Greenhouse gas assessment of olive oil in Portugal addressing the valorization of olive mill waste

This article presents a comparative life-cycle Greenhouse Gas (GHG) assessment of olive oil produced from two alternative extraction processes (three-phase and two-phase extraction). A life-cycle model and inventory was implemented for the entire olive oil chain, including olive cultivation, oil extraction and olive pomace oil extraction. The valorization of olive pomace (produced with olive oil) to produce olive pomace oil and extracted pomace is assessed. Two approaches for dealing with multifunctionality in the oil extraction were analyzed: i) allocation based on economic criteria (market prices) to partition impacts and ii) substitution (“avoided burden approach”) of extracted pomace (displacing conventional fuel in energy intensive processes) and olive pomace oil (used for biodiesel production in Portugal, displacing the current mix of virgin oils). The results showed that the GHG intensity of olive oil greatly depends on the type of extraction process. In addition, the multifunctionality approach adopted significantly influences the results and even reverses the rank order of the extraction process that led to the lowest olive oil GHG intensity. The GHG intensity of olive oil produced from three-phase extraction vary from 0.24 kg CO2 eq L (substitution) to 1.86 kg CO2 eq L (allocation) and, for two-phase extraction, from 0.94 kg CO2 eq L (substitution) to 1.69 kg CO2 eq L (allocation). Olive cultivation was the life-cycle phase that contributes most to the total GHG intensity of olive oil production.