Economic benefits and soil improvement: Impacts of vermicompost use in spinach production through industrial symbiosis

Industrial symbiosis is being increasingly recognized as a valuable tool for promoting a more sustainable production process in agriculture. However, the primary motivation for implementing industrial symbiosis is economic viability. In the context of industrial symbiosis, by linking agriculture and food together, the study examines the impact of the use of vermicompost, derived from agricultural by-products, on spinach yield as well as on nutritional and biochemical soil aspects. Moreover, the economic feasibility for spinach farmers is also investigated. A field experiment with five treatments i) solarization ii) solarization and vermicompost iii) green manure and solarization iv) green manure, solarization, and vermicompost, and v) vermicompost has been realized in “Piana del Sele”, a rural area in Southern Italy. Collected data have been analysed through a Partial Least Square Structural Equation Modeling approach to assess the overall impact (direct and indirect effects) of vermicompost on both spinach yield and soil characteristics. Lastly, the economic profitability of using vermicompost is pointed out for spinach growers. The study findings show that the highest positive impact on yield occurs when vermicompost is combined with solarization (+15 %). Moreover, with regard to soil characteristics, the combination of vermicompost and solarization has a positive impact on nutrients, fungal biodiversity, and the biochemical quality of the soil. The economic profitability of using vermicompost in conjunction with solarization is guaranteed when the price of vermicompost is below € 0.84/kg. In light of these findings, some policy interventions can be implemented to enable industrial symbiosis as a viable tool for a circular economy in the agri-food sector. These include promoting the diffusion of biogas plants to valorize agricultural by-products and promoting the use of vermicompost in farms, by encouraging its purchase by farmers.