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Research Project
Forest Research Centre
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Publications
Thermally modified wood exposed to different weathering conditions: a review
Publication . Godinho, Delfina; Araújo, Solange; Quilhó, Teresa; Cunha Diamantino, Teresa; Gominho, Jorge
ABSTRACT: Outdoor wood applications are exposed to several different biotic and abiotic factors, and for that reason, they require protection to increase their service life. Several technologies of wood protection are already commercialized. One of these technologies is thermal modification, which refers to the structural, mechanical, and chemical transformations occurring in the lignocellulosic material when gradually heated up to specific temperature ranges. In the past few years, several researchers have undertaken weathering resistance evaluations on different wood species. Some cases have considered natural exposure in different countries with different climatic conditions, while others focused on artificial exposure under UV and xenon radiation tests. Most works evaluated the weathering effects on the chemical, mechanical and physical, and anatomical shifts compared to the original characteristics of the material. This review has established a considerable lack of studies in the bibliography focusing on abiotic factors, such as the industrial and maritime environment, or even isolated climatic factors such as salt spray (simulating maritime environments) or pollutant gases (simulating industrial environments). This lack of information can be an opportunity for future work. It could help to understand if thermally modified wood is or is not sensitive to pollutant gases or salinity, or to a combination of both. By knowing the degradation mechanisms caused by these factors, it will be possible to study other forms of protection.
Chemical composition and structural features of cellolignin from steam explosion followed by enzymatic hydrolysis of Eucalyptus globulus bark
Publication . Magina, Sandra; Marques, Susana; Gírio, Francisco; Lourenço, Ana; Barros-Timmons, Ana; Evtuguin, Dmitry V.
ABSTRACT: Bark is one of the main wastes of the chemical and mechanical processing of Eucalyptus globulus wood. The proposed biochemical processing of bark via saccharification pathway involves steam explosion (SE) pretreatment (severity factor log R0 of 4.22) followed by enzymatic hydrolysis using an enzymatic cocktail composed of cellulolytic and xylanolytic enzymes. Almost 70% cellulose saccharification was achieved. The remaining cellolignin residue (CLEZ) was analysed for its chemical composition and structural features by conventional wet chemistry methods and a series of spectroscopic tools (FTIR-ATR, solid-state CP/MAS C-13 NMR spectroscopy and wide-angle X-ray scattering (WAXS)). The main CLEZ component (about 51%) is acid-insoluble lignin, the chemical composition of which in terms of the ratio of syringyl (S), guaiacyl (G) and p-hydroxyphenyl (H) units (70:28:2) is very close to that in the initial bark. This lignin is highly condensed and structurally associated with condensed tannins, which makes CLEZ recalcitrant to delignification by common methods. About one third of cellulose in eucalyptus bark after SE was inaccessible to enzymatic hydrolysis and remained in the CLEZ. This cellulose, structurally similar to microcrystalline cellulose, is imbedded into the lignin-tannins condensed matrix and extremely difficult to purify. In contrast to cellulose, bark hemicelluloses were effectively removed in enzymatic hydrolysis, with only small amounts (<2%) remaining in CLEZ. Among other CLEZ ingredients, proteins and inorganic/organic salts were the most abundant. The latter includes noticeable amounts of calcium oxalate phytoliths (up to 9%), Fe and Si salts. The eventual application areas of CLEZ are discussed.
The behavior of thermally modified wood after exposure in maritime/industrial and urban environments
Publication . Godinho, Delfina; Ferreira, Cristina; Lourenço, Ana; Araújo, Solange; Quilhó, Teresa; Cunha Diamantino, Teresa; Gominho, Jorge
ABSTRACT: Natural and thermally modified Pine, Ash, and Acacia woods were exposed in two different environments: urban and maritime/industrial. The weathering effects were evaluated during 24 months regarding color, chemical, and structural changes. In all wood species, thermal modification induced color, chemical, and structural changes. All woods became darker (Pine Delta L*: -32.01; Ash Delta L*: -36.83; Acacia Delta L*: -27.50), total extractives content increased (Pine: 19 %; Ash: 32 % and Acacia: 18 %), and the samples presented deformation and damaged cells. Total lignin was not significantly changed, although there were detected changes in lignin, namely the reduction of G -units in Pine (approximate to 2 %) and reduction of S/G ratio in Acacia (approximate to 0.04 %). Ash remained almost the same. After weathering, modified woods suffered fewer color changes, indicating that the thermal modification could improve the resistance to color change. Acacia wood, when exposed to maritime/industrial conditions, revealed a higher color change (Delta E: 35.7 at 24 months) when compared with urban conditions (Delta E: 23.5 at 24 months). Delignification, possibly caused by photodegradation, occurred in all wood samples, and the loss of extractive happened, perhaps caused by rain. Modified woods were slightly less resistant to weathering in maritime/ industrial environments. Some structural damage, namely cracked cells, the appearance of molds, blue staining, and particle deposition, was observed. The thermal modification enables color stabilization but does not seem to improve the weathering resistance in all studied wood species. Exposure to the different environments did not lead to significant differences in the morphology and chemical composition of the three natural and modified wood species.
