ISSN 1047-3289 J. Air & Waste Manage. Assoc. 53:523–531
TECHNICAL PAPER
Copyright 2003 Air & Waste Management Association
Variables Affecting Emissions of PCDD/Fs from Uncontrolled
Combustion of Household Waste in Barrels
Paul M. Lemieux and Brian K. Gullett
National Risk Management Research Laboratory, Office of Research and Development,
U.S. Environmental Protection Agency, Research Triangle Park, North Carolina
Christopher C. Lutes and Chris K. Winterrowd
ARCADIS, Inc., Research Triangle Park, North Carolina
Dwain L. Winters
Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency,
Washington, D.C.
ABSTRACT
The uncontrolled burning of household waste in barrels
has recently been implicated as a major source of airborne
emissions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). A detailed, systematic study to understand the variables affecting emissions
of PCDD/Fs from burn barrels was performed. The waste
composition, fullness of the barrel, and the combustion
conditions within the barrel all contribute significantly to
determining the emissions of PCDD/Fs from burn barrels.
The study found no statistically significant effect on emissions from the Cl content of waste except at high levels,
which are not representative of typical household waste.
At these elevated Cl concentrations, the impact of Cl on
PCDD/F emissions was found to be independent of the
form of the Cl (inorganic or organic). For typical burn
conditions, most of the PCDD/F emissions appear to be
associated with the later stages of the burn when the
waste is smoldering. Polychlorinated biphenyls (PCBs)
were also measured for a subset of the tests. For the nominal waste composition, the average emissions were 76.8 ng
IMPLICATIONS
The uncontrolled burning of household waste in barrels is
an important source of PCDD/Fs. In addition, barrel burning
is a common waste management practice in many parts of
the developing world. This paper reports on a systematic
study to refine the emission factor from barrel burning so
that it can be used in the quantitative emissions inventory
for air emissions of PCDD/Fs in the United States. Results
from this paper, when coupled with estimates of activity,
can be used by environmental officials to estimate emissions from barrel burning on a local or national basis.
Volume 53 May 2003
toxic equivalency units (TEQ)WHO98/kg of waste combusted, which suggests that uncontrolled burning of
household waste could be a major source of airborne
PCDD/Fs in the United States.
INTRODUCTION
The uncontrolled burning of household waste in barrels is
practiced in many rural areas of the United States when
no local waste collection is available and is one of the
primary waste management techniques in many parts of
the developing world. This activity typically consists of
placing household waste in a 208-L (55-gal) drum called a
burn barrel and, when a sufficient quantity of household
waste has accumulated, igniting the waste and burning it.
Three previous studies characterized emissions associated with open burning of residential refuse in a backyard burn barrel.1– 4 Results from these studies indicated
that burn barrels could potentially be a major national
source of airborne polychlorinated dibenzo-p-dioxins and
polychlorinated dibenzofurans (PCDD/Fs), given conservative estimates of the frequency of this practice. However, variability in the PCDD/F emissions of several orders
of magnitude was found between seemingly duplicate
runs. Although apparent relationships between PCDD/F
emissions and airborne HCl and Cu emissions were observed, sufficient data were not available to conduct rigorous statistical analyses and determine whether a causal
relationship existed.
Many possible parameters could have a significant
influence on PCDD/F emissions from burn barrels. Many
of these parameters could be caused by variations in practice-related variables that would vary from homeowner to
homeowner. Some of these parameters include physical
Journal of the Air & Waste Management Association 523
Lemieux et al.
condition of the waste in the barrel (e.g., fullness of the
barrel, degree of compression of the waste, distribution of
waste components within the barrel), chemical composition of the waste (e.g., wetness, trace metal content, Cl
content, organic vs. inorganic Cl), and combustion conditions resulting from variations in the previously mentioned physical and chemical characteristics. None of
these have been examined in detail in the past.
