Inventory of Spatio-Temporal Methane Emissions from Livestock and Poultry Farming in Beijing

Livestock and poultry farming sectors are among the largest anthropogenic methane (CH 4 ) emission sources, mainly from enteric fermentation and manure management. Previous inventories of CH 4 emission were generally based on constant emission factor (EF) per head, which had some weaknesses mainly due to the succession of breeding and feeding systems over decades. Here, more reliable long-term changes of CH 4 emissions from livestock and poultry farming in Beijing are estimated using the dynamic EFs based on the Intergovernmental Panel on Climate Change (IPCC) Tier 2 method, and high-resolution spatial patterns of CH 4 emissions are also estimated with intensive field survey. The results showed that the estimated CH 4 emissions derived by dynamic EFs were approximately 13–19% lower than those based on the constant EF before 2010. After 2011, however, the dynamic EFs-derived CH 4 emissions were a little higher (3%) than the constant EF method. Temporal CH 4 emissions in Beijing had experienced four developing stages (1978–1988: stable; 1989–1998: slow growth; 1999–2004: rapid growth and reached hot moments; 2005–2014: decline) during 1978–2014. Over the first two decades, the contributions of pigs (45%) and cattle (46%) to annual CH 4 emission were similar; subsequently, the cattle emitted more CH 4 compared to the pigs. At a spatial scale, Shunyi, Daxing, and Tongzhou districts with more cattle and pigs are the hotspots of CH 4 emission. In conclusion, the dynamic EFs method obviously improved the spatio-temporal estimates of CH 4 emissions compared to the constant EF approach, and the improvements depended on the period and aquaculture structure. Therefore, the dynamic EFs method should be recommended for estimating CH 4 emissions from livestock and poultry farming in the future.