Polylactic acid is a degradable plastic used mostly for packaging. To meet the rising demand, ETH researchers have developed an eco-friendly process to make large amounts of lactic acid from glycerol, a waste by-product in the production of biodiesel.
Plastic waste is one of today’s major environmental concerns. Most types of plastic do not biodegrade but break up into ever smaller pieces while remaining a polymer. Also, most types are made from oil, a rapidly dwindling resource. But there are promising alternatives, and one of them is polylactic acid (PLA): it is biodegradable and made from renewable resources. Manufacturers use PLA for disposable cups, bags and other sorts of packaging. The demand for PLA is constantly rising and has been estimated to reach about one megaton per year by 2020.
The research groups of ETH professors Konrad Hungerbühler and Javier Pérez-Ramírez at the Institute for Chemical and Bioengineering are now introducing a new method to produce lactic acid. The process is more productive, cost-effective and climate-friendly than sugar fermentation, which is the technology currently used to produce lactic acid. The new method’s greatest advantage is that it makes use of a waste feedstock: glycerol.
Waste product of biofuel manufacturing
Glycerol is a by-product in the manufacturing of first-generation biofuels and as such is not high-grade but contains residues of ash and methanol. “Nobody knows what to do with this amount of waste glycerol”, says Merten Morales, a PhD student in the Safety and Environmental Technology group of professor Hungerbühler. This waste substance is becoming more and more abundant, with 3 megatons in 2014 expected to increase to over 4 megatons by 2020. Because of its impurity, glycerol is not suitable for the chemical or pharmaceutical industry. Moreover, it does not burn well and is thus not a good energy source. “Normally, it should go through waste water treatment, but to save money and because it is not very toxic, some companies dispose of it in rivers or feed it to livestock. But there are concerns about how this affects the animals.”
Making use of this waste feedstock by converting it into lactic acid already constitutes an advantage that makes the new method more eco-friendly.
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