According to the report published by the BPEX "Pigs and the Environment How the global pork business is reducing its impact", the principle green house gases associated with pork production are emissions of ammonia, nitrous oxide and methane.
Together with a lesser amount of direct CO2 these are combined into a single CO2 equivalent figure. Provisional estimates from FAO indicate that pork production contributes about 793 million tonnes CO2 equivalent which represents approximately 1.6% of global GHG emissions. This gives an average global emission intensity of about 6.9kg CO2 e/kg carcase weight which is relatively low impact. The analysis also indicates that the vast majority of global emissions result from manure management (42%) and feed production (47%). These calculations include an element of emissions attributed to feed that come from the estimated impact of Land Use Change (LUC).
The emission intensity of pork production as assessed by FAO shows a relatively similar pattern in the worlds main producing regions. Taking the global average of 6.9kg CO2 e/kg cw than the regional variation is very modest, in a range from about 5–8kg CO2 e/kg cw.
June 2012/ BPEX/ United Kingdom.