The limited amount of data and high degree of variability confounded efforts to incorporate burn barrels
into the U.S. PCDD/F inventory, reported in toxic equivalency (TEQ) units. The national emissions from backyard
burn barrel sources were estimated to be greater than
1000 g TEQ/yr, although the uncertainty in this estimate
was too great for it to be included in the U.S. Environmental Protection Agency’s (EPA) quantitative inventory
of PCDD/Fs.5 In an effort to reduce the uncertainty in the
emissions estimation, additional testing was performed
on burn barrels so that the emissions of PCDD/Fs could be
characterized as a function of waste composition, burn
conditions, and other physical properties of the waste in
the barrels (e.g., degree of compaction and wetness). Initial results from these follow-up tests6 –9 showed that
waste composition parameters (e.g., Cl), combustion conditions (e.g., barrel temperature distributions), and resultant emissions (e.g., Cu and CO) can account for a significant portion of the variability of PCDD/F emissions between runs. PCDD/F TEQ values bracketed the 140 ng
TEQ/kg used by EPA in its preliminary estimate of burn
barrel emissions as a part of its 1998 draft dioxin source
inventory.10
The critical questions that this study attempted to
answer are (1) what is the emission factor for PCDD/Fs
from barrel burning; and (2) given that various operating
conditions and compositions are used in this practice, do
they influence emissions? The study attempts to evaluate
the representativeness of the testing methodology by performing a preliminary sensitivity analysis on the effect of
waste composition.
EXPERIMENTAL METHODS
In an effort to simulate burn barrel emissions and determine a representative emission factor, experiments varying the composition and burn conditions, coupled with
PCDD/F analyses, were conducted to determine which of
these variables were important. These experiments resulted in detailed analyses from 25 burn barrel tests and
three blank tests that were performed at EPA’s Open Burning Test Facility (OBTF).3 The OBTF consists of an enclosed structure with a measured volumetric influx of
ambient air, a weigh scale where the mass of the burning
material is continuously weighed, and various sampling
devices, including continuous emission monitors (CEMs),
524 Journal of the Air & Waste Management Association
thermocouples (TCs), and ambient organic sampling
equipment.
To represent common practice for residential waste
burning, the test container consisted of a seasoned, 208-L
(55-gal) steel barrel with 12 2-cm-diameter ventilation
holes evenly spaced around the base. The barrel was initially sandblasted3 to remove residual paint and any remaining contents that might affect emissions. It was
placed on an electronic scale platform to allow the mass
consumed by combustion to be continuously monitored.
An aluminum skirt was placed around the outer circumference of the barrel to minimize the potential for recirculation of combustion gases back through the air inlet
holes. High-volume air handlers provided 52.7 m3/min
(1862 ft3/min) of metered dilution air into the burn hut to
simulate ambient mixing. Additional fans were set up
inside the burn hut to enhance recirculation within the
hut. Most tests consisted of 6.8 kg (15 lb) of waste, randomly mixed for a brief time in a portable concrete mixer
and dumped en masse into the test container before burning. Six TCs were mounted inside the barrel at various
heights.
A baseline waste composition was developed containing materials in quantities representative of domestic
waste based on a New York State Department of Environmental Conservation survey. The average Cl content of
the baseline waste (approximately 0.2%) was based on a
family that removes most of their plastic materials from
the waste before combustion3 and was somewhat less
than what is typically fed into a municipal waste combustion (MWC) facility (approximately 0.5% Cl).11 It must be
noted that this waste composition does not necessarily
reflect rural waste compositions but reflects that of the
general public. Eight replicate tests using the baseline (see
Table 1) composition were performed so the inherent
variability of the burn barrel combustion process could be
characterized. Because it was believed that waste Cl content might have a significant impact on PCDD/F emissions, several runs were performed using varying waste Cl
levels.
