Effects of including nitrogen emissions from soil in environmental systems analysis of waste management strategies

The environmental impacts of nitrogen emissions from soil resulting from the use of organic fertilizers, such as manure, are large compared with the corresponding impacts of mineral fertilizers. However, soil emissions are rarely included in systems analysis of waste management strategies. This study examines whether the inclusion of soil emissions can affect the environmental ranking of systems for managing solid biodegradable waste. Waste management scenarios based on incineration, anaerobic digestion and composting, respectively, were compared. The scenarios were analysed using the organic waste research (ORWARE) simulation model. A simplified model for calculating nitrogen availability and emissions was also constructed. Life-cycle analysis methodology was used for choosing system boundaries and evaluating the results. Global warming, acidification and eutrophication were the impact categories considered. The results indicate the vital importance of considering nitrogen emissions from soil when comparing biological waste management systems with other waste management methods, especially with regard to eutrophication effects. Soil emissions are also important when comparing the environmental impacts of anaerobic digestion and composting systems. However, the variation in nitrogen emissions from soil is large and depends on the spreading technique used, climate, drainage and soil texture