Valorization of guava (Psidium guajava L.) seeds for levoglucosan production by fast pyrolysis

The aim of this work is to show the potential of guava seeds (agro-industrial waste) for obtaining pyrolytic sugar like levoglucosan by fast pyrolysis. Firstly, guava seeds were ground to 30 mesh and then subjected to fast pyrolysis in a pyro-probe reactor coupled to GC/MS at temperatures of 350–600 °C. Thus, in addition to the production of levoglucosan, it was possible to verify the formation profiles of different compounds derived from cellulose, hemicellulose and lignin which may also add value to biomass or be undesirable in the extraction and purification stages of these sugars. Simultaneously, the seeds were subjected to a treatment with acetic acid to leach alkali and alkaline earth metals and to increase the formation of levoglucosan, achieving a yield at 550 ºC after acid washing that was around 14 times higher than that obtained with untreated biomass. These results can be attributed not only to the reduction in K, Mg and Ca but also to the partial removal of fractions of hemicellulose and lignin during the biomass acid washing, thus resulting in a higher cellulose content in the treated biomass. In fact, TG/DTG analyses confirmed that the treated biomass is more thermally stable and that there was a reduction in residual biochar from 23 to 19%, thereby having more cellulose available for levoglucosan formation. The results of this study can contribute to the production of renewable fuels from alternative feedstocks and at the same time add value to the agribusiness of commercialization and processing of guava.