ABSTRACT Background: Patauá (Oenocarpus bataua Mart.) is a palm tree belonging to the botanical family Arecaceae that occurs throughout the Amazon. Like açaí, an edible pulp is extracted from its fruits, remaining a fiber-rich waste. Revealing the potential of such raw or thermochemically modified fibers for producing bioproducts is a novelty in the literature. Therefore, this work aimed to characterize patauá fibers in natural and alkali-treated conditions to support future bioproduct applications. Alkaline treatments were performed under mechanical stirring combining two NaOH levels (5 and 10%) and two temperatures (80 and 100°C). Morphological characterization was performed by light microscopy and scanning electron microscopy (SEM). The contents of the structural and non-structural chemical components were determined, and chemical groups were evaluated by Fourier-transform infrared spectroscopy (FTIR). The physical characterization included moisture content, apparent density, and water absorption tests. Results: The macerate revealed short fibers with typical elongated morphology, mean cell wall thickness (4.10 µm) greater than the mean lumen width (3.01 µm), and mean length of 445 µm. The alkaline treatments partially individualized the fibers from bundles, cleaned extractives from the surface, and unblocked superficial pits by removing silica-rich structures. They substantially removed non-cellulosic components, but FTIR showed condensed lignin exposed on the fiber surface. Density and water uptake increased concerning natural fibers. Patauá’s short length and susceptibility to modification through thermochemical treatments that concentrated cellulose up to 50% indicated great potential for developing composites and nanofibers. Regardless of the NaOH content, 100°C was more efficient in concentrating cellulose. Conclusion: Patauá fibers have unique natural characteristics. They occur as flatted fiber bundles, have silicon-rich structures obstructing their superficial pits, and comprise more lignin than cellulose.

ABSTRACT Background: During de-pulping of açai (Euterpe oleracea) for juice production in the Amazonia, large amounts of fibrous waste are daily discarded, a promising substrate for production of high-value cellulose nanofibrils. Therefore, this study sought to evaluate the modifications of açai surface fibers submitted to chemical pretreatment steps and compare the quality of nanostructured films produced with different cycles of mechanical nanofibrillation. Results: A 2-hour pretreatment (at 5% of NaOH) followed by two NaOH/H2O2 bleaching steps resulted in fibers with increased length and reduced diameter compared to raw fibers while preserving fiber integrity and cellulose I structure. The increase of fibers’ grinding cycles from 3 (minimum to gel point) to 21 (maximum suspension thickness) resulted in nanofibril films with higher crystallinity properties, uniform thickness, compacted morphology, and smoother surface. Nanofibril films formed after different numbers of passages exhibited similar mechanical strength, but distinct barrier properties. Conclusion: Açaí waste films produced with fibers submitted to 3 grinding cycles can be recommended for packaging applications that demand easily dissolving, such as instantaneous food. Oppositely, açaí fibers subjected to 21 cycles in grinder provide films suitable for water-resistant packaging, ideal for secondary coatings of papers and paperboards.

Resumo Apesar da importância social, cultural e econômica para a Região Amazônica, o potencial energético da Mauritia flexuosa, popularmente conhecida como buriti, ainda não foi explorado para ampliar as possibilidades de uso dessa espécie pelas comunidades locais. Assim, o objetivo deste trabalho é comparar o potencial dos tecidos que compõem o pecíolo de Mauritia flexuosa para combustão e carbonização. O miolo e casca do pecíolo foram separados e caracterizados por composição química (extrativos removíveis por água e totais, lignina e cinzas), umidade base úmida, composição imediata (teores de materiais voláteis, carbono fixo e cinzas), densidade básica, poder calorífico superior e análise termogravimétrica em atmosfera inerte de N2. Os dois tecidos do pecíolo de Mauritia flexuosa apresentaram vantagens para finalidades bioenergéticas, como: baixo teor de cinzas (≤ 2%), além de teor de carbono fixo (≈ 18%) e poder calorífico superior (≈ 18 MJ kg-1) adequados. Para miolo e casca, os teores de lignina (19 e 28%, respectivamente), extrativos (8,9 e 5%, respectivamente), e densidade básica (0,041 e 0,267 g cm-3, respectivamente) diferiram significativamente. Contudo, a composição imediata dos tecidos não foi influenciada por essas diferenças, ao contrário do poder calorífico e densidade energética. O comportamento termogravimétrico demonstrou taxa de degradação superior e rendimento final em massa inferior (7%) para o miolo em relação à casca. A casca apresentou melhor qualidade para combustão e carbonização em comparação ao miolo. Esse resultado é vantajoso para as comunidades extrativistas da Amazônia, pois a casca é um resíduo do processamento do pecíolo para obtenção do miolo, destinado à produção de artesanatos. Pela baixa densidade básica, o miolo é mais indicado para torrefação, densificação, pirólise para geração de bio-óleo e produção de filtros naturais e carvões ativados do que para combustão direta e carbonização.

Abstract Despite its social, cultural and economic importance for the Amazon region, the energy potential of Mauritia flexuosa, popularly known as buriti, has not yet been explored in order to expand the possible uses of this species by the local communities. Therefore, the aim of this work was to compare the tissues that comprise the petiole of Mauritia flexuosa for combustion and carbonization. The petiole core and bark were separated and characterized by chemical composition (total and water-soluble extractives, lignin, and ashes), moisture content (based humid mass), proximate composition (contents of volatile matter, fixed carbon, and ash), basic density, higher heating value, and thermogravimetric analysis in N2 inert atmosphere. The two tissues from the Mauritia flexuosa petiole presented advantages for bioenergetic purposes, such as low ash content (≤ 2%) and higher heating value (≈ 18 MJ kg-1), in addition to suitable fixed carbon (≈ 18%). For the core and husk, the lignin contents (19 and 28%, respectively), extractives contents (9 and 5%, respectively), and basic density (0.041 and 0.267 g cm-3, respectively) significantly differed. However, the proximate composition of the tissues was not influenced by such differences, unlike the higher heating value and energy density. The thermogravimetric behavior showed higher degradation ratio and lower final mass yield (7%) for the core in comparison to the husk. The husk showed better quality for combustion and carbonization in comparison to the core. This is an advantageous result for the extractive activities of Amazonian communities because the husk is a waste from the petiole processing in order to obtain the core for handcraft. Due to the low basic density, the core can be noted for its use in torrefaction, densification, pyrolysis for the production of bio-oil and production of natural filters and activated charcoals, rather than direct combustion and carbonization.