Review of Ammonia and Greenhouse Gases Emission Factors from Poultry Housings: Influence of Practices and Rearing Conditions Bertrand Meda1, Mélynda Hassouna1, 2, Claude Aubert3, Paul Robin1, 2, Jean-Yves Dourmad4, 5 1
INRA, UMR1069 Sol Agro et hydrosystème Spatialisation, F-35000 Rennes, France Agrocampus Ouest, UMR1069, Sol Agro et hydrosystème Spatialisation, F-35000 Rennes, France 3 ITAVI, Institut Technique de l’Aviculture, Zoopole Beaucemaine, F-22440, Ploufragan, France 4 INRA, UMR1079 Systèmes d’Elevage, Nutrition Animale et Humaine, F-35000 Rennes, France 5 Agrocampus Ouest, UMR1079, Systèmes d’Elevage, Nutrition Animale et Humaine, F35000 Rennes, France 2
[email protected] Abbreviated title: Gaseous Emissions from Poultry Housings Abstract Ammonia (NH3) and greenhouse gases (GHGs) emissions are two major concerns of agricultural pollution because ammonia contributes to water and soil pollution (eutrophication and acidification) and GHGs are responsible for global warming and climate change. Poultry production is known, as other animal productions, to produce NH3 and GHGs and best management practices and optimal rearing conditions have to be identified in order to reduce the gaseous emissions. Understanding the determinism of gaseous emissions is the first step toward the conception of innovative systems or practices. This paper presents a review of NH3 and GHGs emission factors (EFs) from several studies with a focus on the influence of practices and rearing conditions on gaseous emissions. The analysis of the EFs shows that manure management (e.g. removal frequency or chemical treatment) is the main way to mitigate NH3 and GHGs emissions. Rearing conditions (mainly temperature) and flock management practices (e.g. dietary practices or flock density) also appear to be efficient ways to mitigate the emissions of NH3 and GHGs in poultry housings. Keywords: ammonia; greenhouse gas; poultry; housing; emission factor 1. Introduction Livestock production has been clearly pointed out to have negative impacts on the environment (FAO, 2006) through the production of ammonia (NH3) and greenhouse gases (GHGs). Ammonia contributes to water pollution (eutrophication) and soil pollution (acidification) (Bouwman et al., 2002) while methane (CH4) and nitrous oxide (N2O) are two major GHGs responsible for global warming and climate change (IPCC, 2007). In livestock production systems, these gases are mainly emitted by enteric fermentation (for CH4) and by animal manure. Concerning poultry production, national emissions inventories reported that poultry is a major producer of NH3 (e.g. respectively 11% and 16% of total NH3 emissions in France (Gac et al., 2007) and in the United States (EPA, 2002, 2004)), and in a less extent a producer of GHGs (e.g. about 1.5% of N2O total emissions and 2.2% of CH4 total emissions in France (Gac et al., 2007)). Therefore, in order to decrease its environmental impact, poultry
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production must change its practices and design innovative systems. The first step in this approach is to understand the determinism of gaseous emissions and to identify the main key factors for NH3 and GHGs emissions mitigation. Yet, many production systems are observed in poultry production. These systems differ by livestock management practices, housing type, or manure management practices. In order to compare the level of emissions of these systems and identify best practices for the mitigation of gaseous emissions, a review of NH3 and GHGs emissions factors (EFs) in poultry housings was carried out. Through the comparison of EFs, the influence of rearing conditions and manure management practices on gaseous emissions will be analyzed, and best practices could be identified in order to mitigate NH3 and GHGs emissions. At last, research needs could be pointed out through missing EFs. 2. Database description The database concerning gaseous emissions in poultry housings is composed of 26 studies published between 1997 and 2008 (only 4 were published before 2000). Theses studies will not be necessarily cited in this paper but the full list of references is available beside the authors. The database regrouped 124 EFs. For an easy comparison between systems, all the EFs presented in this study have been converted into the same unit (g of gas per bird per day). The distribution of these EFs according to the geographical region, the production and the gas concerned is given in Table 1. Gaseous emissions from poultry housings are a concern for both European countries and the USA. 54% of the selected EFs are specific to European housings and 37% to American housings. Yet, ammonia remains the most studied gas with more than 75% of the selected EFs, maybe because NH3 is the main gas produced by poultry housings. At last, broiler and layer housings are the most studied housings with respectively 40% and 48% of the selected EFs. The intra-production variability for NH3, CH4 and N2O EFs is represented on Fig. 1. Concerning ammonia, few EFs were available for duck and turkey housings. Therefore, it is difficult to conclude on the variability of NH3 emissions in these housings. For broiler and layer housings, most of the EFs are lower than 1.0 g NH3 per day per bird, with respective means of 0.53 and 0.50 g NH3 per day per bird (standard deviations are 0.33 and 0.39 g NH3 per day per bird, respectively). For broiler housings, the European average EF was of 0.29 g NH3 per day per broiler and the American average EF was of 0.65 g NH3 per day per broiler (standard deviations are 0.16 and 0.20 g NH3 per day per broiler, respectively). This difference in average EFs was found to be statistically significant (p
