Measuring Nitrous Oxide and Methane from Feedlot Pen Surface: Experience with NFT-NSS Chamber Technique

Ken Casey1, Heidi Waldrip2, Rick Todd2, Andy Cole2

1 Texas A&M AgriLife Research – Amarillo, TX2 USDA-ARS CPRL – Bushland, TX

Feedlot GHG Emissions• Emissions inventory is dominated by Enteric emissions.• Emissions inventory for the feedlot manure

management system is dominated by methane in mass terms but by nitrous oxide in CO2e terms.– Little research has been undertaken on CH4 and N2O

emissions from feedlot manure management systems and particularly under climatic conditions and management strategies representative of the major US cattle feeding region.

• IPCC Workbook (& EPA Reporting Rule)– N2O Emission Factor = 0.02 N2O-N/kg Kjdl N excreted

Goals and Objectives• The overall goal is to develop a mechanistic understanding

of factors influencing the emissions of greenhouse gases from cattle feedyards.

Specific Objectives1. Examine the magnitude, spatial and temporal

variability of emissions of N2O and CH4 from the manure management system from cattle feedyards in the Texas High Plains.

2. Develop a functional understanding of the environmental variables that influence and control the emissions of N2O and CH4 from the manure management system from cattle feedyards in the Texas High Plains. Contribute this data to the developers of larger scale, process based models to improve their predictive capability for the conditions prevailing on typical cattle feedyards in the Texas High Plains.

Specific Objectives1. Examine the magnitude, spatial and temporal variability of

emissions of N2O and CH4 from the manure management system from cattle feedyards in the Texas High Plains.

2. Develop a functional understanding of the environmental variables that influence and control the emissions of N2O and CH4 from the manure management system from cattle feedyards in the Texas High Plains. Contribute this data to the developers of larger scale, process based models to improve their predictive capability for the conditions prevailing on typical cattle feedyards in the Texas High Plains.

GHG Emission Measurements• Non-Flow Through – Non-Steady State Chambers

– Widely used in soil and environmental science• Gracenet & other protocols

– Measure relatively small area• Influence of spatial and temporal variability

– Potential to influence emission rate if poorly conducted• Chamber environment (T & BP)• Chamber base installation• Chamber base effect

– Non-real time measurements• Gas Chromatograph

– Automated Chambers• Real time measurements

– Gas Chromatograph– FTIR Spectrometer– Closed path Tuned Diode Laser– Cavity Ring Down Spectrometer– Quantum Cascade Laser

• Area integrating measurement techniques– Open-Path measurements

• OP-FTIR Spectrometer

– Eddy Covariance• Closed path Tuned Diode Laser• Cavity Ring Down Spectrometer• Quantum Cascade Laser

Non-Flow Through – Non-Steady State (NFT-NSS) Chambers

NFT-NSS Chamber Measurements

• Non-flow-through, non-steady-state (NFT-NSS) chambers (Hutchinson and Mosier, 1981) are used to sample GHG emissions from the feedyard pen surfaces.

• Greenhouse gas sampling measurements for all studies are performed starting at 12:00 h US Central Standard Time (CST).

• Ten chamber bases are installed in a recently emptied pen in two rows on a Friday afternoon

• GHG measurements are conducted from the following Monday to Friday for each study

• Four samples collected over 30 min period (0, 10, 20, 30)• Quadratic flux calculation procedure

NFT-NSS Chamber Measurements• Ten chamber bases are installed in a recently emptied

pen.• Emission rate varies spatially

• Greater chamber numbers yield a better average and allows exploration of different areas within pen

• Compromise with labor and resource availability• One operator can manage 10 chambers

• Recently Emptied Pen• Animals would disturb bases & chamber caps

and/or potentially be injured• Cannot practically ‘guard’ bases for any length of

time while animals are present

NFT-NSS Chambers

• 8 in. dia PVC Pipe Cap. • Septa equipped sampling port• 1/8 in. dia balance tube.

• 8 in dia steel pipe Base• Lower edge sharpened to aid installation• Installed 3 – 4 in. into manure pack• Rubber skirt rolled up to seal Cap to Base.

• GHG measurements were conducted from the following Monday to Friday for each study study.

NFT-NSS Chamber

Deployed NFT-NSS Chamber

NFT-NSS Chambers Installation

• Installation of bases can fracture soil, resulting in temporarily enhanced emissions

• Gracenet Protocol• Wait at least 24 hours before taking measurements

• Testing confirmed an enhanced flux following installation of chamber bases in feedlot pens• Wait at least 48 hours before taking measurements

• Chamber bases are installed on a Friday afternoon• GHG measurements are conducted from the

following Monday to Friday for each study

Installing Chamber Bases

Installing Chamber Bases

NFT-NSS Chambers Installation

• 8 in dia steel pipe Base• Installed 3 – 4 in. into manure pack

• Testing evaluated installation of chamber bases in feedlot pens• Steel pipe Base driven 3-4 in. into manure pack• Manure and/or sand piled around chamber• Plastic skirt w/wo weights attached to chamber

• Measured fluxes were higher and more consistent with driven bases –> leakage was occurring with other base systems

Flux Calculation Procedure

• Linear Regression (LR)• Quadratic Method (Quad)• Hutchinson and Mosier (H/M)• Pedersen HMR (HMR)• …udy.

Linear Response

Non-Linear Response

Methane and N2O flux rates were determined by fitting a quadratic regression equation to the measured concentrations at 0, 10, 20 and 30 minutes and solving for the slope at time

zero.

Typical Chamber Layout – 2 rows of 5

Pen#:L-15

FYD: A

Date Installed: 07-11-2014

Chamber # Soil condition Chamber position

1

2

3

4

5

6

7

8

9

10

N

5

3

× ×

Trou

gh

×

10

6

10 2020 40

195

80

1

92

4 5

6

31

31

Met Stn

Gas samples injected into evacuated 12 ml exetainers for storage, transport and analysis

Sample Storage

Vial Preparation

Gas concentration analysis was conducted on a Varian 450 gas chromatograph with a CombiPal auto-sampler equipped with a flame ionization detector for CH4, an electron

capture detector for N2O and a thermal conductivity detector for CO2.

Measured gas concentrations – 1000+ analyses from chambers in cropping and rangeland

Measured gas concentrations – 4400 analyses from chambers in feedyards and dairies

GHG Calibration Standards

GHG Calibration Issues

• Electron Capture Detectors (N2O) are not linear• May be treated as linear by some analysts

over limited range.• A lab running cropping samples may not

know their linear range!• Our system is linear up to about 10 ppm

• Analyze using low range calibration curve• Reprocess any chromatograms with

indicated concentration > 10 ppm

System Minimum Detection Limits and Fluxes

Summary Outcomes• Unique Issues in measuring GHG emissions from waste• Small ‘insignificant’ variations from protocol turn your

results to ‘manure’!• Good measurement strategy and equipment• Sample collection and storage• Sample analysis

• Know your system MDL• Know your concentration range

• Flux calculation• Temporally Variable Results• Large influence of rainfall events• Fast response to changing microclimate• Challenges in data analysis study.

Questions?