Earlier this month, when the news hit the Internet that a plastic-eating fungus had been discovered in the Amazon jungle, polyurethane unexpectedly joined the ranks of the biodegradable plastics. And all of a sudden, bioremediation was the newest buzzword.
Bioremediation is a technology that, simply put, relies on the use of biological agents, such as bacteria or plants, or in this specific case, a fungus, to break down, remove or neutralize contaminants in, for example, polluted soil or water. Earlier examples include the microbes found to be digesting the oil spill in the Gulf of Mexico, and the bug that is currently feasting on the remains of the Titanic. Now, polyurethane joins the options on the microbial menu.
Polyurethane, a synthetic polymer developed in the 1940s found in numerous applications ranging from automotive components to coatings, has excellent resistance to abrasion, oils, solvents, oxidation and more while maintaining high tensile strength and resilience. Very durable, polyurethane does not readily degrade. And while technologies have been developed for the chemical recycling of polyurethane, these are not yet applied on a large scale. Some polyurethane is recycled mechanically; a lot of it is incinerated or goes to landfill - where it remains almost indefinitely. Hence when it was found that a fungus called Pestalotiopsis microspora not only ate, but positively gorged itself on polyurethane, the green scene was quick to spread the good news.
Yale students taking part in the university's Rainforest Expedition and Laboratory course discovered the fungus in the rainforest of Ecuador. Back in the lab, experimenting with the samples gathered in the jungle, the fungus' voracious appetite
for polyurethane emerged. According to one report, the fungus was 10 days old when the experiment started and in only a matter of days it had "significantly decomposed about a quart size amount of the plastic". Shades of the Andromeda Strain, there....
And what did it eat in the wild, one wonders?
The fungus is an endophyte, meaning it lives inside the tissues of its host without causing harm. It occurs in rainforests around the world and seems to play several important roles in both protecting its host plant and in recycling nutrients in the ecosystem. Remarkably, the fungus is able to grow on polyurethane as the sole carbon source under aerobic and anaerobic conditions. The latter is particularly interesting, as these are the same conditions found in landfills, raising the intriguing possibility of using bioremediation to help solve the landfill problem. Currently, studies are in progress to discover whether other hitherto indestructible plastics - such as polystyrene - are just as irresistible other endophytes, as polyurethane is to Pestalotiopsis microspora.
Biodegradability, it would appear, is all in the eye of the beholder!