Low Energy and Carbon Hydroponic Tomato Cultivation in Northern Spain: Nutritional and Environmental Assessment

The agri-food sector is one of the most impactful on the environment in terms of greenhouse gas emissions and is one of the largest consumers of energy and natural resources. In this context, the objective of this study was to evaluate the environmental impacts of hydroponic tomatoes cultivated in northern Spain using a waste product as biomass to heat the greenhouses and solar energy for powering the irrigation system to identify their main environmental hotspots and improvement measures. For this purpose, life cycle assessment (LCA) has been used. The functional units (FUs) chosen were 1 kg of tomatoes and an alternate FU based on nutrition, e.g., NRF9.3. The influence of including biogenic CO₂ emissions has been considered using a “-1/+1″ approach to assess the uptake and release of biogenic carbon throughout the whole life cycle. The main results showed that greenhouse gas emissions varied between 1.4 kg CO₂ equiv and 2.5 kg CO₂ equiv considering biogenic carbon, whereas the total energy demand of the production of hydroponic tomatoes was 9.7 MJ. Fertilization and the greenhouse structure were identified as the main contributors to environmental burdens; hence, improvement opportunities were focused on these critical points.