Nitrogen recovery from a pig slurry and a digestate using a simplified stripping technology Francesca Perazzolo, Alessandro Alberio, Gabriele Mattachini, Martina Cattaneo, Elisabetta Riva, Ezio Naldi, Giorgio Provolo Mail: francesca.perazzolo@unimi.it Università degli Studi di Milano Department of Agricultural and Environmental Sciences

Introduction Nitrogen stripping process can be used to recover the N excess in manures but it is currently expensive and difficult to manage. A simplified slow-release ammonia stripping system was evaluated and applied to a raw pig slurry e digested slurries.

The slow release principle In a storage tank ammonia emissions naturally occur

The slow release principle Pump Air Air+NH3 to scrubber Ammonia emissions can be enhanced by an air stream on the surface, heating and mixing the slurry The air charged with ammonia can be collected and sent to a scrubber

Aim Test the nitrogen removal efficiencies from one pig slurry and one digestate without using chemical additives to raise pH. 2) Digestate (DIG) 90% pig and cattle slurry, cattle farmyard manure and poultry manure and 5% of maize silage Pig slurry (PS) (fattening farm)

Experimental apparatus

Experimental apparatus O2 Air stone 50-L batch reactor

Experimental plan Operational conditions: Temperature 40°C TKN (gkg-1) TAN TS (% tq) VS Alkalinity (mgCaCO3 kg-1) pH PS 4.77 ± 0.05 3.52 ± 0.03 3.38 ± 0.07 1.98 ± 0.06 17102 ± 1733 7.40 ± 0.01 DIG 3.41 ± 0.01 2.20 ± 0.00 2.91 ± 0.01 1.83 ± 0.01 13871 ± 159 7.79 ± 0.13 Operational conditions: Temperature 40°C Air blowing into slurries for the first 48 hours 7 l/min Air flux in the headspace: 13/20 l/min Continuous mixing Batch experiment duration: 12 days Both experiments were conducted in triplicate Monitored parameters: pH, redox, temperature, oxygen monitored in continuous. Chemical analyses: TAN (Total Ammonia Nitrogen), TKN (Total Kjeldhal Nitrogen), TS (Total Solids), VS (Volatile Solids), Alkalinity. NH3 , CO2, CH4, N2O with ETG gas analyzer and a photoacustic gas analyzer

Results

Results Concentrazioni di N2O tra 1 e 0.6 mg/m3

Results: Nitrogen removal efficiencies Removal efficiencies (% TKN) Removal efficiencies (% TAN) PS = 56 % DIG = 64 % PS = 63 % DIG = 90 %

Conclusions The technology appears easy to implement at farm facilities adapting well to the farm removal necessities. The tested conditions are common at biogas plants. Nitrogen removal efficiency of this slow-release system is close to that of faster treatments that require higher pH and temperature with a limited energy consumption. Blowing air into slurry during the first days appear an efficient method to obtain 1-1.5 raising pH rapidly, without activating nitrification processes.

ACKNOWLEDGEMENTS The study was carried within RENUWAL project financed by Fondazione Cariplo: Innovative Manure Management and Treatment Techniques to Reduce Nutrient Nonpoint Source Pollution of Waters in Intensive Livestock Areas

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