title: Environmental impacts of organic and conventional agricultural products--are the differences captured by life cycle assessment?
abstract: Comprehensive assessment tools are needed that reliably describe environmental impacts of different agricultural systems in order to develop sustainable high yielding agricultural production systems with minimal impacts on the environment. Today, Life Cycle Assessment (LCA) is increasingly used to assess and compare the environmental sustainability of agricultural products from conventional and organic agriculture. However, LCA studies comparing agricultural products from conventional and organic farming systems report a wide variation in the resource efficiency of products from these systems. The studies show that impacts per area farmed land are usually less in organic systems, but related to the quantity produced impacts are often higher. We reviewed 34 comparative LCA studies of organic and conventional agricultural products to analyze whether this result is solely due to the usually lower yields in organic systems or also due to inaccurate modeling within LCA. Comparative LCAs on agricultural products from organic and conventional farming systems often do not adequately differentiate the specific characteristics of the respective farming system in the goal and scope definition and in the inventory analysis. Further, often only a limited number of impact categories are assessed within the impact assessment not allowing for a comprehensive environmental assessment. The most critical points we identified relate to the nitrogen (N) fluxes influencing acidification, eutrophication, and global warming potential, and biodiversity. Usually, N-emissions in LCA inventories of agricultural products are based on model calculations. Modeled N-emissions often do not correspond with the actual amount of N left in the system that may result in potential emissions. Reasons for this may be that N-models are not well adapted to the mode of action of organic fertilizers and that N-emission models often are built on assumptions from conventional agriculture leading to even greater deviances for organic systems between the amount of N calculated by emission models and the actual amount of N available for emissions. Improvements are needed regarding a more precise differentiation between farming systems and regarding the development of N emission models that better represent actual N-fluxes within different systems. We recommend adjusting N- and C-emissions during farmyard manure management and farmyard manure fertilization in plant production to the feed ration provided in the animal production of the respective farming system leading to different N- and C-compositions within the excrement. In the future, more representative background data on organic farming systems (e.g. N content of farmyard manure) should be generated and compiled so as to be available for use within LCA inventories. Finally, we recommend conducting consequential LCA - if possible - when using LCA for policy-making or strategic environmental planning to account for different functions of the analyzed farming systems.
authors.affiliation: FiBL - Research Institute of Organic Agriculture, Ackerstrasse 113, P.O. Box 219, 5070 Frick, Switzerland. Electronic address: matthias.meier@fibl.org.
authors.forename: Matthias S
authors.initials: MS
authors.lastname: Meier
authors.affiliation: ETH Zurich - Institute of Environmental Engineering, John-von-Neumann-Weg 9, CH-8093 Zurich, Switzerland. Electronic address: franziska.stoessel@ifu.baug.ethz.ch.
authors.forename: Franziska
authors.initials: F
authors.lastname: Stoessel
authors.affiliation: ESU-services Ltd., Margrit Rainer-Strasse 11c, 8050 Zurich, Switzerland. Electronic address: jungbluth@esu-services.ch.
authors.forename: Niels
authors.initials: N
authors.lastname: Jungbluth
authors.affiliation: ETH Zurich - Institute of Environmental Engineering, John-von-Neumann-Weg 9, CH-8093 Zurich, Switzerland. Electronic address: juraske@ifu.baug.ethz.ch.
authors.forename: Ronnie
authors.initials: R
authors.lastname: Juraske
authors.affiliation: FiBL - Research Institute of Organic Agriculture, Ackerstrasse 113, P.O. Box 219, 5070 Frick, Switzerland. Electronic address: christian.schader@fibl.org.
authors.forename: Christian
authors.initials: C
authors.lastname: Schader
authors.affiliation: FiBL - Research Institute of Organic Agriculture, Ackerstrasse 113, P.O. Box 219, 5070 Frick, Switzerland. Electronic address: matthias.stolze@fibl.org.
authors.forename: Matthias
authors.initials: M
authors.lastname: Stolze
mesh_terms: D000383:Agriculture / Q000379:methods* / Q000706:statistics & numerical data; D000818:Animals; D044822:Biodiversity; D002244:Carbon / Q000032:analysis; D003247:Conservation of Natural Resources / Q000379:methods*; D004777:Environment; D005308:Fertilizers / Q000032:analysis; D008372:Manure / Q000032:analysis; D008962:Models, Theoretical; D009584:Nitrogen / Q000032:analysis*; D058871:Organic Agriculture / Q000379:methods* / Q000706:statistics & numerical data; D011050:Policy Making
chemical_list: D005308:Fertilizers; D008372:Manure; D002244:Carbon; D009584:Nitrogen
keywords: Agriculture; Attributional; Comparative life cycle assessment (LCA); Consequential; Conventional; N-surplus; Organic