NP-balans

Plant adapted fertilizers from biogas plants

The nutrient content in the digestate will be optimized by different techniques like co-digestion, recovery of phosphorous from reject water and digestate or by addition of nitrogen. The plant nutrient utilisation of optimized digestate will be studied in field experiments and greenhouse experiments. We will analyse plant biomass and nutrient content at harvest and compare with plants from unfertilized and mineral fertilized treatments. 

Can we improve the nutrient balance in digestate before or after anaerobic digestion? We will investigate:

• pre-treatment of organic substrates before digestion
• methane potential from co-digestion of different substrates
• phosphorous recycling by struvite precipitation from reject water and digestate
• optimize the nutrient balance by addition of struvite/ nitrogen rich substances to digestate

In forestry

Which are the long term effects of digestate in forest? In six 10-15 year old experiments, we will investigate:

• Risk of leaching of nutrients and heavy metals
• Tree growth

In agriculture

What is the best form for digestate? Liquid or solid? How important is soil incorporation? What season is best for spreading? We will investigate:

• uptake of nutrients and heavy metals in plants
• growth and harvest
• risk of leaching of nutrients
• risk of surface runoff of nutrients and heavy metals

The results will provide a basis for advice on how to use digestate to maximize the benefits and minimize the risks, with the goal to contribute to lowering of eutrophication in rivers, lakes and coastal areas.