Evaluation of nutritional pellets with enriched biochar from forest industry residues (NärSkog)

Important results from the project

With this study we wanted to study whether it is possible to fertilize plants, forest land and reduce soil acidification with a new product based on forest industrial residuals. Sludge, from forest industrial wastewater treatment plants, was converted to biochar and mixed with biofuel ash. Trials were made with biochar + ash in both powder and pellet form. With the study, we wanted to make sure that the new product, the nutritional pellets, affect forests in a positive way instead of being a way to hide waste in the forest.

Expected long term effects

The results show that pine plants fertilized with biochar and ash, grow better than the reference plants. It might be possible to spread > 5 tonnes of nutritional pellets in forest land without exceeding the recommended levels of heavy metals. Biochar, produced with hydrothermal carbonation (HTC), enriched with ash gives a weak alkaline product that can reduce soil acidification. By carbonization, about 30% of the carbon in the sludge is stabilized. This technology can therefore contribute to CO2 storage.

Approach and implementation

In the project, results from cultivation experiments, chemical analyzes and calculations have been evaluated and discussed with actors from the value chain. Competence from the Forest Industry, nursery, forest owners, the Swedish Forest Agency and the academy has made it possible to analyze the innovation from a very broad perspective. The overall result has led the consortium to seek new funding for stage 2 to be able to make larger and longer trials and to evaluate the product technically, environmentally and financially.