Cotton recycling in the soil closes the circle on fibre waste

In an unusual cotton recycling project, two of the fibre’s crops growing in Australia this year have an unusual additive in the soil – shredded cotton bedsheets and clothing.

As part of a “circular economy trial” which could have an impact on reducing greenhouse emissions and increasing carbon in the soil, 20 tonnes of cotton waste from Sheridan and Thread Together have been put into and onto cotton crops in Gunnedah and Goondiwindi.

“This has been such an innovative project to be part of,” says Jaine Morris, chief operating officer and co-founder of Coreo, which develops circular economy projects in Queensland.

“We send to landfill 800,000 tonnes of textiles in Australia each year, and some of that will be 100 percent cotton. If they can be re-used, that’s a preferable solution, but this is a preferred pathway for absolute end-of-life textiles.”

As well as reducing the quantity of landfill, taking cotton out of the waste stream is likely to reduce methane emissions. Initial projections showed that for every 2.3 tonnes of waste cotton buried into the field, 2.07 tonnes of atmospheric CO2 equivalents would be mitigated through the breakdown of these garments in soil rather than landfill.

A smaller trial the previous season on Sam Coulton’s Alcheringa farm at Goondiwindi showed that soil friability and microbe activity actually increased in the soil as a result of the added waste cotton, and there were no notable bad effects.

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As well as being a cotton grower, Coulton is also the owner of garment manufacturer Goondiwindi Cotton.

“We should be responsible for that product – to get rid of that product at the end of its life,” he says. “That should be on every manufacturer’s list – from cradle to grave. The main thing was to get rid of the product and make sure the dyes wouldn’t do anything damaging to our farmland.”

Coulton says if the current trials continue to be successful, he is keen to explore building a factory that would shred waste cotton and potentially pelletise it to make it easier for other growers to apply.

Dr Oliver Knox, Associate Professor of Soil Systems Biology and Coordinator of the Cotton Hub at the University of New England, is overseeing the trials.

He says one advantage of putting the cotton waste in the soil is that it leads to a decrease in nitrogen levels early in the season. His theory is that the waste cotton immobilises nitrogen fertiliser that has been applied to the soil. This is beneficial as it could potentially stop the fertiliser leaching out of the soil too quickly and ending up in waterways. It could also provide a longer-lasting benefit to the crop by acting like a slow-release system.

He says that although testing has not yet shown an increase in soil carbon, it should become evident down the track.

“Generally, you need a five-to-ten-year program before you see changes in soil carbon,” Knox says.