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 jolene_rutter@hotmail.com or Mario Tenuta at mario.tenuta@umanitoba.ca

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