Keynote: When the soil burns to ash, and smouldering episodes of haze

I gave this morning the first keynote lecture at the 4th International Meeting of Fire Effects on Soil Properties, in the pretty and small city of Vilnius. The title was "Fate of Organic Matter and Pyrogenic Char in Smouldering Fires: when soils burn to ash". I have posted a copy of my slides below.

I started by making a direct reference to the ongoing haze episode in South East Asia, caused by smouldering peat megafires. Like most organic soils, peat is flammable, and dry peat is extremely flammable. This haze episode is expected to last one or two more months, and is leading to a respiratory health crisis and hundreds of millions in economic losses in the region. I then did a quick overview of some smouldering fires as a way of illustrating different fire phenomena  (1997 Indonesia, 2006 Scotland, 2008 North Carolina). After an overview of what smouldering combustion is, I then made a case for these fires to be considered the largest on Earth (the most persistent and longest leading to the highest consumption of fuel). I  reviewed the chemistry of peat fires and some of the laboratory work we have conducted to study their horizontal and vertical spread, and the role of moisture content. The last bit is collaboration with soil chemists on the signature left by smouldering fire for paleoenviromental reconstructions of peat core. I concluded with my global views; that smouldering poses a possitive feedback loop for climate change in the Earth system, and that there is a acute need for more research on the topic.

   Fate of Organic Matter and Pyrogenic Char in Smouldering Fires: when soils burn to ash

The lecture was well received with plenty of good questions during the session and the coffee break. In particular I got this question from an American scientists of what would be the best conditions for the production of charcoal/char; it really inspired me and gave me an idea for an experimental and modelling research paper: what is the heat pulse (peak and duration) that leads to the largest production of i) charcoal and ii) char. My guess is that charcoal is maximized by a strong but short pulse (akin to a quick flaming front) whereas char is maximized by the quenching of a propagating smouldering front. 


NOTE: The difference between charcoal and char is that the former, we call it alpha-char, is produced at lower temperatures such that the shape of the original biomass can be identified, and the former, we call it beta-char, is produced at higher temperatures and the shape of the original biomass cannot be identified.

Smouldering mega-fires in the Earth system

I just gave the presentation "Smouldering mega-fires in the Earth system" at the conference Exploring the Mega-fire Reality, Florida State University. It went well very,  good questions (~8) from audience and great feedback. The abstract is below.

Smouldering mega-fires in the Earth system

Abstract
Smouldering fires, the slow, low-temperature, flameless burning of organic matter release anually at a global scale the equivalent to ~15% of man-made carbon emissions. It accounts for the accidental burning of fossil fuels, including natural as well as antropogenic causes. Very large fires of organic matter (mostly in peatlands) have burnt since past millennia for long periods of time (months, years, decades; the longest continuously fires on Earth). Flaming forest fires have been the central focus of most research, but smouldering mega-fires are paramount to the Earth System and have received very little attention. Smouldering is the most persistent type of combustion phenomena; the easiest to ignite, and the most difficult to suppress. Peat fires propagate slowly (~1 mm/min) through organic layers of the ground and can reach depth >5 m when large cracks or a natural piping system exists. It is a 3-dimensional phenomena, spreading deep into the soil and over extensive areas of land. The depth of burn is given by the location of the inert layer, very moist layer (>125%MC) or firefighting attempts. Observed depths of burn reported in the literature range from 0.1 to 5 m, with the average around 0.5 m (=75 kg/m2 of fuel consumption). This is 40 to 90 times larger than flaming fires. In terms of fuel consumption, these are mega-fires. This is of great concern given that world peatlands contain more terrestrial carbon than the forests or the atmosphere. Compared to the natural carbon flux to the atmospherefrom from peatland degradation, smouldering fires is 3,000 times faster. These wildfires burn fossil fuels and thus are a carbon-positive fire phenomenon via soil moisture deficit and self-heating. Warmer temperatures at high latitudes are resulting in more frequent Artic fires and unprecedented permafrost thaw.

Inaugural Lecture on Multiscale Modelling of Tunnel Fires

Last Wednesday 1 June, I gave this Inaugural Lecture on Multiscale Modelling of Tunnel Fires at the I Fire Engineering Conference at Universidad Politecnica de Valencia.

The lecture is based on the PhD thesis of Francesco Colella (2010), my second PhD student.