Innovative approach in sustainable agriculture: Harnessing microalgae potential via subcritical water extraction
Publication . Ferreira, Alice; Vladic, Jelena; Corrêa, D. O.; Butzke, Valéria Louzada Leal; Martins, Pedro L.; Ribeiro, Belina; Santos, Cláudia Marques dos; Acién, F. Gabriel; Gouveia, Luisa
ABSTRACT: Microalgae can contribute to sustainable agriculture and wastewater treatment. This study investigated Tetradesmus obliquus, grown in piggery wastewater (To-PWW), as a biostimulant/biofertilizer compared to biomass grown in synthetic medium (To-B). Subcritical water extraction was tested for disruption/hydrolysis of wet biomass, at three temperatures (120, 170, and 220 °C) and two biomass loads (1:10 and 1:80 (g dry biomass/mL water)). Extracts were evaluated for germination, and root formation/expansion. Residues were quantified for nutrient composition to assess their biofertilizer potential and tested for their affinity to oil compounds for bioremediation. The best germination was achieved by To-B extracts at 170 °C (1:10: 148 % at 0.2 g/L, 1:80: 145 % at 0.5 g/L). Only To-PWW extracts at 0.2 g/L had a significant germination effect (120 °C: 120–123 % for both loads; 170 °C: 115 % for 1:80). To-PWW extract at 120 °C and 1:10 significantly affected cucumber and mung bean root formation (224 and 268 %, respectively). Most extracts significantly enhanced root expansion, with all To-B extracts at 1:10 showing the best results (139–181 %). The residues contained essential nutrients (NPK), indicating their biofertilizer potential, helping decrease synthetic fertilizers demands. To-B residues had high affinity to toluene and diesel but lower to used cooking and car oils. To-PWW showed very low affinity to all oil compounds. Finally, all residues were only able to form stable emulsions with the used car oil. This study fully exploits the use of microalgal biomass in sustainable agriculture, producing biostimulant extracts, and residues for biofertilizer and bioremediation, from a low-cost wastewater source.
Piggery wastewater treatment by solar photo-Fenton coupled with microalgae production
Publication . Ferreira, Alice; Attar, Solaima Belachqer-El; Villaro-Cos, Silvia; Ciardi, Martina; Soriano-Molina, Paula; López, Jose Luis Casas; Lafarga, Tomás; Santos, Cláudia Marques dos; Acién, F. Gabriel; Gouveia, Luisa
ABSTRACT: Pig farming generates highly polluted wastewater that requires effective treatment to minimize environmental damage. Microalgae can recover nutrients from piggery wastewater (PWW), but excessive nutrient and turbidity levels inhibit their growth. Solar photo-Fenton (PF) offer a sustainable and cost-effective pretreatment to allow microalgal growth for further PWW treatment. This study optimized the concentrations of PF reagents to minimise water and nutrient inputs while maintaining microalgae-based treatment efficiency. PF trials were conducted in pilot-scale raceway ponds under solar radiation, testing different concentrations of FeSO4 (4.48 and 8.95 mM) and H2O2 (77, 154, and 309 mM). Following PF, Tetradesmus obliquus was used in a biological treatment of PWW to recover the remaining nutrients. PF achieved high removal efficiencies for turbidity (97.6-99.5 %), total organic carbon (59.2-77.1 %), and chemical oxygen demand (83.8-94.7 %), but ammonium was not significantly removed. Phosphorus was almost completely removed through iron precipitation during neutralisation. Lowering the H2O2 concentration from 309 to 77 mM did not compromise removal efficiency but reducing FeSO4 below 8.95 mM negatively affected the process. Consequently, 8.95 mM FeSO4 and 77 mM H2O2 were selected for microalgae production. The pretreated PWW could be recycled at least once for microalgal production, without nutrient supplementation, improving biomass productivity and PWW treatment, especially targeting ammonium. Phosphorus supplementation, however, did not significantly boost biomass productivity or treatment efficiency. Moreover, the iron sludge generated from PF pretreatment contained enough NPK to be repurposed as an organic fertilizer boosting sustainable agricultural practices. These findings encourage further investigation of this emerging combined technology towards wastewater treatment at large-scale.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
6817 - DCRRNI ID
Funding Award Number
UIDB/00239/2020