Application of open and closed-path lasers for improving the estimates of the agricultural emissions of methane and nitrous oxide

Transcription

1 Application of open and closed-path lasers for improving the estimates of the agricultural emissions of methane and nitrous oxide Raymond Desjardins 1, Matthias Mauder 1,2, Zhiling Gao 1,3, Elizabeth Pattey 1, Devon Worth 1, Tom Flesch 4, Ramesch Srinivasan 5, Natascha Kljun 6 1 Research Branch, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON, Canada K1A 0C6 2 Current affiliation: Atmospheric Environmental Research, Institute of Meteorology and Climate Research, Research Center Karlsruhe (FZK/IMK-IFU), Kreuzeckbahnstr. 19, Garmisch-Partenkirchen, Germany 3 Current affiliation: College of Resources and Environmental Science, Agricultural University of Hebei, 14 Baoding, Hebei, China Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E3 5 National Research Council Canada, Institute for Aerospace Research, Flight Research Laboratory Research Road, Ottawa, ON Canada K1A 0R6 6 Swansea University, U.K.

2 Outline Greenhouse gas emissions from agricultural sources A A tool to to calculate GHG emissions at at the farm level Open-path lasers for for the measurement of of CH 4 and NH 3 emissions from agricultural sources Closed path lasers for for the measurement of of CH 4 and N 2 O emissions (field and regional scales) Summary 2

3 Agricultural GHG Emissions Atmosphere CH 4 CH 4 N 2 O CO 2 Livestock Manure Crop Management Plants Soil

4 Global sources of anthropogenic greenhouse gas emissions: Methane and Nitrous Oxide Global Methane emissions from from the the energy, waste and and agriculture sectors amount to to about Tg TgCH 4 per 4 per year year or or 7350 Tg TgCO 2 eq. 2 eq. (1Tg (1Tg = 1 million tonnes). Nitrous oxide emissions from from all all sectors amount to to Tg TgN 2 O-N 2 O-N per per year year or or Tg TgCO 2 eq. 2 eq. Source: Denman et al. (2007) 4

5 Agriculture s contribution to global methane and nitrous oxide emissions Global Agriculture is is responsible for for approximately 40-50% of of global methane emissions. Agriculture is is responsible for for approximately 50-70% of of global nitrous oxide emissions. 5 Source: Denman et al. (2007)

6 Agricultural Sources of Methane Enteric fermentation (digestion) by by ruminant animals Tg TgCH 4 per 4 per year year Management of of animal manures Tg TgCH 4 per 4 per year year 6 Source: Denman et al. (2007)

7 Agricultural Sources of Nitrous Oxide Agricultural soils soils Direct and and indirect emissions from from application of of synthetic/manure fertilizers, crop crop residue decomposition, waste deposition by by grazing animals and and cultivation of of organic soils soils Tg TgN 2 O-N. 2 Manure Management Direct emissions from from manure storage Tg TgN 2 O-N. 2 7 Source: US EPA (2006)

8 Greenhouse Gas Emissions by Sector in Canada 2006 Energy 8% Industry 3% Waste 78% 9% Agriculture Total emissions 747 Mt CO 2 e 3% Agricultural energy use Greenhouse Gas Emissions (Mt CO 2 e) CH 4 N 2 O 8

9 Canada s Greenhouse Gas Emissions 800 Agricultural Emissions Greenhouse Gas Emissions (Mt CO 2 e) Agricultural GHG emissions are are about 8-9% of of total Canadian emissions Agriculture is is responsible for for about 65% 65% of of national N 2 O 2 emissions and and 25% 25% of of national CH CH 4 emissions 4 +26% +22%

10 Holos A tool to calculate whole farm GHG emissions in Canada Knowledge gained during the Model Farm program has been synthesized in in a user friendly computer program, Holos, which estimates whole farm GHG emissions. Holos Greek, meaning whole or or complete Program available for for download at: at: www4.agr.gc.ca. Follow the Science and Innovation link 10

