Efficient use of bioash in forestry

Today, wood ash is currently recycled primarily in southern Sweden where slash (branches and tops) have been removed after forest operations. But there is a greater potential in recycling more wood ash and thus using it as a resource instead of a waste product. 

When wood ash is returned to the forest, important nutrients are added to the soil, helping to buffer soil conditions and, in some cases, increase tree growth. More efficient, simplified, and cost-effective recycling of wood ash could reduce the need for landfilling while strengthening forest productivity and carbon sequestration.

The project is based on the question of whether current methods for returning wood ash to forest land can be made more efficient. One example is to utilize empty return transports of forestry machines during different forest operations to distribute wood ash in the forest instead of transporting it to landfill.

The project investigates different spreading methods and how they affect forest growth, vegetation dynamics, and soil and soil water conditions. The influence of weather and seasonal variation will also be studied, including how the ash changes over time and how nutrients are released and transported into the soil.

An important part of the project is to understand how elements are chemically bound in wood ash and how available they are to plants. This provides knowledge about how wood ash can be used efficiently and sustainably in future forestry.

In the long term, the results may contribute to shifting the view of wood ash from a waste product to a valuable resource. This could benefit both forest production and carbon sequestration, while helping to maintain nutrient balance in forest soils under changing climate conditions. Increased use of wood ash from the energy sector could also support the development of sustainable and bio-based value chains.

Research team

PhD student: Linnea Larsson, Department of Forest Bioeconomy and Technology, SLU

Main supervisor: Mikael Thyrel, Department of Forest Bioeconomy and Technology, SLU

Assistant supervisors:

Magnus Rudolfsson, Department of Forest Bioeconomy and Technology, SLU

Charlotta Erefur, Unit for field-based forest research, SLU

Eva Ring, the Forestry Research Institute of Sweden

Project period: November 2024 – December 2029

This project is part of WIFORCE – the Wallenberg Initiative in Forest Research, funded by the Knut and Alice Wallenberg Foundation.