Residual biomass potential in olive tree cultivation and olive oil industry in Spain: valorization proposal in a biorefinery context

Paloma Manzanares,Mercedes Ballesteros,Eulogio Castro,Encarnación Ruiz,Juan C López-Linares,Francisco J Gallego,María J Negro

doi:10.5424/sjar/2017153-10868

Abstract

Olive crop and olive oil industry generates several residues, i.e., olive tree pruning biomass (OTPB), extracted olive pomace (EOP) and olive leaves (OL) that could be used to produce high-added value products in an integrated biorefinery. OTPB is generated in the field as a result of pruning operation to remove old branches; EOP is the main residue of the pomace olive oil extracting industry after extraction with hexane of residual oil contained in olive pomace; and OL comes from the olive cleaning process carried out at olive mills, where small branches and leaves are separated by density. In this work, an analysis of the potential of OTPB, EOP and OL residues was addressed by estimating the production volumes at national level and the spatial distribution of these residues using geographic information system software. Information provided by public institutions and personal surveys to the industries was evaluated. Moreover, chemical analysis of the residues was undertaken and the results used to make a first assessment of valorization into biofuels such as bioethanol and bio based chemicals. Results show that close to 4.2 million tons/year of EOP, OL and OTPB derived from olive oil industry and olive tree cultivation in Spain could be available as a raw material for biorefineries in Spain. The analysis of the chemical characteristics indicates the relevant potential of these feedstocks for the production of bioethanol and other compounds such as phenols based on suitable processing and conversion routes, although techno-economic evaluations must be tackled to refine this approach.

Highlights

Olive (Olea europaea L.) oil production has a significant importance in the agroindustry of Mediterranean countries due to the large extension in the growing area of olive tree crop and the number and capacity of olive processing facilities
olive tree pruning biomass (OTPB) is generated in the field as a result of pruning operation to remove old branches; extracted olive pomace (EOP) is the main residue of the pomace olive oil extracting industry after extraction with hexane of residual oil contained in olive pomace; and olive leaves (OL) comes from the olive cleaning process carried out at olive mills, where small branches and leaves are separated by density
In Spain, olive oil production represents the major part of the olive agroindustry, with close to 1,800 operating olive mills that process more than 3 million tons per year of olives for virgin olive oil production

Summary

Introduction

Olive (Olea europaea L.) oil production has a significant importance in the agroindustry of Mediterranean countries due to the large extension in the growing area of olive tree crop and the number and capacity of olive processing facilities. In Spain, and according to the recent estimations from FAOSTAT (http://faostat3.fao.org), 2.5 Mha of olive crop were cultivated in 2014, representing 24.4% of total worldwide production and positioning the country as the leader in olive tree cultivation. The olive tree pruning biomass (OTPB) comprises leaves (~ 25% dry weight basis, dwb), thin branches (~ 50% dwb) and wood of different thickness (~ 25% dwb) (Romero-García et al, 2014). Nowadays, this residual biomass has no specific use except for the higher size wood that is often used in domestic fire. The chopping of pruning residues is important because this mulch can protect the soil for long time periods than cover crops, helping farm workers to prevent land degradation, as found by Rodríguez-Lizana et al (2017) in olive groves

Objectives

Methods

Results