Manure management for greenhouse gas mitigation.

Ongoing intensification and specialisation of livestock production lead to increasing volumes of manure to be managed, which are a source of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O). Net emissions of CH4 and N2O result from a multitude of microbial activities in the manure environment. Their relative importance depends not only on manure composition and local management practices with respect to treatment, storage and field application, but also on ambient climatic conditions. The diversity of livestock production systems, and their associated manure management, is discussed on the basis of four regional cases (Sub-Saharan Africa, Southeast Asia, China and Europe) with increasing levels of intensification and priorities with respect to nutrient management and environmental regulation. GHG mitigation options for production systems based on solid and liquid manure management are then presented, and potentials for positive and negative interactions between pollutants, and between management practices, are discussed. The diversity of manure properties and environmental conditions necessitate a modelling approach for improving estimates of GHG emissions, and for predicting effects of management changes for GHG mitigation, and requirements for such a model are discussed. Finally, we briefly discuss drivers for, and barriers against, introduction of GHG mitigation measures for livestock production. There is no conflict between efforts to improve food and feed production, and efforts to reduce GHG emissions from manure management. Growth in livestock populations are projected to occur mainly in intensive production systems where, for this and other reasons, the largest potentials for GHG mitigation may be found.