Characterization of condensates from an indirect olive oil pomace drying process: The effect of drying temperature

Abstract

Residual oil recovery from olive mill solids-containing residues (pomace) necessitates significant reduction of its water content, usually done in direct-contact dryers producing polluting vapors. An environmentally superior alternative involves pomace drying by indirect heating at modest temperatures, vapor condensation and condensate treatment for utilization or safe disposal. To develop such an integrated process, this study focuses on the condensates from pomace drying by indirect-heating at 70–120°C. These condensates exhibit fairly high concentration of organic substances, significant quantities of phenolic compounds, acidity, and low biodegradability. At the higher temperatures, local overheating of equipment surfaces, especially during the final stage of batch drying, tends to degrade condensate characteristics due to pyrolysis and/or vaporization of organic matter. At relatively low temperatures, condensates exhibit smaller concentration of organic and phenolic compounds, which entail improved biodegradability. Therefore, relatively low temperatures, combined with moderate vacuum, appear to be preferable drying conditions facilitating further condensate treatment.