Carbon footprint and cumulative energy demand of greenhouse and open-field tomato cultivation systems under Southern and Central European climatic conditions

The horticultural industry consumes increasing amounts of energy and water contributing to greenhouse gas emissions and global warming. The aim of this study was to investigate the energy flow and the environmental impact of different tomato cultivation systems when renewable energy sources are implemented in the production chain. Seven scenarios including heated greenhouses and open-field crops, in Southern and Central Europe, were examined in order to identify potentials to reduce energy costs, greenhouse gas emissions and increase water use efficiency along the cultivation phase. The environmental impact category applied in this work (carbon footprint) is related to global warming potential, which includes the basic emitted greenhouse gases contributing to climate change and uses CO2 as reference gas (CO2-equivalents). Additionally, an energy flow indicator (cumulative energy demand) and an inventory flow indicator (water use), both relevant to climate change, agriculture and energy processes were determined to assess the different scenarios. The main results showed that annual carbon footprint values varied between 0.1 and 10.1 CO2-eq/kg tomato. Annual cumulative energy demand presented values from 0.8 to 160.5 MJ/kg tomato. Water use efficiency values ranged between 25.6 and 60.0 L/kg. Hotspots for all seven scenarios were determined, with fossil fuel consumption accounting for most of the environmental impact, where applicable. Open-field tomato cultivation presented lower greenhouse gas emissions and cumulated energy demand, however water use efficiency values were smaller than in greenhouse scenarios. In greenhouse production, the use of renewable energy sources and an increased marketable yield reduced their greenhouse gas emissions drastically, even to the levels of open-field cultivation.