New method to produce bio plastic could use cheese waste
Researchers at KU Leuven have applied for a patent on a new method to produce PLA, which could lower the cost threshold for industry
The biodegradable plastic in question is polylactic acid (PLA). This is a good replacement for conventional plastics since it breaks down easily in the environment, but a bad deal for industry since it costs more to produce.
One of its building blocks, called lactide, is particularly problematic. “Several steps are needed in order for industry to turn lactic acid into lactide, including the use of heavy metals such as tin,” explains Bert Sels, the head of KU Leuven’s Centre for Surface Chemistry and Catalysis. “This conversion accounts for about 30% of the total production cost of PLA.”
The alternative method he and his colleague came up with is beautifully simple. First, lactic acid is mixed with alcohol, which means it vaporises without the need for much heat. This vapour is then passed over a catalyst, which, when the lactic acid and alcohol are separated again, encourages the lactic acid molecules to pair up to form lactide.
No toxic solvents are involved, and the end product is pure lactide, which means it will make high-quality PLA. And any by-products from the process can simply be recycled.
“This is financially advantageous because the conversion is done in one step,” adds Michiel Dusselier, a bio-engineer who also worked on the project. “An additional advantage is that our method can easily be fitted into the existing PLA production process.”
The researchers have applied to patent the new method and are carrying out further work on how it can be used in practice. One idea is that it could feed on the dissolved sugars in whey, a waste stream in cheese production. Dusselier: “Our partners can make lactic acid out of that, and we can then use that lactic acid to produce PLA.”
Photo: Bo Cheng / ETH Zurich
University of Leuven
staff members in 2013
students in 2014-2015 academic year
million euros in annual research budget