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

Abstract

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 °C) and subsequent fast pyrolysis (500 °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 °C with a residence time of 20 s for OP, and at 300 °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 °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.

Theoretical simulation of olive pomace pyrolysis for biomass energy: A sustainable approach to waste reduction and energy efficiency

“…Others [2] focus on the physicochemical attributes of olive pomace, unveiling its potential as a high-energy, sustainable fuel source. Another set of investigations [3] introduces torrefaction as a pre-treatment method, revealing the value-added compounds that can be derived from olive pomace. Meanwhile, [4] explores the utilization of olive pomace for fast pyrolysis, highlighting the role of inorganic metals in influencing product distribution.…”

Control of Reactivity of Formed Coke from Torrefied Biomass by Its Washing with Torrefaction-derived Acidic Water

“…It is known that hemicellulose is the most important source of pyrolytic acetic acid, while it is also formed from cellulose and lignin. 28,29) The hemicellulose undergoes pyrolysis at temperatures lower than the other major components. As a result of this, pyrolysis at 500°C or higher temperatures is not necessarily favored for increasing or maximizing acetic acid yield.…”

“…As a result of this, pyrolysis at 500°C or higher temperatures is not necessarily favored for increasing or maximizing acetic acid yield. 28,29) Recovery of acetic acid from torrefaction at temperatures lower than 300°C, 28,29) if combined with its use for removing AAEM species from the biomass or torrefied biomass, is expected to be more effective than pyrolysis at 500°C or higher.…”