11 How do you build such a tool? Learn Build Apply Measure Develop Model Measure GHG s Verified GHG Models time 11

12 Micrometeorological Mass Balance (Integrated Horizontal Flux) method Appropriate for for heterogeneous and and small small areas areas (<0.2 (<0.2 ha) ha) Difference in in concentration between OUT OUT and and IN IN tower tower ( C) ( C) Wind speed Measuring IN tower Z n Z 2 Z 1 Emitted gases Measuring OUT tower Z n Z 2 Z 1 Strong source with small area (eg. manure tank) 12

13 Mass Balance Technique Modified Micrometeorological Mass Difference approach Simplified approach, does not not require air air sampling on on all all four four sides, only only upwind and and downwind Width of of laser line line should be be at at least 6 times the the width the the of of the the source area area Limited by by wind wind direction, which should not not be be more than than 45º 45º to to the the laser lines lines Laser Tower Reflector Tower 13

14 Testing the MMD technique with a synthetic tracer release The The MMD technique was was tested using a synthetic tracer (CH (CH 4 ) 4 ) release to to simulate on on farm farm release by by cattle. Methane recovery slightly exceeded methane release and and was was found that that it it could identify 10% 10% changes in in the the rate rate of of emission, provided the the rate rate of of emission was was greater than than about mg mg CH CH 4 s ,, equivalent to to roughly dairy cattle. 14 Source: Desjardins et al. (2004)

15 Micrometeorological tools: Inverse Dispersion Modeling Measuring Measuring emissions emissions is is about about relating relating concentration concentration observations observations (C) (C) to to emission emission rates rates (Q). (Q). Inverse-dispersion Inverse-dispersion methods methods use use atmospheric atmospheric dispersion dispersion models models to to make make thec-q thec-qconnection: Measure Measure downwind downwind C Model Model estimates estimates C-Q C-Qrelationship for for given given winds winds & source source configuration configuration Q Q = Measured Measured C ** Model Model (Q/C) (Q/C) Gives Gives substantial substantial economy economy & flexibility flexibility especially especially with with open-path open-path sensors sensors bls bls is is a a widely widely used used variant variant of of the the inverse-dispersion inverse-dispersion method method 15

16 Measurement Tools Open path lasers Boreal Boreal Laser Laser GasFinder or or PKL PKL Spectra-1 open open path path lasers lasers for for measurement of of CH CH 4 and 4 and NH NH 3 emissions 3 from from agricultural sources (e.g. (e.g. feedlots, barns, barns, manure tanks, tanks,....)) Lasers operate in in the the NIR NIR (1,300 (1,300 to to 1,700 1,700 nm) nm) with with a spectral width width of of about about nm nm Approximate sensitivity for for m path path length length CH CH 4 : 4 : ppm; ppm; NH NH 3 : 3 : ppm ppm Path Path length length of of up up to to 1 km, km, depending on on target target gas gas 16

17 Estimating CH 4 emissions from synthetic barn release Wind Barn The area of the experimental barn is approximately 520 m 2 (40 m 13 m), and its height is 6 m (H). #1_3D #2_3D The barn-laser distance will vary as a function of H to determine if there is an optimal measurement distance from the barn. Canada The measurement heights of the lasers is 1.5 m and the lengths of the laser paths are 200 m. 17

18 Preliminary results of barn release in Qbls/Q Recovery h 10h 15h 20h 25h Fetch The The flux flux rates rates from from the the barn barn were were L/min L/min (140 (140 dairy dairy cows) cows) and and L/min. L/min. The The criteria criteria of of the the model model for for u *,Land *,Land z 0 were 0 were met. met. The The barn barn height height h was was 6 m. m. 18

19 Continuous Measurement of Gas Emissions N Laser1 PC1 CSAT Beam 1 Beam 2 Reflector 2 Reflector 3 Beam 3 Tubing Release grid Mass flow controller CH 4 tank Laser2 Set-up: Set-up: 2-lasers mounted on on computer controlled pantiltilt aiming aiming systems, each each pan- monitor monitor two two sides sides of of a rectangular area area Concentration can can be be monitored for for all all wind wind directions, making making continuous measurements possible Beam 4 PC2 Reflector 1 Reflector m Scale Source: Gao et al. (2009) 19

