Smoldering Combustion Dynamics in Porous Media

Smouldering combustion in porous media is characterised by a slow, flameless oxidation front propagating through solid matrices such as soils, biomass residues or engineered waste beds. The process is driven by heterogeneous char oxidation reactions that release heat, coupled with the transport of oxygen and reaction gases by diffusion and convection within interstitial pores. Moisture content, inert filler materials and pore structure govern ignition thresholds, front stability and extinction limits. The reaction zone typically comprises sequential drying, pyrolysis and char oxidation sub-fronts, whose interaction controls temperature profiles and propagation speed. In natural environments, subsurface peat and soil smouldering underlie persistent wildfires with major carbon emissions and ecological impacts. In engineered systems, controlled smouldering enables energy-efficient waste remediation, off-grid sanitation and resource recovery, turning contaminants into value-added by-products. Recent advances in experimental diagnostics and multiscale modelling have deepened understanding of energy balances, oxygen supply–demand dynamics and the role of material heterogeneity, informing optimisation of smouldering processes for both environmental and industrial applications.

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Smoldering Combustion Dynamics in Porous Media publication trend

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Technical terms

Smouldering combustion: Flameless, low-temperature oxidation of char in porous media, sustained by heterogeneous surface reactions and limited oxygen availability.

Porous media: A solid matrix with interconnected voids that permit fluid flow and mass and heat transfer, e.g. soil, sand or engineered waste beds.

Reaction front: The moving zone where exothermic char oxidation occurs, defining smouldering propagation through the medium.

Energy balance: Quantitative accounting of heat release, conduction, convection and radiation that determines temperature distributions and front stability.

Syngas: A synthesis gas mixture, typically containing hydrogen, carbon monoxide and minor hydrocarbons, generated by partial oxidation or gasification of carbon-rich materials.

Co-waste management: Strategy of combining multiple waste streams into a tailored porous fuel to optimise combustion behaviour and by-product formation.

References

1. Elucidating the characteristic energy balance evolution in applied smouldering systems. Energy (2023).
2. Hydrogen-rich syngas derived from smouldering biomass and hydrocarbon wastes. International Journal of Hydrogen Energy (2024).
3. Applied smouldering for co-waste management: Benefits and trade-offs. Fuel Processing Technology (2023).
4. Thermochemical conversion of biomass in smouldering combustion across scales: The roles of heterogeneous kinetics, oxygen and transport phenomena. Bioresource Technology (2016).
5. Computational smoldering combustion: Predicting the roles of moisture and inert contents in peat wildfires. Proceedings of the Combustion Institute (2015).