The following steps define the level of characterization:

• For each category (e.g., CH₄ from enteric fermentation, CH₄ and N₂O from manure management), the individual contribution of a single animal species to the total category emissions must be estimated to identify significant species (i.e., 25-30% or more of total category emissions).
• Determine whether CH₄ from enteric fermentation and CH₄ or N₂O from manure management are key categories.
• If enteric fermentation is a key category, the recommended estimating method is Tier 2 and an enhanced livestock characterization should be used for any significant animal species (normally cattle and sheep).
• If CH₄ or N₂O from manure management are key categories, the recommended estimating method is Tier 2 for CH₄ and use of country-specific data for N₂O and an enhanced livestock characterization should be used for any significant animal species (normally, cattle, sheep, and swine).
• If enteric fermentation and manure management are not key categories, but if the necessary data are available, it is still advisable to develop an enhanced characterization.