By producing synthetic methane using the sun, this team of researchers is working towards closing the carbon loop.
Methane, the main component of natural gas, is a powerful greenhouse gas. Mining for natural gasses such as coal seam gas is also carbon intensive, with processes such as hydraulic fracturing becoming more commonplace in some regions.
But a team of chemical engineers from the University of New South Wales have found a way to create synthetic natural gas using natural materials, which could help to reduce the country’s reliance on natural gas while still benefiting from its myriad uses.
Study author Dr Emma Lovell sat down with create to discuss this innovative method, along with future fuels and products the team has set its sights on replicating.
Offsetting carbon
Whether we like it or not, the world runs on carbon. Aside from relying on fossil fuels to produce electricity, they are also used for heavy transportation, shipping, and making plastics and fertilisers, Lovell explained.
Recycling carbon to fuel the carbon-reliant economy was a key driver for the UNSW team, who investigated different ways to utilise light and heat from the sun to offset energy requirements and convert carbon dioxide into value-added products.
“Similar to the way a dark road heats up very quickly in the middle of summer, we designed catalysts to capture light and convert that light into heat to drive the reaction,” Lovell said.
Along with capturing that light to heat conversion, they were also able to extract “hot electrons”.
“When catalysts are excited by visible light, they produce hot electrons – which also help to drive the reaction,” Lovell said.
The end product is not too dissimilar to natural gas, and can be used in any application that natural gas is currently used, including domestic cooking and industrial purposes.
“By employing specific catalysts and support materials, we have demonstrated a new pathway for visible light to drive the conversion of CO₂ into methane,” she said. “This adds value to the captured CO₂ by creating a valuable chemical product.”
Wide-ranging benefits
Transforming waste CO₂ into synthetic fuel creates a closed-loop system that both reduces the dependency on fossil fuel extraction and reducing emissions, according to co-author Yi Fen (Charlotte) Zhu.
Offsetting power consumption also ensures affordable energy generation.
“Being able to directly use sunlight reduces the costs required for energy generation to facilitate the reaction,” Zhu told create. “This alleviates one of the major challenges in the pursuit and application of CO₂ derived fuel, which is contingent on the availability of low-cost, low carbon energy inputs.”
Because the reaction uses CO₂ and hydrogen, the benefits extend further. With homes also set up to run on natural gas, this process can help to ease the transition to renewable sources in a carbon neutral manner.
“At the moment there is a big push towards the hydrogen economy,” Lovell said. “If we can convert that hydrogen into methane, we can use it within our already established infrastructure.”
Scaling into other areas
With the help of a pilot-scale reactor, the UNSW team is working on producing commercial quantities of synthetic methane.
“The reactor has an electrolyser that splits the water to make hydrogen and we get in the scale of litres per minute of making methane,” Lovell said.
But because natural gas is “incredibly cheap”, the UNSW team is looking for other fuels to produce.
“Producing synthetic natural gas this way is not something that has a huge economic driver because CO₂ emissions aren’t costed,” she said. “So we’re looking at producing more valuable fuels from the mechanism of using light and heat from the sun to drive CO₂ conversion reactions.”
Converting CO₂ into value-added products will likely be essential throughout the energy transition, Lovell predicts.
“The scale and the economics of how we do that really depends on carbon prices and the value of what you’re producing,” she said.
“While producing methane is maybe not the most economically viable approach, other value-added products we’re looking at making from this same mechanism will have a much larger potential scale.”
The small-demonstration reactor highlights the applicability of taking sunlight and heat to produce synthetic fuels – with the team working on applying the same mechanism using pressure.
“That enables us to take CO₂ and use sunlight and heat to produce liquid fuels, which could be synthetic diesel or aviation fuels,” Lovell said. “That can help push the needle on the economic case.”
Other carbon-based products that could be produced on an industrial scale using the light-based approach include cement, biomass gasification and pharmaceuticals.
“In terms of converting the CO₂ into value-added products, this represents a much cleaner alternative than products which currently rely on fossil fuel-derived precursors for their manufacture,” said co-author Associate Professor Jason Scott. “Looking ahead, we are already envisioning a new future direction.”
