Researchers use sunlight and modified sawdust to reversibly capture carbon dioxide

According to the World Meteorological Organization, greenhouse gas concentrations have reached a record high. In the case of carbon dioxide (CO₂),the growth in 2020 exceeded the average for the last decade; despite a 5.6% drop in fossil fuel CO₂ emissions driven by COVID-19 restrictions. This continued rise in CO₂ concentration is directly linked to our massive consumption of fossil fuels.

In a study published in the KeAi journal Green Energy & Environment, a group of researchers from Renmin University of China propose a new method to capture CO₂ using sunlight as the energy source and modified sawdust as the CO₂ absorbent. In addition to capturing CO₂, their method also avoids using the fossil fuels that would create additional CO₂. Importantly, the absorption method they have developed is reversible, so the captured CO₂ can be used to generate other products, such as methanol, ethanol and methane.

Corresponding author Yapei Wang, a professor in the university's Department of Chemistry, explains:

"While a large number of high-performing CO₂ absorbents have been developed in recent decades, people rarely pay attention to the carbon emitted by the adsorbent during its preparation. Moreover, typical industrial CO₂ capture systems show high-energy consumption during the absorber regeneration process.

"To solve these issues, we focused on a solution that not only fabricates low-energy consumption CO₂ absorbents, it also uses sunlight as the single energy input to regenerate those absorbents."

The research team found that sawdust impregnated with an aqueous solution of amine-based polymer was an easy-to-obtain CO₂ absorbent with two important advantages: it doesn't require complicated synthesis, and it can capture CO₂ and be regenerated by proper heating. In addition, a reflector and sunlight absorption layer was used to fabricate the sunlight harvesting systems, heating up the modified sawdust for CO₂ capture.

According to Shiming Zhang, a PhD student who took part in the study, "we were inspired by solar water heaters. Using sunlight as an energy input minimises the need for traditional energy and is more environmentally-friendly." Postgraduate Qianhao Pan, who also participated in the research, adds: "We believe less is more, sometimes a simple preparation process can lead to an effective solution that protects the environment."