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The purpose of this work was the valorization of wood/wastes of two invasive tree species, namely Acacia dealbata and Ailanthus altissima, in the production of polyelectrolytes as high value-added products for a range of applications. Kraft cooking of wood chips followed by the introduction of quaternary ammonium groups into the cellulose backbone using a typical sodium periodate oxidation/Girard’s reagent T cationization was performed. Water-soluble polyelectrolytes were obtained with a cationic group content of 3.0–3.6 mmol/g which were characterized, and, as a proof of concept, evaluated as flocculants in the treatment of an industrial effluent from olive oil mill, a harsh and difficult to treat effluent. Under optimized conditions of pH (4.5–7) and flocculant dosage (50−100 mg/L), an effluent turbidity removal of up to 65 % was achieved. The proposed approach enabled to obtain, for the first-time, valuable polyelectrolytes from very low value woods, with potential interest for application as flocculants in effluent treatment. Additionally, the experiments also proved that there is no need to completely remove lignin from wood before cationization, mild deconstruction procedures allowing to produce water-soluble polyelectrolytes and achieve a good performance in the flocculation process.

Pinus pinaster wood (PPW) was fractionated by two different routes: (1) a two-steps system by soda ethanol organosolv (SEOS) followed by lignin precipitation (LP) and (2) a three-steps procedure encompassing autohydrolysis (AH) followed by SEOS and LP. In the two-steps route, the effect of ethanol mass fraction in the cooking liquor (15-55 wt.%) on pulps and lignins purities was studied. In the three-steps system, the effects of AH temperature (160-180 °C) and reaction time (30 and 60 min) on hemicelluloses removal were evaluated. Then the effects of AH temperature (175 and 180 °C) and ethanol concentration (15-35 wt.%) on SEOS derived pulps and lignins purities were considered. The SEOS reaction temperature (170 °C) and time (90 min) were kept constant in all SEOS experiments. In the case of the two-steps approach, pulps with lignin and hemicellulose contents as low as 6 and 15 wt.% (respectively), as well as precipitates having lignin contents up to 94 wt.% were obtained. Up to 81 wt.% of the cellulose and 66 wt.% of the lignin initially present in PPW were recovered in pulps and precipitates (respectively) by this fractionation pathway. When the three-steps fractionation was applied, up to 17 wt.% of the original biomass was recovered in AH liquors. Pulps having hemicellulose contents as low as 3 wt.% and lignin contents as low as 5 wt.% were produced by sequential AH and SEOS, while LP products presented lignin contents higher than 98 wt.%. The results show the potential of the three-steps fractionation towards a biorefinery-based bioeconomy.

Primary sludge from a Portuguese pulp and paper mill, containing 60% of carbohydrates, and unbleached pulp (as reference material), with 93% of carbohydrates, were used to produce ethanol by simultaneous saccharification and fermentation (SSF). SSF was performed in batch or fed-batch conditions without the need of a pretreatment. Cellic® CTec2 was the cellulolytic enzymatic complex used and Saccharomyces cerevisiae (baker's yeast or ATCC 26602 strain) or the thermotolerant yeast Kluyveromyces marxianus NCYC 1426 were employed. Primary sludge was successfully converted to ethanol and the best results in SSF efficiency were obtained with S. cerevisiae. An ethanol concentration of 22.7 g L−1 was produced using a content of 50 g L−1 of carbohydrates from primary sludge, in batch conditions, with a global conversion yield of 81% and a production rate of 0.94 g L−1 h−1. Fed-batch operation enabled higher solids content (total carbohydrate concentration of 200 g L−1, equivalent to a consistency of 33%) a...

A primary hydrolysis treatment (auto or acid-catalysed) of Eucalyptus globulus wood was performed before the cooking stage to extract part of the hemicelluloses that otherwise would be dissolved in the kraft liquor and burned. As xylose was the main monosaccharide Pichia stipitis was selected to produce bioethanol. Two methods were tested, with different alkalis, to reduce hydrolysates toxicity and adjust pH. A two-step method using Ca(OH)2 leads to better fermentation results. Acid hydrolysates promoted higher ethanol concentrations (12 g L−1) with high productivity and yield values (0.22 geth L−1h−1 and 0.48 geth/gxyl eqs), whilst auto-hydrolysates, even after a secondary hydrolysis, gave low ethanol concentrations (2–4 g L−1). The impacts on kraft cooking and pulp quality were also studied in order to fully understand the feasibility of this biorefinery concept (combining ethanol production and hardwood pulping). A decrease of the overall pulp yield (10% for auto- and 15% for acid-hydrolysis) was observed. However, a decrease on bleaching requirements (up to 15%) and on brightness reversion was registered. Moreover, auto-hydrolysis improves pulp viscosity, whilst acid-hydrolysis is more efficient in metals leaching. Overall, from the pulp production point of view, auto-hydrolysis conditions are more attractive than the acid-catalysed ones.

The aim of this work was to evaluate the potential of Eucalyptus globulus hemicelluloses, mainly xylan, for bioethanol production. Hemicelluloses have been removed prior to pulping by auto-hydrolysis and an acid-catalysed hydrolysis. As the hydrolysates obtained were rich in xylose, the yeast Pichia stipitis was selected for fermentation. It was confirmed that the yeast performance is strongly dependent on pH and the presence of inhibitors, such as lignin. The addition of Ca(OH)2 was successful for lowering the concentration of inhibitors and adjusting the pH. The strain was grown in culture media with increasing volumetric percentages of treated hydrolysates up to 100% (v/v), supplemented with nutrients other than the carbon and energy source. This methodology shortened the lag phase of fermentation and improved the performance of yeast. Maximum ethanol concentration (12 geth l-1), productivity (0.22 geth l-1 h-1), and yield (0.48 geth gxyl eqs -1) were achieved with treated acid-hydrolysates. These results are similar to those obtained by a synthetic medium with an equivalent xylose concentration.

The valorisation of hemicelluloses, as a subproduct of the pulping process, can be achieved with extraction of wood chips by primary hydrolysis (auto or acid catalysed) before cooking, where part of them are dissolved. However, the extracts of the hardwood used in this work (Eucalyptus globulus) could contain oligomers, mainly xylose based, that must be further hydrolysed to become a raw material for fermentation to produce e.g. bioethanol. The primary extract from an acid hydrolysis can be directly metabolised by microorganisms being a secondary hydrolysis worthless. On the other hand, twice the monosaccharides concentration was obtained when a secondary hydrolysis was performed, over the extracts obtained from the primary auto-hydrolysis. The best conditions for that reaction include 3 h of hydrolysis, with 4 %(w/w) of H2SO4 and the highest concentration of solids (i.e. avoiding the dilution of primary extracts), which led to a secondary hydrolysis yield as high as 84 %.