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== SF6 ==
The SF6 technique samples breath over 24 hours, whereas other techniques use spot samples of breath over periods of minutes throughout the day, so diurnal variation has to be considered. The majority of CH<sub>4</sub> (87-99%) is released by eructation (Blaxter and Joyce, 1963<ref>Blaxter, K.L., and Joyce, J.P. 1963. The accuracy and ease with which measurements of respiratory metabolism can be made with tracheostomized sheep. Br. J. Nutr. 17:523-537</ref>; Murray et al., 1976<ref name=":0">Murray, R.M., Bryant, A.M., and Leng, R.A.. 1976. Rates of production of methane in the rumen and large intestine of sheep. Br. J. Nutr. 36:1-14.</ref>), which provides a clear signal for sample processing. Please note that the tracheostomy used in Murray et al. (1976)<ref name=":0" /> may have resulted in a higher percentage, but in both publications, it is clear that the majority of the CH<sub>4</sub> is released via eructation. The SF6 tracer gas technique was developed in an attempt to measure CH<sub>4</sub> emissions by animals without confinement in respiration chambers (Johnson et al., 1994<ref>Johnson, K., Huyler, M., Westberg, H., Lamb, B., and Zimmerman, P. 1994. Measurement of methane emissions from ruminant livestock using a sulfur hexafluoride tracer technique. Environ. Sci. Technol. 28:359-362.</ref>). Air is sampled near the animal’s nostrils through a tube attached to a halter and connected to an evacuated canister worn around the animal’s neck or on its back. A capillary tube or orifice plate is used to restrict airflow through the tube so that the canister is between 50 and 70% full in approximately 24 hours. A permeation tube containing SF6 is placed into the rumen of each animal. The pre-determined release rate of SF6 is multiplied by the ratio of CH<sub>4</sub> to SF6 concentrations in the canister to calculate CH<sub>4</sub> emission rate.
The SF6 technique samples breath over 24 hours, whereas other techniques use spot samples of breath over periods of minutes throughout the day, so diurnal variation has to be considered. The majority of CH<sub>4</sub> (87-99%) is released by eructation (Blaxter and Joyce, 1963<ref>Blaxter, K.L., and Joyce, J.P. 1963. The accuracy and ease with which measurements of respiratory metabolism can be made with tracheostomized sheep. Br. J. Nutr. 17:523-537</ref>; Murray et al., 1976<ref name=":0">Murray, R.M., Bryant, A.M., and Leng, R.A.. 1976. Rates of production of methane in the rumen and large intestine of sheep. Br. J. Nutr. 36:1-14.</ref>), which provides a clear signal for sample processing. Please note that the tracheostomy used in Murray et al. (1976)<ref name=":0" /> may have resulted in a higher percentage, but in both publications, it is clear that the majority of the CH<sub>4</sub> is released via eructation. The SF6 tracer gas technique was developed in an attempt to measure CH<sub>4</sub> emissions by animals without confinement in respiration chambers (Johnson et al., 1994<ref>Johnson, K., Huyler, M., Westberg, H., Lamb, B., and Zimmerman, P. 1994. Measurement of methane emissions from ruminant livestock using a sulfur hexafluoride tracer technique. Environ. Sci. Technol. 28:359-362.</ref>). Air is sampled near the animal’s nostrils through a tube attached to a halter and connected to an evacuated canister worn around the animal’s neck or on its back. A capillary tube or orifice plate is used to restrict airflow through the tube so that the canister is between 50 and 70% full in approximately 24 hours. A permeation tube containing SF6 is placed into the rumen of each animal. The pre-determined release rate of SF6 is multiplied by the ratio of CH<sub>4</sub> to SF6 concentrations in the canister to calculate CH<sub>4</sub> emission rate.


