Nitrogen recovery from digestate with ammonia stripping : results of 27 tests

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1 Nitrogen recovery from digestate with ammonia stripping : results of 27 tests International conference ManuREsource 2013 Manure management and valorization Sergio Piccinini Giuseppe Moscatelli Claudio Fabbri CRPA Research Centre on Animal Production - Reggio E. - Italy December 5 6, 2013 Bruges, Belgium

2 Layout of the stripping treatment in an anaerobic digestion scheme Slurry and biomass Anaerobic Digestion Combined Heat and Power (CHP) Digestate Liquid fraction Stripping Liquid fraction with low ammonia Ammonium sulfate S/L Separation Agronomic use Solid fraction Composting Drying (optional) Fertilizer Industry

3 Layout and characteristics of the stripping pilot plant. Recirculation of air SemiBatch Acid Scrubber Temp: 60 C HRT: 6 ore Capacity reactor: 1 m 3 of slurry Air flow rate= m 3 /h.m 3 of slurry

4 Pilot plant stripping reactor Anti foam Air insuffator Heat exchanger

5 Pilot plant stripping reactor

6 Experimental programme carried out A.D. Plant Power S / L separator Input Substrate to Anaerobic Digestion kwel Screw press Cattle manure and slurry (100%) kwel Screw press Cattle slurry (25%) Energy crops (60%) Agoindustrial by-product (15%) kwel Screw press Energy crops (100%) kwel Sieve drum press Pig slurry (70%) Energy crops (15%) Cattle slurry (15%) kwel Screw press Energy crops (100%) kwel Centrifuge 999 kwel Sieve drum press Pig slurry (90%) Corn flour and molasses (4%) Cattle slurry (6%) 7 60 kwel Screw press Cattle slurry (100%) 8 Cattle slurry and manure (70%) Energy crops (30%) Hot (60 C) stripping of ammonia, without the chemical raising of ph, on several tests with 9 types of clarified digestate (9 types x 3 repetitions) kwel Screw press Pig slurry (30%) Energy crops (30%) Cattle slurry (40%)

7 Characterisation of clarified digestate before and after stripping tests 1 Clarified Digestate PRE-Stripping Clarified Digestate POST-Stripping Thesis ph TS TKN NH + 4 -N ph TS TKN NH + 4 -N [-] [g/kg] [mg/kg] [mg/kg] [%TKN] [-] [g/kg] [mg/kg] [mg/kg] [%TKN] Average 8,09 48, ,7 58,2% 8,59 49, ,7 42,3% S.D. 0,05 0,6 33 4,7 0,5% 0,06 1, ,9 1,9% Average 8,11 54, ,3 60,0% 8,70 58, ,7 45,2% S.D. 0,05 0,4 31 1,2 0,4% 0,01 1, ,0 0,3% Average 7,98 69, ,3 49,1% 8,67 71, ,7 34,6% S.D. 0,11 1, ,9 0,8% 0,15 0, ,9 0,5% Average 7,92 53, ,7 68,9% 8,63 53, ,7 52,5% S.D. 0,26 5, ,8 2,2% 0,09 9, ,9 3,7% Average 7,81 65, ,3 47,7% 8,46 71, ,7 34,2% S.D. 0,07 3, ,6 2,7% 0,06 2, ,9 0,9% Average 7,88 15, ,0 76,0% 8,43 15, ,7 54,3% S.D. 0,09 2, ,3 1,1% 0,06 2, ,1 1,2% Average 7,73 36, ,0 57,1% 8,48 34, ,0 49,4% S.D. 0,07 1, ,4 1,5% 0,03 2, ,4 1,0% Average 7,91 43, ,3 54,9% 8,54 48, ,7 45,5% S.D. 0,11 2, ,8 1,4% 0,02 1, ,8 2,6% Average 7,75 13, ,0 78,1% 8,74 14, ,7 60,1% S.D. 0,08 0, ,2 5,9% 0,10 0, ,7 4,8%

8 Ammonia-N and TKN Removal efficiency observed in the 27 tests (average value and standard deviation -in brackets - of the 3 repetitions of each 9 types of clarified digestates treated) Types of clarified digestates from 9 s Clarified digestate to stripping Effluent after stripping NH + 4 N initial NH + 4 N final N removal efficiency NH 4 + N Power [dm 3 ] [dm 3 ] [g] [%] [%] TKN 1 (330 kwel) 2 (999 kwel) 3 (999 kwel) 4 (630 kwel) 5 (999 kwel) 6 (250 kwel) 7 (60 kwel) 8 (999 kwel) 9 (250 kwel) 310 (11) 263 (6) 603 (19) 276 (12) 54.3 (1.5) 31.6 (1.1) 301 (2) 289 (4) 780 (4) 435 (3) 44.3 (0.7) 26.6 (0.6) 301 (2) 262 (11) 641 (21) 328 (12) 48.8 (0.8) 24 (0.6) 301 (2) 276 (24) 1135 (11) 600 (87) 47.1 (8.2) 32.5 (6.5) 303 (8) 245 (8) 674 (42) 317 (32) 52.9 (2.5) 25.2 (1) 316 (14) 205 (53) 506 (19) 162 (44) 68.1 (7.8) 51.7 (5.4) 339 (5) 273 (4) 463 (14) 254 (6) 45 (0.6) 25.7 (0.9) 320 (9) 275 (22) 617 (3) 362 (53) 41.3 (8.3) 22.7 (5) 318 (7) 211 (19) 433 (24) 160 (7) 63 (0.5) 49.2 (3.7)

9 Average trend of the ammonia concentration and removal during the experiments at 60 C

10 Relationship between removal efficiency of ammonia and total solids content in the influent The removal efficiency of nitrogen is strongly influenced by the content of total solids present in the clarified digestate

11 Relationship between content of ammonia in the influent and removal efficiency of ammonia The greater the ammonia content in the digestate, higher the stripping efficiency

12 Results: characteristics of ammonium sulphate solution extracted from scrubber ph: 4.29 TS: 36.4 % TKN: g/kg (20.1 % TS), about 90% as ammonia

13 Results: some problems Foam formation (but controlled by the slurry mixing system designed to reduce this problem); Ammoniun sulphate dilution in the scrubber s tank, for condensation of the water vapor from air stripping flow; Accumulation of organic matter on the reactor walls and bottom.

14 Conclusion The results of experiments show feasible the stripping of clarified digestate by air insufflation and heating, without chemical raise of the ph; efficiencies, however, are not very high; The lower the solids content in the digestate, the greater the efficiency of stripping; The greater the nitrogen content and the percentage of ammonia in the digestate, higher the stripping efficiency; The ammonia stripping after anaerobic digestion therefore has three advantages: the anaerobic digestion converts most of the organic nitrogen into ammonia, reduces organic acids (less foam) and makes available waste heat from CHP unit.

15 Thank for your attention

IGW S.r.l. Sofia 9 giugno 2015 PIÙ MODERNI, PIÙ COMPETITIVI, PIÙ FORTI AMBIENTE ED EFFICIENZA ENERGETICA IN BULGARIA. Organizzazione a cura di

IGW S.r.l. Sofia 9 giugno 2015 PIÙ MODERNI, PIÙ COMPETITIVI, PIÙ FORTI AMBIENTE ED EFFICIENZA ENERGETICA IN BULGARIA Organizzazione a cura di IGW Srl is a service company that deals with the production