Livestock are produced throughout the world and are a significant contributor to global methane (CH4) emissions. Methane, a greenhouse gas, is produced from the decomposition of livestock manure under anaerobic conditions. These conditions often occur when large numbers of animals are managed in a confined area (e.g., dairy farms, beef feedlots, and swine and poultry farms) where manure is typically stored in large piles or disposed of in lagoons. Nitrous oxide, also a greenhouse gas, is produced during the nitrification-denitrification of nitrogen contained in livestock waste. The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (IPCC Guidelines) provide a general guide to estimating methane emissions from livestock manure. Two approaches may be used to estimate emissions: the Tier 1 approach relies on default emission factors drawn from previous studies, while the more complex Tier 2 approach requires country-specific information on livestock manure characteristics and manure management practices. The Tier 2 approach is recommended when the data used to develop the default values does not correspond well with the country's livestock and manure management conditions or when a country has large dairy and swine populations. To prepare methane estimates, livestock population data characterized by subgroup are required. For Tier 1 estimates, necessary population data should be readily obtainable within the country or from the Food and Agricultural Organization (FAO). The Tier 2 estimates require additional data on manure characteristics and manure management practices, for which country-specific data should be used. These data should be obtained through data collection activities. If necessary, IPCC default values can be used for some of the factors in the Tier 2 calculation. Nitrous oxide estimates also require livestock population and manure management practice data. The value and source of these data should correspond with that used for estimating methane emissions. Reporting of emission estimates for both methane and nitrous oxide is clearly described in the IPCC Guidelines. With few exceptions, confidentiality is not expected to pose a challenge. Ensuring the quality of the inventory will be an important activity, particularly where Tier 2 methods are used. The most important aspect of QA/QC (quality assurance/quality control) is thorough and transparent documentation of the emissions calculation steps, including all activity data and emission factor values.
