New Method to Capture CO2 from Atmosphere Using Sunlight, Modified Sawdust

The World Meteorological Organization reports that the levels of greenhouse gas in the atmosphere have increased like never before.

Massive growth in carbon dioxide (CO₂) levels in 2020 exceeded the 10-year average, despite a 5.6% decrease in fossil fuel CO₂ emissions due to COVID-19 restrictions. The continuous increase in CO₂ concentrations is directly associated with the heavy usage of fossil fuels.

A recent study published in the KeAi journal Green Energy & Environment reports a novel method to capture CO₂ using sunlight as the energy source and modified sawdust as the material that absorbs CO₂. The study was performed by a research team from the Renmin University of China.

Besides trapping CO₂, their approach prevents the use of fossil fuels, which would produce additional CO₂. Crucially, the new absorption method is reversible, which enables the captured CO₂ to be used to produce other products like methane, ethanol and methanol.

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.

Yapei Wang, Study Corresponding Author and Professor, Department of Chemistry, Renmin University of China

“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,” she added.

The researchers discovered that sawdust infused with an aqueous solution of an amine-based polymer acted as a simplified CO₂ absorbent with two significant benefits: it avoids the need for complex synthesis, can capture CO₂ and can be regenerated by heating properly. Furthermore, a reflector and sunlight absorption layer helped to develop the sunlight harvesting systems, which heated the modified sawdust for capturing CO₂.

Shiming Zhang, a Ph.D. student who was part of this study, says, “we were inspired by solar water heaters. Using sunlight as an energy input minimizes the need for traditional energy and is more environmentally-friendly.” According to Postgraduate Qianhao Pan, who was also a part of the research, “We believe less is more, sometimes a simple preparation process can lead to an effective solution that protects the environment.”

Journal Reference:

Zhang, S., et al. (2021) Sunlight-controlled CO₂ separation resulting from a biomass-based CO₂ absorber. Green Energy & Environment. doi.org/10.1016/j.gee.2021.09.001.