Soil N2O emissions, N leaching and marine eutrophication in life cycle assessment - A comparison of modelling approaches

Kajsa Henryson; Thomas Kätterer; Pernilla Tidåker; Cecilia Sundberg

doi:10.1016/j.scitotenv.2020.138332

Soil N₂O emissions, N leaching and marine eutrophication in life cycle assessment - A comparison of modelling approaches

Sci Total Environ. 2020 Jul 10:725:138332. doi: 10.1016/j.scitotenv.2020.138332. Epub 2020 Apr 1.

Authors

Kajsa Henryson¹, Thomas Kätterer², Pernilla Tidåker³, Cecilia Sundberg⁴

Affiliations

¹ Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, P.O. Box 7032, 750 07 Uppsala, Sweden. Electronic address: kajsa.henryson@slu.se.
² Swedish University of Agricultural Sciences (SLU), Department of Ecology, P.O. Box 7044, 750 07 Uppsala, Sweden.
³ Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, P.O. Box 7032, 750 07 Uppsala, Sweden.
⁴ Swedish University of Agricultural Sciences (SLU), Department of Energy and Technology, P.O. Box 7032, 750 07 Uppsala, Sweden; KTH Royal Institute of Technology, Department of Sustainable Development, Environmental Science and Engineering, Teknikringen 10B, 100 44 Stockholm, Sweden.

PMID: 32304962
DOI: 10.1016/j.scitotenv.2020.138332

Abstract

Nitrogen fertilisation is an essential part of modern agriculture, providing food for a growing human population, but also causing environmental impacts when reactive nitrogen (N) is released to the environment. The amount and impact of these emissions are difficult to quantify in life cycle assessment (LCA), due to their site-dependent nature. This study compared seven models for direct soil nitrous oxide (N₂O) emissions, seven models for N leaching and five characterisation models for marine eutrophication impact assessment, selected to represent medium-effort options for accounting for spatial variation in emissions and impact assessment. In a case study, the models were applied to wheat cultivation at two Swedish sites to estimate climate and marine eutrophication impact. Direct N₂O emissions estimated by the models varied by up to five-fold at one of the sites and contributed 21-56% of the total climate impact. Site-dependent models gave both lower and higher N₂O emissions estimates than the site-generic Tier 1 model from the Intergovernmental Panel on Climate Change (IPCC). Estimated N leaching also varied by up to fivefold at one of the sites and contributed 47-93% of the total eutrophication potential, depending on model choice. All site-dependent models estimated lower N leaching than the site-generic IPCC Tier 1 model. Marine eutrophication impact estimates varied by almost an order of magnitude depending on characterisation model choice. The large variation between models found in this study highlights the importance of model choice for N emissions and marine eutrophication impact assessment in LCA of crop cultivation. Due to the divergence of model outcomes and different limitations of some of the models, no general recommendations on choosing soil N₂O emissions model, N leaching model or characterisation model for marine eutrophication could be given.

Keywords: Climate impact; Crop cultivation; LCA; Model choice; Nitrogen fertiliser; Site-dependent.