Cupuaçu husk (CH) is the waste of a common fruit from a native species of the Brazilian Legal Amazon. The current study investigated the influence of ultrasound (US) combined with aqueous, acid, alkaline, and ionic liquid (IL) pretreatments on the chemical and physical aspects of CH and the yield of chemical platforms production, 5-hydroxymethylfurfural (HMF) and furfural (FF), using IL. Scanning electron microscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy were used to feature the raw and pretreated biomass. The highest levels of glucose (9.90 g L-1) were observed in the liquid fraction resulting from the acid + US pretreatment followed by acid hydrolysis. The IL + US pretreatment recorded the best performance in removing lignin. Based on XRD analyses, ultrasound increased crystallinity of all pretreated samples as a result of the removal of cellulose’s amorphous fraction. However, it promoted accessibility to adopted reagents by increasing biomass exposure due to cavitation. The best yields of HMF and FF were recorded from hydrolysis of the solid fraction resulting from the acid + US (12.94%) and alkaline + US (48.84%) pretreatment, respectively. These results indicate satisfactory performance of ultrasound assisted pretreatments to the simplified and economic conversion of biomass into value-added products.

Cocos nucifera L. is a palm tree of paramount importance in the food and chemistry industries, although over 50% of its biomass is discarded as waste. The aim of the study is to investigate different pretreatments in to coconut husks (CH), based on acid, alkaline, ionic liquid (IL), and peroxidative, in order to produce fermentable sugars. Severity factors were calculated for pretreatments; values ranged from 0.3 to 1.7 for peroxide, from 0.01 to 1.4 for alkaline, from 1.4 to 2.8 for acid and from 2.0 to 3.0 for ionic liquid. Pretreatments were optimized (time and temperature) to maximize the sugar yield and to remove the total lignin after acid hydrolysis. Reducing sugar yield (70%) was higher when CH waste was alkaline-pretreated for 2 h at 76.21 °C. The highest lignin removal rate was recorded when alkaline (21.4%) and peroxide solutions (27.2%) were used. The IL did not increase sugar yield and was not effective in lignin removal. These outcomes were confirmed through infrared spectroscopy, whereas scanning electron microscopy showed increased biomass porosity during alkaline, acid and peroxide pretreatments. The IL showed little and non-significant changes. The crystallinity index notably increased after each pretreatment; besides, it was directly associated with sugar content.

The aims of the current study are to investigate the composition of biomass from baru processing and to explore the feasibility of valuing it through the development of bioproducts such as fermentable sugars, furanics and biochar. Baru (Dipteryx alata Vog.) waste (endocarp and mesocarp) has great energetic potential to produce bioproducts due to its chemical composition. Proximate analyses applied to such waste have found low favorable moisture and ash content in it. Bioproduct characterizations after acid hydrolysis have shown that baru endocarp and mesocarp biomass can enable a range of value-added products in biorefinery concepts such as furfural and 5-hydroximetylfurfural (20.0 and 1.5% yield, respectively), and high sugar content (approximately 19.15 and 38.40%, respectively). Pyrolysis processes also present high biochar content (ca. 48%), with satisfactory characteristics to be used as fuel, as well as calorific value higher than 30 kJ g-1.