20 Influence of Atmospheric Stability on Gas Recovery Ratios Periods of extreme atmospheric stability/instability and are unsuitable for use in the model * L = Monin-Obukhov length 20 Source: Gao et al. (2009)

21 Estimating Diurnal Patterns of Emission for CH 4 Periods of of low low wind wind velocity or or atmospheric stability mean mean that that not not all all measurements will will be be acceptable This This is is more more common at at night night Continuous measurement over over a period period of of 6 days days should should yield yield sufficient data data to to generate the the diurnal diurnal curve curve of of emissions Ratio of usable period to total periods in Ottawa, Canada 21 Source: Gao et al. (2009)

22 Estimating Methane and Ammonia Emissions from a Beef Feedlot Set-up: Set-up: Lasers and and reflectors are are established in in the the alley alley of of a large large (500m (500m x 2,500m; 32,000 32,000 head head capacity) beef beef feedlot feedlot Canada 22

23 Estimating Methane and Ammonia Emissions from a Beef Feedlot Methane emissions represent about 4% of Gross Energy Intake by cattle. IPCC default number is 3% Ammonia emissions represent about 72% of nitrogen intake. Source: van Haarlem et al. (2008) 23

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25 Tower-based Flux Measurements Air Intakes Sonic anemometer F g = K ρ z g Closed-Path Tunable Diode Laser 25

26 Nitrous oxide emissions measured in 1996 over a soybean field in Ottawa Canada, using a tower-based system 200 N2O Flux (ng N2O m -2 s -1 ) Feb 1 Mar 1 Apr 1 May 1 Canada 26

27 Tower based N 2 O flux estimates over spring wheat, Tower - Spring wheat 200 N 2 O Emissions (g N2O-N ha -1 d -1 ) Canada 0 15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun Source: Desjardins et al (2009)

28 Hourly binned estimates of N 2 O flux above a fertilized corn field, grouped by day of year Canada 28 Source: Pattey et al. (2006)

29 Relaxed Eddy Accumulation (REA) Technique Alternate Alternate to to eddy eddy covariance covariance technique technique to to measure measure fluxes fluxes of of trace trace gases gases for for situations situations where where fast-response fast-response analyzers analyzers are are unavailable unavailable Air Air samples samples from from updrafts updrafts and and downdrafts downdrafts are are collected collected in in two two separate separate reservoirs reservoirs for for later later analysis analysis In In EA, EA, sample sample flow flow rate rate is is proportional proportional to to w; w; this this requirement requirement is is relaxed relaxed in in REA REA (i.e., (i.e., full full flow flow into into up up or or down down reservoir reservoir depending depending on on the the direction direction of of the the vertical vertical wind) wind) Fχ = w' χ' = Aσw( χ Up χ Down) Diaphragm Pump 12 l/min Relief valve 2-µm Filter Mass-Flow Controller 3-way Valve UP PTFE Sample Bag Inlet ¼ PTFE tubing DC Power supply Vent (Dead band) DOWN 29

30 Comparison of EC and REA Flux Estimates of CO 2 CO2 Flux (REA) (mg CO2 m -2 s -1 ) F REA = (0.84 +/- 0.10) F EC - (0.03 +/- 0.05) R 2 = Forest and agricultural fields Stainless steel canisters, with in-line magnesium percholate to to remove water CO 2 Flux (EC) (mg CO 2 m -2 s -1 ) 30

31 Relaxed eddy accumulation instrumentation Aircraft REA system Laboratory TDL Laser Diaphragm Pump 12 l/min Relief valve 2-µm Filter Mass-Flow Controller 3-way Valve UP PTFE Sample Bag Inlet ¼ PTFE tubing DC Power supply Vent (Dead band) DOWN 31

32 Resolution of the REA system for N 2 O flux measurement FN 2 O = ρ N2O 0.56 σ w dn 2 O dn 2 O (pptv) σ w = 0.3 m s -1 σ w = 0.9 m s g N 2 O-N ha -1 d Mean: pptv SD: 5.2 pptv dn 2 O = up - down (pptv)

