Health In Focus
Highlights:
  • Scientists show that specific blends of plastic can biodegrade under diverse environments
  • A combination of poly lacticacid and polycaprolactone decomposed thoroughly to carbon dioxide, biomass and water under typical home-composting conditions and a majority of the experimental plastics and blends decomposed under conditions of anerobic digestion producing high output biogas
  • While biodegradable plastic blends could create new possibilities, they need careful post-consumer management

Researchers show how certain blends of plastics can decompose under diverse conditions, and with the findings have made a future scenario possible - of decomposing plastics into a household composting bin that will break down the plastic and produce biogas to help power the home.

The findings are reported in the ACS journal Environmental Science & Technology.
Plastic Blends That can be Biodegraded Locally Coming Soon

Plastic waste pollution is a global environmental problem on the ground and particularly in the oceans. Plastic debris that enters the sea can harm or kill sea animals and birds that swallow or get caught in it. How much ever people recycle, most plastic waste still ends up in landfills or the environment.


Pollution caused by plastic waste can be addressed by creating biodegradable plastics
but the ones present today often lack the flexibility, strength or toughness of conventional plastics. Blending different types of bioplastics can offer improved characteristics and help achieve commercially functional properties; however, the environmental fate of these blends is unknown.

Poly (lactic acid) or polylactic acid or polylactidepolylactide (PLA) is one of the world's best-selling biodegradable plastics and had the second highest consumption volume of a bioplastic. A bioplastic can be made from biobased or renewable sources and does not necessarily have to be biodegradable.

PLA is bioactive polyester derived from renewable resources. In the United States and Canada PLA is made out of cornstarch, in Asia it is made out of cassava roots, chips or starch, and in the rest of the world it is produced from sugarcane; however, it requires high temperatures for breakdown and is not home-compostable.

The authors of the current study Tanja Narancic, Kevin O'Connor, Ramesh Babu Padamati and colleagues wanted to examine how neat polymers, like PLA, thermoplastic starch, polycaprolactone (PCL), polyhydroxybutyrate, polyhydroxyoctanoate, and poly(butylene succinate), and their blends would degrade under seven managed and unmanaged conditions. They also show how PLA blended with PCL becomes home-compostable.

Study

The researchers analyzed the fates of 15 different plastics or blends under two kinds of degrading conditions -
  • Managed conditions, such as composting and anerobic digestion
  • Unmanaged environments, including soil and fresh or marine water
The findings were -
  • A blend of PLA and PCL degraded entirely to carbon dioxide, biomass and water under typical home-composting conditions
  • Many of the tested plastics and blends decomposed under conditions of anerobic digestion, a process that produced high output biogas, but with 3-6 times longer degradation times compared to retention times in commercial plants
  • Only two plastics, polyhydroxybutyrate (PHB) and thermoplastic starch (TPS) broke down completely in soil and water
  • All the plastics and their blends degraded with industrial composting
Researchers are hopeful that biodegradable plastic blends could create new possibilities; however, the blends need to be managed carefully after they leave the consumer, and designed better to allow more rapid biodegradation in multiple conditions to decrease their release into the environment.

References :
  1. Tanja Narancic, Steven Verstichel, Srinivasa Reddy Chaganti, Laura Morales-Gamez, Shane T. Kenny, Bruno De Wilde, Ramesh Babu Padamati, and Kevin E. O'Connor "Biodegradable Plastic Blends Create New Possibilities for End-of-Life Management of Plastics but They Are Not a Panacea for Plastic Pollution". Environmental Science & Technology Article ASAP DOI: 10.1021/acs.est.8b02963

Source: Medindia

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