Wetenschap - 17 april 2012

Better conditions for chickens raise emissions

The ban on battery poultry farming leads to higher emissions of ammonia and greenhouse gases and greater land use, assuming the same rate of egg production. This finding has come out of Sanne Dekker’s PhD research.

Dekker conducted a life cycle analysis, identifying the effect of a range of farming systems on greenhouse gas emissions, acidification, soil exhaustion, eutrophication, fossil fuel consumption and land use. This gave her an overview of the environmental impact of batteries, aviary housing systems and systems in which the chickens are on the ground, She drew distinctions between eggs from free-range hens in barns, eggs from free-range hens with access to the outdoors, and organic eggs.
The environmental damage an egg represents depends a lot on the way the chicken feed is made and transported. Organic chicken feed mainly comes from Italy (maize) and the Ukraine (wheat), while standard feeds come from France and Germany. 'The poultry farmers have very little influence on that because the feed supplier decides on the ingredients', says Dekker.
Because the wheat farmers in the Ukraine use very little fertilizer or soil additives, they get low harvests and so the organic egg does not 'produce' much in the way of greenhouse gases, takes little energy and wastes little nitrogen or phosphate. But this method of production has exhausted the soils of the Ukraine so that it now takes much more land to fill a box of organic eggs. According to Dekker, a lot could be gained for the environment by opting for feed ingredients with less environmental impact such as by-products of the food industry.
A second significant environmental factor is the amount of feed a chicken needs to make an egg. It is standard practice for poultry farmers to add amino acids to the feed to improve the conversion of feed into egg. Organic farmers do not do that because the amino acids are made by genetically modified micro-organisms. This is one of the reasons why it takes more feed to produce an organic egg.
A third key characteristic is the type of accommodation the hens are provided with, and the ammoniac emissions that go with it. On this point battery hens score by far the highest because in this system the hens' manure is continuously dried and removed. Aviary housing systems (a floor with bunk beds on which the chickens can lay their eggs) scored averagely on emissions, as the manure is removed every three days. Barns in which all the chickens are together on the floor scored the lowest, as the manure lies for months. In practice it is mainly organic farmers who use this kind of housing. They could reduce their ammoniac emissions considerably by investing in aviary housing systems.
 Dekker does not argue for a reintroduction of battery farming, but for a reduction in the environmental impact of systems with free-ranging hens. She believes this can be done by feeding the chickens differently, by investing in barns which dry and remove the manure, and by breeding chickens that make efficient use of feed and which function well in group housing. She also argues for manure processing on chicken farms so that nitrogen and phosphate can be reused. They could for instance be exported to the Ukraine, the granary for organic eggs, in the form of dried pellets. That would close the mineral cycle.
Sanne Dekker gets her PhD on 20 April from Peter Groot Koerkamp, professor of Business Technology and Imke de Boer, professor of Animal Production Systems.