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 11th , 2010

Department of Environmental Engineering Sciences

University of Florida

A&WMA International Specialty Conference

Leapfrogging Opportunities for Air Quality Improvement

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 NOx 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 mayexhibit 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

– PM2.5

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 CO2 flue gases were continuously

monitored to determine the combustion

efficiency

MCE =∆ CO

2[ ]

∆ CO[ ]+ ∆ CO2[ ]

Methodology: Sampling

Combustion chamber

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

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.

PUF/XAD-2 cartridge holder

Filter

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).

Sample

Probe

DNPH

cartridge

Ozone

Scrubber

Carbonyl Sampling System

Teflon sampling

lineTedlar bag

Exhaust

port Vac-U-

Chamber

Vac-U-Chamber and Tedlar bag

VOCs:

• Gas samples collected in Tedlar bags via negative

pressure.

• Samples analyzed for BTEX & styrene by GC/MS

(performed by CAS)

Methodology: PM2.5

PM2.5 sampling followed EPA Other Test Methods 27 & 28 (modified)– Cyclone used to separate particles based on size. – Filterable PM2.5 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 PM2.5 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

Cx= compound concentration (in excess of background)

Q= flowrate through chamber

t= time of sampling

m= mass of sugarcane burned

EF (mg/ kg) =∆Cx ×Q × t

m

Results: Chamber CE

Combustion efficiency ranges from 80-100%, with an

average around 98.5%�flaming combustion

Figure: Real-time flue gas concentrations

MCE (%)CO EF (g/kg)

CO2

EF (g/kg)

Present Study 98.5±0.2 9.2±3.31255±28

7

AP-42 (Darley, 1974) NA 30-40 NA

Yokelson et al., 2008 97.6 28.3 1838

Table: Sugarcane CO and CO2 EF

comparison

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

– 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)

Experiment Average

EF

Average

Temp

(°F)

Burning Rate

Dry Leaves 232±52 311 1 kg/10 min

Whole Stalks

(test 1)482±16 600 1 kg/3 min

Whole Stalks

(test 2)1401±166 145 0.24 kg/4 min

Table: Comparison of Combustion Conditions

• 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.

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: PM2.5

CPM was not statistically higher (p=0.27) in the sample than in the method blanks� neglected

The average PM2.5 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.

ANY QUESTIONS?

Thanks for your attention!