Multiscale Modelling of Tunnel Fires

Abstract

Tunnels represent a key part of the world infrastructure with a role both in people and freight transport. Past events show that fire poses the most severe threat to safety in tunnels. Indeed in the past decades over four hundred people worldwide have died as a result of fires in road, rail and metro tunnels. In Europe alone, fires in tunnels have brought vital parts of the road network to a standstill and have cost the European economy billions of euros. Within this safety strategy, the ventilation system plays a crucial role because it takes charge of maintaining tenable conditions to allow safe evacuation and rescue procedures as well as fire fighting. Throughout most of a tunnel network the ventilation behaviour may be approximated with a simple 1D flow model. However, there are some important - but relatively small - regions of the tunnel that require CFD analysis. The multi-scale model is the ideal tool for such tunnel studies as it allows accurate flow field predictions in some locations, yet allows simplifications where highly detailed data are not required. It is shown that the accuracy of the multi-scale model is as high as the full CFD approach. The 100 times lower computational time is of great advantage because many ventilation scenarios can be explored and extensive sensitive parametric studies can be conducted.

Forecasting Fire Dynamics - IOP talk

Yesterday 23 May, I gave this invited talk on Forecasting Fire Dynamics at the Institute of Physics Combustion Group meeting on Combustion Modelling for Challenging Applications, University of Southampton.

It is based on the PhD thesis of Wolfram Jahn (2010), my very first PhD student.

Forecasting Fire Dynamics IOP May 2011

Abstract
The concept of fire forecast could lead to a paradigm shift in the response to fire emergencies, providing the Fire Service with essential information borne from the combination of sensor observations and computer modelling. Ideas are being borrowed from weather forecast and high performance computing so the technology is currently being developed. Many questions remain to be answered in the next decade but preliminary working models (zone model and CFD) based on an inverse problem approach are already proving predictions with positive lead times. This talk presents the problem framework and explores concepts and results developed to date.

Oral presentation at EGU: Climate Feedbacks on Smouldering Earth

Yesterday 6 April, I gave this talk on Climate Feedbacks on Smouldering Earth at the 2011 European Geosciences Union, Vienna:

Climate Feedbacks on Smouldering Earth (talk at EGU Vienna 2011)

Abstract:

Climate Feedbacks on Smouldering Earth: Enhancement of Moisture deficit and self-heating of fossil and pre-fossil soils
 
Guillermo Rein
University of Edinburgh, School of Engineering, United Kingdom (G.Rein@ed.ac.uk)

Global smouldering phenomena, the slow, low-temperature, flameless burning of organic soils, is the most persistent type of combustion phenomena and the longest continuously fires on Earth (>6,000 years). It take place since deep times and in many ecosystems, special boreal and tropical ones. These are accidental sources of carbon emissions that during millennia have been slowly burning fuels with zero energy efficiency, consuming large amounts of fossil energy resources (coal seams), destroying natural ecosystems (peatlands) and emitting greenhouse gases and pollutants. The global problem has grown in the last decades to an estimated release varying between 10 to 40% of the man-made carbon emissions, and a coal consumption rate at least 5 times that of Germany. Because it involves the burning of fossil and pre-fossil fuels, this is a carbon-positive wildfire phenomena. This creates feedbacks in the climate system because moisture deficit and self-heating of organic soils
are enchanted under warmer climate scenarios and would lead to more frequent smouldering fires. Warmer temperatures at high latitudes are resulting already in more Artic fires and unprecedented permafrost thaw exposing large soil carbon pools to smouldering for the fist time since millennia.
While flaming fires have been a central focus in fire research, smouldering fires are as important in terms
of ecosystem damage, atmospheric emissions and socioeconomic threats but have received little attention. Moreover, these fires are difficult or impossible to detect with current remote sensing methods because the chemistry is significantly different, their thermal signature is much smaller, and the plume is much less buoyant.

Invited Talk in Madrid: Travelling Fires in Building Structural Design

Last Thursday 24th Feb, I gave this invited talk on Travelling Fires at the 6th International Congress on Performance-Based Design for Fire, Madrid:

G Rein, Travelling Fires in Building Structural Design, Madrid 2011

A related paper has just been accepted for publication:
A Law, M Gillie, J Stern-Gottfried, G Rein, JL Torero, The Influence of Travelling Fires on a Concrete Frame, Engineering Structures, (in press) 2011. doi:10.1016/j.engstruct.2011.01.034