Pantelopoulos A., Magid J., Jensen L.S. Faculty of Science Department of Plant and Environmental Sciences University of Copenhagen Funded by the European Union
Background The digestate solids Dry matter 16% - 36% ph 8,5 Tot. Nitrogen (%DM) 2,2 3 NH4 (%Tot.Nitrogen) 26 49,4 Tot. P (%DM) 1,9 Utilization Direct land application > org. fertilizer Composting > nutrient rich compost Drying > pelletised org. fertilizer Pyrolysis > stabilised, biochar fertilizer Combustion > energy + ash fertilizer
Drying Enhedens navn Drying experiment - Treatments Digestate solids Cattle and pig manure (70%,20%) Total Solids (%) 26.4 Total-C (g kg -1 ) 37.2 Total-N (g kg -1 ) 32,29 Total-P (g kg -1 ) 14.68 ph 9.2 Ventilation Yes (420ml/min) No Temperature 70 C 100 C 130 C 160 C ph 9 6.5 (12.5 μl conc. H 2 SO 4 g -1 solids) 5.5(17.5 μl conc. H 2 SO 4 g -1 solids
Drying Drying experiment-drying curves 160 C 70 C Time Drying up to 85% DM Drying time reduced by 80% at high operating temperatures
Drying NH4-N evolution during drying 160 C 70 C Time 95% loss of NH4-N in non-acidified solids NH4-N loss reduced to 20% and 30% when solids acidified to ph 6.5 and 5.5, regardless of temperature
Incubation Enhedens navn Incubation Experiments Objectives / Hypotheses Estimate how acidification and drying impact on C and N turnover Specifically - Estimate net N mineralization and gross N turnover rates ( 15 N pool dilution and FLUAZ model) - Assess the C degradability of the treated solids Hypotheses - Drying and acidification will increase both gross and net N mineralization rates - Drying and acidification will decrease the C mineralization of the solids
Incubation Enhedens navn Material Incubation experiment treatments-conditions NH4-N (g/kg) NO3-N (mg/kg) Org-N (g/kg) Soil: sandy loam Temperature: 15 Celsius Moisture: 24% (w/w) = field cap. / pf 2 Rate of solids application: 1% D.W Total duration: 160 days Total-C (g/kg) Total C/N Raw digestate 15.2-17.9 370.3 11.2 Acidified raw digestate 21.2-13.9 340.3 9.7 Dried 160 C 1.1-16.9 370.6 20.6 Acidified dried 160 C 15.2-13.5 330.5 11.5 Dried 70 C 2.4-17.3 360.7 18.3 Acidified dried 70 C Control soil 0.52 (mg/kg) 16.7-13.1 330.1 11.1 17.13 1.6 15.1
Incubation NH 4 -N evolution during incubation Net N turnover Higher NH4-N consumption rate in the raw compared to acidified solids Same trend for acidified solids dried at 70 C compared to 160 C
Incubation NO 3 -N evolution during incubation Net N turnover Until day 14, higher nitrification in the raw solids compared to acidified raw solids No differences in NO3-N between acidified and raw solids at the end of incubation Non acidified, dried solids immobilize dramatically
Incubation Inorganic-N evolution during incubation Net N turnover Acidified solids, raw and dried, result in higher inorganic-n Raw solids constantly lower inorganic N content N-immobilization from solids dried at 160 C; at 70 C some mineralization after day 80
Incubation C-mineralization Higher CO2 evolution in raw and dried solids Acidification reduced CO2 emission
15N incubation Ammonium Gross mineralisation (m) Isotope dilution technique Nitrification (n) Gross immobilization (i) ia Organic N in Nitrate 14 N 15 N - 4 Injections times Injection Day 1st 2nd 3rd - ( 15 NH4)2SO4 10 mg N per Kg soil (6 % atom excess) - Soil, sandy loam 0 0 1 3 6 6 7 9 21 21 23 26 60 60 63 66
15N incubation Ammonium Gross mineralisation (m) Isotope dilution technique Nitrification (n) Gross immobilization (i) ia Organic N in Nitrate 14 N 15 N - 4 Injections times Injection Day 1st 2nd 3rd - ( 15 NH4)2SO4 10 mg N per Kg soil (6 % atom excess) - Soil, sandy loam 0 0 1 3 6 6 7 9 21 21 23 26 60 60 63 66
15N incubation Ammonium Gross mineralisation (m) Isotope dilution technique Nitrification (n) Gross immobilization (i) ia Organic N in Nitrate 14 N 15 N - 4 Injections times Injection Day 1st 2nd 3rd - ( 15 NH4)2SO4 10 mg N per Kg soil (6 % atom excess) - Soil, sandy loam 0 0 1 3 6 6 7 9 21 21 23 26 60 60 63 66
15N incubation Ammonium Gross mineralisation (m) Isotope dilution technique Nitrification (n) Gross immobilization (i) ia Organic N in Nitrate 14 N 15 N - 4 Injections times Injection Day 1st 2nd 3rd - ( 15 NH4)2SO4 10 mg N per Kg soil (6 % atom excess) - Soil, sandy loam 0 0 1 3 6 6 7 9 21 21 23 26 60 60 63 66
Inorganic N (mg Kg -1 soil) 15N incubation 200 150 100 50 NH4- RAW NH4- RAW ACID NO3- RAW NO3- RAW ACID NH 4 + and NO 3 - concentration Faster decline of NH 4 -N and NO 3 -N formation at the raw solids during the first 2 time intervals Opposite trend in the last time interval 0 0 5 10 15 20 25 3.0 Day Isotopic N excess (atom%) 2.5 2.0 1.5 1.0 0.5 NH4- RAW NH4- RAW ACID NO3- RAW NO3- RAW ACID 15 N enrichment of NH 4 + and NO 3 - Increased gross mineralization and potential nitrification rates at the raw solids 0.0 0 5 10 15 20 25 Day
15N incubation 15 N enrichment of organic-n Isotopic N excess (atom%) 0.014 Norg- RAW Norg- RAW ACID 0.012 0.010 0.008 0.006 0.004 0.002 0.000 0 5 10 15 20 25 Day Higher gross immobilization rate at raw solids
15N incubation FLUAZ model estimations of gross N turnover rates Higher gross mineralization and immobilization rates in the raw solids
Conclusion Conclusions - Perspectives Drying and acidification enhance net nitrogen mineralization Acidification inhibits nitrogen nitrification Acidification reduces C mineralization Acidification and drying interesting option for digestate solids treatment for areas with nutrient surplus
Enhedens navn