Methods to estimate NH3 emission from field-applied cattle slurry

I. Wind tunnelsII. Micrometeorological methods

III. Passive samplersIV. Flux chambers

V. Apparent herbage N recovery

Egbert LantingaCiska Nienhuis

Contact: egbert.lantinga@wur.nl

Wind tunnels (Misselbrook et al. 2005)

• the turbulence of the air drawn through a wind tunnel may be quite different from that in an ambient situation -> differences in resistance to NH3 emission at the manure surface

• wind tunnels measure emission from a 2 m long plot of land, which in effect, might be considered to be the edge of a manure-applied field.

• clean air entering the upwind edge -> less resistance to emissions -> increased NH3 emission

Field: Ferm et al. (2000)

NH3 concentration at 20 cm height: ~ 1/10 * Ceq

Wind tunnel (2010)

NH3 concentration at 20 cm height: ~ 1/500 * Ceq (~ 50 times lower!)

Sommer (2003)

Overestimation wind tunnel: about a factor 2

Sintermann (2012)

Wind tunnels * ½ ->

Conclusion I

Ammonia fluxes measured in wind tunnels (forced inflow of clean air; very small emitting area) are per definition higher than will take place in the open field

Recommendation 1: field area around the tunnel should also be manured -> more realistic NH3 content of the inlet air -> lower NH3 emission: new field experiment

Effects of wind speed and radiation(Sommer 2003)

Effects of temperature and wind speed (adapted from Schjoerring et al. 1993)

17.51512

.5107.55

11.5

22.5

33.5

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57.5

7.510

1012.5

12.515

1517.5

17.520

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ammonia.prn, X , Y , Z Rank 22 Eqn 2147 z=EXPX(a,b)*EXPY(1,b)

r^2=0.92349514 DF Adj r^2=0.8724919 FitStdErr=2.3195267 Fstat=48.284261a=0.93530461 b=-6.9231236

T (oC)

WS (m/s)

NH3 emissionmicrogr NH3-N / m2.s

Conclusion II

- No clear effects of wind speed on NH3 emission in the open field: interaction with temperature and incoming solar radiation

[Various literature sources: at increasing turbulence intensity of the air not more than about a doubling of the NH3 emission]

Micrometeorological methods

- Mass balance method- Integrated horizontal flux method

(r is the fetch)

As far as we know only two in-situ validations have been carried out:- from beakers with NH4+/HCO3- solution- from an artificial NH3 gas source

Schjoerring et al. (1992): comparsion of direct (from beakers) and indirect measurements (MBM)

M

Mass balance method: ~ 50 % lower established NH3 losses

Mobile Lidar SystemBerkhout et al. (2008)

Conclusion IIITwo evaluations of the MBM in the field with artificial NH3 sources (known released amounts) revealed that there were great inconsistencies:- case 1: 50% underestimation (deposition?)- case 2: 50% overestimation (no possible explanation)

Calculation procedure MBM:- assumption 1: horizontal transport of NH3 at the rate of the wind

speed- assumption 2: calculated NH3 emission dependent on the fetch

(e.g. no significant change in concentration profile central mast with distance -> when fetch * 2 -> ammonia emission * ½ )

- assumption 3: no vertical NH3 emission along the fetch above the height of the central mast

Passive flux samplers (Winsum 2012): height 20 cmfetch 100 – 150 m (point 1 close to field border upwind)

Conclusion IV

- Over distances of a few tenths of meters on average only a small increase in NH3 concentration at a sampling height of 20 cm from the border of the manured grassland field (measuring point 1)

- MBM will therefore calculate relatively very low NH3 emissions between points 1 and 2

- NH3 emission becomes insignificant after 2-6 hours

INNOVA: response time for NH3-> time delay

INNOVA 1412: verification for NH3 and CH4-> time delay for NH3

INNOVA: time pattern of initial NH3 emission rate (factor 2 difference in NH4 application rate)

Static flux chamber (INNOVA)The Green Duo

E

NH3 emission factor ~ 1%Underestimation (absence turbulent wind, time delay INNOVA, gaseous interferences) : multiplication with 7Upscaling to aboveground application: multiplication with 3/2 NH3 emission factor still low (~ 10%)

Initial NH3 emission rates should be ~ 50 times higher to achieve an emission factor of 74%: this is impossible !

