Interlaboratory study: Testing reproducibility of solid biofuels component identification using reflected light microscopy

Agnieszka Drobniak, Maria Mastalerz, Zbigniew Jelonek, Iwona Jelonek, Tushar Adsul, Neža Malenšek Andolšek, Omid Haeri Ardakani, Tara Congo, Batbold Demberelsuren, Bryon S. Donohoe, Ashley Douds, Deolinda Flores, Ranjin Ganzorig, Santanu Ghosh, Andrew Gize, Paula Alexandra Goncalves, Paul Hackley, Javin Hatcherian, James C. Hower, Stavros KalaitzidisSławomir Kędzior, Wayne Knowles, Jolanta Kus, Kacper Lis, Grzegorz Lis, Bei Liu, Qingyong Luo, Meili Du, Divya Mishra, Magdalena Misz-Kennan, Theophile Mugerwa, Jennifer L. Nedzweckas, Jennifer M.K. O'Keefe, Jackie Park, Richard Pearson, Henrik I. Petersen, Julito Reyes, Joana Ribeiro, Genaro de la Rosa-Rodriguez, Piotr Sosnowski, Brett Valentine, Atul Kumar Varma, Małgorzata Wojtaszek-Kalaitzidi, Zhanjie Xu, Alexander Zdravkov, Konrad Ziemianin

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Considering global market trends and concerns about climate change and sustainability, increased biomass use for energy is expected to continue. As more diverse materials are being utilized to manufacture solid biomass fuels, it is critical to implement quality assessment methods to analyze these fuels thoroughly. One such method is reflected light microscopy (RLM), which has the potential to complement and enhance current standard testing, leading to improving fuel quality assessment and, ultimately, preventing avoidable air pollution. An interlaboratory study (ILS) was conducted to test the reproducibility of biomass fuels component identification using a reflected light microscopy technique. The exercise was conducted on thirty photomicrographs showing biomass and various undesired components (like plastics or mineral matter), which were purposely added (by the ILS organizers) to contaminate wood pellets and charcoal-based grilling fuels. Forty-six participants had various levels of difficulty identifying the marked components, and as a result, the percentage of correct answers ranged from 52.2 to 94.4%. Among the most difficult components to distinguish were petroleum products and inorganic matter. Various reasons led to the misidentification, including insufficient morphological descriptions of the components provided to participants, ambiguities of the nomenclature, limitations of the analytical and exercise method, and insufficient experience of the participants. Overall, the results indicate that RLM has the potential to enhance the quality assessment of biomass fuels. However, they also demonstrate that the petrographic classification used in this exercise requires further refinement before it can be standardized. While a new simplified classification of solid biomass fuels components was created as an outcome of this study, future research is necessary to refine the nomenclature, develop a microscopic morphological description of the components, and verify the accuracy of component identification with a follow-up ILS.

Original languageEnglish
Article number104331
JournalInternational Journal of Coal Geology
StatePublished - Sep 1 2023

Bibliographical note

Publisher Copyright:
© 2023 Elsevier B.V.


  • Biomass
  • Biomass fuels
  • Biomass fuels contaminants
  • Charcoal
  • Interlaboratory study
  • Quality assessment
  • Reflected light microscopy
  • Wood pellets

ASJC Scopus subject areas

  • Fuel Technology
  • Geology
  • Economic Geology
  • Stratigraphy


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