Influence of Temperature and Residence Time on Torrefaction Coupled to Fast Pyrolysis for Valorizing Agricultural Waste

Torrefaction is a promising pretreatment technology for valorizing biomass and upgrading pyrolysis products. This study sets out an original procedure consisting of subjecting the biomass to torrefaction before fast pyrolysis to increased value-added compounds based on agricultural waste biomasses production. This study uses a combined biomass treatment consisting of torrefaction (280-320 degrees C) and subsequent fast pyrolysis (500 degrees C) using the same reactor. Under different torrefaction temperatures and residence times, olive pomace (OP) and almond shell (AS) have been evaluated. The study demonstrated OP rather than AS was thermally unstable. The highest total yield of carboxylic acids (mainly acetic acid) was obtained by means of torrefaction at 280 degrees C with a residence time of 20 s for OP, and at 300 degrees C and 20 s for AS. Higher torrefaction temperature and residence time promoted phenolic compounds production for OP. However, OP had a higher lignin content and inherent metals that promoted a catalytic reaction during the procedure. The highest yield (47.7%) was obtained using torrefaction at 320 degrees C with a residence time of 240 s. Overall, the torrefaction of biomass combined with fast pyrolysis constituted a very simple and efficient strategy for valorizing the conversion of agricultural waste biomass into value-added chemicals.

Automated summary

This study proposes a combined treatment method of torrefaction and fast pyrolysis to convert agricultural waste biomass into value-added chemicals. The study found that olive pomace was more thermally unstable compared to almond shell. The highest yield of carboxylic acids was obtained at 280°C for 20 s for olive pomace, with higher torrefaction temperature and residence time promoting the production of phenolic compounds.