8 research outputs found

    Analysis of Inputs Parameters Used to Estimate Enteric Methane Emission Factors Applying a Tier 2 Model: Case Study of Native Cattle in Senegal

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    In the context of the Paris Agreement, and considering the importance of methane emissions from cattle in West Africa, application of a Tier 2 method to estimate enteric methane emission factors is clearly pertinent. The current study has two purposes. Firstly, it aims to detect how much each input parameter contributes to the overall uncertainty of enteric methane emission factors for cattle. Secondly, it aims to identify which input parameters require additional research efforts for strengthening the evidence base, thus reducing the uncertainty of methane enteric emission factors. Uncertainty and sensitivity analysis methodologies were applied to input parameters in the calculation of enteric methane emission factors for lactating cows and adult male Senegalese native cattle using the IPCC Tier 2 model. The results show that the IPCC default input parameters, such as the coefficient for calculating net energy for maintenance (Cfi), digestible energy (DE) and the methane conversion rate (Ym) are the first, second and third most important input parameters, respectively, in terms of their contribution to uncertainty of the enteric methane emission factor. Sensitivity analysis demonstrated that future research in Senegal should prioritize the development of Ym, Cfi and DE in order to estimate enteric methane emission factors more accurately and to reduce the uncertainty of the national agricultural greenhouse gas inventory

    La contribution de l’élevage dans les Ă©missions de gaz Ă  effet de serre des terroirs agro-sylvo-pastoraux de la Haute Casamance au SĂ©nĂ©gal

