Towards energy efficient scheduling in the olive oil extraction industry: Comparative assessment of energy consumption in two management models

Although olive oil is one of the most important food products throughout the Mediterranean region, the main consideration in configuring and operating extraction plants is still the quantity of crop that will be brought by the individual growers, who are often of small and medium size. On this basis, the common configuration is the batch processing line (Ba-PL) for small and medium capacities, with malaxers arranged in parallel, or in larger -capacity industrial mills, the arrangement of malaxers in series for simulation of continuous processing (Co-PL). A review of literature to date reveals that there have been no assessments of the energy use and scheduling strategies for these two processes, therefore the current study undertakes such assessment and comparison of the Ba-PL and Co-PL configurations, within a single mill facility. The results show that energy output for Ba-PL was 105,570.00 MJ day-1 based on inputs of 3212.76 MJ day-1, while outputs from Co-PL reached 422,280.00 MJ day -1 from inputs of 6740.38 MJ day -1. Given that the yield of oil is almost the same in the two processes, the Net Energy (NE) for Ba-Pl then results as 10,2357.24 MJ day -1 versus 41,5539.62 MJ day-1 for the Co-PL configuration, and moreover the later process is seen to achieve almost double the Energy Use Efficiency, at 62.65 versus 32.86 in Ba-PL. Finally, the Overall Equipment Effectiveness (OEE) analysis of performance for the two processes shows values of 93.1 % for the Co-PL configuration but only 51.2 % for Ba-PL, due mainly to dead times in throughput on the Ba-PL machinery, resulting in a 44.7 % decrease in the values for the Performance parameter. The conclusion is that to meet the needs of small producers, there must be new management ap-proaches and improvement in the energy use for batch processing. Some strategies could be: - measure the oil content and moisture in input batches using rapid, non-destructive methods, so that homogeneous batches can be pooled before processing; - reduce dead time by developing automated systems for pumping the olive paste from the malaxers to the separation decanter; - even in the case that they are non-homogenous, consider pooling undersized batches so as to avoid mass flows far below the malaxer capacities. Throughout the Mediterranean, olive oil production using batch processing remains very substantial, therefore further studies are required for the identification and evaluation of solutions for optimising this process.