<- Ceqtime (h)

Conclusion V

• After taking into account one published underestimation of a factor 7 by using static flux chambers still yields a low NH3 emission factor in our experiments for aboveground applied cattle slurry (max. 10%)

• Also here NH3 emission became insignificant after 6 hours

Laboratory slurry 15N experiment: soil cores with grass sward (Chadwick et al. 2001; 8 days)

N balance Surface-applied InjectedNH3 emission 15% 11%Grass 7% 2%Soil – inorg N 24% 55%Soil – org N 6% 8%Unaccounted for 48% 24%

“Lost” N: emissions of N2, N2O and NOx(represented almost 50% of the applied inorganic N!)

Schils & Kok (2003)

Grassland fertilisation experiment on two sandy grassland farms:Apparent Herbage Nitrogen Recovery

Conclusion: aboveground applicationof slurry manure in March –low temperatures- did not lead to significant gaseous N emissions

Conclusion VI

• Surface application: much higher gaseous N losses other than NH3 compared to injection

• After field application in early spring (low temperatures) no difference in the fraction of N recovered in the harvested herbage between the two application methods -> very low NH3 emissions

Three-dimensional characterization of the ammonia plume from a beef cattle feedlot (17,220 head)

Ralf M. Staebler et al. (Atm. Environm., 2009)

Conclusion: within a distance of 4 km from the farm more than 50% of the emitted NH3 has reached a vertical height of more than 135 m

<----------------->Vertical flux

Conclusion VII

Also above manured fields the greatest proportion of the emitted NH3 will escape in vertical direction

However, due to the very low emission levels compared to livestock barns this is difficult to detect

Recommendation 2: two field experiments to evaluate the MBM with (i) a row of at least three high sampling masts along the fetch and (ii) diffusive samplers behind manured plots of diverging lengths

Relationship between atmospheric ammonia concentration and total N yield of unfertilized barley plants (spring-summer 2011: period of 80 days)

Dry NH3 deposition: average NH3 compensation point as determined with biomonitors (method: Sommer, 1988)

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Leith, Scotland (Deschampsia f.)

Sommer, Denmark (Lolium m.)

NH3 compensation point :In the order of 10-15 microgramper m3

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Mts. Duiven (west of Dwingelderveld): 600 dairy cows (no grazing)

NH3 concentrations OPS-model included with background concentrationDry deposition NHx OPS-model included with background depositionPower (Dry deposition NHx OPS-model included with background deposition)Dry deposition NHx based on biomoni-torsLogarithmic (Dry deposition NHx based on biomonitors)

Distance to source (m)

NH3

[µg

m3]

kg--1

ha-

1 yr

-1

Dry deposition OPS model vs. measurements:- Underestimated around the livestock barns (< 300 m)- Overestimated away from the farm (> 400 m: undetectable )

Recommendation 3:Continuation, also including“Natura 2000” areas with mosses

Conclusion:OPS model has a number ofshortcomings -> overestimationof dry N deposition in “Natura2000” areas

1985 1990 1995 2000 2005 2010 20150

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4

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atmospheric NH3-conc

Manure-N - 30%

- 25%

The Netherlands 1990-2012

Overall: good correlation

Conclusion: adaptations in manure application techniques and housing systems since 1990 have not contributed to the observed decrease in atmospheric NH3 concentrations ; only thedecrease in the total amount of excreted N by the Dutch livestock sector played a role

- 40%

1990-1998: - 55% (but no effects on atmospheric NH3 concentrations!)