Finnish researchers have found a way to make railways more environmentally sustainable by replacing concrete sleepers with those made from recycled plastics. 

A study published in Frontiers in Sustainability highlights how this approach could save greenhouse gas emissions on a large scale. 

“Here we show that recycled plastics could be used as the material for railway sleepers and that overall emissions would be reduced,” said Dr Heikki Luomala, the lead researcher from Tampere University.

The materials tested - liquid packaging board (LPB) and acrylonitrile butadiene styrene (ABS) - are currently incinerated as waste.

Railways are already a low-carbon transport mode, emitting about 31 grams of CO2 per passenger kilometre - half that of electric vehicles. 

However, infrastructure materials like concrete and steel contribute significantly to emissions, particularly on low-traffic lines where they represent up to 30 per cent of total railway emissions.

The research team manufactured prototype sleepers and subjected them to mechanical and thermal tests. 

Results showed that recycled ABS outperformed LPB, demonstrating strength and heat resistance comparable to conventional materials. 

“Recycled ABS is much more suitable as railway sleeper material than recycled LPB,” Luomala noted, citing its superior stiffness and ability to endure high temperatures.

Recycled plastic sleepers offer benefits such as lower cost, easier handling, and resistance to environmental conditions. 

Additionally, using recycled materials reduces waste and supports circular economy goals. 

However, challenges remain, including the need for long-term durability tests and concerns over UV resistance and potential microplastic generation.

The Finnish Transport Infrastructure Agency has expressed interest in scaling up these findings. 

“Their long-term behaviour, for example in terms like UV resistance, should also be tested,” Luomala said.

Similar innovations have already been successfully implemented in Victoria, where recycled plastic railway sleepers have been in use for several years. 

In 2019, 190 sleepers made from 85 per cent recycled plastic waste were installed at Richmond Train Station as part of a maintenance trial conducted by Metro Trains. 

Produced in Mildura by Integrated Recycling, the sleepers are made from agricultural and industrial plastic waste, including cotton bale wraps, vineyard covers, and mining pipes, which would otherwise be sent to landfill. 

These sleepers last up to 50 years - three times longer than traditional timber sleepers - and require far less maintenance. 

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