ethanol, or methanol that can be used for mining, aviation, transport, or domestic applications. These chemicals can be generated by reacting CO₂ with hydrogen (H₂), which like captured CO₂, can also be cleanly obtained via electrolysis (that is, electrical splitting) of water (H₂O) sourced renewably from the sea or from waste treatment. This process is known as hydrogenation.

This is an important process, as CO₂ is a stable molecule and difficult to convert. However, reacting CO₂ with hydrogen can overcome this limitation and generate economically viable fuels. Sourcing green (renewable) instead of grey (non-renewable) CO₂ or H₂ is more costly, but is also expected to gain popularity with time, therefore becoming more affordable.

The fastest means of accomplishing this is by utilising a material known as a catalyst, which can accelerate the chemical reaction by attracting the key gases onto its surface to be reacted and then releasing the products. Utilising a catalyst, especially at the nano-level, significantly enhances surface area, increasing CO₂ consumption and fuel generation. Cost-effective catalysts such as copper and nickel boost revenue.

Catalysts also reduce the energy needed for chemical reactions. Though thermochemical, electrochemical, and photochemical methods exist, solar energy stands out as an attractive option. Despite lower efficiency, ongoing research promises improved solar energy utilisation, reducing operating costs and fostering a more environmentally-friendly process. There is a vast amount of research being conducted in this space, and more extensive efforts should be made to commercialise such plants that can generate clean, renewable energy fuels from CO₂.

Carbon Recycling International, based in Iceland, exemplifies successful catalytic conversion of CO₂ to methanol. With a copper-based catalyst, they generate clean energy and have been operating a commercial plant since 2022. These practices, integrated with electrolysis and renewable sources, provide a clear direction for globally commissioning similar plants.

Overall, enhancing public awareness of catalysis, electrolysis, and renewable energy sources is crucial in controlling atmospheric CO₂ levels. Continued research and development can expedite the conversion of CO₂ into profitable fuels and chemicals, offering a viable solution to our ongoing climate change crisis.

Header image: Anne Nygård on Unsplash