The Role Organics Can Play Post COP26

By Christopher Rochfort MAIH, CEO CORE

Cross-Sectional design of a Bio-Swale system with Bio-Filter treating road run-off before discharging to waterways. Image/ Chris Rochfort, CORE

It’s not easy sometimes seeing the wood for the trees. This could be the case with for the horticulture industry as it navigates its way through COP26 and a strong focus on energy emissions. There are the obvious benefits horticulture can offer such as more shade trees for addressing the heat island effect and greening of the urban landscapes but there is more much more.

But first I want to take a step back and recognise the role plant material plays in methane generation in landfills if not recycled. I’ve been at the forefront of organics recycling since 1992 helping to form two key industry organizations, conducting government supported research into markets for end products and initiating Australian Standards for Composts, Soil Conditioners and Mulches.

By far the most important body of work though has been through CORE (The Centre for Organic Research & Education) in unpacking the critical role organic material can play in water management.

By water management I’m not only referring to moisture holding capacity benefits; for instance I’m referring to the role organic material can treat and remove pollutants that are in urban, industrial and agricultural run-off. This run-off often contains nutrients, heavy metals, toxic compounds such as hydrocarbons and microplastics.

Recycled organics when combined with a number of other materials such as glass, sand, charcoal and other recycled materials can physically, chemically and biologically treat the above-mentioned pollutants. We have even removed uranium and PFAS, for instance. The removal rates are often in the 90th percentile and it is difficult to find any other product or machine for that matter that can do better.

Manly, NSW Stormwater Treatment & Reuse System showing Bio-Filter surrounding drainage and storage tanks used to irrigate grass areas of Manly beach using treated stormwater. Image/ Chris Rochfort, CORE

Lyne Park, Rose Bay Sydney during rainfall event showing run-off dispersing over Bio-Filter bed. Image/ Chris Rochfort, CORE

Cross Sectional design for Lougheed Highway, BC, Canada using CORE designed Bio-Filtration Media in median strip to protect nearby salmon streams receiving road run-off. Image/ Chris Rochfort, CORE

Through CORE, we have conducted long-term research on materials and pilot sites around Australia and fifteen other cities around the world where the results have been replicated. Traditionally city engineers and researchers had opted for sand filter technology to remove pollutants from run-off using the same principles as a “sand filter” used in swimming pools.

However, they soon tried to adopt the technology to vegetated filter systems such as rain gardens and bioswales with often less than favourable results. Testing was carried on adding a small amount of organic matter however they found this leached impurities into the waterways. This was because the organic matter chosen was unstable and not suited for the purpose.

CORE research has found that if the organic matter is properly prepared and particle sized there is almost no leaching occurring. This finding has enabled a higher percentage (up to 50 %) or organic matter can now be used in biofiltration systems that results in optimum plant growth. The plants can also contribute to the treatment process through “phyto-remediation”.

Another important factor is these systems resilience in the era of climate change with plants coping much better in either drought or localised flood events. A wider palette of plants can be used whereas with sand filters primarily monocotyledon plants were used. With increased organic matter levels there are other benefits such as reduced flooding and higher carbon sequestration.

In summary plant material and horticulture have a lot to offer in cleaning waterways and managing climate change.

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