Greenhouse gas emissions from ruminant supply chains – A global life cycle assessment

Greenhouse gas
emissions from
supply chains
A global life cycle assessment


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Food and Agriculture Organization of the United Nations
Rome 2013


In decades to come, the global demand for livestock products will continue to increase driven by growing populations, incomes and urbanization. As a consequence the sector needs to produce more but in a context of increasing natural resource scarcity and challenges posed by climate change. In 2010, the ruminant sector contributed about 29 percent to global meat production (equivalent to 81 million tonnes) of which 79 percent is from the cattle sector and the remaining from buffalo and small ruminants. Global milk production in 2010 was 717 million tonnes with milk production from the cattle sector contributing the bulk, about 83 percent of global production. While ruminants play an important role in providing high quality protein essential for human diets, they are an important source of greenhouse gas (GHG) emissions. The demand for bovine meat, mutton and milk is forecasted to grow at a rate of 1.2 percent, 1.5 percent and 1.1 percent, respectively, during the period 2006-2050. To avoid significant increases in total GHG emissions from the sector, a reduction of the intensity of emissions is required. This report presents a life cycle analysis of the GHG emissions arising from ruminant supply chains around the year 2005. This first comprehensive and disaggregated global assessment of emissions enables the understanding of emission pathways and hotspots. This is a fundamental and initial step to identify mitigation strategies and inform public debate.

Table of Contents

Definitions of commonly used terms
Executive summary

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1. Introduction

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1.1 Background
1.2 Scope of this report
1.3 The Global Livestock Environmental Assessment Model
1.4 Outline of this report

2. Overview of the global monogastric sector


3. Methods

3.1 Choice of Life Cycle Assessment (LCA)
3.2 General principles of LCA
3.3 Use of LCA in this assessment
3.4 Overview of calculation method
3.5 Data sources and management
3.6 Allocation of emissions between products, by-products and services
3.7 Production system typology

4. Results

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4.1 Cattle
4.2 Buffalo

4.3 Small Ruminants
4.4 Summary of results

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5. Discussion

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5.1 Methane emissions from enteric fermentation
5.2 Emissions from feed production
5.3 Emissions from manure management
5.4 Comparison with other studies
5.5 Analysis of uncertainty

6. Conclusion

6.1 Commercial systems (layers, broilers, industrial and intermediate pigs)
6.2 Backyard systems
6.3 Gaps in emission intensity within systems and regions



Overview of the Global Livestock Environmental Assessment Model (GLEAM)

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Data and data sources


Changes in carbon stocks related to land use and land-use change

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Postfarm emissions


Emissions related to energy use


Relative value of slaughter by-products and effect on allocation of emissions



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1. Distribution of dairy cattle populations
2. Distribution of beef cattle populations
3. Distribution of buffalo populations

4. Distribution of goat populations
5. Distribution of sheep populations
6. Proportion of milk protein in total protein from cattle dairy herds

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7. Average feed digestibility for dairy cattle
8. Average feed digestibility for beef cattle
9. Manure methane conversion factor for dairy cattle

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10. Manure methane conversion factor for beef cattle
11. Proportion of feed N retained in product – dairy cattle herds
12. Proportion of feed N retained in product – beef cattle herds

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Country list

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