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    In West Africa (WA), the default emission factors (EF) recommended by the Intergovernmental Panel on Climate Change (IPCC) are commonly used to estimate greenhouse gas emissions (GHG) from agriculture. However, the use of adapted EF to the local production context is important to discuss environmental matters and react to climate change mitigation issues. In the WA region, integrated crop-livestock systems are dominant and many resources (especially feedstuff) are managed collectively. The objective of the thesis was to provide a better understanding of GHG emissions linked to agro-sylvo-pastoral production systems (SPASP) in the Haute Casamance region, Senegal. The village was considered as a relevant scale of investigation. As such, the SarĂ© Yoro Bana territory (12 ° 49'N: 14 ° 53'W) served as a case study. To assess the territory's GHG emissions, the principal agricultural activities were inventoried. The IPCC Tier 2 method was expended to calculate the contextualized EFs of enteric methane for cattle and small ruminants. Also, existing management practices of animal waste were taken into account in the estimates. Through our approach which considers the variation of the intake, the feed digestibility, the stages of undernourishment, the average values of EF developed are respectively, for lactating cows (VL) and other cattle (AB), 30.7 CH4/head/ year and 15.1 kg CH4/head/year. These developed EFs are much lower than the default EFs proposed for the WA region (e.g., respectively 46 CH4/head/year and 31 CH4/head/ year for VL and AB). For small ruminants, our results show an overestimation of EF values for sheep (2.3 CH4/head/year against 5 CH4/head/year) and goats (2.0 CH4/head/year against 5 CH4 /head/year). Total GHG emissions (without carbon storage) were, respectively, per hectare and per capita 2.0 t CO2eq and 2.6 t CO2eq. The enteric fermentation of animals (65%), burning savannah (13%) and the direct deposition of animal waste on the rangelands (10%) are the most contributor to total territory emissions. Expressed in kilograms of animal products, the emission intensities (EI) of milk and meat are respectively 4.9 kg CO2eq/kg of milk and 18.5 CO2eq/kg live weight. The EI was 12.0 CO2eq/kg live weight for small ruminants. The impact of crop production activities was 11.8 CO2eq/kg of grain produced. In addition, these agro-sylvo-pastoral ecosystems are the place of carbon storage, in particular in the areas of wooded areas. So, the storage flow should be evaluated to see if these territories are sources or sinks of carbon. Mitigation options, considering the key GHG emission were discussed (e.g., introduction of cultivated forage, animal waste management practices). These options promote efficient recycling of nutrients and carbon in the soil. Similar work should be replicated at national scales to reduce uncertainties. Indeed, this approach will allow to achieve activity data and EF, hence to capture the authenticity of the studied SPASP.En Afrique de l’Ouest (AO), les facteurs d’émissions (FE) recommandĂ©s par dĂ©faut du Groupe d'experts intergouvernemental sur l'Ă©volution du climat (GIEC) sont couramment utilisĂ©s pour estimer les Ă©missions de gaz Ă  effet de serre (GES) de l’agriculture. L’utilisation de FE adaptĂ©s au contexte local de production est cependant essentielle pour argumenter autour des questions environnementales et rĂ©pondre aux enjeux d’attĂ©nuation du changement climatique. Dans la rĂ©gion d’AO, les systĂšmes intĂ©grĂ©s agriculture-Ă©levage sont dominants et de nombreuses ressources, notamment fourragĂšres sont gĂ©rĂ©es collectivement. L’objectif de la thĂšse Ă©tait d’apporter une meilleure comprĂ©hension des Ă©missions de GES liĂ©es aux systĂšmes de production agro-sylvo-pastoraux (SPASP) dans la rĂ©gion de la Haute Casamance au SĂ©nĂ©gal. Le terroir villageois a Ă©tĂ© considĂšre comme Ă©chelle pertinente d’analyse. A ce titre, le terroir villageois de SarĂ© Yoro Bana (12°49’N : 14°53’O) a servi de terrain d’étude. Pour Ă©valuer les Ă©missions de GES du terroir, les principales activitĂ©s agricoles ont Ă©tĂ© inventoriĂ©es. La mĂ©thode de niveau 2 (Tier 2) du GIEC a Ă©tĂ© utilisĂ©e pour calculer les FE contextualisĂ©s de mĂ©thane entĂ©rique pour les bovins et les petits ruminants. Aussi, les pratiques actuelles de gestions des dĂ©jections animales ont Ă©tĂ© prises en compte dans les estimations. Avec notre approche qui considĂšre la variation des quantitĂ©s ingĂ©rĂ©es, la digestibilitĂ© de la ration et les pĂ©riodes de sous-alimentation des animaux, les valeurs moyennes de FE dĂ©veloppĂ©s sont respectivement, pour les vaches en lactation (VL) et les autres bovins (AB), de 30,7 CH4/tĂȘte/an et 15,1 kg CH4/tĂȘte/an. Ces FE sont bien infĂ©rieurs Ă  ceux proposĂ©s par dĂ©faut pour la rĂ©gion d’AO (respectivement 46 CH4/tĂȘte/an et 31 CH4/tĂȘte/an pour les VL et AB). Pour les petits ruminants, nos rĂ©sultats indiquent Ă©galement une surestimation des valeurs de FE pour les ovins (2,3 CH4/tĂȘte/an contre 5 CH4/tĂȘte/an) et les caprins (2,0 CH4/tĂȘte/an contre 5 CH4/tĂȘte/an). Les Ă©missions totales de GES (sans intĂ©gration du stockage de carbone) Ă©taient respectivement, par hectare et par habitant de 2,0 t Eq-CO2 et 2,6 t Eq-CO2. La fermentation entĂ©rique des animaux (65 %), les feux de savanes (13 %) et le dĂ©pĂŽt direct des dĂ©jections animales sur les parcours (10 %) sont les postes qui contribuent le plus aux Ă©missions totales du terroir. ExprimĂ©es en kilogramme de produits animaux, les intensitĂ©s d’émission (IE) du lait et de la viande de bovins sont respectivement de 4,9 kg Eq-CO2/kg de lait et de 18,5 Eq-CO2/kg de poids vif. L’IE Ă©tait de 12,0 Eq-CO2/kg de poids vif pour les petits ruminants. L’impact des activitĂ©s de productions vĂ©gĂ©tales Ă©tait de 11,8 Eq-CO2/kg de grain produit. Ces terroirs agro-sylvo-pastoraux sont aussi le lieu de stockage de carbone, notamment dans les espaces de parcours arborĂ©s. Il conviendrait d’évaluer ce flux de stockage pour voir si ces terroirs sont des sources ou des puits de carbone. Des pistes d’attĂ©nuation, considĂ©rant les postes-clĂ©s d’émission de GES, ont Ă©tĂ© discutĂ©es, comme l’introduction de fourrages cultivĂ©s et de pratiques de gestion des dĂ©jections animales qui favorisent un recyclage efficient des nutriments et du carbone dans le terroir. Des travaux similaires doivent ĂȘtre reproduits Ă  des Ă©chelles nationales pour rĂ©duire les incertitudes dans les inventaires nationaux de GES. En effet, cette approche favorise l’obtention de donnĂ©es d’activitĂ© et des FEs reprĂ©sentatifs de la rĂ©alitĂ© des SPASP Ă©tudiĂ©s
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