Impact of post-torrefaction process on biochar formation from wood pellets and self-heating phenomena for production safety

Emmanuel Arriola, Wei Hsin Chen, Yi Kai Chih, Mark Daniel De Luna, Pau Loke Show

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The advancement of torrefaction in the industry raises safety issues lately. This work aims to investigate the impact of post-torrefaction upon biochar formation and the self-heating phenomena of torrefied wood pellets. Three operating scenarios are taken into account. Specifically, dried wood pellets are first torrefied in nitrogen at various temperatures (200–300 °C) followed by immediate exposure to N2 or air with/without keeping temperature, namely, the post-torrefaction, to examine the self-heating behavior. Meanwhile, the influences of torrefaction temperature, duration, and self-heating on biochar's characteristics are analyzed. It is found that self-heating with the highest temperature rise of 61 °C is triggered when the biochars are in an oxidative post-torrefaction process with keeping temperature. Alternatively, oxidative post-torrefaction without keeping temperature can efficiently intensify the pellets’ calorific value up to 42%. The X-ray photoelectron spectroscopy analysis reveals the depletion of the CO functional group. It is concluded that uncontrolled self-heating in large scale production will lead to combustion and make biochar unsafe. Alternatively, if heat accumulation inside the biochar piles can be prevented, the oxidative environment that causes self-heating can open a lot of research opportunities that can help in the advancement of torrefaction technologies for biomass as an alternative source of energy.

Original languageEnglish
Article number118324
Publication statusPublished - 2020 Sep 15

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Building and Construction
  • Pollution
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering

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