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

7/28/2019 Fate of Organic Matter and Pyrogenic Char in Smouldering Fires: when soils burn to ash

1/45

Dr Guillermo ReinDepartment of

Mechanical Engineering

KEYNOTE Fate of Organic Matter andPyrogenic Char in Smouldering Fires:

when soils burn to ash

4th Int. Meeting of Fire Effects on Soil Properties,Vilnius, July 2013


2/45

CONTENTS:ROOTS OF HAZE

EPISODES

LARGEST FIRES ON

EARTHFATE OF ORGANIC

MATTER

PYROGENIC CHAR

Haze 2013, South East Asia


3/45

22 Oct 1997 smoke plumeNASA TOMS satellitePage et al. Nature 420, 2002

Sign at NTU Singapore, 2011

The 1997 smouldering peat fires in Borneo released between 0.8and 2.6 billion tons of carbon into the atmosphere. That is

equivalent to 13 to 40 % of all emissions from burning fossil fuels


4/45

The Evans Road fireSummer 2008, North Carolina, USAPocosin Lakes National Wildlife Refuge


5/45

National Geographic 2008 / AP Photo/MODIS

The Evans Road fireburned for 7 months

During worst drought on record

16,500 ha burned (2x year avg.)1 m deep into the soilby flooding and excavation$20 million in suppression costs


6/45


"Think of it as one giant

charcoal briquette. It willignite and the fire will sinkinto the soil

State Forest ManagerNC, 2008

Equivalent to 1340% ofmanmade globalcarbon emissions(and not account forby IPCC yet)

salvemoslastablas.blogspot,Toms Beldad, 2009


7/45

Russian Haze,summer 2010


8/45

by G Rein, 2006

Rothiemurchus Wildfire, July 2006


9/45

by G Rein, 2006



10/45


by G Rein, 2006


11/45

by G Rein, 2006



12/45


13/45

World Map of PeatlandsFrom shallow (30 m)Contain more terrestrial carbon than the forests or theatmosphere

Gore, 1983


14/45

Organic Soils - Ignition Limits

no ignition

Ignition

Frandsen, Can. J. For. Res. 1997

dry base


15/45

Smouldering Combustion

FlamelessLow peak temperature ~600CLow heat of combustion ~5 kJ/g

Creeping propagation ~1 mm/min

Incomplete combustion

Heterogeneous combustion on poresurfaceFuels: peat, coal, duff, organic soils

Rein, Smouldering Fires and Natural Fuels - Wiley 2013

(solid)Ash(solid)Char(gas)PyrolyzateHeat(solid)Biomass

(solid)AshgasesotherOHCOHeatO(solid)Char 222

Incomplete combustionHeterogeneous combustion on poresurfaceCocktail of emissions CO 2, CO, PM, CH4,PAH...


16/45

igniter


17/45


18/45

Transition to Flaming Combustion30 min1 h 1 s1 s

Torero 1992,UCB/NASA

no transition

transition

oxygen fraction

f l o w v e

l o c i t y

( m / s )

0. 3 0. 4

3

0. 35

2

1

Bar-Ilan et al, Proc. Comb. Inst. 30,

pp 2295-2302, 2005


19/45

Most persistent fires on EarthSmouldering fires are the easiest to ignite

Ignition with much smaller heat sources (8 vs. 15 kW/m 2)Selfheating possible at ambient temperatures (ie, 30 C)

Smouldering fires are most difficult to suppressLarger amounts of water (>50% larger kg H2O/kg fuel )

Lower critical oxygen concentration (10% [O 2] vs. 16%)Much longer holding times for smothering (~months vs. min)

The oldest continuously burning fire on Earth is asmouldering coal seam in Australia ignited >6,000 years old



20/45


21/45

Spread over dry/wet patternsChecker board

Longitudinal split

Top view, 5 cmdeep peat layer.

20 x 20 cmsquare box

Perpendicular split


22/45

Peat Reactivity

Huang and Rein, Combustion and Flame 2013


23/45

Carbon Balance

Hadden et al, Proceedings of the Combustion Institute , 2012

Carbon fraction in char is ~1.5 times higher than peat Carbon fraction in ash is ~35 times lower than char During fires peat soil goes from 77 to 0.7 kgC/m 3


24/45

Pyrogenic Char

Hadden et al, Proceedings of the Combustion Institute , 2012

Char is simultaneously product andreactant in pyrolysis and oxidationreactions, which initially results

in net char production and laterbecome net char consumption .


25/45

Peat Reactivity TGA and Kinetics

Huang and Rein, Combustion and Flame 2013Chen et al, Energy & Fuels 2011


26/45

Simulations of Indepth spread


The 1step drying and 4step

decomposition kinetics schemeexplains the order of the reactions

during indepth combustion:

Drying first, then Pyrolysis and last

is Oxidation


27/45

Soil Heating vs. Soil BurningExperimental measurements of thermal severity

Medical sterilization of surgery instruments

smouldering

flaming

s o i

l d e p t h

Rein et al, Catena 2008


28/45

Fires in the Fossil RecordCurrent science:

Char abundance is a proxy to fire abundanceImplicit assumption: char abundance increases with fire

intensity and frequencyThis is correct for flaming fires.

