Pyrolysis of açai stems (Euterpe oleracea Mart.) and cocoa husks (Theobroma cacao L.) residues for the generation of added-value products in rural areas

Abstract

Generally, agriculture activities represent the main economic income of rural areas, and during these, huge amounts of biomass are generated. This biomass is considered as garbage due to its high storage cost. However, energy and added-value products can be recovered from biomass. Within this context, açai stems and cocoa husks were collected from different rural areas of Bolivia due to their high importance in the local and international markets as two of the most available products of the country. The preliminary study will contribute in the field of green energy recovery and resource management. Thus, in this study, both residues were tested as renewable feedstocks for the generation of added-value products from pyrolysis at 500 °C for 30 min. Açai stems were found to be more suitable to biochar based with yields up to 49.1% ± 2.4%, but also for biogas production (33.9% ± 2.0%). Cocoa husk was also found to be more suitable for biochar production (38.1% ± 1.7%) but also for bio-oils (33.6% ± 17.6%). Both resulting biochars had basic pH (between 10 and 12) and low density (287.2 kg/m3 and 401.7 kg/m3). Additionally, the lack of heavy metals on the surface makes both biochar products good candidates for soil amendment applications. Furthermore, the bio-oil composition is complex and varied, and products such as Maltol, 2-methyl furane, and D-allose have direct applications in the food industry. Moreover, the presence of phenolic compounds and hydrocarbons with more than five carbons in the structure makes the obtained bio-oils suitable for upgrading processes for biofuel production. Finally, the obtained biogases can be applied for local electricity generation, or to reduce the energy requirements for the pyrolysis reactor. Graphical Abstract