BUSCADOR RECOLECTA

The upswing of argan’s oil for the cosmetic industry has increased the farming of this plant and originated an unexplored residue of complex treatment, its nutshells. This work deals with the characterization of this feedstock, its pretreatment via torrefaction and its gasification either with or without the pretreatment stage. Torrefaction was carried out in a continuous auger reactor at two temperatures, 220 and 250 °C. Hemicellulose was almost totally removed from argan nutshells after torrefaction. Compared to the raw argan shells, the torrefied solids showed an increased content of fixed carbon, a noticeable reduction in the O/C ratio and a significant increase in the HHV, the higher the torrefaction temperature. Chemical thermodynamic equilibrium calculations were implemented to the gasification stage to calculate the equivalence ratio for auto-thermal operation and to assess the effect of temperature and steam-to-biomass ratio on gas yield and composition. Air-steam gasification was also experimentally tested for the raw and torrefied materials at the operational conditions drawn from the simulation results. The torrefied material gasification yielded four times more char than the raw material, while tar production from the torrefied material was only reduced in the presence of steam (anyway starting from a low value: 0.7 g/m3STP for raw argan shells vs 0.3 g/m3STP for the torrefied material). Nor gas production, neither the H2/CO ratio nor the energy content in syngas were improved by gasifying the torrefied material, so torrefaction does not appear to be a profitable pretreatment stage for the gasification of argan nutshells from the point of view of syngas quality.

For efficient utilization of lignocellulosic biomass components, reductive catalytic fractionation appears as a promising biorefinery strategy. In this work, this concept of biomass valorization was used to study the potential of an unexplored feedstock, argan shells. This material was processed in a non-catalytic route and over a Pd/C catalyst in two different reaction media. The effects of the treatment temperature (250, 275, and 300 °C), as well as the catalyst loading (catalyst/argan shells mass ratio of 0.05 and 0.1 g/g), were also studied. The main product (lignin-derived oil) was thoroughly characterized using GC/MS/FID, SEC, and NMR. The highest monomer yields of 48–49 wt% based on the lignin content were obtained for n-butanol/water reaction medium at 300 °C using a Pd/C catalyst load of 0.1 g/g and for methanol reaction medium at 275 °C and 0.05 g/g. Significantly lower monomeric phenol yields were obtained in the non-catalytic route (4–19 wt% for n-butanol/water and 9–16 wt% for methanol). The main phenolic monomers in the catalytic pathway were 4-n-propanolguaiacol, 4-n-propanolsyringol, and 4-alkyl guaiacols and syringols, with some differences in the selectivities from one solvent to another.

An integral valorization route based on a pyrolysis process has been proposed to find sustainable applications for argan shells focused on the simultaneous production of activated biochar and antioxidant additives from bio-oil. The bio-oil obtained in the pyrolysis process was furtherly upgraded (hydrothermal treatment and extraction process) to obtain antioxidant additives. On the other hand, the biochar obtained in the pyrolysis was used as a feedstock to produce high-quality activated biochar (by physical activation with CO2). The increase in the pyrolysis temperature (350–550 °C) hardly affected the pyrolysis products distribution (biochar yields of 28–34 wt.% and bio-oil yields between 51 and 55 wt.%), but it led to a slight decrease in the content of phenolic monomers extracted from bio-oil (from 63 wt.% at 350 °C to 53 wt.% at 550 °C). When these extracted fractions were blended with biodiesel (<1 wt.%), improvements of up to 300% in biodiesel oxidation stability were attained. The hydrothermal treatment of the bio-oil did not show noteworthy effects either on the production or antioxidant performance of the extracted fractions if compared with the fractions extracted from the raw bio-oil. Regarding the valorization of argan shells biochar, the activated biochar prepared from it showed considerable potential as an adsorbent material for CO2 (125 mg of CO2 per g of the activated biochar) or phenols (complete removal of 99.6% in 4 h of contact time). It was characterized by a high BET surface area (up to 1500 m2/g), a high carbon content (up to 95 wt.%), low ash content (around 2 wt.%), and a pH of around 8.

Nowadays, a high percentage (> 50%) of the paper produced in Europe uses recovered paper (secondary fibers) as raw material. In order to improve the mechanical properties of the paper produced, different kinds of additives are usually incorporated into the paper. Emerging renewable materials based on agricultural or forest residues, such as cellulose nanomaterials, have recently proved good capacities as reinforcing agents for different applications. In this work, pulp from wheat straw with a content of cellulose nanomaterial has been produced and tested as a mechanical reinforcing agent for paper production. A soda semi-chemical process was applied for the delignification of straw, to produce pulp with high cellulose content. Posteriorly, pulps with cellulose nanofibers were obtained in a high-pressure homogenizer, applying three different pretreatments to the cellulose pulp (acid hydrolysis, enzymatic hydrolysis and thermal treatment with glycerol) in order to facilitate the obtention of cellulose nanomaterial. Handsheets of paper were prepared from two sources of secondary fiber (fluting paper and old corrugated containers), adding different percentages of wheat straw derivatives (0, 3.5, 5 and 7%). The fibers' morphology and the papers' mechanical properties were investigated. Noticeable improvement rates (up to 25%) were observed for some mechanical properties of paper containing nanocellulose produced after the enzymatic and acid pretreatments. The quality of the secondary fibers source also affected the improvement rates achieved, with higher percentage changes for the lower-quality recycled paper.

