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Predicting the Environmental Impacts of Chicken Production Systems

5 March 2012, at 12:00am

Feed accounted for the majority of the overall environmental impact of both broiler and egg production in typical UK systems, according to researchers based at Newcastle University, and less intensive systems were associated with greater overall environmental burden as a result.

Researchers based at Newcastle University have calculated the environmental impacts of different egg and broiler systems in the United Kingdom through life cycle assessment (LCA), publishing two papers recently in the journal, Poultry Science.

Illka Leinonen from Newcastle and co-authors there and at Cranfield University and the University of Nottingham explain that the aim of their studies was to apply the LCA method, ‘from cradle to gate’, to quantify the environmental burdens per 1,000kg of expected edible carcass weight for broilers1 and per 1,000kg of eggs2.

For broiler production, they compared the three main production systems in the United Kingdom: 1) standard indoor, 2) free–range and 3) organic and they examined four major egg production systems: 1) cage, 2) barn, 3) free–range and 4) organic. In each case, they aimed to identify the main components of these burdens.

The researchers explained that the LCA method evaluates production systems logically to account for all inputs and outputs that cross a specified system boundary, and it relates these to the useful outputs.

Their analysis was based on an approach that applied a structural model for the respective industry and mechanistic submodels for animal performance, crop production and major nutrient flows. Baseline feeds representative of those used by the UK industry were used. Typical UK figures for performance of the birds and farm energy and material use were applied.

Broiler Study Results

The researchers found that the length of the production cycle was longer for free–range and organic systems than standard indoor system, and as a result, the feed consumption and manure production per bird were higher in the free–range and organic systems. These differences accounted for much of the variation in environmental burdens between the systems.

Feed production, processing and transport resulted in greater overall environmental impacts than any other components of broiler production. For example, 65 to 81 per cent of the primary energy use and 71 to 72 per cent of the global warming potential of the system were due to these burdens.

Farm gas and oil use had the second highest impact in primary energy use (12 to 25 per cent) followed by farm electricity use. The direct use of gas, oil and electricity were generally lower in free-range and organic systems than in the standard indoor system.

Manure was the main component of acidification potential and also had a relatively high eutrophication potential.

Layer Study Results

The number of birds required to produce 1,000kg of eggs was highest in the organic and lowest in the cage system, the Newcastle-based researchers found. Similarly, the amount of feed consumed per bird was highest in the organic and lowest in the cage system. These general differences in productivity largely affected the differences in the environmental impacts between the systems.

Feed production, processing and transport caused greater environmental impacts than those from any other component of production; that is, 54 to 75 per cent of the primary energy use and 64 to 72 per cent of the global warming potential of the systems.

Electricity (used mainly for ventilation, automatic feeding, and lighting) had the second greatest impact in primary energy use (16 to 38 per cent). Gas and oil (used mainly for heating in pullet rearing and incineration of dead layer birds) used between seven and 14 per cent of the total primary energy.

As with the broilers, manure had the greatest impact on the acidification and eutrophication potentials of the systems because of ammonia emissions that contributed to both of these potentials and nitrate leaching that only affected eutrophication potential.

Leinonen and co-authors concluded that the LCA method allows for comparisons between systems and for the identification of hotspots of environmental impacts that could be subject to mitigation.

Comparing & Contrasting the Broiler & Layer Studies

For both broiler and egg production, feed had by far the greatest environmental impact. The proportions of primary energy use and global warming potential arising from feeding tended to be higher per unit weight of broiler meat than eggs.

Because of the strong influence on feed on both primary energy use and global warming potential in this study, the less intensive systems, such as organic and free-range, were associated with a larger overall environmental impact per unit of product, be it chicken meat or eggs.

For broiler production, gas and oil use had the second highest impact on total primary energy use, followed by electricity use. These were reversed for egg production. The direct use of all these fuels was lower in free-range and organic broiler systems than in the standard indoor system.

Ammonia emissions from both broiler and layer manure was a major component of acidification and eutrophication potential.

The researchers say the results of their work indicate that future research into reducing the environmental burden associated with poultry production should prioritise improving the efficiency of feed use, for example through breeding, and finding more environmentally friendly feed ingredients.

References

1 Leinonen I., A.G. Williams, J. Wiseman, J. Guy and I. Kyriazakis. 2012. Predicting the environmental impacts of chicken systems in the United Kingdom through a life cycle assessment: Broiler production systems. Poult. Sci. 91(1):8-25. doi: 10.3382/ps.2011-01634. To view this paper (fee payable), click here.

2 Leinonen I., A.G. Williams, J. Wiseman, J. Guy and I. Kyriazakis. 2012. Predicting the environmental impacts of chicken systems in the United Kingdom through a life cycle assessment: Egg production systems. Poult. Sci. 91(1):26-40. doi: 10.3382/ps.2011-01635. To view this paper (fee payable), click here.

For more information on the this project at Newcastle University, click here.

March 2012