Polyvinyl chloride (PVC) plastic was used most of the
time to vary the waste Cl content because it is relatively
easy to distribute uniformly through the waste. The waste
Cl content was perturbed from the baseline Cl content
with three PVC levels (0, 1, and 7.5% by weight) using
pipe forms. When PVC levels were varied, the bulk waste
heating value was adjusted by substituting high-density
polyethylene and Fe (both also in pipe form), in an effort
to approximate consistent physical and energy properties of the waste across all batches while varying Cl. For
two experiments, however, an inorganic Cl source was
used instead of PVC. Inorganic Cl levels were derived by
Volume 53 May 2003
Lemieux et al.
Table 1. Waste composition.
Waste Category
Paper
Plastic resin
Food
Textile/leather
Wood
Glass/ceramics
Metals (ferrous)
Metals (nonferrous)
Total
Waste Description
Newspaper, books, office paper
Magazines and junk mail
Corrugated cardboard, Kraft paper
Paperboard, milk cartons, drink boxes
Polyethylene terephthalate (PET) #1, soda bottles
High-density polyethylene (HDPE) #2, detergent
bottles, pieces
Polyvinyl chloride (PVC) #3, schedule 40 pipe
Polystyrene (PS) #6, food trays
Mixed #7, Poly-Fil polyester
Frozen processed potatoes
Rubber and leather sneakers
Chipboard, plywood
Bottles, jars
Broken ceramics, flower pots
Iron (cans), dog food cans
Aluminum cans, foil, soda cans
Wire, Cu pipe, batteries
Target
wt %
32.8
11
7.6
10.3
0.6
6.6
0.2
0.1
0.1
5.7
3.7
1.1
9.7
0.4
7.3
1.7
1.1
100
Note: Inorganic Cl tests were conducted with CaCl2-saturated newspapers (using Prestone Driveway Heat) such that [Cl] ⫽ 7.5 wt %. HDPE #2 ⫽ 3.3 wt %, 224.53 g; PVC
⫽ 0 wt %, 0 g; iron cans ⫽ 3.3 wt %, 224.53 g; the 0 wt % PVC test consisted of
HDPE #2 ⫽ 6.7 wt %, 455.86 g; PVC ⫽ 0 wt %, iron cans ⫽ 7.4 wt %, 503.49 g;
the high Cu mix test consisted of bottles/jars ⫽ 8.7 wt %, 591.94 g; iron cans ⫽ 6.4
wt %, 435.45 g; wire, Cu pipe, batteries ⫽ 3 wt %, 204.12 g.
soaking the paper portion of the waste in a CaCl2-based
deicer followed by drying.
Tests were also performed to evaluate the combustion
characteristics of waste with a higher moisture content,
which might occur if the waste was rained on before
combustion. For those tests, some of the newspaper was
soaked in water before combustion. These test conditions
were designated “wetted.” To simulate other commonly
expected practices, tests (designated “compacted”) were
also performed in which the waste was compacted by
allowing a 91-kg (200-lb) person to stand on the bed of
waste in the barrel before ignition. Additional test conditions (designated “double”) used twice the normal mass
of waste, which also required compaction so the larger
quantity of waste would fit into the barrel. A set of tests
(designated “high Cu”) were performed in which additional Cu was added in the form of short pieces of bare Cu
wire. (Note that a small amount of Cu wire was contained
in the baseline mix as well.) Finally, a single test (designated “open pile”) was performed where the baseline
composition waste was burned in an open pile as opposed
to inside a barrel.
The experimental facility and experimental procedures were the same as reported before3,4 except (1) the
Volume 53 May 2003
ceiling of the hut was lined with aluminum foil to reduce
the danger of the hut’s catching fire because of the more
vigorous combustion that resulted from the double
charges; (2) the PCDD/F samples were collected using
Method TO912 and were analyzed using high-resolution
gas chromatography and high-resolution mass spectrometry using EPA Test Method 8290;13 and (3) several tests
were performed where the PCDD/F sampling occurred for
three consecutive 30-min intervals to understand the
temporal emissions of PCDD/Fs. For those runs, three
sampling trains were set up, and the pumps were started
and stopped so their samples reflected elapsed times of
0 –30, 31– 60, and 61–90 min. The barrel was emptied
between runs but was not washed.
