The effect of reactor scale on biochars and pyrolysis liquids from slow pyrolysis of coffee silverskin, grape pomace and olive mill waste, in auger reactors

Cristina Del Pozo, Filipe Rego, Neus Puy, Jordi Bartrolí, Esteve Fàbregas, Yang Yang*, Anthony V Bridgwater

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Several studies have addressed the potential biorefinery, through small-scale pyrolysis, of coffee silverskin (CSS), grape pomace (GP) and olive mill waste (OMW), which are respectively the main solid residues from coffee roasting, wine making and olive oil production processes. However, increasing the scale of reactor to bring these studies to an industrial level may affect the properties, and hence applications, of the resulting products. The aim of this study is therefore to perform pilot scale experiments to compare and verify the results of analytical study (TGA) and bench scale reactor runs, in order to understand the fundamental differences and create correlations between pyrolysis runs at different scales. To this end, pyrolysis liquids and biochars from the slow pyrolysis of CSS, GP and OMW, performed using different scale auger reactors (15 kg/h and 0.3 kg/h), have been analysed (TGA, pH, density, proximate and ultimate analyses, HHV, FTIR, GCMS) and compared. The results showed no major differences in biochars when the temperature and the solid residence time were fixed. However, regarding pyrolysis liquids, compounds from the lab reactor were more degraded than pilot plant ones, due to, in this case, the vapour residence time was longer. Regarding the properties of the pyrolysis products, GP 400 °C biochars showed the best properties for combustion; CSS biochars were especially rich in nitrogen, and 400 °C GP and OMW pyrolysis liquids showed the highest number of phenolics. Hence, this study is considered a first step towards industrial scale CSS, GP and OMW pyrolysis-based biorefinery.

Original languageEnglish
Pages (from-to)106-116
Number of pages11
JournalWaste Management
Volume148
Early online date3 Jun 2022
DOIs
Publication statusPublished - 1 Jul 2022

Keywords

  • Agricultural wastes
  • Biochar
  • Pyrolysis auger reactor
  • Pyrolysis liquid
  • Scale-up

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