Biogas Plant with Ammonia Recovery Using FGD-Gypsum for Biobased Fertilisers

This study examines a full-scale biogas refinery plant in Germany that recovers nitrogen from nitrogen-rich digestate using vacuum NH3 stripping and FGD-gypsum scrubbing. The process produces ammonium sulphate solution and liming substrate, recovering 57% of ammonium nitrogen as 22% AS with a production cost of 5.8 € per ton of digestate. The system enables sustainable biogas production from high-nitrogen feedstocks like corn silage and chicken manure, preventing ammonia inhibition. Nutrient recovery efficiency reaches 66% for NH4–N, and the resulting biobased fertilisers meet EU fertiliser regulations (EU 1009/2019), supporting circular economy goals. The technology is economically viable, with a net benefit of ~7 € per ton of digestate, and offers a renewable alternative to fossil-based nitrogen fertilisers. The plant, located at Benas farm, processes 174,000 tonnes of feedstock annually and demonstrates energy efficiency and environmental benefits.