Chemical Evaluation via High-Resolution Techniques and Biopesticide Potential of Bio-Oil and Aqueous Phase from Slow Pyrolysis of Passion Fruit Seed Cake

This work showcases the valorization of passion fruit seed cake by slow pyrolysis, the individual molecular chemical characterization of organic compounds in the liquid bioproducts via high-resolution analytical techniques, and the evaluation of the bio-oil as a potential biopesticide. Slow pyrolysis was used for the first time to valorize the passion fruit seed cake (PFSC) (Passiflora Edulis) residue, obtaining bio-oil, aqueous phase, biochar, and gas. Two working temperatures were selected, 300 degrees C and 400 degrees C, to investigate the final composition of the liquid products separated by density difference: bio-oil (BO300 and BO400) and aqueous phase (AP300 and AP400). The bio-oils were obtained with an average yield of 15.6% BO300 and 13.8% BO400, whereas the aqueous phases were obtained with a higher average yield than the bio-oils, being 27.9% AP300 and 29.2% AP400. Thus, the total liquid bioproducts yield for both pyrolysis processes was about 43%. The composition of the liquid products had little variation as a function of temperature. PFSC bio-oil is qualitatively composed mainly of phenolic compounds, nitrogen derivatives, and nonpolar compounds such as aliphatic and aromatic hydrocarbons, while the aqueous phase has a higher proportion of nitrogenous compounds in its composition and a very polar characteristic, suggested as potential biopesticides. In the evaluation of toxicity by fumigation used in this work, the aqueous phases showed no bioinsecticidal activity against Sitophilus zeamais and Rhyzopertha dominica. BO300 was moderately toxic against the species S. zeamais and mortality was above 92% for the species R. dominica. BO400, on the other hand, showed high toxicity for both species evaluated with mortality from 90 to 100% after 96 h. The results showed that despite the high concentration of phenols in bio-oils, the presence of these lignin derivatives alone is not enough to justify the biological activity. Thus, other compounds present in bio-oil such as nitrogen derivatives and aromatic hydrocarbons may be contributing to an increase the bio-pesticide effect of bio-oils, and even the synergistic effect between all the substances present.

Automated summary

This work examines the valorization of passion fruit seed cake by slow pyrolysis, focusing on the organic compounds in the liquid bioproducts and their potential as biopesticides. The study finds that the aqueous phase of the pyrolysis process shows promising biopesticide activity, with a higher proportion of nitrogenous compounds. Furthermore, the presence of nitrogen derivatives and aromatic hydrocarbons in the bio-oil may contribute to its biopesticide effect.