Assuming that the gases inside the burn hut are perfectly mixed, estimated emissions of PCDD/Fs per unit
mass burned can be calculated using eq 1:
E ⫽ 共C sample Q hut t run 兲 Ⲑ 共m burned 兲
(1)
where E ⫽ the estimated emissions in ng/kg waste consumed, Csample ⫽ the concentration of the pollutant in
the sample (ng/m3), Qhut ⫽ the flow rate of dilution air
into the burn hut (52.7 m3/min), trun ⫽ the run time (30
or 90 min), and mburned ⫽ the mass of waste burned (kg).
When analyzing and reporting the results, all nondetects
(NDs) and incidences of questionable analytes were set to
zero. TEQ emission values caused by PCDD/Fs (TEQDF)
were calculated using toxic equivalence factors (TEFs)
from the World Health Organization (WHO).14
RESULTS
PCDD/F and PCB Data
Table 2 lists the total PCDD/F and TEQDF emissions in
terms of ng emitted/kg of waste burned (calculated using
eq 1), as well as the total polychlorinated biphenyls
(PCBs) and TEQPCB calculated using the WHO TEFs14 for
those runs where PCB data were acquired. For most runs,
PCDD/F isomers were present in quantities above the
detection limits, which results in TEQDF data that are not
based on how the nondetects are handled. There were
also relatively few instances of estimated maximum possible concentrations (EMPCs) in the data set. EMPCs are
cases where a signal is seen in both of the dioxin- or
furan-selected ion-monitoring channels of the gas chromatograph/mass spectrometer, but the ratio of areas between the channels for the given analyte does not meet
the acceptance ratio. This can indicate a positive interference in the channel potentially overlapping with the signal from the PCDD/F. Nondetects and EMPCs were set to
zero for the calculations of total concentrations and TEQs
reported in this work, which is a conservative, low-emission assumption.
Journal of the Air & Waste Management Association 525
Lemieux et al.
Table 2. PCDD/F and PCB estimated emissions (ng/kg waste burned and ng
TEQWHO98/kg waste burned).
Run
Description
TEQDF
Total
PCDD ⴙ PCDF
TEQPCB
PCB Total
A
B
C
K
D
L
M
O
P
E
S
T
U
Q
W
G
X
Z
AA
Y
AC
AD
AH
AF
AE
Baseline
Baseline
Baseline
0% PVC
Baseline
1% PVC
1% PVC
7.5% PVC
7.5% PVC
Baseline
0% PVC
CaCl2
CaCl2
High Cu
Wetted
Compressed
Baseline
Double
Compressed
High Cu
Baseline
Wetted
Open
Double
Double
139
84
25
2
9
242
179
3,543
6,655
148
28
610
934
2,725
253
358
61
40
9
19
50
992
61
251
231
11,887
4,601
1,756
306
599
12,095
10,940
248,037
425,247
14,418
2,792
55,392
79,549
252,536
18,679
28,213
4,521
1,744
562
1,428
2,823
51,714
4,760
10,217
17,504
0.03
6.61
0.01
0.01
0.02
13.8
0.06
137.5
282.6
0.04
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
136,663
181,712
123,877
75,411
66,869
148,354
88,452
493,899
817,758
120,698
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
NM
Note: NM ⫽ not measured.
The seven baseline tests had emissions ranging from
9 to 148 ng TEQ/kg, a range of more than an order of
magnitude. The mean and median emissions were 73 and
61 ng TEQ/kg, respectively. The large variation in baseline
emissions, despite careful attention to standardized composition and procedures, suggests that random factors,
such as waste orientation and the path of the combustion
air through the waste in the barrel, may have a significant
impact on PCDD/F emissions. One open-burn (waste-pile)
test (“Open”) with baseline waste composition resulted in
emissions of 61 ng TEQ/kg. This was within the variability
of the baseline burn barrel results and, therefore, no obvious conclusions regarding the potential differences between barrels and piles can be drawn from this test.
