Metsä Board has partnered with Finnish circular economy company Soilfood for the upcycling of side stream fibre fractions created during paperboard production.
Strong demand for natural solutions
In practical terms, Soilfood produces wood-based soil improvement fibres from fractions produced as side streams at Metsä Board’s cardboard mills. These fibres increase the fertility of the soil and improve its water retention capacity. The use of wood fibre is also an effective method of water conservation as it can reduce the run-off of phosphorus from fields by up to 50%. Thus, what was once considered waste, is now re-utilised into soil improvement fibres. “The result is a product that not only recycles the nutrients of wood fibre back into soil, but also stores the carbon of the wood into soil,” explains Metsä Board in a statement.
Each weekday, Soilfood currently collects at least two truckloads worth of side streams from Metsä Board’s mills in Kemi and Äänekoski, Finland. In addition to Soilfood’s soil improvement fibres, the side streams from Metsä Board’s mills are being utilised for energy production and landscaping purposes.
"Together with farmers and our industrial partners, we are replacing virgin raw materials with recycled ones and using natural resources wisely. The demand for recycled nutrients and soil improvement fibres has been growing strongly in recent years. The growth is currently limited mainly by the availability of raw materials," says Sampo Järnefelt, Chief Commercial Officer at Soilfood.
Results backed up by research
Metsä Board’s cooperation with Soilfood started with a research project initiated in 2015 by the Natural Resources Institute Finland to study the ability of wood based fibre sludge to stabilise the structure of field soil and thus reduce erosion and nutrient leaching from fields to water bodies. The field experiments of this study have found soil improvement fibres to reduce the risk of nutrient leaching by up to 50%. 
Side streams can be burned to create energy, but using them as soil improvement fibres is more valuable from a circular economy perspective. The nutrients in the wood-based material are returned to the soil and part of the carbon is stored for the long term. In one treatment cycle, the farmer adds up to 5 tonnes of carbon to the field, some of which is broken down by biological processes to feed the microbiota of the soil and some of which is sequestered in the soil forming a carbon storage for more than 20 years.
The utilisation of side streams is also included in Metsä Board’s 2030 sustainability targets.
"Currently, more than 99 per cent of our production side streams are used either as materials or energy. We aim to make 100% use of all production side streams to ensure our processes do not generate any landfill waste after 2030," says Markku Leskelä, Development Director at Metsä Board. "Our cooperation with Soilfood is a good example of a circular economy that benefits all parties involved," he concludes.