Photograph showing carbon capture from air and its photoelectrochemical conversion into fuel with simultaneous waste plastic conversion into chemicals.
Newswise — Scientists have showcased the ability to seize carbon dioxide from industrial operations – or even directly from the atmosphere – and convert it into eco-friendly, renewable fuels solely utilizing solar energy.
The University of Cambridge scientists created a sun-powered device that changes collected CO2 and plastic waste into sustainable fuels and other valuable chemical commodities. During experiments, CO2 was transformed into syngas, a vital component for eco-friendly liquid fuels, while plastic bottles were converted into glycolic acid, extensively employed in the cosmetics sector.
In contrast to previous trials of their solar fuels innovation, the researchers obtained CO2 directly from real-life origins, including industrial emissions or the ambient air. They successfully captured and concentrated the CO2, subsequently transforming it into sustainable fuel.
While further advancements are required to enable the implementation of this technology on an industrial level, the findings, published in the journal Joule, signify another significant stride towards generating clean fuels capable of energizing the economy, all without relying on environmentally detrimental oil and gas extraction methods.
Over the course of multiple years, Professor Erwin Reisner's research team, situated in the Yusuf Hamied Department of Chemistry, has dedicated their efforts to crafting sustainable, carbon-neutral fuels influenced by the mechanism of photosynthesis. Inspired by how plants convert sunlight into sustenance, they have devised artificial leaves capable of harnessing the sun's energy to convert CO2 and water into fuels.
Until now, their solar-powered trials have utilized concentrated and pure CO2 sourced from a cylinder. However, for the technology to be applicable in practical scenarios, it must have the capability to actively capture CO2 from industrial operations or directly from the atmosphere. Nevertheless, accomplishing selectivity in converting highly diluted CO2 poses a significant technical challenge due to the presence of various other molecules in the air we breathe.
"We're not solely focused on decarbonization; we aim to de-fossilize our energy systems entirely, paving the way for a truly circular economy," emphasized Reisner. "While in the near future, this technology can aid in curbing carbon emissions by capturing them from industrial sources and repurposing them, our ultimate goal is to eliminate fossil fuels altogether and actively capture CO2 from the atmosphere."
The researchers took their inspiration from carbon capture and storage (CCS), where CO2 is captured and then pumped and stored underground.
"Carbon capture and storage (CCS) is a technology favored by the fossil fuel sector, offering a means to decrease carbon emissions while maintaining oil and gas exploration," Reisner acknowledged. "However, if we shift our focus from carbon capture and storage to carbon capture and utilization, we can transform CO2 into something beneficial rather than burying it underground, which carries uncertain long-term implications. This approach presents an opportunity to completely eradicate the dependence on fossil fuels."
The research team successfully modified their solar-driven technology to operate efficiently with flue gas from industrial processes or even directly from the air. By harnessing the power of the sun, they are able to convert CO2 and plastics into valuable fuels and chemicals.
To selectively capture CO2 from the air, the researchers employ a process in which air is passed through an alkaline solution. This method traps the CO2 while allowing other gases like nitrogen and oxygen to be released harmlessly as bubbles. By concentrating the CO2 in the solution through this bubbling process, the researchers simplify its handling and utilization.
The integrated system comprises a photocathode and an anode, divided into two compartments. In one compartment, the captured CO2 solution undergoes conversion into syngas, which serves as a basic fuel. Simultaneously, in the other compartment, plastics are transformed into valuable chemicals solely utilizing sunlight. This setup allows for the simultaneous production of syngas from CO2 and the conversion of plastics into useful chemical compounds within the same system.
"The inclusion of the plastic component is a crucial aspect of this system," explained co-first author Dr. Motiar Rahaman. "Working with CO2 captured from the air presents challenges in terms of the chemistry involved. However, by introducing plastic waste into the system, the plastic acts as an electron donor to the CO2. As a result, the plastic breaks down into glycolic acid, a valuable compound extensively utilized in the cosmetics industry, while the CO2 is converted into syngas, a readily usable fuel."
“This solar-powered system takes two harmful waste products – plastic and carbon emissions – and converts them into something truly useful,” said co-first author Dr Sayan Kar.
"Rather than storing CO2 underground as done in CCS, we have the opportunity to capture it directly from the air and transform it into clean fuel," Rahaman explained. "By eliminating the involvement of the fossil fuel industry in the fuel production process, we aim to mitigate the risk of climate devastation and work towards a more sustainable future."
Kar expressed, "The ability to efficiently extract CO2 from the air and create valuable products from it is truly remarkable. It is gratifying to witness that we can accomplish this feat solely through the power of sunlight. It underscores the potential of solar-driven technologies in addressing environmental challenges and paving the way for a more sustainable future."
The scientists are presently engaged in developing an enhanced and practical bench-top demonstrator device to showcase the advantages of combining direct air capture with CO2 utilization as a viable route towards achieving a zero-carbon future. By focusing on improving efficiency and feasibility, they aim to highlight the potential benefits of this approach and its significance in addressing climate change.
The research received partial support from various organizations including the Weizmann Institute of Science, the European Commission Marie Skłodowska-Curie Fellowship, the Winton Programme for the Physics of Sustainability, and the Engineering and Physical Sciences Research Council (EPSRC), which is a part of UK Research and Innovation (UKRI). Erwin Reisner holds a Fellowship and Motiar Rahaman is a Research Associate at St John's College, Cambridge. Erwin Reisner also heads the Cambridge Circular Plastics Centre (CirPlas), which aims to tackle plastic waste through a combination of innovative ideas and practical measures.
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