Can You Convert CO2 into Methane?

Scientists have known of the existence of several methods of converting carbon dioxide (CO2) into methane for many years now. As both a viable energy source in its own right and a valuable carrier of other gases (such as hydrogen), methane is a more useful substance than CO2, which is often a waste product with greenhouse gas warming properties.

However, all previous techniques of converting CO2 into methane have relied upon the use of excessively hot temperatures above 300°C. This not only makes the process expensive and inefficient, but also does not facilitate conversion of smaller amounts of gas at short notice. To address the problem, a team of researchers at Waseda University in Tokyo, Japan, have pioneered a new method which is capable of achieving the same results within the 100°C range.

Lesser of two evils

Both CO2 and methane are powerful greenhouse gases which can have an undesirable warming effect on the planet’s temperature. In fact, methane is up to 84 times more potent at absorbing the sun’s rays and thus heating the atmosphere than CO2. However, it persists in the environment for a much shorter period of time; whereas carbon dioxide can endure for centuries, methane particles normally break down inside a decade. Sophisticated methods of measuring methane concentrations have revealed that the atmosphere is around 200 times less saturated with methane than it is with CO2.

CO2 is a largely useless waste product of many processes (including human respiration), and although it is absorbed by plants and crops (and can be used to create optimal conditions in commercial greenhouses, for example), methane can be put to a number of different purposes. It can be used as a fuel source to power cars and other forms of transport, or as a hydrogen transporter. For example, some parts of the world (such as Germany) are storing electricity in the form of compressed gas, which is then delivered to private households and businesses, where it is converted back into usable energy. Methane can assist with the delivery phase of this process.

A better conversion method

Scientist have long known how to convert CO2 into methane, but their methods of doing so have traditionally incurred great expense. That’s because these techniques relied upon the use of a ruthenium-based catalyst to force a reaction between hydrogen and CO2 at temperatures between 300°C and 400°C. Obviously, this is not ideal, since it limits how, where and when the process can occur. Additionally, previous research had indicated that conversion at a lower temperature would be more efficient and result in greater amounts of methane produced at the end of the process.

With that in mind, the team from Wakeda University developed a new conversion method which involves the use of nanoparticles known as cerium oxide. These nanoparticles are then mixed with CO2 in the presence of the ruthenium catalyst, alongside an electric field. This last element is crucial in allowing the catalyst to maintain stable catalytic activity and achieved the desired outcome, all at temperatures far lower than in traditional techniques. As such, the discovery could prove instrumental in establishing a low-cost, reliable and scalable solution for CO2 to methane conversion