Manure-DNDC: a biogeochemical process model for quantifying greenhouse gas and ammonia emissions from livestock manure systems

Authors: LI, CHANGSHENG - University Of New Hampshire; SALAS, WILLIAM - Applied Geosolutions, Llc; ZHANG, RUIHONG - University Of California; KRAUTER, CHARLEY - California State University; Rotz, Clarence - Al; MITLOEHNER, FRANK - University Of California

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2012
Publication Date: 5/13/2012
Citation: Li, C., Salas, W., Zhang, R., Krauter, C., Rotz, C.A., Mitloehner, F. 2012. Manure-DNDC: a biogeochemical process model for quantifying greenhouse gas and ammonia emissions from livestock manure systems. Nutrient Cycling in Agroecosystems. DOI: 10.1007/s10705-012-9507-z.

Interpretive Summary: Air emission from livestock farms is a complex phenomenon, which involves multiple processes driven by multiple environmental factors varying differently across farm components. Because of the vast information and the many interactions within the farm that must be integrated, tools are needed to develop improved manure management strategies to reduce emissions to the environment. Manure-DNDC is a tool resulting from our long-term efforts on modeling terrestrial ecosystems based on classical scientific knowledge. Functions within Manure-DNDC represent the biochemical and geochemical processes that govern the transport and transformation of carbon and nitrogen throughout the manure life cycle in a farming system. Built upon the principles of thermodynamics and chemical reaction kinetics, the model can be applied to various environmental conditions across livestock facilities as well as cultivated soils. Case study evaluations illustrate how changes in specific management practices can simultaneously affect a number of carbon and nitrogen emissions from several components of the livestock system. By modeling greenhouse gas emissions, ammonia volatilization, nitrate leaching, and crop yields, Manure-DNDC provides a wide spectrum of data to help assess the best management practices based on their impacts on ecosystem services. As public domain software, the Manure-DNDC model with a User’s Guide is available at http://www.dndc.sr.unh.edu.

Technical Abstract: From the point of view of biogeochemistry, manure is a complex of organic matter containing minor minerals. When manure is excreted by animals, it undergoes a series of reactions such as decomposition, hydrolysis, ammonia volatilization, nitrification, denitrification, and fermentation from which carbon dioxide, nitrous oxide, methane, and ammonia can be produced. Based on the principles of thermodynamics and reaction kinetics, these reactions are commonly controlled by a group of environmental factors such as temperature, moisture, redox potential, pH, and substrate concentration gradient. The relations among the reactions, the environmental factors and gas production have been incorporated in a process-based model, Manure-DNDC, to describe manure organic matter turnover and gas emissions. Manure-DNDC was constructed by integrating five farm components (i.e., feedlot, liquid and solid manure treatment/storage, anaerobic digester and cropping field). Manure-DNDC calculates variations of the environmental factors for each component based on its technical specifications, management practices, and the weather and soil conditions; and then utilizes the environmental parameters to drive the biogeochemical reactions. To verify the applicability of Manure-DNDC for livestock farms, seven datasets of air emissions measured from farms across the U.S. plus a pasture in Scotland were used for model evaluation with encouraging results. A dairy farm in New York was used to assess the impacts of alternative management practices on mitigation at a farm scale. The modeled results showed that changes in management practices could reduce greenhouse gas emission by 30% and ammonia emission by 36% at the farm scale.