Overview
Methane emissions attributed to livestock derive from both enteric (gut) fermentation and from manures. In both cases, the methane results from degradation of feed by microbes in an air-free (anaerobic) environment. For monogastric livestock, the majority of emissions come from manure, but for ruminants, most emissions are from enteric fermentation within the digestive tract of the animal.
The methods described below are appropriate for measuring the total daily production of enteric methane from individual ruminants in litres/day or grams/day. There are other methods (not described here) such as open path laser and FTIR methods, suitable for measuring total emission from herds or flocks of animals.
Measurement Techniques
📘 Respiration Chambers
In respiration chambers, the animal is confined in a sealed box and its gas production rates determined. Globally, the respiration chambers used for ruminants are of the “Open Circuit” type, in which fresh air is drawn through the sealed box at a known rate. Methane production is determined by measuring the methane concentration of (fresh) air entering the chamber and exhaust air leaving the chamber and multiplying the difference by the measured air flow.
Usually, measurements are made with one animal in a chamber at a time, and each measurement is for 21–24 hours. This is considered the ‘gold standard’ for accurate emission measurement, but it is also a measurement in an artificial environment, so care should be exercised in assuming the emissions from a free-range animal will exactly match those measured in respiration chambers.
📄 Download : Livestock Research Group Technical Manual: Respiration Chamber Designs, September 2018
📘 SF6 Tracer Method
The SF6 tracer method was developed to measure enteric methane emissions from individual grazing animals. It can be used with housed animals but is most appropriately employed when used for free-range animals.
It operates by inserting a small permeation device into the reticulo-rumen that releases gas (sulphur hexafluoride) into the rumen at a known rate, then the ratio of SF6 to methane in exhaled air is determined. Multiplying the SF6 release rate by the methane:SF6 ratio provides a measure of methane emission rate.
These studies typically take continuous samples of exhaled gases over 24 h, each day for 5 days. Very high-level analytical skills are required to measure SF6 at very low concentrations, that may be below 0.01 parts per billion.
📄 Download: SF6 Tracer Technique Guidelines for Ruminants, April 2014
📘 Headbox Respiration Systems
In headbox systems, the animal is tethered in a pen with its head in a hood, and fresh air is drawn past at a known rate. Calculations are the same as for full-body respiration chambers, but emissions voided in the flatus are not included in the emission estimate.
The headbox system allows most of the animal’s body to be open to the atmosphere so that it can be cooled by fans and misters in hot climates, and for this reason headboxes are popular in tropical countries.
There are some published designs (e.g., Animals, 10(2), p.227; Journal of Animal Science, 94(suppl_5), pp.576–577), but there is technical advice available to potential users, so that is provided in the files supplied HERE
These files and videos were generated for an international workshop on headbox design and use run by New Zealand under its Climate Smart Agriculture Initiative. The workshop was held at and co-hosted by Cambodia’s Royal University of Agriculture in Phnom Penh in 2025.
📄 Download: Headbox Best Practice.pdf
📘 Greenfeed Emission Monitor
The Greenfeed is a patent-based, commercially manufactured emission device that monitors emissions from large or small ruminants over multiple short periods (2–5 min) each time they come to the Greenfeed to receive a supplement. The data is processed remotely by the manufacturer (C-Lock Inc., South Dakota), so good data communication capability is vital.
A Greenfeed unit can be used in a group-pen or paddock situation where many animals access the same unit voluntarily as other animals leave it free, or in a more controlled environment where the animals are led to the Greenfeed exactly when a measurement is required.
C-Lock provides a range of advisory information on their website and can supply a corporate training program for new users. The information provided below is the material and videos of a privately run training workshop held in the Philippines as part of the New Zealand-funded Climate Smart Agriculture Initiative in 2025.
📄 Download: GreenFeed Learning Resources.pdf
