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

Transcription

1 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

2 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

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

4 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)

5 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

6 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

7 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

8 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

9 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 Analyzed at the Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan

10 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

11 Results: Chamber CE Combustion efficiency ranges from %, 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± ±3.3 AP-42 (Darley, 1974) NA NA Yokelson et al., Figure: Real-time flue gas concentrations

12 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%

13 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.

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

15 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± kg/10 min Whole Stalks (test 1) 482± kg/3 min Whole Stalks 1401± kg/4 min (test 2)

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

17 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.

18 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

19 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

20 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

21 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

22 HAP Emission Inventory Estimates

23 HAP Emission Inventory Estimates (cont d)

24 HAP Emission Inventory Estimates (cont d)

25 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.

26 Thanks for your attention! ANY QUESTIONS?