Many research centres have used the SF6 technique with variations in design of sampling and collection equipment, permeation tubes, and gas analysis (Berndt et al., 2014<ref>Berndt, A., Boland, T.M., Deighton, M.H., Gere, J.I., Grainger, C., Hegarty, R.S., Iwaasa, A.D., Koolaard, J.P., Lassey, K.R., Luo D., Martin, R.J., Martin, C., Moate, P.J., Molano, G., Pinares-Patiño, C., Ribaux, B.E., Swainson, N.M., Waghorn, G.C., and Williams, S.R.O. 2014. Guidelines for use of sulphur hexafluoride (SF6) tracer technique to measure enteric methane emissions from ruminants. Pages 166. M. G. Lambert, ed. New Zealand Agricultural Greenhouse Gas Research Centre, New Zealand. </ref>). Reliable results depend on following standard protocols, with greatest variation coming from accuracy of determining SF6 release rate from permeation tubes and control of sampling rate. With capillary tubes, sampling rate decreases as pressure in the canister increases, whereas an orifice plate gives a steadier sampling rate over 24 hours (Deighton et al., 2014<ref>Deighton, M.H., Williams, S.R.O., Hannah, M.C., Eckard, R.J., Boland, T.M., Wales, W.J., and Moate, P.J. 2014. A modified sulphur hexafluoride tracer technique enables accurate determination of enteric methane emissions from ruminants. Anim. Feed Sci. Technol. 197:47-63.</ref>). A source of error that has not been evaluated is that animals might interact and share CH<sub>4</sub> emissions when the sampling tube of one animal is near the head of another animal. There is good agreement between CH<sub>4</sub> emissions measured by the SF6 technique and respiration chambers, although results from the SF6 technique are more variable (Grainger et al., 2007<ref>Grainger, C., Clarke, T., McGinn, S.M., Auldist, M.J., Beauchemin, K.A., Hannah, M.C., Waghorn, G.C., Clark, H., and Eckard, R J. 2007. Methane emissions from dairy cows measured using the sulfur hexafluoride (SF6) tracer and chamber techniques. J. Dairy Sci. 90:2755-2766.</ref>; Muñoz et al., 2012<ref>Muñoz, C., Yan, T., Wills, D.A., Murray, S., and Gordon, A.W. 2012. Comparison of the sulfur hexafluoride tracer and respiration chamber techniques for estimating methane emissions and correction for rectum methane output from dairy cows. J. Dairy Sci. 95:3139-3148.</ref>).
Many research centres have used the SF6 technique with variations in design of sampling and collection equipment, permeation tubes, and gas analysis (Berndt et al., 2014<ref>Berndt, A., Boland, T.M., Deighton, M.H., Gere, J.I., Grainger, C., Hegarty, R.S., Iwaasa, A.D., Koolaard, J.P., Lassey, K.R., Luo D., Martin, R.J., Martin, C., Moate, P.J., Molano, G., Pinares-Patiño, C., Ribaux, B.E., Swainson, N.M., Waghorn, G.C., and Williams, S.R.O. 2014. Guidelines for use of sulphur hexafluoride (SF6) tracer technique to measure enteric methane emissions from ruminants. Pages 166. M. G. Lambert, ed. New Zealand Agricultural Greenhouse Gas Research Centre, New Zealand. </ref>). Reliable results depend on following standard protocols, with greatest variation coming from accuracy of determining SF6 release rate from permeation tubes and control of sampling rate. With capillary tubes, sampling rate decreases as pressure in the canister increases, whereas an orifice plate gives a steadier sampling rate over 24 hours (Deighton et al., 2014<ref>Deighton, M.H., Williams, S.R.O., Hannah, M.C., Eckard, R.J., Boland, T.M., Wales, W.J., and Moate, P.J. 2014. A modified sulphur hexafluoride tracer technique enables accurate determination of enteric methane emissions from ruminants. Anim. Feed Sci. Technol. 197:47-63.</ref>). A source of error that has not been evaluated is that animals might interact and share CH<sub>4</sub> emissions when the sampling tube of one animal is near the head of another animal. There is good agreement between CH<sub>4</sub> emissions measured by the SF6 technique and respiration chambers, although results from the SF6 technique are more variable (Grainger et al., 2007<ref>Grainger, C., Clarke, T., McGinn, S.M., Auldist, M.J., Beauchemin, K.A., Hannah, M.C., Waghorn, G.C., Clark, H., and Eckard, R J. 2007. Methane emissions from dairy cows measured using the sulfur hexafluoride (SF6) tracer and chamber techniques. J. Dairy Sci. 90:2755-2766.</ref>; Muñoz et al., 2012<ref>Muñoz, C., Yan, T., Wills, D.A., Murray, S., and Gordon, A.W. 2012. Comparison of the sulfur hexafluoride tracer and respiration chamber techniques for estimating methane emissions and correction for rectum methane output from dairy cows. J. Dairy Sci. 95:3139-3148.</ref>).
== ZELP Sense ==
[https://www.zelp.co/ ZELP] is a company based in the UK, which has developed a wearable device for cows called [https://www.zelp.co/measurement/ ZELP Sense]. The device continuously measures methane (CH₄) and carbon dioxide (CO₂) emissions from individual cows, in real-world settings, together with estimated dry matter intake (DMI).
=== System description ===
ZELP Sense consists of three key parts: a headpiece, nosepiece, and gas sensing unit. The headpiece, made from ventilated neoprene, correctly positions the nosepiece without restricting the cow's natural movements or behaviours. The gas sensing unit sits below the cow's neck. The full device is lightweight and quick and easy to fit to the animal. The headpiece and nosepiece come in multiple sizes to ensure an optimal fit for a wide range of cows.
The device samples ambient and eructed air from close to the cow's nostrils through the nosepiece. These samples are processed by the gas sensing unit, which contains sensors to track ventilation rate and measure gas concentrations. Data from the device is offloaded via a WiFi connection and processed by ZELP's Machine Learning models. The device has local data storage allowing it to be used in areas with intermittent connectivity.
Users receive daily CH₄ and CO₂ emission totals (g/day), hourly CH₄ and CO₂ emissions for every hour of data collected (g/hour), and estimated DMI (kg/day), via ZELP's mobile-optimized web-app. The data can be downloaded for further analysis.
==== Internal chamber trial (2024): ====
Three cows, each fitted with a ZELP Sense device, were tested in respiration chambers over a 3-week period, with two 3-day testing sessions, separated by a one-week break. The daily emission totals provided by ZELP Sense showed an average difference of less than 10% versus those provided by respiration chambers.
For more details, you can download the latest version of ZELP’s White Paper [https://www.zelp.co/measurement/ here]. These results have been shared at the British Society for Animal Science Conference 2025, EAAP’s AI4AS Conference 2025, and at the ASGGN & ICAR Feed & Gas Workshop held at the 9th International Greenhouse Gas & Animal Agriculture Conference 2025. The poster presentation is available [[:File:ZELP Sense - Chamber Comparison Poster.pdf|here]].
==== External chamber trials (2025): ====
Multiple third-party trials of ZELP Sense have now been completed at different research institutions and universities. The trials focused on comparing the methane and carbon dioxide measurements provided by ZELP Sense with those from respiration chambers. Analysis is underway and results are expected to be published in early 2026.
=== Commercial availability ===
ZELP Sense is available for pre-order now, with ZELP’s team allocating devices from their upcoming commercial production run on a first-come, first-serve basis. Delivery is expected in the second half of 2026. For more information, and to request a quote, please contact: [Mailto:sense@zelp.co sense@zelp.co].

