Development of efficient selective separation methods for Agroflorestal biomass fractionation: From intermolecular interactions to new lignin-based Materials of Added Value.

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Engineering novel phenolic foams with lignin extracted from pine wood residues via a new levulinic-acid assisted process

Publication . Melro, Elodie; Duarte, Hugo; Antunes, Filipe E.; Valente, Artur J.M.; Romano, Anabela; Norgren, Magnus; Medronho, Bruno

Phenolic foams are typically produced from phenolic resins, using phenol and formaldehyde precursors. Therefore, common phenolic foams are non-sustainable, comprising growing environmental, health, and economic concerns. In this work, lignin extracted from pine wood residues using a "green" levulinic acid-based solvent, was used to partially substitute non-sustainable phenol. The novel engineered foams were systematically compared to foams composed of different types of commercially available technical lignins. Different features were analyzed, such as foam density, microstructure (electron microscopy), surface hydrophilicity (contact angle), chemical grafting (infrared spectroscopy) and mechanical and thermal features. Overall, it was observed that up to 30 wt% of phenol can be substituted by the new type of lignin, without compromising the foam properties. This work provides a new insights on the development of novel lignin-based foams as a very promising sustainable and renewable alternative to petrol-based counterparts.

2023-09Journal article

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Poly(butylene succinate)-based composites with technical and extracted lignins from wood residues

Publication . Melro, Elodie; Duarte, Hugo; Eivazi, Alireza; Costa, Carolina; Faleiro, Maria Leonor; Rosa Da Costa, Ana; Antunes, Filipe E.; Valente, Artur J. M.; Romano, Anabela; Norgren, Magnus; Medronho, Bruno

Poly(butylene succinate) (PBS) has been drawing attention as a reliable biodegradable and sustainable alternative to synthetic petroleum-based polymers. In this study, PBS-lignin composites were developed using a recently extracted lignin (LA-lignin) from pine wood residues employing an innovative sustainable approach. These composites were systematically compared with PBS-based composites formed with commonly used technical lignins. The molecular weight of the lignins was evaluated, along with various structural and performance-related properties. The LA-lignin/PBS composites display a remarkably low water solubility (ca. < 2%), water uptake (ca. 100 degrees). Moreover, the rigidity and thermal stability of the LA-lignin-PBS composites were higher than those of the systems formed with technical lignins. Although all composites studied present remarkable antioxidant features, the novel LA-lignin-PBS systems stand out in terms of antiadhesion activity against both Gram-positive and Gram-negative bacteria. Overall, the systematic analysis performed in this work regarding the impact of various lignins on the formed PBS composites enables a better understanding of the essential structural and compositional lignin features for achieving biobased materials with superior properties.

2024Journal article

Open access

Revisiting lignin: a tour through its structural features, characterization methods and applications

Publication . Melro, Elodie; Filipe, Alexandra; Sousa, Dora; Medronho, Bruno; Romano, Anabela

Lignin is a complex organic polymer found in the plant cell wall with important biological functions, such as water transport, mechanical support, and resistance to various stresses. It is considered the second most abundant biopolymer on earth and the largest natural source of aromatics. Despite being annually co-produced in massive amounts, during cellulose fragmentation in the pulp industry and ethanol biorefinery, it is clearly undervalued; most of it is discarded or burned as fuel for energy production and, so far, only ca. 1-2% of lignin has been utilized as a high-value product. This underuse makes lignin the future resource of choice to produce green fuels and a wide range of added-value biomaterials and chemicals, which can contribute to the transition to more sustainable industries. However, its great variability between plant families combined with its complex and chemically inert structure is challenging researchers who seek for strategies regarding its valorization. With this scope, several different approaches have emerged regarding the development of better and efficient isolation methods, purification and characterization techniques, and improved methodologies for lignin chemical modification and blending with other compounds. These improvements represent important opportunities for the creation of value-added lignin-based biopolymers and materials and some have already shown potential to be scaled up. All these aspects are pedagogically introduced and discussed in this review.

2021-04Review

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Lignin extraction from waste pine sawdust using a biomass derived binary solvent system

Publication . Magalhães, Solange; Filipe, Alexandra; Melro, Elodie; Fernandes, Catarina; Vitorino, Carla; Alves, Luís; Romano, Anabela; Rasteiro, Maria G.; Medronho, Bruno; MDPI

Lignocellulosic biomass fractionation is typically performed using methods that are somehow harsh to the environment, such as in the case of kraft pulping. In recent years, the development of new sustainable and environmentally friendly alternatives has grown significantly. Among the developed systems, bio-based solvents emerge as promising alternatives for biomass processing. Therefore, in the present work, the bio-based and renewable chemicals, levulinic acid (LA) and formic acid (FA), were combined to fractionate lignocellulosic waste (i.e., maritime pine sawdust) and isolate lignin. Different parameters, such as LA:FA ratio, temperature, and extraction time, were optimized to boost the yield and purity of extracted lignin. The LA:FA ratio was found to be crucial regarding the superior lignin extraction from the waste biomass. Moreover, the increase in temperature and extraction time enhances the amount of extracted residue but compromises the lignin purity and reduces its molecular weight. The electron microscopy images revealed that biomass samples suffer significant structural and morphological changes, which further suggests the suitability of the newly developed bio-fractionation process. The same was concluded by the FTIR analysis, in which no remaining lignin was detected in the cellulose-rich fraction. Overall, the novel combination of bio-sourced FA and LA has shown to be a very promising system for lignin extraction with high purity from biomass waste, thus contributing to extend the opportunities of lignin manipulation and valorization into novel added-value biomaterials.

2021-03-30Journal article

Open access

New deep eutectic solvent assisted extraction of highly pure lignin from maritime pine sawdust (Pinus pinaster Ait.)

Publication . Fernandes, Catarina; Melro, Elodie; Magalhaes, Solange; Alves, Luis; Craveiro, Rita; Filipe, Alexandra; Valente, Artur J. M.; Martins, Gabriela; Antunes, Filipe E.; Romano, Anabela; Medronho, Bruno

Lignocellulosic biomass is a renewable and sustainable feedstock, mainly composed of cellulose, hemicellulose, and lignin. Lignin, as the most abundant natural aromatic polymer occurring on Earth, has great potential to produce value-added products. However, the isolation of highly pure lignin from biomass requires the use of efficient methods during lignocellulose fractionation. Therefore, in this work, novel acidic deep eutectic solvents (DESs) were prepared, characterized and screened for lignin extraction from maritime pine wood (Pinus pinaster Ait.) sawdust. The use of cosolvents and the development of new DES were also evaluated regarding their extraction and selectivity performance. The results show that an 1 h extraction process at 175 ?C, using a novel DES composed of lactic acid, tartaric acid and choline chloride, named Lact:Tart:ChCl, in a molar ratio of 4:1:1, allows the recovery of 95 wt% of the total lignin present in pine biomass with a purity of 89 wt%. Such superior extraction of lignin with remarkable purity using a ?green? solvent system makes this process highly appealing for future large-scale applications. ? 2021 Elsevier B.V. All rights reserved.

2021-04Journal article

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