an official journal of: published by:
Editor in Chief: RAFFAELLO COSSU


  • Mariana Cruz - LEPABE, Departamento de Engenharia Metalúrgica e de Materiais, Faculdade de Engenharia,, Portugal
  • Emanuel Costa - LEPABE, Departamento de Engenharia Metalúrgica e de Materiais, Faculdade de Engenharia, Portugal
  • Manuel Fonseca Almeida - LEPABE, Departamento de Engenharia Metalúrgica e de Materiais, Faculdade de Engenharia, Portugal
  • Maria da Conceição Alvim-Ferraz - LEPABE, Departamento de Engenharia Química, Faculdade de Engenharia,, Portugal
  • Joana Maia Dias - LEPABE, Departamento de Engenharia Metalúrgica e de Materiais, Faculdade de Engenharia, Portugal

DOI 10.31025/2611-4135/2018.13728

Released under CC BY-NC-ND

Copyright: © 2018 Cisa Publisher

Editorial History

  • Received: 26 Jun 2018
  • Revised: 01 Oct 2018
  • Accepted: 04 Nov 2018
  • Available online: 14 Nov 2018


The by-products acid oil from soapstock of vegetable oil refining and olive pomace oil were evaluated for biodiesel production. Enzymatic hydroesterification was studied to convert the acid oil ( ̴ 34 wt.% free fatty acids) into methyl esters; due to the low free fatty acid content of the fresh olive pomace oil ( ̴ 2 wt.%), alkaline transesterification was conducted. The results from the enzymatic hydrolysis (35˚C, 24 h, 200 rpm) showed a clear influence of enzyme concentration (0.1 – 5 wt.%, relative to oil) and water:oil ratio (1:0.25 and 1:0.5 w:w) towards free fatty acid production. After applying the best established conditions (3 wt.% of enzyme and 1:0.5 water: oil ratio, w:w), enzymatic esterification was performed (35˚C, 7 h, 200 rpm, 2 wt.% of enzyme and 2:1 molar ratio of methanol to acid). Hydroesterification led to a product with a methyl esters content of about 84 wt.% whereas the esterification alone allowed reaching only around 65 wt.%. The olive pomace oil was obtained from chemical extraction of fresh olive pomace ( ̴ 18 wt.% of oil). By performing direct alkaline transesterification (65˚C, 1 wt.% NaOH, 1 h and 6:1 molar ratio of methanol to oil) a product with a purity of 90 wt.% was obtained. The olive pomace storage in the air during 2 weeks led to an increase in the oil free fatty acid content of almost 2 fold showing the relevance of developing storage and conservation strategies to ensure a sustainable recovery of this by-product. Both by-products showed potential for biodiesel production.



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