Fique (Furcraea spp.) generates both primary fibers and industrial bagasse during fiber extraction, but the potential of these two lignocellulosic streams for nanofiber production has not been adequately compared. In this study, cellulose nanofibers from fique fibers (CNF_FF) and holocellulose nanofibers from fique bagasse (HNF_FB) were isolated by sequential alkaline treatment, controlled delignification, and mechanical fibrillation using a Super Masscolloider. The resulting nanofibers were evaluated for morphology, chemical composition, structure, thermal stability, and rheological behavior. FESEM analysis showed smaller diameters for HNF_FB (25.90–36.91 nm) than for CNF_FF (52.11–93.72 nm). These findings indicate differences in fibrillation response associated with the raw material source. Chemical analysis confirmed the high α-cellulose content of CNF_FF (86.9%), whereas HNF_FB retained hemicellulose (10.85%) and residual lignin (5.66%). FTIR-ATR and TGA showed that these non-cellulosic components, together with the anatomical heterogeneity of bagasse, influenced the structural and thermal behavior of the nanofibers. Both suspensions exhibited shear-thinning behavior, consistent with entangled nanofibrillar networks. These results demonstrate that industrial fique bagasse, generated during primary fiber extraction, is a valuable underutilized feedstock for producing holocellulose nanofibers intended for sustainable material applications.
The aim of this study was to investigate the patterns governing the conversion of oilseed flax straw into retted straw under the climatic conditions of southern Ukraine through examining moisture absorption, moisture desorption, and the associated microbiological processes. It was established that stem moisture content approaching 100% is reached within 10 min of moistening, after which the process shifts from adsorption of free water to absorption of bound water. Analysis of the moisture desorption curves demonstrated that a single moistening event is insufficient to sustain the moisture level required for active microbial proliferation, as moisture content decreases by approximately 45% within the first hour and gradually reverts to baseline values thereafter. The mathematical modeling results indicate that without supplementary moistening, the biological conversion of straw into retted straw is virtually negligible. It was found that twice-daily moistening promotes the dominance of pectinolytic microorganisms, ensuring efficient breakdown of pectic substances and the formation of high-quality retted straw. However, after 5–6 days of retting, a sharp increase in the numbers of cellulolytic and pathogenic microflora is observed, which may lead to degradation of the cellulose complex and deterioration of fiber properties. The obtained findings can be used to optimize bast biomass processing technologies, develop predictive systems for the retting process, and improve the quality of the resulting fiber.
Biomass is an abundant renewable feedstock for combustion, co-firing, gasification, and pyrolysis, but in its raw form, it is a low-grade fuel. Low energy density, high moisture, and high contents of alkali and alkaline earth metals (AAEMs) and chlorine drive slagging, fouling, and corrosion in thermal equipment. Pretreatment is therefore required to meet the fuel-quality specifications. This review critically examines biomass pretreatment technologies, including physical, chemical, and biological, and then focuses on the two routes most relevant to solid-fuel upgrading, namely water/solvent washing (leaching) and torrefaction (thermochemical). Washing removes water-soluble and organically bound AAEMs, directly reducing slagging and fouling propensity, but it adds moisture, requires a drying step, and does not increase energy density. Torrefaction raises the higher heating value and carbon contents, lowers oxygen and moisture contents, and improves grindability and hydrophobicity, but the accompanying mass loss concentrates the residual AAEMs, so the treated fuel can retain or worsen its slagging tendency. Because the two methods correct complementary deficiencies, deashing versus deoxygenation and energy densification, this review evaluates the combined washing-torrefaction route as an integrated strategy. The combined route delivers what neither single method achieves alone: high AAEMs removal, increased higher heating value (HHV) and carbon content, reduced oxygen and moisture, and balanced bio-oil and biochar yields in subsequent pyrolysis. The review further compares the methods against the fuel specifications of each end-use, summarises the limited pilot and demonstration-scale evidence, and techno-economic questions that currently keep combined pretreatment at the laboratory stage.
Grape pomace (GP), a major wine industry residue, contains substantial amounts of phenolic bioactive compounds whose valorization potential remains underexploited. In this study, pomaces from the Syrah, Malbec, Cabernet Sauvignon, Tempranillo, Nebbiolo-Sangiovese (blend), Cabernet Franc, Merlot, and Ensamble varieties were characterized in terms of total phenolic content (TPC), flavonoids, anthocyanins, tannins, and antioxidant capacity. Grape pomace flour (GPF) was obtained by drying, milling, and sieving (<250 µm) GP at 60 °C, and its functional properties were compared with GP and two commercial pomace flours (H1 and H2). The GPFs had a TPC of 3.48–12.06 mg gallic acid equivalents g−1 dry basis (d.b.), flavonoid content of 11.78–71.65 mg quercetin equivalents g−1 d.b., anthocyanin content of 41.46–291.85 mg cyanidin-3-glucoside equivalents g−1 d.b., tannin content of 18.85–45.98 mg (+)-catechin equivalents g−1 d.b., and antioxidant capacity of 304.2–768.3 μmol Trolox equivalents g−1 d.b. The Malbec variety exhibited the best bioactive profile and was incorporated into a gelatin-based gummy matrix. Color and bioactive compound stability were measured over 30 days of storage at 40 °C and compared with a commercial flour (H1). The valorization of GP through drying and milling is a viable strategy for obtaining a flour with potential as a functional ingredient due to its bioactive composition and as a natural colorant in the food industry.
Calcium-rich biological wastes offer potential low-cost precursors for heterogeneous catalysts used in biodiesel processing. This study prepared a CaO-rich catalyst from snail shell, eggshell and periwinkle shell wastes and applied it to the transesterification of Gliricidia sepium seed oil. Shell proportions were evaluated using a constrained three-component mixture design, while the calcined materials were characterised by X-ray fluorescence and qualitative X-ray diffraction. Acid esterification reduced the free fatty acid content of the oil from 10.01% to 2.19%. Transesterification was subsequently investigated using a 25-run experimental matrix comprising methanol-to-oil molar ratio, catalyst loading, reaction temperature and reaction time. The mean oil yield was 34.50 ± 10.85%. The 20:20:60 snail shell:eggshell:periwinkle shell formulation produced the highest XRF-measured CaO content of 89.672%. The highest recovered product yield was 85.00%, obtained at a 12:1 methanol-to-oil molar ratio, 3 wt% catalyst loading, 50 °C and 30 min. GC–MS qualitatively identified methyl linoleate in the recovered product. The findings demonstrate that three waste-shell sources can be combined to produce a CaO-rich material for oil transesterification. However, the gravimetric recovery value does not represent quantitative FAME content or triglyceride conversion, which require validated chromatographic determination.