Latest revision as of 12:26, 22 December 2025

NOTE: This version of Section 20 has been approved by the working group's Chair. Please be aware that further revisions may occur before final review and approval by the Board and ICAR members per the Approval of Page Process.

SF6

The SF6 technique samples breath over 24 hours, whereas other techniques use spot samples of breath over periods of minutes throughout the day, so diurnal variation has to be considered. The majority of CH4 (87-99%) is released by eructation (Blaxter and Joyce, 1963[1]; Murray et al., 1976[2]), which provides a clear signal for sample processing. Please note that the tracheostomy used in Murray et al. (1976)[2] may have resulted in a higher percentage, but in both publications, it is clear that the majority of the CH4 is released via eructation. The SF6 tracer gas technique was developed in an attempt to measure CH4 emissions by animals without confinement in respiration chambers (Johnson et al., 1994[3]). Air is sampled near the animal’s nostrils through a tube attached to a halter and connected to an evacuated canister worn around the animal’s neck or on its back. A capillary tube or orifice plate is used to restrict airflow through the tube so that the canister is between 50 and 70% full in approximately 24 hours. A permeation tube containing SF6 is placed into the rumen of each animal. The pre-determined release rate of SF6 is multiplied by the ratio of CH4 to SF6 concentrations in the canister to calculate CH4 emission rate.

Many research centres have used the SF6 technique with variations in design of sampling and collection equipment, permeation tubes, and gas analysis (Berndt et al., 2014[4]). Reliable results depend on following standard protocols, with greatest variation coming from accuracy of determining SF6 release rate from permeation tubes and control of sampling rate. With capillary tubes, sampling rate decreases as pressure in the canister increases, whereas an orifice plate gives a steadier sampling rate over 24 hours (Deighton et al., 2014[5]). A source of error that has not been evaluated is that animals might interact and share CH4 emissions when the sampling tube of one animal is near the head of another animal. There is good agreement between CH4 emissions measured by the SF6 technique and respiration chambers, although results from the SF6 technique are more variable (Grainger et al., 2007[6]; Muñoz et al., 2012[7]).

ZELP Sense

ZELP is a company based in the UK, which has developed a wearable device for cows called ZELP Sense. The device continuously measures methane (CH₄) and carbon dioxide (CO₂) emissions from individual cows, in real-world settings, together with estimated dry matter intake (DMI).

