Comparative life cycle assessment of technologies and strategies to improve nitrogen use efficiency in egg supply chains

A non-trivial challenge along egg supply chains is inefficient use of nitrogen, which may have a combination of negative economic, human/animal health, and environmental implications. A variety of technologies and management strategies have been proposed to improve nitrogen use efficiency (NUE) and reduce emissions at key supply chain stages. This study considered seven scenarios representing NUE strategies: (1) biochar addition to the soil and (2) application of the 4Rs approach to fertilizer management in feed input production; (3) a reduced crude protein supplemented with synthetic amino acids diet; (4) use of acid scrubbers in poultry barns; (5) biochar addition to stored manure; (6) manure incorporation at the time of land application; and (7) joint application of all strategies. ISO 14044 compliant environmental life cycle assessment (LCA) along with NUE calculations were performed to analyze and compare these mitigation options. The functional unit was one tonne of egg production at the farm gate in Canada. The most significant increase in NUE (13%) resulted from the application of the scrubber in the layer barn. The scrubber also significantly lowered acidifying (21%) and eutrophying (16%) emissions compared to the baseline. The combined application of all strategies increased NUE by 15% compared to the baseline scenario and reduced acidification, global warming, and eutrophication potential, but at the cost of a large increase in energy consumption. Each strategy might be more or less suitable depending on the considered environmental impacts, as well as NUE outcomes. Use of LCA is essential to informed decision making in this context.

Automated summary

In this study, different nitrogen use efficiency (NUE) strategies were considered and analyzed using ISO 14044 compliant environmental life cycle assessment (LCA) and NUE calculations. The application of scrubbers in layer barns was found to significantly increase NUE, reduce acidification and eutrophication emissions. Furthermore, the combined application of all strategies led to a further increase in NUE but at the cost of increased energy consumption.