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Development of methane emission factors specific to pasture-based dairy systems


In New Zealand and Ireland methane from dairy cattle accounts for 19 and 13% of national greenhouse gasses (GHG), respectively, making it an important GHG to target. Feed intake is a key driver of methane output; however, in pasture-based systems, methane output varies with cow physiology and intake, pasture season, management, and species. When anti-methanogenic technologies such as rumen modifiers are used the methane abatement response varies

Currently, in NZ and Ireland, a standard methane emission factor, based on feed eaten, is used to calculate methane emissions. There are no methane emission factors that account for the methane abatement response when rumen modifiers are used. 


The objectives of Emissions4Pasture are:

  1. Quantify cow and pasture effects on methane emissions
  2. Determine the methane abatement response when rumen modifiers are used in pasture-based systems
  3. Generate a database containing methane outputs from pasture-based systems to refine and improve the accuracy of on-farm and national GHG inventories.
  4. Support uptake of viable and scalable methane abatement practices and technologies in dairy sectors in NZ and Ireland.

To achieve these objectives, the project includes a multidisciplinary team of researchers, students, professors, and database technology experts. It  will use world-leading methane-measurement facilities, collaboration with key stakeholders, and existing engagement and communication channels in NZ and Ireland.

The team will collate data from the Tasks in Emissions4Pasture, and from relevant literature to explore the relationships between cow physiology, pasture season, management, species, rumen modifiers and methane emissions. These data will be used to develop new pasture-specific methane emission factors that will be incorporated into a refined Tier 3.0 agricultural inventory model.


Ultimately, the project outputs will be disseminated to end users to drive widespread adoption of practical methane abatement strategies and improve accounting of methane emissions in pasture-based dairy systems. Existing engagement and communication initiatives within DairyNZ and Teagasc will be leveraged to facilitate and support end-user adoption of these mitigation practices.

Lead researcher

Teagasc lead researcher Ben Lahart