Reusing drainage water and substrate to improve the environmental and economic performance of Mediterranean greenhouse cropping

The objective of this study is to provide decision makers and policy makers with adequate information to support the diffusion of reuse strategies in Mediterranean greenhouses. Sixteen alternative scenarios are compared through eco-efficiency analysis, combining four technologies to manage drainage water (open-loop fertigation vs. wastewater treatment plant vs. cascade cropping vs. closed-loop fertigation) with two substrate materials and two substrate management options at end-of-life. System differences are modelled through detailed primary data, collected and validated via a multi-step process. Results show that cascade cropping and closed-loop fertigation have, respectively, the highest and second-highest eco-efficiency, with respect to their ability to reduce freshwater eutrophication (up to −6,63 kg P) and marine eutrophication (up to −47.1 kg P eq), while generating profits for the farmer. Selecting a biodegradable substrate and reusing it on farm can increase greenhouse profitability by 20%. This article is a new contribution to the literature by (i) supporting the improvement and harmonisation of eco-efficiency analysis in the agricultural sector; (ii) providing a comprehensive comparative assessment that is missing from the published literature; (iii) giving special emphasis to data and the data collection process, to provide input to further research; (iv) by generating lessons learnt of practical usefulness for reducing uncertainty in decision making and policy making; (v) by delivering policy recommendations to address key barriers to the diffusion of eco-efficient greenhouse cropping. The involvement of local and multidisciplinary stakeholders is required to improve the methodological approach and the acceptability of the proposed solution, especially in case of trade-offs among the different impact domains, and to identify and prioritise tailored interventions on the conditions and stakeholder needs.