The technology, designed to help cities cope with increasingly frequent heavy rainfall and drought periods, uses recycled materials including crushed brick, marl rubble and compost. Researchers say the solution could be used in green roofs, terraces, rain gardens, bus stops with retention plants and other elements of urban infrastructure.

“We investigated the possibility of using construction waste as a substrate that optimally accumulates rainwater while also allowing to easily support selected plants”, said Mirosław Żelazny from the Institute of Geography and Spatial Management at Jagiellonian University, quoted in a university press release.

He added that the best results were achieved using crushed brick or marl rubble mixed with compost.

“In such a substrate, we plant Breckland thyme or other thyme species, which cope well with the harshest weather conditions”, he said.

Researchers demonstrated that the composite retains up to approximately 95% of rainwater, while during periods of low rainfall retention rises to 100%.

“Compared to other currently available solutions, our composites retain water for 20 days longer. These are excellent results”, Żelazny emphasised.

According to the university, existing urban infrastructure often channels rainwater too quickly into storm sewers, contributing to overheating in public spaces and the drying out of greenery during droughts.

The researchers said the new technology also supports circular economy principles by reusing waste materials that would otherwise end up in landfills.

An important part of the system is the selection of drought-resistant plants, particularly Breckland thyme.

“Our technology is comprehensive. We combine the substrate with a stress-resistant plant species. We propose thyme, primarily Breckland thyme, for a reason”, said Alina Stachurska-Swakoń from the university’s Institute of Botany.

“This plant has a high aesthetic value and requires no maintenance. At the same time, as a honey plant, it provides an excellent food source for pollinators”, she pointed out.

The researchers said the plants tolerate drought and frost, regenerate naturally and require minimal maintenance, allowing installations to function across multiple seasons with limited human intervention.

Anna Bojarczuk from the Institute of Geography and Spatial Management said compost also plays a key role in the system.

“The purpose of compost is to provide organic matter and nutrients that support plant growth and the activity of soil microorganisms, without compromising the permeability of the substrate”, she said.

According to the researchers, this enables the substrate to function not only as a water reservoir but also as an environment supporting filtration and biological processes.

The team said many current urban greening solutions prioritise visual appearance over long-term water retention and durability.

“The visual effect is crucial for everyone at the time of investment completion, when everything must be green and aesthetically pleasing. The problem is that due to improper water management, these installations often quickly deteriorate and lose functionality”, Żelazny said.

He added that many existing systems rely on expensive, highly processed substrates and plants with limited drought tolerance.

“Our solutions address this problem in a systemic manner: they combine resilient native plants with a substrate that act as a natural water reservoir”, he emphasised.

The solutions have been submitted for patent protection in Poland as two separate technologies. Commercialisation is being handled by the Centre for Technology Transfer CITTRU.

“The use of innovative retention and filtration solutions in urban spaces enables proper stormwater management, which translates into reduced temperatures in the urban environment, improved air quality, and support for biodiversity”, said Gabriela Konopka-Cupiał.

The technology was developed under a pilot project financed through the university’s Excellence Initiative strategic programme as part of the Campus Living Lab – Useful Research HUB flagship project. Companies CEGMAR, Marek Pochcioł and Stefan Gawroński Ecological Research and Horticultural Services, as well as the Jagiellonian University Botanical Garden, also participated in the project. (PAP)

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