Implementing an appropriate metric for the assessment of greenhouse gas emissions from livestock production: A national case study

• Published in: Animal (Cambridge, England) England), 2022-10, Vol.16 (10), p.100638-100638, Article 100638
• Main Authors: Hörtenhuber, S.J., Seiringer, M., Theurl, M.C., Größbacher, V., Piringer, G., Kral, I., Zollitsch, W.J.
• Format: Article
• Language: English
• Subjects: Agriculture; Animal; Global warming; GWP; GWP100
• ISSN: 1751-7311; 1751-732X
• DOI: 10.1016/j.animal.2022.100638

•The effect of methane is assessed on climate impact of livestock production.•Climate impact is quantified using the new global warning potential (GWP*).•Livestock products show substantially lower climate impacts when assessed by GWP*.•Reducing methane from livestock helps to tackle global warming in the short term.•For Austria, this effect is 2.5 times higher than that of CO2 sequestration. Livestock farming is of major economic relevance but also severely contributes to environmental impacts, especially greenhouse gas (GHG) emissions such as methane (CH4; particularly from ruminant production) and nitrous oxide (N2O; mainly from manure management and soil cultivated for feed production). In this study, we analyse the impact of GHG emissions from Austrian livestock production, using two metrics: a) the commonly used global warming potential (GWP) over 100 years (GWP100 in CO2-equivalents, CO2-e), and b) the recently introduced metric GWP*, which describes additional warming as a function of the timeline of short-lived GHG emissions (unit CO2 warming equivalents, CO2-we). We first compiled the sectoral (i.e. only direct emissions without upstream processes) GWP100 for different livestock categories with a focus on dairy cattle, beef cattle and pigs in Austria between 1990 and 2019. We also estimated product-related (i.e. per kg carcass weight or per litre of milk) GWP100 values, including upstream processes. We then calculated the corresponding GWP* metrics, both sectoral and product-related, and compared them with the GWP100 values. Decreasing livestock numbers and improved production efficiency were found to result in strong sectoral emission reductions from dairy production (–32 % of GWP100 from 1990 to 2019) and from pigs (–32 % CO2-e). This contrasts with low reductions from other livestock categories and even increases for cattle other than dairy cows (+3 % CO2-e), mainly due to rising suckler cow numbers. Allocated results per kg milk and kg body mass show quite similar results. Using the GWP* metric, the climate impacts of Austrian livestock production are less severe. When assuming constant management and emission intensity over a period of at least 20 years, the CO2-we (GWP*) is almost 50 % less than CO2-e (GWP100) per kg Austrian raw milk due to the different impacts of the short-lived CH4. A similar trend applies to an average cattle carcass (-40 % warming impact). The emission reductions of the shrinking Austrian livestock population represen