9.2.1. Direct Methods
The direct methods of calculation of emissions from livestock include: respiration chambers, Green-Feed Systems, and SF6 tracer techniques are the commonly used ones to measure emissions from livestock including dairy cattle. The details of each technique are explained below:
Respiration Chambers
Respiration chambers are specialized chambers that enclose individual animals, allowing for the collection and analysis of exhaled gases (including methane). They offer precise measurements but can be expensive and may not be suitable for all animal types or management systems.

Green-Feed Systems
The Green-Feed System use a head-only enclosure to measure gas exchange and can be used for individual animals in their natural environment, with less disruption than facemasks.

SF6 Tracer Technique
This technique involves introducing a tracer gas (sulfur hexafluoride) into the animal’s system and measuring its concentration alongside methane. It allows for measurements in larger groups of animals in their natural environment and is less costly than respiration chambers.
