Abstract
Livestock and poultry farming sectors are among the largest anthropogenic methane (CH4) emission sources, mainly from enteric fermentation and manure management. Previous inventories of CH4 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 CH4 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 CH4 emissions are also estimated with intensive field survey. The results showed that the estimated CH4 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 CH4 emissions were a little higher (3%) than the constant EF method. Temporal CH4 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 CH4 emission were similar; subsequently, the cattle emitted more CH4 compared to the pigs. At a spatial scale, Shunyi, Daxing, and Tongzhou districts with more cattle and pigs are the hotspots of CH4 emission. In conclusion, the dynamic EFs method obviously improved the spatio-temporal estimates of CH4 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 CH4 emissions from livestock and poultry farming in the future.
Highlights
Methane (CH4) has a 28-fold greater global warming potential than carbon dioxide (CO2) on a centennial scale and is the second most important greenhouse gas, contributing approximately one-third of the total radiative forcing since 1750s [1]
The annual CH4 emissions in this study derived from the lower dynamic emission factor (EF) were approximately 13–19% lower than the previous results [12] based on the constant EF before 2010 (Figure 3)
The present study showed that the time series of CH4 emission from livestock and poultry had four periods and reached its peak in 2003, which is generally consistent with the previous long-term results in China as well as its specific areas [9,16,18] and in East Asia [25]
Summary
Methane (CH4) has a 28-fold greater global warming potential than carbon dioxide (CO2) on a centennial scale and is the second most important greenhouse gas, contributing approximately one-third of the total radiative forcing since 1750s [1]. Body weight and milk production of livestock are dynamic and in turn affect the EF because of the development in breeding technology and changes in animal diet and production systems [13,14]. For this reason, the new guideline of IPCC Tier 2 (using dynamic EFs of each livestock and poultry types during the past three decades) is more reliable and used more widely [9,10]. It is important to estimate CH4 emissions from livestock and poultry farming in China as well as its regional spatio-temporal patterns of hotspots
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