Eggs are an increasingly significant source of protein for human consumption, and the global poultry industry is the single fastest-growing livestock sector. In the context of international concern for food security and feeding an increasingly affluent human population, the contribution to global greenhouse-gas (GHG) emissions from animal protein production is of critical interest, according to R.C. Taylor of the British Trust for Ornithology in Thetford, Norfolk and co-authors at Bangor University.

In their paper in Poultry Science, they explain that that they calculated the GHG emissions footprint for the fastest-growing sector of the UK egg market: free-range production in small commercial units on mixed farms.

Emissions are calculated to current Intergovernmental Panel on Climate Change and UK standards (PAS2050): including direct, indirect and embodied emissions from cradle to farm gate compatible with a full product life-cycle assessment.

They presented a methodology for the allocation of emissions between ruminant and poultry enterprises on mixed farms.

Greenhouse gas emissions averaged a global warming potential of 2.2kg of carbon dioxide equivalent (CO2e) per dozen eggs, or 1.6kg of CO2e per kg, assuming average egg weight of 60g.

One kilogram of protein from free-range eggs produces 0.2kg of CO2e, lower than the emissions from white or red meat (based on both kilo of meat and per kilo of protein). Of these emissions, 63 per cent represent embodied carbon in poultry feed.

A detailed GHG emissions footprint represents a baseline for comparison with other egg production systems and sources of protein for human consumption.

Taylor and co-authors comment that eggs represent a relatively low-carbon supply of animal protein but their production is heavily dependent on cereals and soy, with associated high emissions from industrial nitrogen production, land-use change and transport. They add that alternative sources of digestible protein for poultry diets are available, may be produced from waste processing, and would be an effective tool for reducing the industry's GHG emissions and dependence on imported raw materials.

Reference

Taylor R.C., H. Omed and G. Edwards-Jones. 2014. The greenhouse emissions footprint of free-range eggs. Poultry Science. 93 (1):231-237. doi: 10.3382/ps.2013-03489

January 2014