Coffee-cut stems are a potential fermentable sugars source, which can be upgraded in different valueadded products and energy vectors. Nevertheless, there are few reports focused on the acid pretreatment and saccharification processes. Thus, this paper evaluates the effect of the acid pretreatment and saccharification conditions of coffee cut-stems to find the highest sugar yield. Thereafter, the influence of the residence time in the acid pretreatment and the b-glucosidase supplementation in the saccharification process were analyzed. The combined severity factor and crystallinity index were used as metrics to evaluate both processes. In all assays, an increase in the crystallinity index was observed. Furthermore, a nonlinear trend of the combined severity factor respect to the residence time in the acid pretreatment was evidenced. The highest sugar yield was 66.75% with a combined severity factor of 1.84. The better saccharification process was achieved at combined severity factor of 2.01 with a digestibility of 43%. The addition of b-glucosidase in the enzymatic hydrolysis allows increasing the value to 69.07%. Hence, low temperatures, acid concentrations, and the b-glucosidase supplementation allows obtaining a high sugar yield from coffee cut stems.

The industrial applicability of exotic and wild fruits has been investigated as stand-alone processes framed to obtain a single main product. However, their combination and the valorization of the processing residues in a biorefinery scheme have not been explored. Therefore, this work aims to assess the technical and economic feasibility of low-scale biorefineries based on annatto and açai as raw materials. Therefore, the actual processing of both fruits was carried out experimentally. For annatto, the extraction of dye paste was performed, obtaining mass yields of up to 58.4% by working with ground seed. Regarding the açai, pulp was obtained with a polyphenol content of 23.56 mg of gallic acid equivalent per gram of sample. The residues generated in both processes were used as substrates for biogas production, achieving biomethane yields between 186–533 mL per gram of volatile solids. These results were the basis for the design and simulation of process scale-up in low-scale biorefinery contexts. Five scenarios were evaluated, involving the production of annatto dye paste, açai pulp, biogas from exhausted annatto seeds, slurry and seeds of açai, and feedstock integration. As the main energy result, it was found that the individual production of açai pulp can fully supply the required energy of the process through the self-generation index. From the economic perspective, it was found that there is economic feasibility working with flows below the regional and national production in Colombia for all scenarios.

Lignocellulosic materials are usually processed toward C5 and C6 corresponding sugars. Trifluoroacetic acid (TFA) is a pretreatment method to solubilize hemicellulose to sugars such xylose without degrading cellulose. However, this pretreatment has not been compared to other processes. Thus, this paper focuses on the techno-economic comparison of the C5–C6 production of C5–C6 as raw materials platforms using non-centrifuged sugarcane bagasse (NCSB) and Pinus patula wood chips (PP). Hydrolysates using TFA 2.5 M as an acid were characterized through HPLC regarding arabinose, galactose glucose, xylose, and mannose sugars. Then, simulations of the processes according to the experimental results were done. The economic assessment was performed, and compared with some common pretreatments. The mass and energy balances of the simulations indicate that the process can be compared with other pretreatments. From the economic perspective, the main operating expenditures (OpEx) are related to raw materials and capital depreciation due to the cost of TFA corrosion issues. The processes showed a CapEx and OpEx of 0.99 MUSD and 6.59 M-USD/year for NCSB, and 0.97 MUSD and 4.37 MUSD/year for PP, considering a small-scale base (1 ton/h). TFA pretreatment is innovative and promising from a techno-economic perspective.

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