Valorization of olive oil industry subproducts: ash and olive pomace fast pyrolysis

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Environmental problems have encouraged investigation of renewable energies. The organic waste treating through fast pyrolysis seems to be a highly promising option for decreasing pollutants. Olive pomace, a major source of waste in countries with high production of olive oil (mainly Spain, Italy, and Greece), is a clear target for valorisation. Dried olive pomace together with the ashes obtained during the drying process was blended to study the influence of the inorganic metals inherently present in the ashes (K, Na, Ca and Mg) for fast pyrolysis product distribution. The results determined that these metals increased yields of phenolic compounds until a maximum was reached, whereas carboxylic acid yield fell due to the action of metals. In addition, aromatic hydrocarbons and polyphenols were obtained for those samples with a large amount of ash. Moreover, the formation of organic acids, such as acetic acid, requires a smaller proportion of ash in the blend. Finally, it has been found that the ashes could be used as a catalyst for producing better quality bio-oil, thereby avoiding extra costs and thus valorizing the industrial treatment olive pomace.