INTRODUCTION

PROGRESS REPORT ON THE DEVELOPMENT & HIGH-PRECISION METHANE MEASUREMENTS WITH LOW-POWER LOW-MAINTENANCE CLOSED-PATH CH4-CO2-H2O GAS ANALYZER

I. Begashaw1, M. Johnson1, A. Komissarov1, W. Miller1, K. Skolaut1, D. Trutna1, R. Walbridge1, J. Welles1 and G. Burba1,2*

1LI-COR Biosciences, Lincoln, Nebraska, United States; 2School of Natural Resources, University of Nebraska-Lincoln, United States, *Corresponding author: george.burba@licor.com

KEY APPLICATIONSNEW TECHNOLOGY & EXPECTED SPECIFICATIONS

LI-COR is a registered trademark of LI-COR, Inc. All other trademarks belong to their respective owners

REFERENCES

This new technology enables amultitude of methods and approaches:

i. Approaches relying on very highprecision CH4 concentrations, oftenemployed by WMO-GAW and EPAcommunities: a family of the InverseFlux Methods, Lagrangian Modeling,Mass Balance Method, Fence-LineMonitoring, etc.

ii. Chamber flux measurements,including both CH4 and CO2 fromthe same gas analyzer

iii. Micrometeorological tower methodsrelying on slow well-resolved CH4,such as Disjunct Eddy Covariance,Eddy Accumulation, Aerodynamic,Resistance, Integrated Horizontal Flux,ControlVolume, Bowen Ratio, etc.

iv. Distributed sensors techniquesbeing currently developed forMegacities/ Green Cities projects

v. Mobile flux monitoring and CH4mapping from moving platforms

vi. Eddy Covariance method fromtowers taller than about 10 m whenlong intake tubes are deployed

Closed-path LI-7810 OF-CEAS technology:

Optical Feedback Cavity Enhanced Absorption Spectroscopy [2-12]

Continuous deployment Infrequent calibrations Relatively low cost

CH4: 0.1-50 ppm CO2: 1-10000 ppm H2O: 100-60000 ppm

Operating T: -25 °C to 45 °C Operating P: 70-110 kPa Response (10-90%): 1-2 s

Flow rate: 280 cc min-1

Cell volume: 6.41 cm3

System volume: 15.8 cm3

Power: 15-20 W nominal Internal battery: 6 hrs

continuous operation Weight: 9 kg Size: 51x18x33 cm

Wireless† & Ethernet Embedded web server Data Storage: ≈ 1 moǂ

Low field maintenance: pre-filter, chemicals, pump

Low factory service costs

ACKNOWLEDGEMENTSThe initial principles and some portions of the new technology presented hereinwere developed in part based on the grants from the U.S. DOE Office of Scienceunder the award numbers DE-FOA-0001019 and DE-FOA-0000760, and from theU.S. DOE Advanced Research Projects Agency-Energy (ARPA-E) MONITORProgram under the award number DE-AR0000537

Beta-version of the LI-7810 model

[1] WMO, 2016. WMO-GAW Report No. 229, World Meteorological Organization,Geneva, Switzerland

[2] Motto-Ros, V., Durand, M. and Morville, J., 2008. Extensive characterizationof the optical feedback cavity enhanced absorption spectroscopy (OF-CEAS)technique: ringdown-time calibration of the absorption scale. Applied PhysicsB, 91(1), pp.203-211.

[3] Romanini, D., Ventrillard, I., Méjean, G., Morville, J. and Kerstel, E., 2014.Introduction to cavity enhanced absorption spectroscopy. In Cavity-EnhancedSpectroscopy and Sensing (pp. 1-60). Springer, Berlin, Heidelberg.

[4] Kachanov, A. and Koulikov, S., LI-COR Biosciences, 2014. Cavity EnhancedLaser Based Gas Analyzer Systems and Methods. U.S. Patent 8,885,167

[5] Koulikov, S. and Kachanov, A., LI-COR Biosciences, 2014. Cavity EnhancedLaser Based Isotopic Gas Analyzer. U.S. Patent 8,665,442

[6] Koulikov, S. and Kachanov, A., LI-COR Biosciences, 2014. Laser based cavityenhanced optical absorption gas analyzer with laser feedback optimization.U.S. Patent 8,659,758.

