Microwave Assisted Organosolv Pretreatment of Olive Tree Pruning and Cardoon Stalks to Obtain Cellulose

Microwave assisted pretreatment with acetone as organosolvent was performed for both olive tree pruning (OTP) and cardoon stalks (CS) biomasses in order to produce a rich cellullose material. Two different designs based on the Response Surface Methodology (RSM) were applied to check the effect of variables such as reaction time, temperature and concentration of acetone acid solution on OTP and CS original biomasses fractionation. Adequate second-degree fitting models have been obtained for the percentages of cellulose and acid insoluble lignin of the treated solids as well as for the percentage of solubilized cellulose and removed lignin. The optimization process was carried out in a simultaneous way attending to maximize both the cellulose content and the removed lignin, and minimizing the lignin composition of the obtained solids and the solubilized cellulose. The obtained results show that the pretreatments carried out are reasonably successfully in order to obtain solids with a high content of cellulose (>88%), easy to hydrolyze enzimatically, and a liquid solution valorizable due to the lignin solubilized in it. Thus, this work can be considered as the first step of an integrated biorefinery process and these agricultural biomasses, which need to be treated, can generate an important benefit because the proposed process reduces both costs and environmental impact.