Hydroponic system and desalinated seawater as an alternative farm-productive proposal in water scarcity areas: Energy and greenhouse gas emissions analysis of lettuce production in southeast Spain

Abstract

In south-eastern Spain, alternative water sources, such as desalinated seawater, and technologies for irrigation, such as hydroponic systems are required, as agriculture is currently using 80% of water resources. The present manuscript assesses the energy consumption and greenhouse gas emissions associated to two lettuce production systems, conventional soil cultivation and hydroponic system, with three desalinated seawater and freshwater blends scenarios (i.e. 0%–50%–100% of desalinated seawater). The implementation of a hydroponic system improved yield, water productivity and specific greenhouse gas emissions with respect to soil cultivation. However, specific energy consumption increased by 17% compared to soil cultivation (3.61 MJ kg−1 versus 4.23 MJ kg−1) production. Specific greenhouse gas emissions were notably lower for the hydroponic system (0.11 kg CO2eq kg−1) compared to those in the soil cultivation (0.23 kg CO2eq kg−1). The progressive replacement of conventional water resources by desalinated seawater linearly increased energy consumption and greenhouse gas emissions in both production systems. However, the hydroponic system was less sensitive to such replacement than the soil cultivation. The results indicated that, under the expected scenarios of water limitation for agriculture, desalinated seawater coupled with hydroponic system could be a valuable strategy to sustain a high productive agriculture; albeit also highly dependent on energy. Using renewable energy could reduce emissions by 9% in hydroponic and by 2% in soil cultivation systems.