Treatment of dairy cattle slurry for biogas production and nitrogen recovery

Anaerobic digestion (AD) is widely distributed within livestock farms, although not providing any reduction of excessive nutrients. This paper investigates AD coupled with ammonia stripping as an integrated management strategy for manure deriving from intensive livestock breeding. Biomethane potential tests were performed considering three different mixtures of feedstock, representative of a seasonal feeding of a real-scale AD plant in Southern Italy. Results show that the specific cumulative methane production obtained under the three conditions investigated ranged between 133 and 155 NmL CH4/g VS. Ammonia stripping allows considerably reducing the N content of the digestate. Specifically, N ranged from 1531.46 to 563.19 mg N-NH4/+L and from 1189.71 to 425.24 mg N-NH4+/L, for dairy slurry digestate and winter digestate, respectively.