Fungi used to compost plastics

Sofas, shoes, cables and paints made with difficult-to-recycle polyurethane plastics could be degraded in compost heaps using fungi.

This is the result of a Biotechnology and Biological Sciences Research Council-funded study led by Geoff Robson of Manchester University’s life-sciences department.

His team found that certain fungi can degrade the plastic in soil.

Furthermore, the rate of degradation increases when the volume of these fungi is increased or nutrients are added to the soil to boost the fungi’s activity.

The team is now carrying out further studies to make sure the degradation of polyurethanes does not adversely affect the composting process or its products.

Robson said: ‘This is a significant finding. Polyurethanes are used to make many, many products and can take up a large amount of volume in landfill sites, which are rapidly running out of space. This makes it a major environmental pollutant.

‘This study opens the possibility that fungi could be used to degrade these materials instead of dumping them into landfill sites.’

The team placed polyurethane pieces in soil containing fungi and bacteria.

As the polyurethane – which is made from petroleum – degraded, the number of fungi increased as they digested the by-products, showing that it was indeed the fungi that were breaking down the plastic.

Robson added: ‘Fungi that naturally occur in soils have a remarkable capacity to degrade dead plants and animals, playing a pivotal and essential role in nutrient cycling in the environment. This study demonstrates that some of these fungi also have the ability to degrade man-made polyurethanes.

‘We demonstrated increased degradation of polyurethanes when buried in soil either by enhancing the activity of fungi already present by adding nutrients to the soil or by adding specific fungi to the soil that had previously been isolated from the surface of degrading polyurethane.’

The team is now investigating how best to apply its findings to polyurethane waste management. One possible method would be to spray fungi onto the polyurethane; another would be to compost polyurethane along with other compostable materials, using existing facilities.

Robson, a biochemist and plant biologist, said fungi are the classic underdogs and are used to make a variety of important products, including penicillin and immunosuppressant drugs.

‘There is very little research on fungi compared with other microorganisms and only a fraction of them are actually known – around 20 per cent have been identified.

‘These latest findings show what amazing organisms they are.’