Improved screening of biochar compounds for potential toxic activity with microbial biosensors

Oliver G. G. Knox*, Hedda J. Weitz, Peter Anderson, Maria Borlinghaus, James Fountaine

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Biochar is a carbon rich product destined for agricultural use, which can be produced using an array of feedstock and pyrolysis conditions. As such, the resultant biochar product can exhibit characteristics that result in either beneficial or detrimental environmental effects. We set out to establish what the environmental hazards might be for a range of softwood biochars. To facilitate this we conducted biochar headspace analysis, plant germination and bacterial biosensor assays. Our headspace analysis indicated the presence of aldehyde and ester based compounds, which were affected by pyrolysis conditions and in some cases contained compounds that were hazardous to human and environmental health. Germination assays, utilising barley, buckwheat, white clover and oil seed rape, showed that the plants responded differently to the same biochar samples and that in some instances, where germination was unaffected, there were visible physiological effects on seedlings. Finally, we screened water extracts of the biochars under buffered pH, for the presence of potentially toxic elements and compounds using bioluminescence-based bacterial biosensors. Bioluminescence inhibiting compounds were present in extracts prepared from biochar samples pyrolysed at 500 degrees C under conditions with inadequate control of biochar-volatile interaction. The findings were taken as an indication that bacterial biosensors could be used as a rapid method to screen anomalous biochar products for potential ecotoxicity hazard assessment. (C) 2018 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)254-264
Number of pages11
JournalEnvironmental Technology and Innovation
Early online date2 Jan 2018
Publication statusPublished - Feb 2018

Bibliographical note

This work was supported by the Scottish Government Workpackage 3.3, ‘The soil, water & air interface and its response to climate and land use change’. GC–MS analysis was undertaken by the Scottish Environmental Technology Network (SETN), supported by the European Regional Development Fund, the Scottish Funding Council and University of Strathclyde . The biosensors P. fluorescens 8866 Tn5 luxCDABE and P. putida F1 Tn5 luxCDABE were kindly provided by Hedda Weitz, University of Aberdeen. Biochar samples utilised in these experiments were produced by Ondřej Mašek and Juan Turrion-Gomez at the UK Biochar Research Centre, University of Edinburgh, for inclusion in the joint SRUC and University of Edinburgh, School of GeoSciences PhD ‘Implications of biochar on UK barley systems: a biological perspective’. We would express our thanks to Saran Sohi, Ondřej Mašek and the undisclosed reviewer who contributed to the review of this manuscript.


  • Phytotoxicity
  • Bioluminescence Hazard analysis
  • Risk assessment
  • Pseudomonas fluorescens 8866 Tn5 luxCDABE
  • Pseudomonas putida F1 Tn5 luxCDABE


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