Prefeasibility analysis of low-scale biorefineries: annatto and açai case

Abstract

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.

Valorization Alternatives of Tropical Forest Fruits Based on the Açai (Euterpe oleracea) Processing in Small Communities

“…These productivities are very low compared to the literature, supported by the optimal carbon/nitrogen ratio of 20-30 [49]. In this work, the ratio ranged from 5 to 11 for all substrates, results previously described for exotic and wild fruits by Poveda-Giraldo et al [9]. Figure 2 shows apparent high yields for SCN, SCA:SCN, and SCA:SCZ:SCN due to a possible higher amount of soluble compounds of low molecular weight that are easily digested by the microbial medium.…”

“…The fruits were processed without agricultural residues. The production of the fruit pulp was performed manually, considering the experience of pulp-producing companies in Chocó [9]. The process began with fruit washing using tap water in a ratio of 1 L per kg of feedstock.…”

“…The process began with fruit washing using tap water in a ratio of 1 L per kg of feedstock. Then, the fruits were disinfected with a sodium hypochlorite solution at 100 mg/kg in a 4:3 solid-to-liquid ratio and subjected to high temperatures for three minutes, followed by a cooling process [9]. Finally, the fruits were manually pulped, generating two fractions: (i) fruit pulp and (ii) seeds and peels.…”

“…At first, 0.15 g of the pulp was mixed with 1 mL of ethanol:water:HCl mixture (96:6:1 vol.) in an Erlenmeyer and carried to an ultrasonic bath at 37 kHz and 22 • C. Then, the extract was centrifuged and the supernatant was stored in amber vials at 4 • C [9]. The extract (15 µL) was mixed with 240 µL of distilled water, 15 µL of Folin-Ciocalteu solution (1 N), and 30 µL of sodium carbonate (20%, w/v).…”

“…The valorization of tropical forests can be achieved using exotic fruits that coexist within them. Exotic fruits are not usually cultivated constantly, and their consumption is regional [9]. Among the exotic fruits present in the Colombian Pacific are açai, araza, and noni.…”