System description

ZELP Sense consists of three key parts: a headpiece, nosepiece, and gas sensing unit. The headpiece, made from ventilated neoprene, correctly positions the nosepiece without restricting the cow's natural movements or behaviours. The gas sensing unit sits below the cow's neck. The full device is lightweight and quick and easy to fit to the animal. The headpiece and nosepiece come in multiple sizes to ensure an optimal fit for a wide range of cows.

The device samples ambient and eructed air from close to the cow's nostrils through the nosepiece. These samples are processed by the gas sensing unit, which contains sensors to track ventilation rate and measure gas concentrations. Data from the device is offloaded via a WiFi connection and processed by ZELP's Machine Learning models. The device has local data storage allowing it to be used in areas with intermittent connectivity.

Users receive daily CH₄ and CO₂ emission totals (g/day), hourly CH₄ and CO₂ emissions for every hour of data collected (g/hour), and estimated DMI (kg/day), via ZELP's mobile-optimized web-app. The data can be downloaded for further analysis.

Internal chamber trial (2024):

Three cows, each fitted with a ZELP Sense device, were tested in respiration chambers over a 3-week period, with two 3-day testing sessions, separated by a one-week break. The daily emission totals provided by ZELP Sense showed an average difference of less than 10% versus those provided by respiration chambers.

For more details, you can download the latest version of ZELP’s White Paper here. These results have been shared at the British Society for Animal Science Conference 2025, EAAP’s AI4AS Conference 2025, and at the ASGGN & ICAR Feed & Gas Workshop held at the 9th International Greenhouse Gas & Animal Agriculture Conference 2025. The poster presentation is available here.

External chamber trials (2025):

Multiple third-party trials of ZELP Sense have now been completed at different research institutions and universities. The trials focused on comparing the methane and carbon dioxide measurements provided by ZELP Sense with those from respiration chambers. Analysis is underway and results are expected to be published in early 2026.

Commercial availability

ZELP Sense is available for pre-order now, with ZELP’s team allocating devices from their upcoming commercial production run on a first-come, first-serve basis. Delivery is expected in the second half of 2026. For more information, and to request a quote, please contact: sense@zelp.co.

  1. ↑ Blaxter, K.L., and Joyce, J.P. 1963. The accuracy and ease with which measurements of respiratory metabolism can be made with tracheostomized sheep. Br. J. Nutr. 17:523-537
  2. ↑ 2.0 2.1 Murray, R.M., Bryant, A.M., and Leng, R.A.. 1976. Rates of production of methane in the rumen and large intestine of sheep. Br. J. Nutr. 36:1-14.
  3. ↑ Johnson, K., Huyler, M., Westberg, H., Lamb, B., and Zimmerman, P. 1994. Measurement of methane emissions from ruminant livestock using a sulfur hexafluoride tracer technique. Environ. Sci. Technol. 28:359-362.
  4. ↑ Berndt, A., Boland, T.M., Deighton, M.H., Gere, J.I., Grainger, C., Hegarty, R.S., Iwaasa, A.D., Koolaard, J.P., Lassey, K.R., Luo D., Martin, R.J., Martin, C., Moate, P.J., Molano, G., Pinares-Patiño, C., Ribaux, B.E., Swainson, N.M., Waghorn, G.C., and Williams, S.R.O. 2014. Guidelines for use of sulphur hexafluoride (SF6) tracer technique to measure enteric methane emissions from ruminants. Pages 166. M. G. Lambert, ed. New Zealand Agricultural Greenhouse Gas Research Centre, New Zealand.
  5. ↑ Deighton, M.H., Williams, S.R.O., Hannah, M.C., Eckard, R.J., Boland, T.M., Wales, W.J., and Moate, P.J. 2014. A modified sulphur hexafluoride tracer technique enables accurate determination of enteric methane emissions from ruminants. Anim. Feed Sci. Technol. 197:47-63.
  6. ↑ Grainger, C., Clarke, T., McGinn, S.M., Auldist, M.J., Beauchemin, K.A., Hannah, M.C., Waghorn, G.C., Clark, H., and Eckard, R J. 2007. Methane emissions from dairy cows measured using the sulfur hexafluoride (SF6) tracer and chamber techniques. J. Dairy Sci. 90:2755-2766.
  7. ↑ Muñoz, C., Yan, T., Wills, D.A., Murray, S., and Gordon, A.W. 2012. Comparison of the sulfur hexafluoride tracer and respiration chamber techniques for estimating methane emissions and correction for rectum methane output from dairy cows. J. Dairy Sci. 95:3139-3148.
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