Figure 1 shows a bar graph of TEQ emissions from all
the runs. Note that the y axis of Figure 1 is a logarithmic
scale spanning several orders of magnitude. PCDD/Fs
from replicate baseline runs were spread over approximately an order of magnitude. The baseline results highlight the inherent variability of emissions from barrel
burning that is caused by variables other than those
526 Journal of the Air & Waste Management Association
controllable by the investigators. In Figure 1, runs plotted
toward the right are varied composition cases. The gray
region shows the emission ranges bounded by the baseline tests. Note that most of the tests, including many of
those that constituted extremes in possible waste composition, fall in or near that range. The 0% PVC case had one
run that was well within the range of variability observed
in baseline tests. At high levels of Cl, an effect can be seen,
but at levels more closely approximating what is found in
practice, other effects dominate. Purposely removing the
concentrated sources of chlorinated material from the
waste did not eliminate emissions of PCDD/Fs.
Time-Resolved Emissions of PCDD/Fs
Runs X, Z, AA, AC, AD, and AE were all performed in such
a way that PCDD/F samples were acquired at three 30-min
intervals during the run. This enabled the measurements
of PCDD/Fs with respect to time, and Figure 2 shows a bar
graph highlighting these results. In Figure 2, the sum of
the three columns for each run totals 1. It is interesting
that, for all runs except the wetted run, the majority of
the emissions occurred during the later stages of the burn,
which represented the smoldering phase. For the wetted
run, more PCDD/Fs were emitted during the initial phase
as water was driven from the waste. This observation may
have implications for landfill fires (burning dumps),
where the smoldering stage could constitute the majority
of the fire.
PCBs versus PCDD/Fs
PCBs showed the same general trends in emissions as total
PCDD/Fs, which is consistent with the theory that these
compounds have either a common or parallel formation
mechanism in combustion systems.15 TEQPCB also
tracked very well with dioxins, although the PCB-based
TEQ was strongly influenced by the handling of nondetects because many of the dioxin-like PCBs were present
Figure 1. TEQDF for all runs.
Volume 53 May 2003
Lemieux et al.
Figure 2. TEQ vs. time. Bars represent normalized estimated emissions.
at levels below the detection limits. Total PCBs were approximately a factor of 200 greater than total PCDD/Fs;
however, TEQPCB is approximately 5% of TEQDF, which is
stage of the burn, then tapers off as the smoldering stage
becomes dominant.
an observation that is consistent with data from MWCs.16
This suggests that, in burn barrels, the PCBs that are
formed are predominantly the nonplanar (ortho-substituted) PCBs that do not exhibit dioxin-like activity in
biological systems.
Other Data
Table 4 lists some of the other measured and calculated
data, including the gas-phase HCl and Cu emissions; the
maximum burning rate (MAXBURN), defined as the maximum change in charge mass with respect to time (kg/
min) over the entire burn; the time at which the maximum burning rate occurred (MAXTIME); and
temperature-based parameters that reflect the relative
fraction of the total burn time when the thermocouples
showed temperatures within certain key temperature
ranges reflective of the optimal PCDD/F formation temperature window. It was desired to develop a dimensionless parameter reflecting the temperature of the barrel
over the duration of the transient experiment. Because
TC1 and TC2 were positioned inside the burning mass
and exhibited wide temporal variations throughout the
burn period, parameters were selected that included all
thermocouples and that included the set of thermocouples excluding TC1 and TC2. The continuously measured
temperature data (1-min averages taken over 90 min)
were parsed, and the dimensionless TS1–TS4 parameters
were calculated as follows:
TS1 ⫽ 1 for each point between 250 and 450 °C on all
thermocouples;
TS2 ⫽ 1 for each point between 250 and 450 °C,
excluding TC1 and TC2;
TS3 ⫽ 1 for each point between 300 and 400 °C on all
thermocouples; and
TS4 ⫽ 1 for each point between 300 and 400 °C,
excluding TC1 and TC2.
