Circular economy strategy of reusing olive mill wastewater in the ceramic industry: How the plant location can benefit environmental and economic performance

Abstract

The olive mill wastewater (OMWW) is one of the highly pollutant residue in olive oil producing countries around the Mediterranean Sea, due to its large organic load and the presence of a variety range of contaminants. The valorization and the recycling of this by-product can represent a successful strategy for the implementation of circular economy models in the agri-food industry. For this purpose, the incorporation of OMWW in the brick-making process represents a promising solution, which not only can avoid the impacts due to its disposal but also reduce the heat required during the ceramic production process, resulting in lower greenhouse gas emissions and economic benefits. However, many factors should be considered, including the transport activity of the OMWW from the mill to the factory that can affect both the environmental and economic benefits. The present study aims to assess the performance of an open-loop circular economy system based on the reuse of the OMWW in the fired clay brick production, in terms of technical feasibility, environmental and economic sustainability. To evaluate environmental impacts, a comparative Life Cycle Assessment is performed between a conventional production and a system in which OMWW is directly integrated in the brick-making process, considering scenarios with different transport distances. Furthermore, an economic sensitivity analysis was implemented, taking into account energy savings and the additional costs due to transport. The results showed that the overall Global Warming Potential (GWP) decreases up to 3.1% for OMWW-based bricks with respect to conventional ones, as well as the Abiotic Depletion of fossil fuels is reduced by 4.3%. On the other hand, no significant variations were observed for the toxicity impact category, that ranges from −1.1% to 0.7%. Furthermore, the water consumption increases for OMWW-based brick production up to 7.8%. Finally, in terms of GWP, it has been found that to make the benefits persist, the oil mill should be placed in a distance of less than 150 km from the brick factory, indicating a more restrictive constraint than the economic one, corresponding to a distance of 207 km.