Bonefire example:char remains at flameout vs. ash remains the day after

Char abundance decreases with smouldering intensity and

frequencyPossible sources of lower char: a) Smouldering fire; or b)Residual smouldering postflaming fire

Suggests: In addition to char, look for ash


29/45

Chemical Analysis of soil residue at thesmouldering front

Smouldering column tests of Sphagnum peat at different initial moisture

contents (MC) ignited at the top:, dry conditions ( MC50% ), undisturbed

conditions ( MC100% ), and wet conditions ( MC200% ).

Dry Undistr. Wet

MC50% MC100% MC200%

Zaccone et al., EGU 2012-4795, XY648

h d l l ( )


30/45

0

40

80

120

160

0 10 20(%)

Ashcontent

100%MC

Fresh peat

0

40

80

120

160

40 60 80(%)

TC

100%MC

Fresh peat

0

40

80

120

160

0 2 4 6(%)

TN

100%MC

Fresh peat

0

40

80

120

160

0 20 40 60

C/N

ratio

100%MC

Fresh peat

0

40

80

120

160

0 10 20 30

C/Hratio

100%MC

Fresh peat

0

40

80

120

160

3 6 9

pH

100%MC

Fresh peat D e p t h f r o m

f r o n t ( m m

)

D e p t h f r o m

f r o n t ( m m

)

Ash, pH and elemental composition ( MC100% vs. FP)

h


31/45

R = 0.9846

R = 0.8799

R = 0.192

0

5

10

15

20

25

0 10 20 30 40 50 60

C / H

C/N

C/H vs. C/N

MC50% MC100%

MC200% FP

Data show:

a higher production of aromatic and

condensed molecules, as underlined by thehigher C/H values;

the increase of the total N and decrease of

C/N ratio suggesting the incorporation of, andthe relative enrichment in, N during charring.


32/45

Energy and Climate Crisis

World energy use and climate change sciencehas led to international concerns on:

Fossil fuel energyCarbon emissionsEnvironmental protectionSustainability

Most attention is paid to increased energyefficiency , lower resource consumption anddevelop clean energy technologies


33/45

Accidental Sources

But accidental sources of fossil fuel burning

contributing to the problem are largely ignored

This includes nonanthropogenic sources aswell:

Smouldering Megafires in Peatlands


34/45

Smouldering Natural Fuels

10 years 1,000 years 1,000,000 years 300,000,000 years

Most important: duff, humus, peat, coalDecayed vegetation matter, from shallow (30 m).


35/45


Flaming fires consumegrasslands , shrubs andforests . These take 10-10 2 yearsto grow back and sequester backthe carbon = Renewable & CarbonNeutral

Flaming vs. Smouldering

Smouldering fires consume peat ,organic soils and coal . These take 10 4

to 109

years to grow again =Not Renewable & Carbon Positive

Smouldering fires burn

ancient carbon (akin to fossil fuels)


36/45

Feedback Mechanism in the Earth System

topics I work onPermafrost thaw are already resulting inlarge smouldering artic fires (e.g., Alaska 2010).

C l i


37/45

ConclusionsSmouldering combustion of peatlands leads tothe largest fires on Earth

100 times higher fuel consumption per area than flamingfires

Consume organic matter and release ancientcarbon stored deep in the soil ( accidental fossil fuelburning )

Soil goes from 77 to 0.7 kgC/m 3

Pose a positive feedback mechanism to climatechange via moisture deficit, thaw and selfheating

Topic of global interest linked to ecosystem perturbation,carbon sequestration and climate change


38/45

Thanks

Belcher et al, PNAS 2011

Rein et al, Catena 2008

Rein et al., Proc Combustion Institute 2009

Hadden et al, Proc Combustion Institute 2012



M fi


39/45

Megafires

320

0 3)( t S S dt mt m ld

t

t t

00

)( t S dt mt m d t

Smouldering spreads in area and indepth.

It is a volumetric phenomenon (flaming is a surface phenomenon)

Combustion Dynamics


40/45

Combustion Dynamics

As the intensity of the fire increases (proxy via increasing oxygen

concentration), the fraction of residual char rapidly decreases to zero.


41/45

1999 A Belenky / SPT

July 1999 Anomalous climate conditions led to first reported smouldering wild-urban interface.

Peat fires burn south of the city for weeks and haze covered five districts. That sameyear, other peat fires forced President Yeltsin to change holyday resort.

Days in July 1999

NYT Smoke Shrouds Moscow as Peat bog fire rages


42/45

NYT Smoke Shrouds Moscow as Peat bog fire rages@ New York Times, 1972

1972:


43/45


44/45

Sign at the sports centre of the Nanyang

Technological University, Singapore, 2012


45/45

Mechanical Engineering Building, 2nd [email protected]

http://www.imperial.ac.uk/people/g.rein

This is home to the experimental branch of the Imperial Haze Lab, research group of Dr

Guillermo Rein at the Department of Mechanical Engineering. We study the heattransfer, condensed-phase chemistry and

thermodynamics of reactive solids. Ourcontributions help understand and solve

global environmental problems, threats toenergy resources and the protection of

infrastructure.

Documents

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