Today, the growing demand for energy is coupled with the increased use of renewable resources such as biomass. Wood burning generates ash, which is currently sent to landfill since its trace-metal levels exceed authorised thresholds in Switzerland for the spreading of recycling fertilisers on agricultural land. This approach represents a sizeable loss of natural fertilising substances, even as the quantity of ash continues to grow as a consequence of the interest in green energies.
Since 2011, Agroscope’s Plant Nutrition team in Changins has been studying the agronomic effects of spreading bottom ash. The objectives of this study are
- to characterise the composition and chemical form of the macroelements and
trace metals (TMs) contained in the ash,
- to identify the origin of these TMs, and
- to evaluate the effects of the ash on soil chemical and biological properties, yield, and TM uptake by the crops.
Thanks to the encouraging results of this study, a project for developing and producing phosphorus-potassium (PK) mineral fertilisers based on granulated bottom ash is currently being developed with partners from the fertiliser trade.