Kekkilä Group is the Nordic market leader in home gardening, substrate and landscaping products. Their products are developed and marketed for professional growers, landscapers and hobby gardeners.
“One of our business areas specializes in substrates for big landscaping projects like public parks and urban spaces. We use bark sand as a raw material in these products,” explains project development manager Pekka Järvenpää from Kekkilä.
Bark sand is a side stream of the pulp and paper production process. Wood coming to the mill is peeled in the barking drum, after which bark sand is separated on the precipitation conveyor. Bark sand is a mixture of fine bark, soil and sand wedged in the trees.
Improving soil biodiversity
The main raw material of horticultural substrates is sand and composted peat. The proportion of bark sand in the end product is rather small, but the composted bark increases the activity of microbes and thus improves the biodiversity of soil.
“A good-quality soil always contains a lot of fungi, bacteria and invertebrates that feed on bark. The substrate is also more weatherproof and generally of better quality when there are plenty of microbes in the end product.”
The Kymi mill has been supplying bark sand to Kekkilä since summer 2014. There is a constant need for the raw material, says Järvenpää, so the Kymi mill makes an excellent supplier for the company.
“I am confident that we can use up all the bark sand coming from the Kymi mill as we produce hundreds of thousands of tonnes of landscaping substrate per year in Finland. Although it is a seasonal product, we fabricate it for storage as well,” adds Järvenpää.
Exploiting side streams
The collaboration between UPM and Kekkilä started at the suggestion of waste management partner Lassila & Tikanoja. Both benefit from the cooperation as UPM aims to recycle all the side streams of its production processes. Before the collaboration began, the bark sand was used as landfill.
“We also recycled all the ash from the mill’s power plant last year. The sludge from the effluent treatment plant will be incinerated to produce energy and the lime waste will be provided to fertilizer manufacturers,” says environmental technician Teija Ahola from the Kymi mill.
“But a suitable end-use for soda precipitate from pulp production is yet to be found,” she adds.