Gas Sensing – Monitoring Agricultural Methane Emissions

Shutterstock | irin-k

The second most prevalent greenhouse gas emitted as a result of human activities is methane (CH4). In 2014, CH4 accounted for 11% of all US greenhouse gas emissions, and the majority of these emissions were the result of agriculture.

Methane is emitted from a wide range of natural sources including marshlands, livestock farming, and leakage from natural gas systems.1 Domestic livestock including sheep, goats, and cattle produce substantial amounts of CH4 due to the normal digestive processes in the ruminant stomach system.

Bacteria are present in gastrointestinal systems of ruminant animals, such as cattle, to help the breakdown of plant material. Some of the microorganisms (methanogens) use the acetate available from the plant material to produce methane.1,2

Whenever the animal defecates or eructates (burps), it simultaneously emits a substantial amount of methane. Rotting animal manure stockpiled for use by farms in fertilizing fields can be another potent source of the gas. From a global perspective, agriculture is the chief source of CH4 emissions, and methods to measure the effect and reduce the overall emissions are constantly being made.3

The Environmental Impact of Methane

Methane is an active part of the carbon cycle but the natural processes in soil and chemical reactions in the atmosphere that help to remove it from the environment are being overtaken by gas production and industrial-scale farming activities.4

In the atmosphere, methane has a lifetime that is much shorter than carbon dioxide (CO2), which is the best known greenhouse gas and lasts for about 12 years. However, CH4 traps radiation more efficiently than CO2.5 Over a hypothetical 100-year period, the impact of CH4 on climate change is over 25 times more than CO2.

Methane produces a dominant greenhouse gas effect, and approximately 44% of anthropogenic livestock emissions (3.1 Gigatonnes CO2 equivalents in a year) are in the form of CH4.

The rest of the emissions are shared between nitrous oxide (N2O, 29%) and carbon dioxide (CO2, 27%). Methane is more devastating to the climate than CO2, although it doesn't remain in the atmosphere for as long. For effective reduction of the impact of climate change, CO2 and CH4 emissions must be addressed.6

Methane has a 25 times greater impact on climate change than CO2. Shutterstock | JeffreyRasmussen

Monitoring Agriculture Methane Levels

It is well known that dairy and beef herds are important producers of CH4. Protracted experiments involving a cow in a respiration chamber have to be conducted for several days to accurately determine the amount of the CH4 produced. One method being developed is the use of gas sensors in cow sheds and milking parlors to monitor the CH4 produced by animals over a set time.

Although the respiration chamber is the benchmark, the gas sensor technique provides accurate and quick estimates of CH4 emissions which, in contrast to a respiratory chamber, do not disrupt agricultural activities.7

The emission measurements are generally made during ‘milking’, which is done 3 – 6 times daily. The data is invaluable for developing methane-reducing diets and identifying low emission cow species.

Recently, researchers at the University of Queensland, Australia, have investigated the development of a vaccine from Kangaroo stomach bacteria against methane-producing bacteria in ruminant digestive systems, as kangaroos do not produce stomach methane.8,9

On-farm monitoring has the potential to decrease uncertainty, or at least to quantify sources of variation, and to test the outcomes of mitigation strategies, by measuring indicators of emissions under commercial conditions [10,11].

Professor Philip Garnsworthy, School of Biosciences, University of Nottingham

Cattle are a significant source of agricultural methane emissions. Shutterstock | andaq

Case Studies on Agricultural Methane Monitoring

In 2012, a study was conducted involving 82 cows in a commercial farming environment to determine the amount of CH4 emissions from individual cows using a unique method to sample the air released by eructation of cows during milking.12 The CH4 emission rate was estimated using methane released per event and eructation frequency.

The Guardian Plus, a single infra-red methane analyzer with a range of 0 to 10,000 mg/kg was used to measure CH4 concentrations for each milking station. An integral pump between the analyzer and the gas inlet port was used to draw air through the instrument.

It was observed that there was a good correlation between in situ infra-red measurements and benchmark respiration chamber measurements.13 The study also established the validity of the IR method by making a comparison of cows fed on a high methane diet with a control group fed on a normal diet.

Another 2012 study involving 215 cows analyzed the CH4 emission rate during milking for a five-month period using automatic gas analyzers in milking stalls.14 The study provided additional validation to the non-invasive IR gas analysis procedure and also compared CH4 production from various cow species fed on different diets.

