Historical evolution of olive oil production processes focusing on the role of water, the contribution of energy sources, and the by-product management: The case-study of Crete, Greece.

There are numerous studies dealing with olive oil management from ancient civilizations to the mid last century, but they are limited on the historical value of information. At the same time, much knowledge is widely available and accessible on the contemporaneous production of olive oil, the necessary inputs (water and energy) and outputs (by-products) of the production process. The present study aims to shed light on olive oil extraction management from antiquity to present and to bridge the gap between archaeological and modern agricultural, engineering, and environmental disciplines. For the purposes of this study, Crete, Greece, a well-known and traditional olive oil producing region is investigated. This study is dedicated to unveil practices concerning: (a) the processing of the olives, (b) the various energy aspects per era, (c) the role of water and energy at each stage of the extraction process, and (d) management of by-products per era. The main findings support that: (a) the evolution of the extraction processes was relatively slow and remained almost the same from Minoan times until the middle of the 20th century, (b) the importance of water has been demonstrated from the beginning in the efficient extraction of the maximum amount of olive oil, (c) wastewater was first reported during the Hellenistic-Roman period due to the increased quantities produced, (d) by-product management was only considered in the previous century for environmental purposes, (e) olive oil production has been a human-based process for centuries and was greatly increased by the introduction of animals, and (f) olive oil production was further increased with the utilization of mechanical and electrical energy. It can be therefore clearly concluded that past practices have both similarities and differences with the present ones, which in turn have been optimized in terms of energy sources, water uses, olive mill equipment, and environmental considerations, to result in maximum olive oil production with minimum environmental impacts. Based on this work, important lessons can be drawn that show the historical evolution of extraction and management practices.