LCA of local and imported tomato: an energy and water trade-off

The environmental impact of imported fresh agricultural products, such as off-season vegetables transported over long distances, is under growing scrutiny. We hypothesised that the environmental Life Cycle Assessment (LCA) ranking between local and imported vegetables might change depending on the impact category considered. We focused on the case study of off-season tomatoes produced in Morocco under unheated greenhouses in a water-scarce area, which covers 68% of the fresh tomatoes imported to France. First, we performed a cradle-to-market gate LCA of the Moroccan production using primary data based on a field survey. Second, we applied the same Life Cycle Impact Assessment (LCIA) method to published cradle-to-farm-gate results of the French tomato cropping system, which also provides off-season tomatoes to the French market and which is characterised by heated greenhouses with a high level of inputs. In addition to typical environmental impact categories, the freshwater use impact was included. The ranking between imported and local tomatoes was different depending on the impact category. Freshwater use had greater impacts under the Moroccan arid climate: 28.0 L H2Oeq kg?1 of Moroccan tomato and 7.5 L H2Oeq kg?1 of French tomato. Conversely, the higher level of artificialisation of the French production resulted in greater impacts on total energy consumption, global warming, and eutrophication, even including transport to France for the Moroccan tomato. This reveals a trade-off between freshwater use impacts and the usual/other impacts, mostly energy-related. At the farm gate, we found that the Moroccan tomato water consumption highly contributed to the total damages to Human Health (14%), and Ecosystems (20%) (contribution to Resources depletion was only 2%). Therefore, ignoring the impacts of freshwater use in LCA also underestimates the damages. Moreover, we showed that the assessment of freshwater use impacts and damages still has shortcomings, leading to an underestimation of the impact for the Moroccan tomato case. These results emphasised the importance of considering all of the impact categories when performing an agricultural LCA and the need for a more comprehensive method for assessing the impacts of freshwater use. In particular, the use of an operational tool for estimating water and solute fluxes at the field level is recommended to feed freshwater impact assessment methods. (Résumé d'auteur