Here's how carbon dioxide can be used to make biodegradable plastics

A new system that uses carbon dioxide to produce biodegradable plastics, or bioplastics, could replace the nondegradable plastics used today, researchers say.

The research addresses two challenges: the accumulation of nondegradable plastics and the remediation of greenhouse gas emissions.

Today’s petroleum-based plastics do not degrade easily and create a massive issue in the ecosystems and, ultimately, oceans, says Susie Dai, associate professor in the plant pathology and microbiology department at Texas A&M University.

To address these issues, the researchers and their teams worked for almost two years to develop an integrated system that uses CO2 as a feedstock for bacteria to grow in a nutrient solution and produce bioplastics.

“Carbon dioxide has been used in concert with bacteria to produce many chemicals, including bioplastics, but this design produces a highly efficient, smooth flow through our carbon dioxide-to-bioplastics pipeline,” Dai says.

“In theory, it is kind of like a train with units connected to each other,” she says. “The first unit uses electricity to convert the carbon dioxide to ethanol and other two-carbon molecules—a process called electrocatalysis. In the second unit, the bacteria consume the ethanol and carbon molecules to become a machine to produce bioplastics, which are different from petroleum-based plastic polymers that are harder to degrade.”

Using CO2 in the process could also help reduce greenhouse gas emissions. Many manufacturing processes emit CO2 as a waste product.

“If we can capture the waste carbon dioxide, we reduce greenhouse gas emission and can use it as a feedstock to produce something,” Dai says. “This new platform has great potential to address sustainability challenges and transform the future design of carbon dioxide reduction.”

The major strength of the new platform is a much faster reaction rate than photosynthesis and higher energy efficiency.

“We are expanding the capacity of this platform to broad product areas such as fuels, commodity chemicals, and diverse materials,” Dai says. “The study demonstrated the blueprint for ‘decarbonized biomanufacturing’ that could transform our manufacturing sector.”

Bioplastics are currently more expensive than petroleum-based plastics, Dai says. But if the technology is successful enough to produce bioplastics at an economic scale, industries could replace traditional plastic products with ones that have fewer negative environmental impacts. In addition, mitigating CO2 emissions from energy sectors such as gas and electric facilities would also be a benefit.

“This innovation opens the door for new products if the bacterium is engineered to consume carbon dioxide-derived molecules and produce target products,” Dai says. “One of the advantages of this design is the condition the bacteria grow in is mild and adaptable to industry-scale conditions.”

The study is published in the journal Chem. Additional researchers from Texas A&M and Washington University in St. Louis contributed to the work. The Texas A&M University System has filed a patent application for the integrated system.