1. 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:
Università degli Studi di Milano
Department of Agricultural and Environmental Sciences

2. 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.

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

4. 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

5. 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)

6. Experimental apparatus

7. Experimental apparatusO2
Air stone
50-L batch reactor

8. 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

9. Results

10. Results
Concentrazioni di N2O tra 1 e 0.6 mg/m3

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

12. 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 raising pH rapidly, without activating nitrification processes.

13. 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

14. Thank you for your attention