New solar-powered technology can transform CO2 and plastic waste into sustainable fuels and cosmetics.
Researchers have discovered a way to turn plastic waste and carbon dioxide captured from the air into a clean fuel using solar power.
University of Cambridge scientists have developed a solar-powered reactor that can turn planet-heating CO2 gas into syngas, a key building block for sustainable liquid fuels.
The breakthrough is a major milestone in energy research - unlike preceding experiments which relied on pure CO2, the reactor can use waste gas from industrial plants.
It could eventually be scaled up to industrial use.
Unlike existing carbon capture techniques, this technology could help us bypass fossil fuels altogether by providing an alternate energy source, says lead researcher Professor Erwin Reisner from the Yusuf Hamied Department of Chemistry.
“We’re not just interested in decarbonisation, but de-fossilisation - we need to completely eliminate fossil fuels in order to create a truly circular economy,” says Reisner.
“In the medium term, this technology could help reduce carbon emissions by capturing them from industry and turning them into something useful, but ultimately, we need to cut fossil fuels out of the equation entirely and capture CO2 from the air.”
How does the generator work?
Existing carbon capture and storage (CCS) systems pull CO2 from the air and store it underground.
But this system makes use of the captured gas.
“CCS is a technology that’s popular with the fossil fuel industry as a way to reduce carbon emissions while continuing oil and gas exploration,” explains Reisner.
“But if instead of carbon capture and storage, we had carbon capture and utilisation, we could make something useful from CO2 instead of burying it underground, with unknown long-term consequences, and eliminate the use of fossil fuels.”
The research team was inspired by photosynthesis - the process by which plants convert sunlight into food.
Carbon capture techniques are well established. But it is very difficult to separate CO2 from the various molecules present in the air we breathe.
The researchers came up with a novel solution.
By bubbling air through an alkaline solution, they trapped the CO2 while other gases like nitrogen and oxygen bubble out.
Once they concentrated the CO2, they used chemical reactions to convert it into syngas.
“Instead of storing CO2 underground, like in CCS, we can capture it from the air and make clean fuel from it,” says Dr Motiar Rahaman from the university’s Department of Chemistry.
“This way, we can cut out the fossil fuel industry from the process of fuel production, which can hopefully help us avoid climate destruction.”
A pioneering system for addressing plastic waste
The generator also successfully converted plastic waste into glycolic acid, a compound that is used in the cosmetics industry.
“This solar-powered system takes two harmful waste products - plastic and carbon emissions - and converts them into something truly useful,” says co-first author Dr Sayan Kar.
Approximately 300 million tonnes of plastic waste - an amount equivalent to the weight of the human population - are produced every year, according to the UN Environment Programme.
However, only 9 per cent is recycled, leaving the rest to accumulate in landfills or pollute our oceans with microplastics.
Chemical recycling, where plastic is converted into fuels, requires extremely high temperatures. The high cost and inefficiency of this process act as disincentives, but this new solar powered system could change that.
“Converting waste into something useful using solar energy is a major goal of our research,” says Reisner.
“Plastic pollution is a huge problem worldwide, and often, many of the plastics we throw into recycling bins are incinerated or end up in landfill.”
Why is this solar-powered recycling system so groundbreaking?
Other similar solar-powered systems are being developed but, to date, they have not recycled plastic waste and reduced greenhouse gases in a single process.
“A solar-driven technology that could help to address plastic pollution and greenhouse gases at the same time could be a game-changer in the development of a circular economy,” says Subhajit Bhattacharjee, the paper’s co-author.
The system works by integrating catalysts into a light absorber.
“Generally, CO2 conversion requires a lot of energy, but with our system, basically you just shine a light at it, and it starts converting harmful products into something useful and sustainable,” says co-author Dr Motiar Rahaman.
“Prior to this system, we didn’t have anything that could make high-value products selectively and efficiently.”
Bhattacharjee adds that in the future, the system could become even more versatile and make more complex products, just by changing the catalyst.
The researchers hope that the system could someday be used to develop a recycling plant powered entirely by solar energy.