Researchers at the KU Leuven Centre for Surface Chemistry and Catalysis (www.kuleuven.be/english) in Louvain / Belgium have developed a new route to polylactic acid (PLA) that they claim will simplify production and make it waste-free, thus making the biodegradable plastic cheaper and greener. The patent for the process has been sold to an unidentified chemical company, which will try to develop the technology to industrial scale. “This,” said team leader Professor Bert Sels, “is a great example of how the chemical industry and biotechnology can join forces.”

As PLA is biocompatible, it is suitable for medical use, and it is also one of the few plastics that are suitable for 3D printing. However, the research team notes that the degradable polymer is not yet a full alternative to petroleum-based plastics due to the complexity and costliness of its production. In the route currently used, lactic acid is fed into a reactor and converted into a pre-plastic under high temperature and in a vacuum. The precursor is then broken down into building blocks for PLA. “In other words,” Sels says, “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.”

Toward finding a better process, the Belgian researchers applied a petrochemical concept to biomass. In a first step, they speeded up and guided the chemical process in the reactor using a zeolite catalyst. By selecting a specific type on the basis of its pore shape, they then were able to convert lactic acid directly into the building blocks for PLA without making the larger by-products that do not fit into the zeolite pores.

“Our new method has several advantages compared to the traditional technique: we produce more PLA with less waste and without using metals," says postdoctoral researcher Michiel Dusselier. In addition, “the production process is cheaper, because we can skip a step.”