Study of Air Toxics Released from the Pre- Harvest Burning of ...

A&WMA International Specialty Conference
Leapfrogging Opportunities for Air Quality Improvement
Study of Air Toxics Released from the Pre-
Harvest Burning of Sugarcane
Danielle Hall, Jun Wang, Kuei-Min Yu, Krisha Capeto, Chang-Yu
Wu, James Stormer, Guenter Engling, Yu-Mei Hsu
May 11 th , 2010
Department of Environmental Engineering Sciences
University of Florida

Introduction: Sugarcane Burning Practice
The pre-harvest burning of sugarcane
is a common practice used to
facilitate harvesting.
– Removes unwanted biomass
– Reduces snake and insect hazards
– Concentrates sugar through water
evaporation
Palm Beach County’s 2008
emissions inventory showed
sugarcane pre-harvest burning
contributed to:
– 20% of VOC emissions
– 48% of PM emissions
– 22% of CO emissions
– 11% of NO x emissions

Introduction: Sugarcane EFs
Current EFs are based from one study of Hawaiian
sugarcane (Darley, 1974) and are rated unreliable
(category “D”) in AP-42.
- Limited data set
- Sugarcane from different areas may
exhibit significant EF differences
- Limited data available for specific HAPs

Objective
Investigate the emission factors
– Hazardous Air Pollutants
Polycyclic Aromatic Hydrocarbons (PAHs)
– 16 “priority PAH Pollutants” + 3 other PAH of concern.
Carbonyls
– Formaldehyde, acetaldehyde, propionaldehyde,
crotonaldehyde, butyraldehyde, benzaldehyde, valeraldehyde,
2,5-dimethylbenzaldyde
Volatile Organic Compounds (VOCs)
– Benzene, toluene, ethylbenzene, o,m,p-xylenes, styrene
– PM 2.5
Elemental Carbon (EC)
Organic Carbon (OC)

Methodology: Chamber Design
A combustion chamber used to simulate
field burning.
Stack sampling methods used.
Stack velocity and chamber flowrate was
determined following EPA Method 2.
– Pressure drop and temperature were measured
with a s-type pitot tube and thermocouple across
a horizontal traverse.
CO and CO 2
flue gases were continuously
monitored to determine the combustion
efficiency
MCE =
[ ]
[ ]
∆ CO 2
∆[ CO]+ ∆ CO 2

Methodology: Sampling
Two experimental conditions tested:
•Dry sugarcane leaves
-Feed rate ~ 100g / 40 sec
•Whole sugarcane stalks
(containing wet + dry leaves)
-Fed to maintain near constant
burning conditions.
-Heterogeneous nature of biomass
led to more variable combustion
conditions
Combustion chamber

Methodology: PAHs
Sampling and analysis based
from EPA Method TO-13A
(adapted for stack sampling).
PAHs isokinetically sampled and
collected on quartz filters and
PUF/XAD-2 resin cartridges.
Filters and cartridges were sent
to Columbia Analytical Services
(CAS) where they were Soxhlet
extracted, concentrated, and
analyzed by GC/MS.
Filter
PUF/XAD-2
cartridge
holder
Sampling
nozzle

Methodology: Carbonyls & VOCs
CARBONYLS:
Sampling and analysis based
on EPA Method TO-11A.
– DNPH sorbent cartridges with KI
ozone scrubbers
Samples extracted with
acetonitrile, and analyzed by
HPLC (performed by CAS).
Ozone
DNPH
Scrubber
cartridge
VOCs:
• Gas samples collected in
Tedlar bags via negative
pressure.
• Samples analyzed for BTEX
& styrene by GC/MS
(performed by CAS)
Sample
Probe
Vac-U-
Chamber
Tedlar bag
Teflon sampling
line
Exhaust
port
Carbonyl Sampling System
Vac-U-Chamber and Tedlar bag

Methodology: PM 2.5
PM 2.5 sampling followed EPA Other Test Methods 27 & 28 (modified)
– Cyclone used to separate particles based on size.
– Filterable PM 2.5 collected on a glass fiber filters and tissuquartz filters (for
EC/OC analysis)
– Condensable particulate matter (CPM) collected in a dry impinger train
and on Teflon CPM filter.
Glass fiber filters were pre- and post weighed.
Impingers and the Teflon filter rinsed with water and solvent to collect CPM.
The extracts were evaporated and the remaining residue (CPM) was
weighed.
EC/OC fraction of the PM 2.5 was determined using an OCEC Carbon
Aerosol Analyzer (Sunset Laboratory) following NIOSH method 5040.
• Analyzed at the Research Center for Environmental Changes, Academia
Sinica, Taipei, Taiwan

