(July 6, 2015) Biodegradable
drinking cups or vegetable wrapping foil: the bioplastic known as polylactic
acid (PLA) is already a part of our everyday lives. And yet, PLA is not yet
considered a full alternative to traditional petroleum-based plastics, as it is
costly to produce. Researchers from the KU Leuven Centre for Surface Chemistry
and Catalysis now present a way to make the PLA production process more simple
and waste-free. Their findings were published in Science.
The bioplastic PLA is derived from renewable resources,
including the sugar in maize and sugarcane. Fermentation turns the sugar into
lactic acid, which in turn is a building block for polylactic acid. PLA
degrades after a number of years in certain environments. If it is collected
and sorted correctly, it is both industrially compostable and recyclable. In
addition, PLA is biocompatible and thus suitable for medical use, for instance
in absorbable suture threads. PLA is also one of the few plastics that are
suitable for 3D printing.
However, PLA is not yet a full alternative for
petroleum-based plastics due to its cost. The production process for PLA is
expensive because of the intermediary steps. “First, lactic acid is fed into a
reactor and converted into a type of pre-plastic under high temperature and in
a vacuum”, Professor Bert Sels from the Centre for Surface Chemistry and
Catalysis explains. “This is an expensive process. The pre-plastic – a
low-quality plastic – is then broken down into
building blocks for PLA. In other words, you are first producing an
inferior plastic before you end up with a high-quality plastic. And even though
PLA is considered a green plastic, the various intermediary steps in the
production process still require metals and produce waste.”