The TS1–TS4 parameters represent the fraction of the
barrel that was within a given temperature range over the
entire duration of the run.
Continuous Emission Monitors, Weight, and
Thermocouple Data
Table 3 lists the weight data (the mburned parameter in eq
1) as well as the CEM and TC average and maximum data.
Note that some of the runs include multiple entries. These
runs denote experiments where 0 –30, 31– 60, and 61–90
min PCDD/F samples were acquired.
In general, temperatures and CO rose rapidly after
ignition to a peak and then tapered off. Based on qualitative observations, there was an initial phase of the burn
where flames were readily visible and occasionally protruded from the top of the barrel, even for those runs
where the barrel was not highly filled. This yielded two
distinct stages of the burn: a flaming stage lasting approximately 30 –35 min, and a smoldering stage that continued for the remainder of the burn. Generally, the CO rose
rapidly and then tapered off as the burn went from the
flaming stage to the smoldering stage. The double charge,
however, exhibited a generally higher peak temperature;
the compressed charge tended to not have as well-defined
a flaming stage; and the wetted charge tended to drop
into the smoldering stage sooner, with the temperature
above the burning bed rapidly returning to near ambient
levels much more quickly than for the other conditions.
The majority of the weight loss occurs during the flaming
Volume 53 May 2003
Journal of the Air & Waste Management Association 527
528 Journal of the Air & Waste Management Association
Baseline
Baseline
0% PVC
Baseline
1% PVC
1% PVC
7.5% PVC
7.5% PVC
Baseline
0% PVC
CaCl2
CaCl2
High Cu
Wetted
Compressed
Baseline
Double
Compressed
High Cu
Baseline
Wetted
Open
Double
Double
B
C
K
D
L
M
O
P
E
S
T
U
Q
W
G
X
Z
AA
Y
AC
AD
AH
AF
AE
9.36
7.73
3.01
4.80
5.38
5.11
5.34
9.45
4.82
4.89
5.63
4.82
4.64
4.90
4.77
4.78
5.10
4.88
4.94
4.89
4.89
4.60
5.05
5.05
4.89
(kg)
20.9
20.9
20.7
20.6
20.6
20.5
20.6
20.8
20.3
20.4
20.9
20.0
20.0
20.7
20.0
19.9
20.0
20.0
19.8
19.9
19.8
19.4
19.7
19.6
20.4
20.8
20.2
20.5
20.7
16.4
16.4
20.3
16.4
16.3
13.5
13.2
16.6
14.7
16.3
17.7
14.0
20.8
20.6
20.9
21.3
21.3
21.0
21.2
20.5
20.6
20.1
20.2
21.9
21.4
23.4
20.6
19.9
(%)
15.8
20.7
20.5
20.8
21.1
21.2
20.9
21.1
20.4
20.4
19.9
19.5
20.8
20.7
21.3
20.5
19.3
(%)
O2
Max
Test results listed chronologically; N/A ⫽ not available.
Baseline
A
a
Description
Testa
O2
Avg.
Waste
Burned
Table 3. Continuously measured data.
CO2
CO2
0.10
0.17
0.41
0.19
0.24
0.09
0.61
0.79
0.24
0.36
0.44
0.33
0.10
0.25
0.57
0.10
0.23
0.27
0.08
0.16
0.49
0.19
0.11
0.08
0.09
0.08
0.07
0.11
0.15
0.11
0.26
0.76
0.27
0.83
0.09
0.81
1.57
0.35
0.37
0.7
0.62
0.12
0.39
0.69
0.12
0.37
0.44
0.09
0.23
0.77
0.43
0.34
0.29
0.55
0.43
0.31
0.43
0.56
0.54
0.25
⫺0.01
0.08
0.58
0.58
0.16
0.59
0.62
0.741
(%)
Max
0.17
0.04
0.11
0.18
0.19
0.23
(%)
Avg.