Molybdenum carbide supported on activated carbon (β-Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow-Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT-RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT-RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13-15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT-RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two-step non-equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs., This research was funded by the Gobierno de Navarra, grant number PC177-178 Reducenano 2.0 and Spanish Ministry of Science (AbFine, PID2020-114936RB-I00). The APC was funded by the Universidad Pública de Navarra (UPNA).

Lignocellulosic residues have the potential for obtaining high value-added products that could be better valorized if biorefinery strategies are adopted. The debarking of short-rotation crops yields important amounts of residues that are currently underexploited as low-grade fuel
and could be a renewable source of phenolic compounds and other important phytochemicals.
The isolation of these compounds can be carried out by different methods, but for attaining an
integral valorization of barks, a preliminary extraction step for phytochemicals should be included. Using optimized extraction methods based on Soxhlet extraction can be effective for the isolation of phenolic compounds with antioxidant properties. In this study, poplar bark (Populus Salicaceae)
was used to obtain a series of extracts using five different solvents in a sequential extraction of 24 h
each in a Soxhlet extractor. Selected solvents were put in contact with the bark sample raffinate
following an increasing order of polarity: n-hexane, dichloromethane, ethyl acetate, methanol, and
water. The oily residues of the extracts obtained after each extraction were further subjected to flash
chromatography, and the fractions obtained were characterized by gas chromatography coupled
with mass spectrometry (GC–MS). The total phenolic content (TPC) was determined using the
Folin–Ciocalteu method, and the antioxidant activity (AOA) of the samples was evaluated in their
reaction with the free radical 2,2-Diphenyl-picrylhydrazyl (DPPH method). Polar solvents allowed for higher individual extraction yields, with overall extraction yields at around 23% (dry, ash-free
basis). Different compounds were identified, including hydrolyzable tannins, phenolic monomers
such as catechol and vanillin, pentoses and hexoses, and other organic compounds such as long-chain alkanes, alcohols, and carboxylic acids, among others. An excellent correlation was found between TPC and antioxidant activity for the samples analyzed. The fractions obtained using methanol showed the highest phenolic content (608 g of gallic acid equivalent (GAE)/mg) and the greatest antioxidant activity., This research was funded by the Gobierno de Navarra, grant number PC177-178 Reducenano 2.0 and Spanish Ministry of Science (AbFine, PID2020-114936RB-I00). The APC was funded by the Universidad Pública de Navarra (UPNA).

Bio-oil obtained from biomass pyrolysis has great potential for several applications after being upgraded and refined. This study established a method for separating bio-oil into different fractions based on polarity and molecular size to extract phenolic and polyphenolic compounds with antioxidant properties. The fractions were analyzed using various spectroscopic and chromatographic techniques, such as GC/MS, FTIR, UV-vis, SEC, DOSY-NMR, 13C-NMR, and 31P-NMR. The antioxidant properties of these fractions were tested by examining their ability to improve the oxidative stability of biodiesel. The results strongly connected the bio-oil's chemical functionalities and antioxidant power. During solvent fractionation, dichloromethane could extract phenolic structures, which were subsequently size-fractionated. The subfractions with lower molecular weight (in the order of monomers and dimers) outperformed the antioxidant potential of the crude bio-oil. Heavier subfractions from dichloromethane extraction did not show good antioxidant abilities, which was related to the low hydroxy group content. After solvent extraction, phenolic oligomers remained in the water-insoluble/dichloromethane-insoluble fraction, which showed good antioxidant potential despite its low solubility in biodiesel., The authors express gratitude to Agencia Estatal de Investigación in Spain (Project PID2020-114936RB-I00), Aragón Government (Research Group ref T22_23R), and Navarra Government (Project 'PC177-178 Reducenano 2.0') for providing frame support for this work. I.F. acknowledges Fondo Social Europeo, Agencia Estatal de Investigación and Universidad de Zaragoza because of the postdoctoral fellowship (RYC2020-030593-I).

For efficient utilization of lignocellulosic biomass components, reductive catalytic fractionation appears as a promising biorefinery strategy. In this work, this concept of biomass valorization was used to study the potential of an unexplored feedstock, argan shells. This material was processed in a non-catalytic route and over a Pd/C catalyst in two different reaction media. The effects of the treatment temperature (250, 275, and 300 °C), as well as the catalyst loading (catalyst/argan shells mass ratio of 0.05 and 0.1 g/g), were also studied. The main product (lignin-derived oil) was thoroughly characterized using GC/MS/FID, SEC, and NMR. The highest monomer yields of 48-49 wt% based on the lignin content were obtained for n-butanol/water reaction medium at 300 °C using a Pd/C catalyst load of 0.1 g/g and for methanol reaction medium at 275 °C and 0.05 g/g. Significantly lower monomeric phenol yields were obtained in the non-catalytic route (4-19 wt% for n-butanol/water and 9-16 wt% for methanol). The main phenolic monomers in the catalytic pathway were 4-n-propanolguaiacol, 4-n-propanolsyringol, and 4-alkyl guaiacols and syringols, with some differences in the selectivities from one solvent to another., The authors express gratitude to Agencia Estatal de Investigación in Spain (Project PID2020-114936RB-I00), Aragón Government (Research Group Ref. T22_23R), and Navarra Government (Project 'PC177-178 Reducenano 2.0') for providing frame support for this work. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.