Loughborough University
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Characterization of solid fuel chars recovered from microwave hydrothermal carbonization of human biowaste

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journal contribution
posted on 2017-06-13, 12:31 authored by Oluwasola AfolabiOluwasola Afolabi, M SohailM Sohail, Paul Thomas
Microwave hydrothermal carbonization (M-HTC) is reported in this study as a viable sanitation technology that can reliably overcome the heterogeneous nature of human faecal biowaste (HBW) and realize its intrinsic energy value. Solid chars produced from the M-HTC process at 180°C and 200°C were characterized to further the understanding of the conversion pathways and their physicochemical, structural and energetic properties. The study revealed solid chars recovered were predominantly via a solid-solid conversion pathway. In terms of yield, more than 50% of solid chars (dry basis) can be recovered using 180°C as a benchmark. Additionally, the carbonized solid chars demonstrated enhanced carbon and energy properties following the M-HTC process: when compared to unprocessed HBW, the carbon content in the solid chars increased by up to 52%, while the carbon densification factor was greater than 1 in all recovered chars. The calorific values of the chars increased by up to 41.5%, yielding heating values that averaged 25MJ.kg-1. Thermogravimetric studies further revealed the solid fuel chars exhibited greater reactivity when compared with unprocessed HBW, due to improved porosity. This work strengthens the potential of the M-HTC sanitation technology for mitigating poor sanitation impacts while also recovering energy, which can complement domestic energy demands.


The authors wish to thank the Bill & Melinda Gates Foundation for its funding to Loughborough University, UK, on the ‘Reinvent the Toilet Challenge’ project.



  • Architecture, Building and Civil Engineering

Research Unit

  • Water, Engineering and Development Centre (WEDC)

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74 - 89


AFOLABI, O.O.D., SOHAIL (KHAN), M. and THOMAS, C.L.P., 2017. Characterization of solid fuel chars recovered from microwave hydrothermal carbonization of human biowaste. Energy, 134, pp. 74–89.


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  • AM (Accepted Manuscript)

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This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

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This paper was accepted for publication in the journal Energy and the definitive published version is available at https://doi.org/10.1016/j.energy.2017.06.010




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