[7] Kachanov, A. and Koulikov, S., LI-COR Biosciences, 2015. Cavity enhancedlaser based gas analyzer systems and methods. U.S. Patent 9,194,742

[8] Koulikov, S., LI-COR Biosciences, 2015. Systems and Methods for Controllingthe Optical Path Length Between a Laser and an Optical Cavity. U.S. Patent9,116,047

[9] Kachanov, A. and Koulikov, S., LI-COR Biosciences, 2016. Cavity enhancedlaser based gas analyzer systems and methods. U.S. Patent 9,304,080

[10] Koulikov, S. and Kachanov, A., LI-COR Biosciences, 2017. Cavity EnhancedLaser Based Isotopic Gas Analyzer. U.S. Patent 9,678,003

[11] Koulikov, S. and Kachanov, A., LI-COR Biosciences, 2017. Cavity EnhancedLaser Based Isotopic Gas Analyzer. U.S. Patent 9,759,654

[12] Koulikov, S., LI-COR Biosciences, 2017. Systems and Methods for Controllingthe Optical Path Length Between a Laser and an Optical Cavity. U.S. Patent9,581,492

†Most but not all countries;

ǂLogging full dataset

Test of an early LI-7810 pre-prototype at ARPA-e facility

Design of the LI-7810 & LI-7815 sampling cell [4-12]

Upcoming CH4 & CO2 soil flux measurements with a SmartChamber

The major sources of CH4 includeagricultural and natural production,landfills, oil and gas development, andnatural gas distribution networks.

Agricultural & Natural CH4

Mostly occurs in areas with littleinfrastructure or grid power (e.g., ricefields, arctic, mangroves, etc.)

In the past, mostly relied on grid-powered closed-path analyzers orlow-power open-path analyzersrequiring maintenance every 2-4 weeks

Grid power and/or high maintenancemay be why CH4 is often measured ataccessible locations with power, andnot where the most CH4 is produced

Landfill CH4 Production

Traditionally assessed via point-in-time measurements taken at monthlyor longer time intervals

Subject to large uncertainties due tothe snapshot nature of such methods

Continuously operating CH4 stationin the middle of an active landfillrequires a low-power approach

Oil&Gas and Urban CH4 Emissions

Mostly variable-rate point sources ordiffused spots in challenging terrains

Locating sources and measuringemission rates is challenging usingtraditional micrometeorology

Most promising new methods includemobile mapping and distributedsensor networks

New Technology

In 2018, a new lightweight high-precision technology was developedaddressing the needs listed above

The goal was to allow cost-effectivelow-maintenance WMO-quality [1]measurements of CH4 in LI-7810model, and to do the same for CO2 inthe concurrent LI-7815 model

This presentation describes firstresults from LI-7810 prototypes

PRELIMINARY RESULTS

Expected Accuracy, Monthly Calibration

CH4: ≈2 ppb @ 2000 ppb, 25 °C CO2: ≈1.5 % @ 400 ppm, 25 °C H2O: ≈1.5 % @ 10000 ppm, 25 °C

Expected Precision (1s)

CH4: ≈0.5 ppb @ 5 s, 2000 ppb, 25 ° C CO2: ≈0.5 ppm @ 5 s, 400 ppm, 25 ° C H2O: ≈5 ppm @ 5 s, 10000 ppm, 25 °C

Expected Accuracy without Calibration

CH4: ≈7 ppb @ 2000 ppb, 25 °C CO2: ≈1.5 % @ 400 ppm, 25 °C H2O: ≈1.5 % @ 10000 ppm, 25 °C

Beta LI-7810: controlled lab settings

Calibration

Water Vapor Dilution

Beta LI-7810: controlled lab settings

Inst

rum

en

t C

H4, p

pm

Calibration Gas, ppm

Inst

rum

en

t C

H4, p

pm

H2O, %0.4 1.0 1.6

1988

1987

1986

Temperature, °C

CH4 Stability Across Wide Temperature Range

-10

-7.5

-5

-2.5

0

2.5

5

-30 -20 -10 0 10 20 30 40 50

2000 ppb 4180 ppb 7070 ppb 10010 ppb 25200 ppb

At 2 ppm CH4, the drift is <2.5 ppb across 68.4 °C

DC

H4

acro

ss t

he

T ra

nge

, pp

b

At 7 ppm CH4, the drift is <2.5 ppb across 68.4 °C

At 4.2 ppm CH4, the drift is <2.5 ppb across 68.4 °C

Beta LI-7810: lab, steady-state

OF-CEAS

CO2 Resolution

Beta LI-7810: lab, steady-state

WMO rec. for the Southern hemisphere,0.05 ppm [1]

Averaging Time

WMOrecommendation for compatibility

goal in the Northern

hemisphere, 0.1 ppm [1]

WMO expanded compatibility

recommendation,0.2 ppm [1]

sC

O2, p

pm

Beta LI-7810: lab, steady-state

CH4 Resolution

Better than WMOrecommendation for compatibility goal,

2 ppb [1]

Averaging Time

sC

H4, p

pb

CH4 & CO2 Stability at Constant Temperature

Beta LI-7810: lab, steady-state

Time, days

2040

2039

2038

0 2 4 6

1 ppb, 1 Hz

CH

4, p

pb

5 ppm, 1 Hz

1 3 75