Biorefinery of olive pruning using various processes A. Requejo a , S. Peleteiro b , G. Garrote b , A. Rodríguez a , L. Jiménez a,⇑ a Chemical Engineering Department, University of Córdoba, Spain b Chemical Engineering Department, University of Vigo, Spain article info Article history: Received 1 December 2011 Received in revised form 24 January 2012 Accepted 25 January 2012 Available online 14 February 2012 Keywords: Olive pruning Hydrothermal treatment Organosolv pulping Combustion Bioethanol abstract Biorefinery developed involve separation of olive pruning into two parts: main (OPM) (stems > 1 cm diameter), and residual (OPR) (stems < 1 cm diameter, and leaves). OPM was submitted to hydrothermal treatment, separating: a liquid fraction (HL), rich in products of hemicelluloses decomposition, and other solid (HS), rich in cellulose and lignin. HS is subject to pulping, resulting: a liquid fraction (HPL), rich in lignin, and other solid (HPS), rich in cellulose. Up to 42% of the polysaccharides from OPM were recovered in HL as valuable compounds. HPS can be used for the bioethanol production by saccharification and fermentation, reaching a bioethanol conver- sion of 90.6% of the theoretical value. In addition, HPS obtained paper with lower strength properties than those of paper obtained from OPM pulp directly. OPR provided 18.70 MkJ/t heating values, 1094–2234 °C flame temperature, and 45–53 °C dew point temperature, with a cost of the unit of heat (3.20 €/MkJ) much lower than fossil fuels fluids. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction There is currently much interest in the use of all the constitu- ents of all parts of lignocellulosic materials. This is due to the need of obtaining more chemicals and energy; as an example is enough to consider that the market for petroleum fuels will increase by 50% in the next 15 years (Vancov and McIntosh, 2011; David and Ragauskas, 2010). In this context, the use of new vegetables raw, which are a renewable, clean, inexpensive and high availability, for the manufacture of chemicals and fuels is a strategic objective today. These raw materials will be an alternative and will replace petroleum (Hoekman et al., 2011; Lynd et al., 2009; Wang and Cheng, 2011). Vegetable raw is usually composed of various fractions (logs, stems, bark, leaves...) containing different proportions of the main components: cellulose, hemicellulose, lignin, and extractives. Moreover, these raw materials give rise to residues of the activities that are used: agricultural, agro-industrial, and forestry, mainly. In summary, it can be seen that vegetables provide different fractions, in which the main components are presented in different amounts. Therefore, for the full utilization of a lignocellulosic material (origi- nal vegetal or residue) has to proceed to a separation of different fractions or parts, and apply to each of these parts processes that make better use its various components. Thus, a hydrothermal process (treatment with water at high temperature) applied to rich holocellulose fractions, causes decomposition of the hemicellu- loses, leading to a liquid fraction (HL) in which there are several products (oligosaccharides, monosaccharides, organic acids, and dehydration products of sugars) that can be used in the chemical, pharmaceutical and food industries. (Parajó et al., 2004; Moure et al., 2006). The solid fraction (HS) resulting from hydrothermal treatment (rich in cellulose and lignin) can be treated with an or- ganic solvent; in this way gets a pulp (HPS), rich in cellulose, and a liquid (HPL), rich in lignin solubilized. The HPS can be used for paper production (Jiménez et al., 2006; Caparrós et al., 2008; Rodríguez et al., 2009; Sánchez et al., 2011) or undergo hydrolysis processes (acid or enzymatic) of cellulose to make sugars, which can be fermented to bioethanol (Garrote et al., 2001; Qing and Wy- man, 2011). Finally, from the HPL can be separated lignin, which can be obtained several high-value products (Rodríguez et al., 2010). The hydrothermal treatment is not only interesting for the separation of decomposition products of hemicelluloses but also because chemical and/or structurally modifications in raw materi- als, increasing its reactivity in other post process, such as enzy- matic hydrolysis of cellulose to obtain fermentable sugars for bioethanol, or pulp production by organosolv processes, with the separation of sulfur-free lignin in pulping liquors residual (Garrote et al., 2001; Parajó et al., 2004; Caparrós et al., 2008; Rodríguez et al., 2009, 2010). On the other hand, others fractions less noble can be used, for example, as fuel directly to produce energy by combustion (Arvelakis and Koukios, 2002; Ozturk and Bascetinlik, 2006; Overend and Wright, 2008). 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2012.01.156 ⇑ Corresponding author. Address: Chemical Engineering Department, Campus of Rabanales, University of Córdoba, Córdoba, Spain. Tel.: +34 957 218658; fax: +34 957 218625. E-mail address: iq1jiall@uco.es (L. Jiménez). Bioresource Technology 111 (2012) 301–307 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech