LIFE+Futur Agrari (LIFE12 ENV/ES/000647) M. Torrellas J. Noguerol V. Riau, L. Burgos L. Tey A. Antón A. Bonmatí Air emission inventories of cattle manure processed at a biogas plant Measured and estimated emission accounting 3th International Symposium on Emissions of Gas and Dust from Livestock Saint-Malo, France 21 st to May 24 th, 2017
1. Introduction Objectives Objectives of the study To develop an air emission inventory from the processing of manure at a biogas plant, by field measurements. To provide an approach to estimate these emissions. To evaluate the relevance of an emission inventory in environmental assessments (LCA).
Scenario for the study Biogas plant Co-substrate Cow manure Electricity Thermal energy CHP 500 kw Biogas Digestate Liquid fraction, storage pond Fertilization Solid fraction, composting piles Mechanical separation
Scenario for the study Reference situation Storage pond
Sampling Sampling at the biogas plant Time period: 2 years Liquid and solid samples Monthly sampling Determination of parameters - TS, VS, TKN, NH 4 -N, ph, CE, SO 4, P, K, Cu, Zn.
Sampling Emission sampling Sampling every two months Sampled emissions: - CH 4 - N 2 O-N direct - NH 3 -N - H 2 S Global warming Acidification Influent storage (IS) Liquid fraction storage (LFS) Solid fraction storage (SFS)
Sampling Data from emission sampling Data were used to prepare an emission inventory per storage compartments Emissions IS LFS SFS NH 3 -N mg m -2 s -1 0.032 0.356 0.152 CH 4 mg m -2 s -1 0.983 0.235 0.136 N 2 O-N dir mg m -2 s -1 0.0016 0.0019 0.0025 H 2 S mg m -2 s -1 0.027 0.019 0.020 Influent storage (IS) the highest CH 4 and H 2 S emissions Liquid fraction storage (LFS) the highest NH 3 -N emissions Solid fraction storage (SFS) the highest N 2 O-N dir emissions
Sampling Sampling in situ Advantages - Emission measurement per compartment - Direct information for the plant characterisation in real conditions Drawbacks - Time consuming - Required equipment and trained personnel - Economic cost
Emission estimation Estimations with calculation methods IPCC Model (Intergovernmental Panel on Climate Change) Guidance on methods to estimate emissions of CH 4 from enteric fermentation in livestock, and CH 4 and N 2 O from manure management
Emission estimation Estimated emissions NH 3 -N N 2 O indirect CH 4 Influent pond Final pond Compost N 2 O direct Compost Indirect N 2 O emissions are due to NH 3 -N volatilization Direct N 2 O emissions from liquid/slurry: Emission factor is 0 according to IPCC
How we applied IPCC models REFERENCE SITUATION Slurry application Slurry EF NH 3 -N 1 EF N 2 O 1 ind 1 B 0 MCF 1 CURRENT SITUATION Digestate application Influent pond Anaerobic digestion Mechanical separator Final pond Slurry + cosubstrate Biogas Liquid fraction L EF NH 3 -N 1 EF NH 3 -N 1 EF N 2 O ind 1 B 0 1 MCF 1 Time spent 2 Degraded VS in AD 45% 3 B 0 (m 3 CH 4 /kg VS) 0.121 S Bulking agent? VS 2 Separator efficiency 4? B 3, 5 EF NH 3 -N 1 0 4 Digestate N VS Liquid fraction 94% 77% Solid fraction 6% 23% Composting Compost EF N 2 O dir 1 1 IPCC, 2006, 2 El Mashad i Zhang et al., 2010; 3 Rodhe et al., 2015; 4 Moller et al., 2002; 5 Experimental data
Results Models comparison Reference situation kg y -1 Tier 1 (IPCC) Tier 2 (Local) Tier 3 (Analysis) N excreted by animal 100 80 - N total farm 86,613 69,880 126,309 VS excreted by animal 5.1 4.45 - VS farm 1,717,234 1,498,371 2,409,269 140,000 Tier 1 IPCC Tier 2 Local Tier 3 Analysis 120,000 100,000 kg y -1 80,000 60,000 40,000 20,000 0 NH3-N CH4 N2Oindir 3 -N 4 N 2 O indirect
Results Current situation 50.000 40.000 NH 3 -N CH 4 50.000 40.000 kg y -1 30.000 20.000 kg y -1 30.000 20.000 10.000 10.000 0 IS LFS SFS Total 0 IS LFS SFS Total kg y -1 700 600 500 400 300 200 100 0 N 2 O indirect IS LFS SFS Total kg y -1 400 350 300 250 200 150 100 50 0 N 2 O direct IS LFS SFS Total 1.000 Tier 1 Tier 2 Tier 3 Measurements
Results CO 2 eq balance For the generation of electricity at CHP Avoided electricity for medium voltage production mix, Spain 2013 (1 kwh electricity 335 g CO 2 eq) 1.000 Tier 1 Tier 2 Tier 3 Measurements Tonnes CO 2 eq y -1 500 0-500 -1.000 Total emissions Net emissions -1.500 Avoided electricity emissions
Results Contribution LCA (Life cycle assessment) Functional unit: 1 kwh Avoided electricity for medium voltage production mix, Spain 2013 Method: ILCD 2011 Midpoint 100% 80% 60% 40% 20% 0% -20% -40% -60% -80% -100% Avoided electricity Electricity imported Cosubstrate transport Cosubstrate Infrastructure Emissions Impact categories
100 80 60 40 20 2. Determination of emissions Results Contribution % LCA (Life cycle assessment) Comparison of environmental impacts considering different emission inventories Tier 1 emissions Tier 2 emissions Tier 3 emissions Measurements 43% 36% 49% % -20-40 -60 Climate change Particulate matter Acidification Marine eutrophication 75% -80-100 Impact categories
3. Conclusions Regarding the methods used Emission measurement is complex due to the technical requirements and not always possible. Emission estimation methods can be useful to determine emissions. It is necessary to adapt these methods for the conditions at a biogas plant. Emission inventories are a key point in environmental assessments such as LCA.
Marta Torrellas marta.torrellas@irta.cat Thank you very much for your attention!!