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Development of an Automated System for Greenhouse and Nitrogen Gas
Flux Determinations from Compost J. Rutter1*, M. Tenuta1, M. Gervais1
1Department of Soil Science, University of Manitoba, Winnipeg, MB R3T 2N2
Greenhouse (CO2, CH4, N2O) and nitrogen (NH3, NO,
NO2) gas fluxes during composting of animal wastes can be
considerable. Characterizing these emissions can lead to
understanding the microbial processes and compost
practices to reduce greenhouse and nitrogen gas losses.
Static vented chambers do not lend themselves to
determination of fluxes of all these gases and do not
provide sufficient coverage of temporal variation.
To improve gas flux estimations from compost
windrows we evaluated the effectiveness of combining a LI-
8100a automated chamber system (LICOR BioSciences)
and Fourier Transform Infrared Spectroscopy (FTIR) multi-
gas analyzer (Gasmet DX4015) in series to allow frequent
automated simultaneous gas flux measurements.
Soil Ecology Laboratory at The University of Manitoba
Biota
Management
Environment
Sommer, S.G., McGinn, S.M., Hao, X., Larney, F. J. 2004. Techniques for measuring gas emissions from a
composting stockpile of cattle manure. Atmospheric Environment, 38, 4643–4652.
For additional information or updates please contact Jolene Rutter at [email protected] or Mario Tenuta at [email protected]
Reference
Introduction System Setup Linear Gas flux Determinations
Conclusions The system was effective at simultaneously collecting and
measuring gas concentrations from multiple gases. Linear gas fluxes
can be calculated for all the gases except NH3.
The high frequency of flux estimation allowed determination of
underestimation of fluxes due to lateral wind.
After resolution of NH3 fluxes and wind effect the system should
be an effect tool to research best management methods for windrow
composting.
FTIR Linear gas fluxes (F) were estimated in g-C or
N m-2s-1 and calculated from:
Where:
A = surface area of the chamber collar
∆t = time of estimation period
∆C = change in gas concentration* during
estimation period
* Ideal gas law converts ppm to g-C or g-N
Used for CO2, N2O, CH4, NO, and NO2 gases.
Gas Flux Underestimation Caused by Wind
Obs Post Purge
17 mins 3
mins 10 mins
NH
3 C
on
ce
ntr
atio
n
Pre-Purge Scenario Description
1
Rise in NH3 conc. delayed 10-30
seconds, observation time 3
minutes.
2
Rise in NH3 conc. delayed 10
seconds, rapid rise when chamber
opens.
3 Rise in NH3 conc. delayed 3
minutes (until chamber opens).
4
Decrease in NH3 conc. until
chamber opens. NH3 conc.
increases to background levels
Ammonia Flux Determinations
Total estimation time =
4 measures = 30-36
seconds (Figure 3).
FTIR stores
concentration
measures every
10.5 s on average.
Estimation time
delimitated using
Microsoft Excel Macro. Figure 3. Example of ∆C/∆t used in linear flux calculation.
Ammonia increases were not always linear due to interactions with surfaces. Four NH3 response scenarios
were observed (Figure 4). Ammonia fluxes need to be calculated using other approaches (ex. mass balance).
Figure 4. Description and examples of ammonia flux scenarios.
Figure 6. Relation of CO2 flux from a straw-based compost pile
versus wind speed during October 18-22, 2012. Figure 5. Chamber and anemometer setup at field site.
Chambers were setup on top of windrows to capture
preferential gas emissions due to “chimney effect” (Figure
5). Frequent flux estimations allowed identification of
underestimated gas fluxes due to lateral wind causing
gases emissions from the sides of the windrow (Sommer
et al., 2004). Figure 6 shows how high wind speed
correlated with decreased CO2 flux.
Options for correcting for wind speed are being considered
such as:
1) Remove gas fluxes above wind threshold
2) Adjust fluxes based on wind/flux relationships
A LI-8100a automated chamber system and FTIR was
used in series to create a closed loop system that
collects and measures the accumulation of gas emitted
from the compost windrow when the chamber is
deployed (Figure 1).
Our system is capable of using 8 chambers and
collecting a flux measurement from one of those
chambers every 30 minutes. This time interval allows for
a 17 minute pre-purge, 3 minute chamber deployment
and 10 minute post-purge (Figure 2).
The chamber was deployed for 3 minutes to allow
enough time for air in the system to mix and for the
FTIR to measure 4 concentration points for the flux
calculation. The purge-time was necessary to purge the
NH3 from the internal surfaces of the system.
Figure 1. LI-8100a automated chamber system and FTIR connected in series.
Figure 2. Time sequence of two chamber deployments.
Chamber
Status:
Deployed Open
Funding Support