Initial Investigation of the Solar Drying Method for the Drying of Olive Oil By-Products

In this study, a greenhouse-type solar dryer was developed in order to demonstrate an olive oil by-product and agro-residue Managing System, which uses solar drying processes for the treatment of olive oil mill residues to decrease the high energy consumption of the drying operations, thus decreasing the environmental impact of these residues. The resulting by-products, once dried out, have a final application as fuel. The greenhouse, with a roof height of 3.5 m and total area of 150 m2, consisted of three 3.0 × 1.5 × 0.20 m concrete tanks, where the drying of olive pomace (two- and three-phase olive mills), leaves and biomass from pruning for the production of solid biofuels was examined. The two-phase olive mill by-products required more drying time than three-phase olive mill by-products due to higher moisture content. Moreover, the moisture rate was positively related to minimum relative humidity and the highest material and ambient temperature. Using free solar energy for drying olive oil by-products can be beneficial from the point of view of energy consumption and, consequently, the drying system cost. The main innovation of the process is using the most abundantly available energy source in Greece—and the Mediterranean basin generally—the sun.