Evaluation of methane measuring techniques

Evaluation of different techniques to quantify methane emissions from South African livestock

Industry Sector: Cattle and Small Stock

Research focus area: Sustainable natural resource utilization

Research Institute: University of Pretoria

Researcher: Dr JL Linde du Toit

Title Initials Surname Highest Qualification
Prof WA van Niekerk PhD
Mr J van Wyngaard MSc
Mrs Z Goemans BSc(Agric)

Final report approved: 23 August 2018

Aims of the project

  • 1. To measure methane emissions from livestock using the SF6 technique
  • 2. To measure methane emission from livestock using the handheld laser methane detector (LMD) technique
  • 3. To compare the results of the SF6 and the LMD techniques

Executive Summary

The need to verify greenhouse gas inventories demands the development of high throughput, economical yet accurate short-term measurement techniques, such as the laser methane detector (LMD). The aim of this project was to compare methane (CH4) emission rates as measured by the LMD to the sulphur hexafluoride tracer gas (SF6) technique from lactating dairy cows grazing pasture and to evaluate the practicality of the LMD measurement protocol under grazing conditions in the temperate coastal region of South Africa. Methane production was determined from six lactating Jersey cows on pasture using both techniques. The data generated by the LMD had a superior daily repeatability compared to the SF6 technique in the present study. A higher between-cow coefficient of variation (CV) (0.6 vs. 0.4) from the LMD compared to the SF6 technique was observed and this was ascribed to the sensitivity of the LMD to ambient conditions, animal movement while grazing and time of measurement. Methane production as measured by the SF6 technique (348 g/d) was higher (P<0.05) compared with the LMD technique (82.6 g/d). Results from this study indicated that the LMD yielded approximately a 70% lower average daily CH4 production when compared to the SF6 techniques under the experimental conditions and daily CH4prediction models using the same animals and dry matter intakes. The lack of a third measuring technique and a standardized LMD methodology makes an accurate comparison between techniques and published data difficult. Both the SF6 and the LMD methods are viable methods to evaluate differences between mitigation options, for ranking of animals for selection purposes and to identify differences between dietary treatments. More research is needed before new techniques such as the LMD can be employed to determine absolute CH4 daily emissions which can be up scaled for inventory purposes.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Linde du Toit on linde.dutoit@up.ac.za