Citrus fruit production is a major food business with global relevance in the agricultural sector. The surface area of citrus irrigated with desalinated seawater in Spain, the leading citrus producer of Europe, has increased dramatically in the last decade. Desalinated seawater has alleviated water scarcity, but is facing environmental and agronomical challenges due to its high energy consumption and high boron content. The latter particularly affects citrus production due to its sensitivity to boron, since additional water treatment may be required to prevent phytotoxicity damage. The objective of this work was twofold: to quantify and compare, for the first time, the life cycle environmental footprint of (i) organic and conventional grapefruit systems irrigated with desalinated seawater, and (ii) two on-farm boron reduction technologies, namely reverse osmosis and ion exchange resins. Life Cycle Assessment has been used to evaluate the grapefruit production systems and the two technologies. The systems compared had similar characteristics (cultivar and planting density), to enable a fair comparative assessment between organic and conventional woody crops. The results show that the organic grapefruit production had better environmental performance than the conventional system in all selected impact categories and both, land and mass, functional units. The comparison of deboronation technologies showed that ion exchange resins caused a much (one order of magnitude) lower environmental footprint than reverse osmosis. Overall, this study shows that the most environmentally friendly grapefruit system irrigated with desalinated seawater was organic production combined with the use of ion exchange resins for deboronation.

This research was supported by the projects SEA4CROP (PID2020-118492RA-C22), funded by MCIN/AEI/10.13039/501100011033 (Spain), and Solution4Farming (PCI2021-122031-2A), funded by MCIN/AEI/10.13039/501100011033 (Spain) and the European Union's NextGenerationEU/PRTR, Horizon2020 Research & Innovation Programme, Joint Call of the Cofund ERA-Nets (grant agreements 696356, 771134, 862665 and 696231). Additional financial support was provided by the AGROALNEXT programme supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Fundación Séneca with funding from Comunidad Autónoma Región de Murcia (CARM) and the European program NextGenerationEU by the Science and Innovation Missions 2021, Recovery, Transformation and Resilience Plan, NextGenerationEU under the CDTI project SOS-AGUA-XXI" (MIG-20211026). B. Gallego-Elvira acknowledges the support from the Spanish Ministry of Universities (‘Beatriz Galindo’ Fellowship BEAGAL18/00081). Imbernón-Mulero acknowledges the financial support for his PhD work from the project SEA4CROP and the predoctoral program of the Technical University of Cartagena (RV- 484/21, UPCT, Spain).