Wheat straw and eucalyptus residues were pretreated in a biphasic system, constituted of butanol (n-butanol) or 2-methyltetrahydrofuran (2M-THF) and aqueous oxalic acid solutions. The pretreatments were carried out in a 300 mL Parr reactor (Autoclave Buchi Limbo-li^®) with a solid load of 5 wt.%, the temperature in the range 140–180 °C, oxalic acid load from 0 to 10 wt.% and a duration of 30–90 min. The obtained slurry was then fractionated in three streams: the aqueous phase which contained solubilized hemicellulose, the organic phase which contained the solvated lignin, and the solid residue which contained cellulose. The solid was hydrolyzed using a commercial mix of enzymes to assess cellulose digestibility and glucose production. The pretreatment was optimized to maximize the purity of the cellulose and hemicellulose fractions and the glucose recovery as free sugar. The optimization was done by using an experimental design and response surface methodology. The mass flow details of the four optimized processes were obtained. In terms of biomass fractionation, butanol demonstrated significant advantages over 2M-THF in the same range of process conditions as shown by the recovery yield of free glucose which reached 98% of the theoretical value with butanol but was 67% with 2M-THF. Tests at low temperature and low enzyme loading highlighted the importance of the solvent choice over the operating conditions. 2M-THF showed interesting performances only in the delignification step, with 90% efficiency for the straw. Regarding the use of different feedstock, fractionation and recovery were generally higher for wheat straw than for eucalyptus wood residues.

The advantage of using paddle dryers (PD) in the production of sugars and 2nd generation ethanol from pretreated wheat straw was investigated. This machinery was employed in order to detoxify steam-exploded substrates and to mix different slurries in the hydrolysis step. The obtained hydrolysate was fermented by the yeast Saccharomyces cerevisiae. Acetic acid and furfural were reduced up to 11 and 26 fold respectively in the detoxified substrate. When fermentation was carried out at low solid suspension, the use of PD was as effective as water extraction in detoxifying exploded biomass, giving ethanol yields of 90% at 0.05 solid/liquid ratio (S/L) and 80% at 0.10 S/L. Moreover, by using PD the cellulose conversion yield was significantly improved in the hydrolysis step: when operating at higher S/L (0.4), the hydrolysis efficiency was twice the one achieved by using a bioreactor with a Rushton stirrer.

The use of lignocellulosic biomass to obtain biofuels and chemicals produces a large amount of lignin as a byproduct. Lignin valorization into chemicals needs efficient conversion processes to be developed. In this work, hydrocracking of organosolv lignin was performed by using nickel Raney catalyst. Organosolv lignin was obtained from the pretreatment of eucalyptus wood at 170 °C for 1 h by using 1/100/100 (w/v/v) ratio of biomass/oxalic acid solution (0.4% w/w)/1-butanol. The resulting organic phase of lignin in 1-butanol was used in hydrogenation tests. The conversion of lignin was carried out with a batch reactor equipped with a 0.3 L vessel with adjustable internal stirrer and heat control. The reactor was pressurized at 5 bar with hydrogen at room temperature, and then the temperature was raised to 250 °C and kept for 30 min. Operative conditions were optimized to achieve high conversion in monomers and to minimize the loss of solvent. At the best performance conditions, about 10 wt % of the lignin was solubilized into monomeric phenols. The need to find a trade-off between lignin conversion and solvent side reaction was highlighted.

Inulin is accumulated as a reserve carbohydrate in the roots and tubers of many plants belonging to the Asteraceae family. At present, most of the inulin for nutraceutical purposes is produced from Jerusalem artichoke (Helianthus tuberosus L.) and Chicory (Cichorium intybus L.), and cardoon is proved to synthetize and store a high quantity of inulin in roots. Inulin in the roots of cardoon reaches the maximum content before the beginning of flowers formation in May. Due to the limited favorable period for harvesting the roots, storage plays a key role in the supply chain. The complete drying of cardoon roots before the storage has been proved to prevent the degradation of inulin up to 6 months of storage. Because drying is a costly operation, in the present study, energy-saving and the effect on percentage inulin content in cardoon roots dried at different moisture contents before storage were assessed. From 48.2% inulin retrievable at the beginning of the investigated period (100% dry matter), after 1 month of storage, about 2% reduction was recorded on average in H0 and H12.5 treatments, while about 10% reduction was shown (with no statistical differences) in treatments at higher moisture contents (TQ, H50, and H25). These values remained constant until the end of storage, except for TQ treatment, where inulin content decreased progressively up to 38.7% w/w. From an economic point of view, limiting the drying time and storing roots at a moisture content higher than 0% leads to an income loss of 2,000–3,000 €/t of roots. Therefore, full drying is the most cost-effective solution in the optic of producing the highest possible amount of inulin and could be avoided just in the case of immediate roots extraction and processing in a few days.

Pre-treatments at relatively high temperatures (range 160 °C–220 °C) are currently used to transform lignocellulosics into biofuels and chemicals. In this step, several molecules with an inhibitory effect in the subsequent fermentation processes are generated. These inhibitors include low-molecular-weight molecules and lignin fragments that can be removed by water washing. However, this procedure also removes valuable soluble carbohydrates which are then difficult to recover from the diluted stream. In this work, a new method to detoxify steam-exploded substrates is reported. The procedure is based on the evaporation of low-weight acids and aldehydes, which leaves all the sugars in the solid matrix, while the cellulose hornification (an irreversible modification of the cellulose fibres that depresses the saccharification yield) is prevented by adding steam to the hot fluidizing flow stream. Two systems were tested: a 0.1 kg/batch oscillating fluidized bed and a continuous fluidized bed dryer operating downstream of a steam explosion plant with a treatment capacity of 150 kg/h. The detoxified substrates were subjected to enzymatic hydrolysis and fermentation to obtain bioethanol, with a yield that was 14% higher than that obtained from substrates detoxified with conventional methods of drying or washing.