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BACKGROUND: Pretreatments are critical in biorefinery analysis, affecting further reactions and downstream processes. However, most pretreatments are studied and optimized as single‐step schemes, focusing on maximizing a side stream. Sequential pretreatments have been shown to improve the selective isolation of platforms for further valorization. However, pretreatment performance can consider not only technical but also economic, environmental, and social concerns. This work assessed the sustainability of sequential pretreatments in rice husk‐based biorefineries. RESULTS: Four biorefinery scenarios were designed, simulated, and assessed considering dilute acid and wet air oxidation pretreatment technologies in sequential and single‐step schemes. Economic feasibility was demonstrated for sequential pretreatments when phenolic compounds are contemplated, generating gross incomes of 4.76 M‐USD yr−1. From an environmental perspective, the rice supply chain generated a carbon footprint of 2.17 kg CO2 eq kg−1 of rice husks, where the producer link is the largest contributor due to fertilizer use. Likewise, it was shown that supplying energy demands using black liquor as fuel relieves operating costs and reduces the carbon footprint. The social dimension showed that between 69 and 77 jobs could be generated annually along the value chain and the biorefinery schemes. However, biorefineries have a high risk due to the high volume of cooling water. CONCLUSIONS: All dimensions were weighted to calculate a sustainability index, where it was concluded that sequential pretreatment biorefineries improved sustainability against the single‐step schemes. However, the scenario of valorization of the three fractions (Sc1) is the best scheme to be implemented as it has always demonstrated economic feasibility. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Many plant species characterize tropical forests, and a small fraction has been studied to favor small communities in the food and medicinal fields. The high biodiversity of these regions allows for the proposed alternatives for the valorization of exotic fruits due to their rich content of value-added compounds that benefit human health. This work focuses on improving the nutritional characteristics of the açai production chain by mixing it with noni and araza. As a main result, it was possible to enhance the organoleptic and nutritional characteristics of the fruits after freeze-drying. Then, the seeds and peels of the fruits were valorized by the extraction of bioactive compounds with conventional methods and biogas production by anaerobic digestion. The best compositions of antioxidant capacity and total phenolic compounds were obtained for the extracts based on the araza peel, with values of 116.4 µmol and 276.6 mg of gallic acid per 100 g of raw material, respectively. Regarding biogas production, the anaerobic digestion performance was influenced by the C/N ratio. The experimental results were used as input to simulate small-scale processes. From a technical point of view, the scheme of açai, noni, and araza mixture (Sc. 4) showed the highest mass yields (0.84 kg products/kg RM) and energy requirement (2.54 kW/kg RM). On the other hand, the processing of single açai (Sc. 1) presented the lowest capital costs (1.37 M-USD) and operating costs (0.89 M-USD/year). However, all scenarios showed techno-economic feasibility and demonstrated the potential of these fruits to valorize the açai market. [ABSTRACT FROM AUTHOR]

Featured Application: In the last decade, pretreatment has been considered the core stage in the design of biorefineries. Different schemes could be proposed depending on the design objective, either pretreatments for the feedstock fractionation or pretreatments to obtain a platform product. Nevertheless, many have been described as single-step pretreatments specific to a sub-stream, decreasing the integral valorization performance. This work demonstrates the possibility of sequential pretreatment schemes to maximize the fractionation of lignocellulosic biomass. Through different operational, technical, and economic assessment indicators, the best schemes that would help increase the overall process yields and, certainly, the economic viability are described. Therefore, a good pretreatment design will affect the upstream and downstream performance of the biorefineries. Pretreatment technologies are proposed to break the crosslinked biomass matrix and facilitate bioconversion processes or chemical agent attacks in reaction schemes. However, most of the pretreatments are studied in single-step schemes, limiting the integral valorization of the feedstock composition. Therefore, sequential pretreatments could maximize this valorization by isolating more biomass fractions or removing unwanted compounds. This work focuses on proposing and assessing different sequential pretreatments for the isolation of lignocellulosic fractions. After a pretreatment screening, ten technical and economic indicators were assessed through a heuristic analysis. Data from the literature were used to evaluate five operational indicators and as the specification of processing units in simulation schemes to also evaluate five techno-energetic and economic indicators. As a main result, it was concluded that the sequential pretreatments of dilute acid (DA) with wet air oxidation (WAO) could be the most optimal for cellulose isolation, steam explosion (SE) with DA for hemicellulose fractionation, and DA with kraft process for lignin solubilization. Additionally, the DA and WAO sequence may be the most efficient in biorefinery designs since it maximizes biomass fractionation, producing two hydrolyzed liquors, one rich in sugars and the other in soluble lignin, as well as a cellulose-rich solid. [ABSTRACT FROM AUTHOR]