Pyrolysis of Hass Avocado (Persea americana) Seeds: Kinetic and Economic Analysis of Bio-oil, Gas, and Biochar Production

Abstract

The avocado seed is a major waste generated by the avocado agroindustry in different countries. This waste can be valorized by producing biofuels and other products through a circular economy approach. In this work, the Kissinger–Akahira–Sunose (KAS) and Ozawa-Flynn Wall (OFW) isoconversional methods were used to estimate the activation energy of pyrolysis, which ranged from 24.17 to 226.34 kJ/mol. Additionally, avocado seeds were pyrolyzed in laboratory equipment to generate biochar, gas, and bio-oil. Bio-oil was obtained with a yield of 4% and a maximum caloric value of 21.641 kJ/kg, with a high hydrocarbon content. Biochar (37.5 wt.%) was also obtained, which gained energy and activated carbon. Gas is significant in the pyrolysis process, with 60% productivity. Three cases of pyrolysis processes were simulated, which presented better experimental performance related to biochar and bio-oil yields. These cases were assessed via a sensitivity analysis of the economic component, where the economic margin of both pyrolytic products is positive for any sale price. In the minimum price of biochar, the economic margin was approximately 2%, whereas in the maximum price, the profit was approximately 60%. For the case of bio-oil, the maximum profit was approximately 35%. This research demonstrated the high potential of rapid pyrolysis of avocado seed residues for obtaining bio-oil and biochar fuels with high energy values and promoting a circular economy.