Measuring Livestock CH4 Emissions with the Laser Methane Detector: A Review

Diana Sorg

doi:10.3390/methane1010004

Abstract

The handheld, portable laser methane detector (LMD) was developed to detect gas leaks in industry from a safe distance. Since 2009, it has also been used to measure the methane (CH4) concentration in the breath of cattle, sheep, and goats to quantify their CH4 emissions. As there is no consensus on a uniform measurement and data-analysis protocol with the LMD, this article discusses important aspects of the measurement, the data analysis, and the applications of the LMD based on the literature. These aspects, such as the distance to the animal or the activity of the animals, should be fixed for all measurements of an experiment, and if this is not possible, they should at least be documented and considered as fixed effects in the statistical analysis. Important steps in data processing are thorough quality control and reduction in records to a single point measurement or “phenotype” for later analysis. The LMD can be used to rank animals according to their CH4 breath concentration and to compare average CH4 production at the group level. This makes it suitable for genetic and nutritional studies and for characterising different breeds and husbandry systems. The limitations are the lower accuracy compared to other methods, as only CH4 concentration and not flux can be measured, and the high amount of work required for the measurement. However, due to its flexibility and non-invasiveness, the LMD can be an alternative in environments where other methods are not suitable or a complement to other methods. It would improve the applicability of the LMD method if there were a common protocol for measurement and data analysis developed jointly by a group of researchers.

Highlights

Ruminants produce methane (CH4 ) in their rumen and hindgut through enteric fermentation
The application of the laser methane detector (LMD) can be extended to various research questions and has already been demonstrated exemplarily for nutrition, physiology, and genetics
Some research groups have developed their own working protocol, which they have applied in subsequent studies

Summary

Introduction

Ruminants produce methane (CH4 ) in their rumen and hindgut through enteric fermentation. When CH4 emissions are to be measured on-farm, other methods such as the GreenFeed (GF) breath-analyser station (C-Lock Inc., Rapid City, SD, USA; [6]), non-dispersive infrared (NDIR)/Fourier-transformed infrared (FTIR) breath analysers (“sniffers”) installed in feed bins [7,8], or the sulphur hexafluoride (SF6 ) tracer gas technique [9] are used. All these methods have their own advantages and disadvantages in terms of purchase and running costs, labour, repeatability, behaviour change, and throughput [10] (Table 1), and they meet different requirements [11] Another on-farm technique is the portable laser methane detector (LMD), which has comparatively low purchase and running costs and results in only low-to-moderate behavioural changes of the animals but requires relatively high labour resources and has a moderate throughput in terms of the number of records per time [10]

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