Hydrothermal carbonization coupled with fast pyrolysis of almond shells: Valorization and production of valuable chemicals

In this study, it was found that hydrothermal carbonization (HTC) can be an effective method for almond shell (AS) valorization. The severity of HTC treatment had a significant effect on hydrochar yields, with higher severity promoting carbonization but reducing yields. Furthermore, the work found that HTC treatment effectively demineralized biomass samples by removing inorganic material that could catalyze carbonization. As residence time or temperature increased, the amount of carbon increased, while the amount of oxygen decreased. An acceleration in thermal degradation was detected for hydrochars after pretreating for 4 h. The hydrochars showed they had a higher volatile content than untreated biomass, making them potentially useful for producing quality bio-oil through fast pyrolysis. Finally, HTC treatment led to the production of valuable chemicals such as guaiacol and syringol. For syringol production, HTC residence time had more effect than HTC temperature. However, high HTC temperatures benefited levoglucosan production. Overall, the results demonstrated the potential for HTC treatment to be an effective method for valorizing agricultural waste, offering the possibility of producing valuable chemicals.

Automated summary

This study found that hydrothermal carbonization (HTC) is an effective method for valorizing almond shell (AS). The severity of HTC treatment affected hydrochar yields, with higher severity promoting carbonization but reducing yields. HTC treatment effectively demineralized biomass samples, thereby removing inorganic material that catalyzes carbonization. Increased residence time or temperature led to increased carbon content and decreased oxygen content. HTC treatment also produced valuable chemicals like guaiacol and syringol, with residence time having a greater effect on syringol production and high HTC temperatures benefiting levoglucosan production. Overall, the results demonstrate the potential of HTC treatment for valorizing agricultural waste and producing valuable chemicals.