Emission Factor Calculation
EF (mg/ kg) = ∆C ×Q × t
x
m
C x = compound concentration (in excess of background)
Q= flowrate through chamber
t= time of sampling
m= mass of sugarcane burned

Results: Chamber CE
Combustion efficiency ranges from 80-100%, with an
average around 98.5%flaming combustion
Table: Sugarcane CO and CO 2 EF
comparison
MCE (%)
CO EF
(g/kg)
CO 2
EF
(g/kg)
1255±28
7
Present Study 98.5±0.2 9.2±3.3
AP-42
(Darley, 1974) NA 30-40 NA
Yokelson et
al., 2008 97.6 28.3 1838
Figure: Real-time flue gas concentrations

Results: PAHs
The average PAH EFs were 7.13 ± 0.94 mg/kg (n=4) and 8.18 ± 3.26
mg/kg (n=3) for dry and whole stalk experiments, respectively.
Emissions dominated by low molecular weight compounds.
– 2-ring PAH compounds comprise 66%
– 3-ring PAH compounds comprise 27%

Results: PAHs (cont’d)
PAH EFs are comparable, but on the low end of other EFs
reported for agricultural residue burning.
Consistent dominance of phenanthrene and acenaphthylene
compounds.

Results: PAHs (cont’d)
PAH compound ratios were found that can
possibly serve as source markers for source
apportionment studies.
Table: Characteristic PAH ratios

Results: Carbonyls
• Total carbonyl EFs were 231.8±52.3 mg/kg (n=5) and
909.6±527.7 mg/kg (n=4) for dry and whole stalk
experiments, respectively.
• EFs for whole stalk experiments exhibited more
variability and were higher than dry leaf experiments.
– Variable combustion conditions
– Biomass composition
Moisture content may inhibit
complete combustion leading to
higher pollutant emissions.
Sugarcane sources also differed
– may have different treatment
practices (i.e., fertilizer and
pesticide application)
Table: Comparison of Combustion
Conditions
Experiment
Burning Rate
Average
EF
Average
Temp
(°F)
Dry Leaves 232±52 311 1 kg/10 min
Whole Stalks 482±16 600 1 kg/3 min
(test 1)
Whole Stalks 1401±166 145 0.24 kg/4 min
(test 2)

Results: Carbonyls (cont’d)
Emissions dominated by low molecular weight
compounds

Results: VOCs
Benzene and toluene dominate VOC emissions.
– Benzene/toluene ratio was 0.32, which may be a unique marker
pattern.
Comparable to EFs for almond and walnut prunings.

Results: VOCs (cont’d)
In general, VOC EFs are lower than other reported
EFs, including those for sugarcane.
Differences attributed to:
– Measurement technique
– Sugarcane source, condition, and burning characteristics (i.e., CE)
Table: VOC EF (mg/kg) comparison

Results: PM 2.5
CPM was not statistically higher (p=0.27) in the
sample than in the method blanks neglected
The average PM 2.5 EF was 2.49±0.66 g/kg (n=4)
for dry leaf experiments.
Agrees very well with current EFs and other
agricultural burning studies.
Table: PM EF (mg/kg) comparison

Results: EC/OC
EC emissions dominated OC emissions.
Sugarcane EC emissions are high compared to
other studies and OC emissions are low
– Function of high CE and biomass composition
Unique trend may be helpful for source
apportionment studies.
Table: EC and OC EF comparison

HAPs Emission Estimates
HAPs emissions were estimated and compared
with the 2005 National Air Toxics Assessment Data
for Palm Beach County (2005) and the state of FL.
*Disclaimer: these estimates and statements do not
represent the conclusions of the Palm Beach County
Health Department.
Inputs:
– the upper limit EF of the 95% confidence interval
– Assumed 335,650 acres of sugarcane burned (based on
2008)
– Fuel loading = 7 tons/acre

HAP Emission Inventory Estimates

HAP Emission Inventory Estimates (cont’d)

HAP Emission Inventory Estimates (cont’d)

Summary & Conclusions
The data from this research further validate and expand the
current AP-42 emission factors.
– EFs are expected to highly variable during the fire event and throughout
harvesting season—dependant on burning conditions and biomass
conditions.
Marker and tracer compounds and patterns identified can be
used in future source apportionment studies to allocate ambient
pollution to specific sources.
With a more reliable and comprehensive understanding of the
emissions from sugarcane pre-harvest burning, regulators can
make better decisions about the permitting and management of
this practice to better protect human health and the environment.

Thanks for your attention!
ANY QUESTIONS?