RESEARCH ARTICLE


Valorization of Agricultural Residues by Fractionation of their Components



Luis Jiménez*, Alejandro Rodríguez
Departamento de Ingeniería Química, Universidad de Córdoba, Spain


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© 2010 Jiménez and Rodríguez

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this autor at the Departamento de Ingeniería Química, Universidad de Córdoba, Spain; Tel: +34 957 21 86 25; Fax: +34 957 21 86 58; E-mail: iq1jiall@uco.es


Abstract

The combined production of the most abundant agricultural residues in Spain (viz. cereal straw, sunflower stalks, vine shoots, cotton stalks, olive, orange and peach tree prunings, and horticultural and related residues) amounts to over 50 million tons per year, more than 20% of which is generated by Andalusia alone.

Agricultural residues must be disposed of for various reasons including the facts that they promote contamination and pest growth, occupy large expanses of land and hinder agricultural work. Ideally, the disposal method used should allow their major components (cellulose, hemicellulose and lignin) or their chemical potential energy to be exploited.

Agricultural residues can be valorized by converting their components jointly (combustion, pyrolysis, gasification, liquefaction) or separately (fractionation).

The most useful method for exploiting such components separately involves isolating cellulose fibres for papermaking purposes. In recent times, this valorization method has led to the development of the biorefining concept. Biorefining involves the fractionation or separation of the different lignocellulosic components of agricultural residues with a view to their integral exploitation rather than the mere use of cellulose fibre to obtain paper products.

Biorefining replaces the classical pulping methods based on Kraft, sulphite and soda reagents with a hydrothermal treatment followed by organosolv pulping. The hydrothermal treatment provides a liquid phase containing hemicellulose decomposition products [both oligomers and monomers (glucose, xylose, arabinose)] and a solid phase rich in cellulose and lignin. By contrast, the organosolv process gives a solid fraction (pulp) and a residual liquid fraction containing lignin and other useful substances for various purposes.

Keywords: Agricultural residues, biorefinery, fractionation, pulping, hydrothermal treatment.