The role of composting in recycling manure nutrients

Recently, composting has been gaining increased attention as an alternative means of handling manure generated by the livestock industry. Composting is not a new technology, it merely controls what is a natural decomposition process. A major advantage of composting is reduced mass, volume and water content compared with fresh manure which in turn reduces transportation requirements. Concomitant benefits include elimination of pathogens, parasites, weed seeds and odour emissions on land application. However, carbon (C) and nitrogen (N) losses and greenhouse gas (GHG) emissions are associated with composting. Nutrients are stabilized during composting which slows their release once soil-applied. Compost also enhances soil physical and biological properties and has a disease suppression effect. Where the supply of manure currently exceeds land availability for application, or in some future scenario, if producers need to comply with stricter manure application rate regulations, composting may be an option to encourage nutrient export from high-loading watersheds to soils that may benefit from nutrient and organic matter inputs. Composting may be seen as a means of maximizing the potential for recycling manure nutrients by soils and crops while protecting surface and groundwater resources from manure-related contamination.