33 Crop types in the aircraft footprint LEGEND cereals pasture/grass N Casselman Morewood alfalfa forest soybean corn town 5 km 0 5 km 33

34 No Data Coniferous Forest Mixed Forest Broadleaf Forest Low Density Forest Bare Soil Corn Soybean Cereals Alfalfa Open Field Water Builtup Areas % of Average Footprint Wetland Land use information in 2001 within footprint of aircraft transects Casselman Morewood

35 N 2 O emissions during and right after snowmelt at the Eastern Canada study sites in N 2 O Emissions (g N 2 O-N ha -1 d -1 ) Casselman Morewood Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun Each Each data data point point represents represents the the average average of of 3 3 samples, samples, collected collected during during two two consecutive consecutive km km flight flight 35legs legs (total (total flight flight distance distance for for one one data data point point is is km) km)

36 N 2 O emissions right after snowmelt and after planting at the Eastern Canada study sites in Casselman Morewood 15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun N2O Emissions (g N2O-N ha -1 d -1 )

37 Multi-year comparison of aircraft and modeled estimates of N 2 O emissions Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun 15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun N2 O Flux (g N 2 O-N ha-1 d -1 ) 15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun 15-Mar 25-Mar 4-Apr 14-Apr 24-Apr 4-May 14-May 24-May 3-Jun 13-Jun 2000 DNDC Casselman

38 Multi-year comparison of N 2 O emissions: Summary of results Year kg N 2 O-N ha -1 Modeled estimated 2000 of Mar 21 to of N Apr 2 O 2 10 emissions are are on on average % 23% less 0.33 less than than the the 0.34 measured estimates of of N 2 O 2001 Mar 19 to Apr 27 2 emissions However, modeled 2003 Mar estimates 27 to only Apr 25 and only represent direct 1.87 direct emissions, whereas 1.34 using 1.44 using the the IPCC IPCC methodology indirect May 15 to indirect emissions Jun 12 are are about about 20% 20% of of total total emissions Measurement Period Mar 29 to Jun 4 Casselman* 1.77 Morewood * 1.29 DNDC * Measured using the aircraft-based REA method 1 Modeled by DNDC using the crop distribution for the Casselman flight track 38

39 Resolution of the REA system for CH 4 flux measurement FCH 4 = 0.56 σ w dch4 dch4(ppbv) σ w = 0.3 m s -1 σ w = 0.9 m s kg km -2 y Mean: ppbv SD: 0.31 ppbv dch 4 = up - down (ppbv)

40 Estimating regional scale methane emissions For For each each geo-referenced geo-referenced barn barn location, location, there there is is an an estimate estimate of of animal animal type, type, population population and and manure manure management management system system Canada Geo-referenced Geo-referenced database database from from which which to to estimate estimate methane methane emissions emissions 40

41 Estimated Agricultural CH 4 Emissions Canada 41

42 Regional CH 4 Emissions, 2003 and 2004 Date CM MW CM MW Aircraft REA Estimate Barn Estimate within flux footprint *) Sept. 3, 2003 Sept. 18, 2003 Jul. 21, 2004 Oct. 8, 2004 kg CH 4 km -2 yr -1 kg CH 4 km -2 yr Avg *) Results calculated using the backward Lagrangian stochastic model of Kljun et al. (2002) 42 42

43 Summary Several examples were presented of of laser based techniques to to measure CH CH 4 and 4 and N 2 O 2 emissions from from agroecosystems These techniques allow measurements for for scales ranging from from point sources to to regions First example of of verification of of GHG inventory at at a regional scale using the the relax eddy accumulation technique- The The measurements show that that N 2 O 2 and and CH CH 4 emission 4 estimates in in the the Canadian GHG inventory appear to to be be realistic There is is a need to to improve upon the the accuracy of of the the methane concentration measurements. There is is also also a need to to obtain more regional flux flux measurements to to better capture the the diurnal and and annual cycles 43

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