IR gas analysis is useful and inexpensive, and quickly provides accurate measurements for CH4 from ruminants.15

The Gascard NG from Edinburgh Sensors

The Gascard NG for Agricultural Gas Monitoring

A perfect adjunct to any automatic gas detection system to measure CH4 levels during milking is the Gascard NG Infrared Gas Sensor. If required, the sensor can be used with other gas detection technologies.

The Gascard NG infrared gas sensor can be easily integrated with gas detection systems that require accurate, high quality and reliable measurement of concentration of common gases including CH4, CO2, and CO.

The system is flexible and incorporates many important features including:

  • Real-time temperature compensation
  • On-board barometric pressure correction in the 800 – 1150 mbar range
  • True on-board RS232 communications as well as the option of TCP/IP communications protocol
  • Operating voltage from 7 – 30 V
  • Field serviceable IR source

The Gascard NG employs a patented dual wavelength infra-red (NDIR) sensor technology, which offers accurate pressure and temperature compensation for CH4 gas levels, consistency of measurement, and compatibility with other data handling systems.

The Gascard NG is reliable, robust, and accurate, and is a perfect IR sensor for farm environment use.

Download the Gascard NG Brochure for More Information

References

  1. Gerber, P.J., Steinfeld, H., Henderson, B., Mottet, A., Opio, C., Dijkman, J., Falcucci, A. & Tempio, G., 2013. Tackling climate change through livestock – A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO), Rome.
  2. EPA (2010). Methane and Nitrous Oxide Emissions from Natural Sources. U.S. Environmental Protection Agency, Washington, DC, USA.
  3. Methane: The other important greenhouse gas, https://www.edf.org/methane-other-important-greenhouse-gas Accessed 13/12/2016
  4. Zhou, Yiqin (2011). Comparison of Fresh or Ensiled Fodders (e.g., Grass, Legume, Corn) on the Production of Greenhouse Gases Following Enteric Fermentation in Beef Cattle. Rouyn-Noranda, Qué.: Université du Québec en Abitibi-Témiscamingue. N.B.: Research report.
  5. FAO (2006). Livestock's Long Shadow–Environmental Issues and Options. Rome, Italy: Food and Agriculture Organization of the United Nations (FAO). Retrieved October 27, 2009.
  6. IPCC AR5 WG1 (2013). "Climate Change 2013: The Physical Science Basis - Anthropogenic and Natural Radiative Forcing Supplementary Material" (PDF). Cambridge University Press
  7. Bell MJ, Potterton SL, Craigon J, Saunders N, Wilcox RH, Hunter M, Goodman JR and Garnsworthy PC, 2014. Variation in enteric methane emissions among cows on commercial dairy farms. Animal: An international journal of animal bioscience. 8(9), 1540-6
  8. Rachel Nowak (25 September 2004). "Burp vaccine cuts greenhouse gas emissions". New Scientist. Retrieved 4 November 2011.
  9. A.D.G. Wright, et al., Reducing Methane Emission in Sheep by Immunization against rumen methanogens, Vaccine (vol 22, p 3976- 3985
  10. Bell MJ, Saunders N, Wilcox RH, Homer EM, Goodman JR, Craigon J and Garnsworthy PC, 2014. Methane emissions among individual dairy cows during milking quantified by eructation peaks or ratio with carbon dioxide. Journal of dairy science. 97(10), 6536- 46
  11. AO. 2010. Greenhouse Gas Emissions from the Dairy Sector: A Life Cycle Assessment. Food and Agriculture Organization of the United Nations, Rome, Italy.
  12. P. C. Garnsworthy , J. Craigon , J. H. Hernandez-Medrano , and N. Saunder, On-farm methane measurements during milking correlate with total methane production by individual dairy cows, J. Dairy Sci. 95 :3166–3180
  13. Gardiner, TD, Coleman, MD, Innocenti, F, Tompkins, J, Connor, A, Garnsworthy, PC, Moorby, JM, Reynolds, CK, Waterhouse, A and Wills, D, 2015. Determination of the absolute accuracy of UK chamber facilities used in measuring methane emissions from livestock Measurement. 66, 272-279
  14. P. C. Garnsworthy , J. Craigon , J. H. Hernandez-Medrano , and N. Saunders, Variation among individual dairy cows in methane measurements made on farm during milking, J. Dairy Sci. 95 :3181–3189
  15. Methane and Climate Change, edited by Pete Smith, David Reay, Andre Van Amstel, 2010, Earthscan

This information has been sourced, reviewed and adapted from materials provided by Edinburgh Sensors.

For more information on this source, please visit Edinburgh Sensors.

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