Performance-based criteria for safe and circular digestate use in agriculture

Anaerobic digestion turns organic waste into renewable biogas and a nutrient-rich material called digestate. However, digestate must be proven safe before it can be widely used as a fertilizer. Researchers tested samples from 23 biogas plants in Sweden, Norway, and Denmark and identified three substances that can prevent seeds from germinating: ammonia nitrogen, potassium, and boron. When all three exceeded specific limits, seed germination fell below 50%. The study proposes a simple screening method to determine whether digestate is safe for crops and what treatment it may require. This could increase farmers’ confidence, improve nutrient recycling, and reduce harmful emissions.