A new study published in Science Advances suggests that polyesters like polybutylene adipate terephthalate (PBAT) could be a practical solution to alleviating detrimental plastic accumulation in the environment. The PBAT biodegrades within about six weeks thanks to soil micro-organisms, according to the researchers, led by Michael Thomas Zumstein of Switzerland's ETH Zürich university.
Plastic agricultural film is used by many large-scale farmers as a method of mitigating weed growth in vegetable crops, retaining soil moisture, increasing soil temperature and speeding up germination and cultivation cycles. The report from the researchers said that while the biodegradation process “has been suspected” to occur, “it has not been conclusively proven until now.”
One example is the use of mulch films, which are placed on agricultural fields to improve soil conditions. Most mulch films are composed of non-biodegradable plastics and are removed improperly after use, said the report, posing a threat to the environment. Mulch films made of polymers that biodegrade in soil are an alternative solution, and researchers have suggested that PBAT could be biodegradable based on changes in mass loss and the physical-chemical characteristics it exhibits.
Direct evidence of true PBAT biodegradation—including carbon from PBAT turning into CO2 or soil micro-organisms incorporating PBAT carbon into their biomass—has not been achieved in agricultural soil, said the authors of the study.
Zumstein and colleagues created three variants of PBAT using the carbon-13 isotope as a “label” to demonstrate biodegradation of PBAT in agricultural soil. After soil incubation for six weeks, they used isotope-selective nanoscale secondary ion mass spectrometry (NanoSIMS) to determine whether the carbon from the PBAT had been processed by the soil micro-organisms. They found that soil incubation of all PBAT variants resulted in 13CO2 formation.