Research suggests that plastic can be broken down by bacteria found in the stomach of cows.
Plastic has been used to make more than 8bn tons of plastic since the 1950s. This is equivalent in weight and size to 1 billion elephants. The main drivers are single-use containers, packaging, wrapping, bottles, and single-use containers. Plastic pollution is now all-pervasive in the environment, water, and air. People are unknowingly ingesting and breathing in microplastic particles. Researchers have been trying to harness the power of microscopic insects to destroy the hardened material in recent years.
Existing microbes are capable of degrading natural polyester. This can be found in tomato peels or apples. Scientists suspected that the bovine stomach would be rich in natural polyesters since cow diets are high in them.
Dr Doris Ribitsch of the University of Natural Resources and Life Sciences, Vienna, and her coworkers obtained liquid from the cow’s rumen (a portion of a cow’s stomach) from an Austrian slaughterhouse to test this theory. Ribitsch noted that a cow can produce a rumen volume of around 100 litres. You can see the enormous amount of rumen liquid that accumulates in slaughterhouses each day. It’s not a waste.
The liquid was then incubated in the following types of polyesters: PET (a synthetic plastic commonly used in textiles, packaging); PBAT(biodegradable plastic used in compostable plastic bags); PEF (a biobased material from renewable resources). Each plastic was tested both in powder and film form.
All three types of plastics can be broken down in the laboratory by microorganisms derived from cow stomachs. Plastic powders were more efficient than plastic film. She explained that the next step was to identify the microbes responsible for plastic degradation among the thousands of bacteria in the rumen and then to produce the enzymes. Once the enzymes are identified, they can then be manufactured and used in recycling plants.
Plastic waste is mainly burned at the moment. It is sometimes melted to make other products. However, plastic waste becomes too damaged to be reused again. Chemical recycling is another option. This involves turning plastic waste into base chemicals. However, this is not environmentally friendly. Enzymes are a type of green chemical recycling.
Researchers are also working to scale such enzymes. A super-enzyme was created in September by linking two enzymes that were both found in the plastic-eating insect discovered in a Japanese landfill in 2016.
Researchers created an engineered version in 2018 of the first enzyme, which began breaking down plastic within a matter of days. The super-enzyme works six times faster. The French company Carbios discovered a new enzyme in April that was originally found in a pile of leaves. It can degrade 90% of plastic bottles in just 10 hours.
It appears that there is not only one type of enzyme in the rumen liquid. There may be several enzymes working together to cause degradation. The authors suggest in Frontiers in Bioengineering and Biotechnology.
Ribitsch noted that Carbios was currently scaling up its technology. Ribitsch noted that Carbios was working to increase its technology.