Wood ash and compost for fertilizing forests

Photo: Krista Kimmo
Metsäbiotalouden tulevaisuuskuvasto / Forest Bioeconomy Future Catalogue

Aalto University, Natural Resources Institute Finland and Lahti Region Development LADEC Ltd have joined forces to develop a new, biobased forest fertilizer made of wood ash and composted organic matter. Using the fertilizer, the nutrients contained in local biomass streams can be brought to improve forest growth and carbon sequestration.

’The recycled fertilizer is the result of combining composted matter and wood ash as well as other suitable sidestreams, such as grain dust and concrete slurry,’ says Johanna Kilpi-Koski, Business Development Manager at LADEC.

Using recycled fertilizers improves Finland’s self-sufficiency in fertilizer production. The sidestreams used contain the principal nutrients required by plants, including nitrogen (N), phosphorus (P) and potassium (K), and also trace nutrients from wood ash. Moreover, the composted matter contains plenty of organic carbon, which improves soil water retention and microbial activity, among other things.

This reduces the need to import mineral fertilizers and their raw materials, as well as the production of energy-intensive raw materials, such as nitrogen. The manufacturing process can be replicated anywhere that suitable sidestreams are available.

The carbon footprint of the new fertilizer is considerably smaller than with corresponding artificial fertilizers. ’As a rule, the factor constraining forest growth on mineral soils is the shortage of nitrogen. Nitrogen-rich peatlands generally suffer from a shortage of phosphorus and potassium, and therefore non-nitrogenous PK fertilizers are used in peatland forests,’ Kilpi-Koski adds.

The fertilizer composition can be regulated to produce suitable fertilizers for both heath- and peatlands. The environmental impact of both will be calculated. At the development stage, Aalto University is in charge of fertilizer production.

’We are now carrying out more detailed studies with a view to setting up an industrial plant later on. We are also updating the technological and financial calculations for such a plant and making a life span analysis covering the stages from manufacturing up to the spreading of the fertilizer,’ Kilpi-Koski says.

The contribution of Natural Resources Institute Finland is to conduct laboratory and field experiments on the rate of leaching of the fertilizer granules.

LADEC is in charge of identifying companies which would be part of the fertilizer value chain. The operation will involve both fertilizer manufacturers and companies producing suitable sidestreams, such as heat plants. As fertilizer users, forest management associations, forest owners and forestry services companies are also part of the target group.
The project is supported by the European Regional Development Fund.

Write a comment