Two of our most pressing environmental issues are non-recyclable plastic waste and carbon dioxide (CO2) emitted into the atmosphere due to smokestack emissions. We’ve seen scientists turn waste CO2 into plastics, fuels, and sustainable edible proteins in recent years. And now, a Rice University team has developed a new process that uses plastic waste to trap CO2 emissions.
The novel method is a variant of an existing pyrolysis-based plastic recycling process. Pyrolysis is defined as the thermal degradation of materials at high temperatures in an inert atmosphere.
The process begins with plastic trash being ground into powder, then mixed with potassium acetate – the special ingredient – and heated for 45 minutes at 1,112°F (600°C). As a result, the plastic powder is transformed into sorbent particles with nanoscale pores that are highly effective at trapping carbon dioxide molecules in the air.
Each particle can store 18% of its weight in CO2 at room temperature. However, when heated to roughly 167°F (75°C), the stored carbon dioxide is released, which could be used to create building materials or fuels. In addition, since approximately 90% of the sorbent particle’s pores reopen as CO2 is released, it can then be reused.
Additionally, when the particles are first generated, a wax byproduct is also produced, which can be used in lubricants or detergents. Furthermore, while frequently used plastics like polypropylene and high- and low-density polyethylene are challenging to recycle chemically, they are highly suitable for converting CO2-capturing particles.
According to the researchers, the cost of utilizing sorbent filters to remove CO2 from flue gas streams is estimated to be around US$21 per ton. In contrast, an existing technique for removing CO2 from natural gas streams that use organic compounds called amines reportedly costs $80 to $160 per ton. Furthermore, it is expected that the sorbent will outlast the amines.
Professor James Tour, a co-lead author of the study, concluded:
“Point sources of CO2 emissions like power plant exhaust stacks can be fitted with this waste-plastic-derived material to remove enormous amounts of CO2 that would normally fill the atmosphere. It is a great way to have one problem, plastic waste, address another problem, CO2 emissions.”
Other co-authors of the study include Paul Savas, Wala Algozeeb, and Zhe Yuan. Their research was published in ACS Nano’s journal on April 5, 2022.
