Projections of NH emissions from manure generated by livestock production in China to 2030 under six mitigation scenarios.

China's rapid urbanization, large population, and increasing consumption of calorie-and meat-intensive diets, have resulted in China becoming the world's largest source of ammonia (NH) emissions from livestock production. This is the first study to use provincial, condition-specific emission factors based on most recently available studies on Chinese manure management and environmental conditions. The estimated NH emission temporal trends and spatial patterns are interpreted in relation to government policies affecting livestock production. Scenario analysis is used to project emissions and estimate mitigation potential of NH emissions, to year 2030. We produce a 1km×1km gridded NH emission inventory for 2008 based on county-level activity data, which can help identify locations of highest NH emissions. The total NH emissions from manure generated by livestock production in 2008 were 7.3TgNH·yr (interquartile range from 6.1 to 8.6TgNH·yr), and the major sources were poultry (29.9%), pigs (28.4%), other cattle (27.9%), and dairy cattle (7.0%), while sheep and goats (3.6%), donkeys (1.3%), horses (1.2%), and mules (0.7%) had smaller contributions. From 1978 to 2008, annual NH emissions fluctuated with two peaks (1996 and 2006), and total emissions increased from 2.2 to 7.3Tg·yr increasing on average 4.4%·yr. Under a business-as-usual (BAU) scenario, NH emissions in 2030 are expected to be 13.9TgNH·yr (11.5-16.3TgNH·yr). Under mitigation scenarios, the projected emissions could be reduced by 18.9-37.3% compared to 2030 BAU emissions. This study improves our understanding of NH emissions from livestock production, which is needed to guide stakeholders and policymakers to make well informed mitigation decisions for NH emissions from livestock production at the country and regional levels.