Post-Extractivism and Bioeconomy: An Experimental Analysis of Combustion and Pyrolysis Processes as Alternatives to Add Value to Agro-Residues (Coffee Husks) Generated in Farmer Cooperatives of the Ecuadorian Amazon

Abstract

A post-extractivist development model for communities in the Amazon that is not based on non-renewable resource extraction demands the study and demonstration, in the field, of alternative economic activities that add value to currently generated residual biomass. Following the principles of bioeconomy, this study presents an experimental analysis of a retort burner and a pilot-scale auger-type pyrolysis reactor used to convert coffee husks generated in a collection and post-harvesting center of a farmer’s cooperative into thermal energy and biochar, respectively. This study shows that coffee husks, whether used as feedstock for combustion or pyrolysis processes, can supply the thermal energy required by the post-harvesting processes. The combustion or pyrolysis of coffee husks avoids its accumulation and decomposition while replacing fossil fuels used in post-harvesting operations, reducing costs and making farmers independent of fossil fuel subsidies. Unlike combustion (11,029.4 mg/Nm3), the CO concentration in the flue gas during the pyrolysis process was 458.3 mg/Nm3, which is below the eco-design standard of 500 mg/Nm3. According to the European Biochar Certificate, carbon content (67.4 wt%) and H/Corg, O/Corg (0.6 and 0.1, respectively) are within the typical values of biochars used for soil amendment and carbon sequestration. Nonetheless, the concentration of polycyclic aromatic hydrocarbons must be assessed to fully regard this material as biochar. Finally, further studies are required to assess the ability of cooperatives to generate and trade carbon credits linked with the application of biochar in their cropping systems.

Keywords

• coffee husks
• pyrolysis
• biochar
• combustion
• bioeconomy
• post-extractivism