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.

Water hyacinth is classified as a high-risk invasive species but is a source of biomass to obtain bio-oil and biochar by pyrolysis reaction. The Kissinger- Akahira-Sunose model (KAS), Ozawa-Flynn Wall (OFW), and Friedman model, determined the pyrolysis activation energy to be 213.19 kJ mol⁻¹, 222.55 kJ mol⁻¹, and 248.09 kJ mol⁻¹, respectively. Bio-oil was obtained with a 2.2% yield, and a maximum calorific value of 21,641 kJ kg⁻¹. The composition was 44% hydrocarbons, 27% aromatic hydrocarbons, 6% alcohols and phenols, 4% acids, and 19% aldehydes, ketones, ethers, nitriles, and others. A 48.84 wt% biochar was also obtained, gaining energy and active carbon. Bio-oil could be a candidate for the production of refined chemical products.

Hydrogen produced by microorganisms is a topic of growing interest because of its potential for derivation from several agro-industrial by-products. In this study, we evaluated the hydrogen production of strains of genus Clostridium (Clostridium acetobutylicum and Clostridium butyricum) using glycerol as a carbon source. Fermentation studies were conducted using three initial concentrations of glycerol: 10, 30 and 50 g/L. The micro-organism growth kinetics and the amounts of solvents and gases were recorded over 48 h. The strain C. acetobutylicum exhibited the best results in terms of hydrogen production, the highest production yield (Y _p/s) of 0.37 mol H₂/mol glycerol and the highest level of productivity (0.75 mg H₂/(L·h)). Based on these results, it is reasonable to conclude that glycerol could be effectively exploited as a carbon source for hydrogen production, which adds value to this primary by-product of standard biodiesel processes.