Livestock GRACEnet: A Workgroup Dedicated to Evaluating and Mitigating Emissions from Livestock Production.

Ammonia, greenhouse gases, and particulate emissions from livestock operations can potentially affect air quality at local, regional, and even global scales. These pollutants, many of which are generated through various anthropogenic activities, are being increasingly scrutinized by regulatory authorities. Regulation of emissions from livestock production systems will ultimately increase on farm costs, which will then be passed onto consumers. Therefore, it is essential that scientifically based emission factors are developed for on-farm emissions of air quality constituents to improve inventories and assign appropriate reduction targets. To generate a larger database of on-farm emissions, the USDA-ARS created the workgroup Livestock GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement Network). This introduction for the special section of papers highlights some of the research presently being conducted by members of Livestock GRACEnet with the intent of drawing attention to critical information gaps, such as (i) improving emissions measurements; (ii) developing emissions factors; (iii) developing and validating tools for estimating emissions; and (iv) mitigating emissions. We also provide a synthesis of the literature with respect to key research areas related to livestock emissions, including feeding strategies, animal housing, manure management, and manure land application, and discuss future research priorities and directions.