Determination of the Lignocellulosic Components of Olive Tree Pruning Biomass by Near Infrared Spectroscopy

José Luis Fernández,Eulogio Castro,Paloma Manzanares,María José Negro,Felicia Sáez,Mercedes Ballesteros

doi:10.3390/en12132497

Abstract

The determination of chemical composition of lignocellulose biomass by wet chemistry analysis is labor-intensive, expensive, and time consuming. Near infrared (NIR) spectroscopy coupled with multivariate calibration offers a rapid and no-destructive alternative method. The objective of this work is to develop a NIR calibration model for olive tree lignocellulosic biomass as a rapid tool and alternative method for chemical characterization of olive tree pruning over current wet methods. In this study, 79 milled olive tree pruning samples were analyzed for extractives, lignin, cellulose, hemicellulose, and ash content. These samples were scanned by reflectance diffuse near infrared techniques and a predictive model based on partial least squares (PLS) multivariate calibration method was developed. Five parameters were calibrated: Lignin, cellulose, hemicellulose, ash, and extractives. NIR models obtained were able to predict main components composition with R2cv values over 0.5, except for lignin which showed lowest prediction accuracy.

Highlights

Within the last two decades, components of biomass materials such as lignocellulosic residues have increasingly received more attention in the science community due to their potential for the production of biofuels, as well as new value-added compounds and biomaterials utilizing a “biorefinery” approach.Olive trees are usually native to the Mediterranean countries, but cultivation has spread globally during the past two decades due to healthy benefits attributed to olive oil consumption
A sub-sample of milled olive tree pruning was used for analysis of chemical composition and another sub-sample for Near infrared (NIR) spectroscopy
In Olive tree pruning (OTP) biomass, cellulose content is in the range of 8.6–19.8% (w/w)

Summary

Introduction

Within the last two decades, components of biomass materials such as lignocellulosic residues have increasingly received more attention in the science community due to their potential for the production of biofuels, as well as new value-added compounds and biomaterials utilizing a “biorefinery” approach.Olive trees are usually native to the Mediterranean countries, but cultivation has spread globally during the past two decades due to healthy benefits attributed to olive oil consumption. Olive trees are cultivated in more than 40 countries, and the total dedicated surface is about 10.8 million ha in 2017 [1]. In the Mediterranean region, residual biomass from olive tree pruning yield ranges from 1 to 5 and from 4 to 11 oven dry t ha−1 respectively for Spanish and Italian orchards [2]. Older branches are cut down, gathered into to the center of each row of trees, and further treated. This agricultural residue must be promptly eliminated from the cultivation fields; otherwise a risk for vegetal diseases may arise. Two different applications for this pruning biomass exist, either grinding it or scattering the chips over the field or direct burning. It has been proposed to use this waste as raw material for Energies 2019, 12, 2497; doi:10.3390/en12132497 www.mdpi.com/journal/energies

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