This case study focusses on the use of forest biomass for energy production and the subsequent recycling of wood ash in North Karelia, Finland.

In North Karelia, generating energy from forest based biomass produces large quantities of wood ash. Some of the wood ash is used as fertiliser in forestry and also in road construction. However, the majority of ash is regarded as waste with power plants and other industrial facilities incurring large disposal costs.

'Read more' for further details on the case study, updates from the forest demonstration - 'The use of wood ash as a fertiliser on mineral forest soil', and the summary forest demonstration leaflet on Wood Ash:

Contact: Samuli Joensuu; This email address is being protected from spambots. You need JavaScript enabled to view it.

Location: North Karelia, eastern Finland
Main land use: Forestry
Stakeholders: Forest owners, forest owner organisations, logging entrepreneurs, forest industry, heat entrepreneurs, energy producers, ash processors, researchers, decision makers and politicians
Key issues:
o    Environmental impact of wood ash recycling (e.g. heavy metals, aluminium)
o    Ecosystem services
o    Use of ash for construction
o    Achieving sustainability in the forest based bioenergy supply chain
o    Ash recycling best practice
o    New spreading systems
o    Impacts of using wood ash fertiliser on mineral soils

VALERIE theme covered:
 6. Recycling and smart use of biomass and food waste, in particular waste generated during primary production ►

Case study updates:
• A kick off meeting was held in summer 2014 with a representative cross-section of stakeholders from forest owners to industry. The main obstacles and research needs were identified along with additional stakeholders.

• A first workshop was held in mid-January 2015 in Joensuu with a representative cross-section of stakeholders from forest owners to industry; including many new stakeholders. Positive feedback was given on the VALERIE innovation factsheets reviewed, although with a recommendation to include more practical details. Testing ash fertilisation on mineral soils was identified as a suitable topic for a field trial.

• At the VALERIE project meeting held in Finland, June 2015, participants took part in a field trip learning more about sustainable forestry in Finland and the case study on Sustainable Forest Biomass, based in Joenssu. See a presentation of the event here.

Field trials:
• Issues to be addressed in the field trials:
o    Impacts of using wood ash fertiliser on mineral soils
o    The barriers, benefits & feasibility of using wood ash as a fertiliser

• Use of wood ash on nutrient poor mineral soils will lead to a better recycling of wood ash and may have positive effect on forest growth and income for the forest owner. The trial aims are:
o    To test wood ash fertilization in forests on nutrient-poor mineral soil
o    To collect information about the barriers, the benefits and the feasibility to use wood ash as a fertilizer

• Trials are planned to start in 2016.

• Wood ash is an excellent forest fertilizer and can be very beneficial for forest growth. However, currently this useful side-product (which is often labelled as a waste product) is not used to its full potential.

Granulated wood ash


Wood ash spreading equipment mounted on a forwarder


 • The case study held a field trip on 8th June 2016. A group of stakeholders and researchers spent a rainy Wednesday in the North Karelian forests discussing the use of recycled wood ash from various perspectives. It was a surprise to learn that even a cycle path can be made from wood ash! There was a demonstration of spreading wood ash for use as a fertilizer and people could witness with their own eyes the positive influence of wood ash on forest growth.



With wood ash as a fertiliser


Without wood ash as a fertiliser


• Details of the field trip have been posted to Facebook and published as a newspaper article (in Finnish) in the Karjalainen, the newspaper from North Karelia. A short version of the newspaper article can be found on the web at:

• On the 29th of November 2016, a wood ash recycling workshop was organised for the Finnish stakeholders. During the workshop it became obvious that, although there is a lot of knowledge available on wood ash recycling, it doesn’t reach all practitioners. VALERIE aims to address this challenge through improving access to scientific knowledge for foresters, farmers and advisers.  The workshop was one of the first occasions where the ‘virtual adviser’ tool,, was tested and it was well received by stakeholders.  Further testing will take place in early 2017.


• In May 2017, Finnish stakeholders attended a field trip to trace the path and use of recycled wood ash, and to visit the VALERIE field trial. The visit generated great interest, including the possibility of utilising wood ash in a similar way in southern Finland.


• The stakeholders were shown a new pilot area in Kiihtelysvaara where wood ash will be used as a fertiliser for forest regeneration. The trees were felled & harvested in 2016, and in June 2017 the clear felled area was cultivated and planted. In mid-August the Natural Resources Institute Finland (LUKE) led by Hannu Ilvesniemi, will establish a network of experiment areas (30 x 30 m) with a range of wood ash treatments (0, 3000 and 9000 kg of ash). Prior to ash spreading, soil and plant samples will be collected.
The stakeholders also visited Stora Enso Kitee Saw Mill which produces woodchips and bark, and Kiteen Lämpö Oy, a small thermal power plant in Kitee, where woodchips are the main fuel.


• Ash from the power plant is used by a local company, Tuhka Hukka Ltd., as a fertiliser in agriculture and forestry.

• A brief summary of the wood ash recycling field trip can be found on the European Forest Institute (EFI) Facebook page:

• The summary (including results) forest demonstration leaflet, 'Demonstrating the use of wood ash as a forest fertilizer on mineral forest soils in the Joensuu area, Finland' (English version) can be downloaded here