Irish scientist invents a way to recycle plastic

Kevin O’Connor at UCD is developing a process that uses micro-organisms to break down plastic and turn it into a biodegradable form

Jan Battles

An Irish scientist believes he has a way of reducing plastic waste that could see Ireland break into a market worth billions of euros.
Most plastics that are manufactured from petroleum products end up as waste in landfill where they will never decay. Kevin O’Connor uses bacteria to break down plastic bottles before turning them into a reusable form of the material that is biodegradable once thrown away.
The breakthrough has the potential to not only reduce plastic waste, but also double its usefulness and ensure it can eventually be disposed of without causing any damage.
After screening 400 types of micro-organism, the University College Dublin (UCD) scientist found three types of bacteria in Irish soil that can degrade plastic and turn it into a bio-plastic called polyhydroxyalkanoate (PHA).
The bacteria that are used in the process are common in Irish soil and can be grown quickly under laboratory conditions. The process, which takes two days, involves heating the plastic in the absence of oxygen, which breaks it down into its constituent parts.
The substance is put into a fermenting tank containing the special bacteria, which feed on it, breaking it down further in their digestive system.
“When it melts you are basically breaking all the bonds in the plastic so you are releasing its individual components — what are referred to as monomers,” said O’Connor, who works at UCD’s School of Biomolecular and Biomedical Science.
“The bacteria are treating this melted plastic like food. They’ll eat it and break it down, just like you would break down pasta or a banana or whatever.
“When they break it all down we can trick them into thinking that their environment is becoming a bit like autumn or winter,” he said. “When they sense this they start to put on fat — like a bear gains weight to store for the winter. The fat is actually a plastic material.”
A chemical can then be used to dissolve away the organic matter of the bugs, he said, killing them, and leaving just the new plastic that was inside them. “That plastic can be used again for packaging and at the end of its lifecycle is biodegradable,” said O’Connor.
Although the bugs are microscopic in size they are used in very high densities inside the reactor — turning from a watery liquid to a thick soup as they get bigger.
The bugs’ ability and the process involved has been patented by O’Connor and UCD, which has set up a company to develop it into a plant-sized process. The method is similar to how bacteria is used in sewage treatment to purify waste water by extracting various compounds from it.
O’Connor said there is a “massive” demand for biodegradable plastic worldwide. “If you look at the US alone, the petrochemical plastics market is worth $300 billion (€215 billion) a year,” he said. “If you can get 5% of that you have a billion-dollar product.
“The EU and the US predict that bio-plastics will make up 20-25% of the current petrochemical market so there is a massive potential to not only deal with the waste we are generating but also then produce biodegradable plastic that is highly desired by the market. We really believe there is a huge opportunity.”
Unlike plastics manufactured from petrochemicals, which will not decay at all in landfill, the plastic made by the bugs will biodegrade within six to nine months when composted, depending on the temperature.
Because the plastic has been produced by bacteria, when other bacteria come across it in the soil they will naturally break it down as well.
There are other advantages to the process too. In the initial heating stage a gas is emitted that can be used to generate electricity to power the fermentor or to fire up the heat treatment. The idea is that the plant that would recycle these plastics would become self-sustainable.
The research is one of several new projects funded by the Environmental Protection Agency (EPA) under its Science, Technology, Research and Innovation for the Environment (Strive) programme.
Micheal Lehane, the EPA programme manager, said: “The market potential is enormous, not just within Ireland but in the world.
“As far as we know there is nobody else in the world doing this. The innovation is that it’s creating a brand new plastic that you can fire into your compost bin and it is gone in six to nine months.”