96
87
85
152
124
86
145
164
78
211
139
195
131
212
197
333
387
161
143
165
236
77
118
99
100
117
112
77
115
150
107
91
45
27
51
99
78
(ppmv)
CO Avg.
113
119
253
618
279
100
170
352
104
313
276
352
156
264
321
385
443
334
163
196
671
211
215
221
278
401
182
159
299
337
178
186
117
82
175
320
222
(ppmv)
CO Max
214
336
181
415
N/A
137
195
157
35
127
312
110
368
411
303
79
70
12
349
404
433
148
298
216
169
174
146
278
229
173
308
262
177
167
278
198
173
231
492
656
594
N/A
145
220
280
51
266
628
238
381
428
593
82
135
20
401
434
547
606
771
544
794
617
472
433
790
273
589
692
705
618
795
545
636
385
615
547
492
345
107
350
265
181
613
510
408
68
200
545
493
606
43
54
134
415
272
396
505
387
388
251
529
342
515
270
504
445
371
299
418
283
(ⴗC)
444
735
770
613
400
130
476
579
365
704
683
726
97
315
654
528
716
86
75
227
677
574
848
672
826
635
576
628
899
612
659
584
637
693
729
643
664
(ⴗC)
131
380
390
210
N/A
24
97
396
42
136
451
296
45
130
384
317
407
509
N/A
N/A
N/A
115
191
217
196
204
235
202
164
167
167
222
132
194
154
153
170
(ⴗC)
196
648
672
725
N/A
28
147
622
60
235
567
515
66
208
512
336
532
655
N/A
N/A
7
465
579
609
662
685
658
636
641
652
590
570
630
626
589
603
516
(ⴗC)
117
218
175
200
N/A
16
70
306
23
65
317
112
42
113
266
55
111
195
35
121
254
N/A
118
137
112
124
153
124
145
140
146
146
117
154
133
107
140
(ⴗC)
150
265
335
702
N/A
19
109
572
32
119
492
457
59
167
368
63
163
367
49
195
451
N/A
378
446
602
434
411
527
444
489
544
564
508
462
453
415
420
(ⴗC)
93
207
364
195
107
20
80
258
29
64
287
108
50
137
262
65
118
233
40
96
235
106
111
109
99
83
90
103
142
125
133
108
101
104
133
94
126
(ⴗC)
118
324
617
704
143
22
128
515
40
103
587
495
69
196
318
70
178
482
53
154
369
309
428
321
486
325
271
404
458
447
400
401
404
323
515
309
406
(ⴗC)
73
167
340
156
30
13
61
255
19
49
211
27
30
91
198
45
77
155
25
62
160
1333
124
129
157
96
102
117
172
150
136
132
131
120
170
121
168
(ⴗC)
93
278
547
589
100
15
99
544
27
73
404
N/A
42
143
239
49
119
362
35
98
250
427
615
326
542
335
324
462
575
561
454
472
555
461
543
439
564
(ⴗC)
20
58
113
52
27
N/A
12
53
6
16
76
36
18
32
78
13
24
67
8
22
64
34
24
35
26
22
34
30
43
32
18
20
14
24
25
22
104
(ⴗC)
26
103
175
184
82
N/A
19
93
8
30
103
112
21
51
96
14
33
132
11
38
107
74
56
75
207
73
74
73
97
77
64
70
60
70
76
63
399
(ⴗC)
15
38
62
32
24
N/A
6
29
2
8
23
14
14
22
30
9
15
21
5
13
30
28
20
27
12
13
27
24
35
26
5
14
9
18
18
20
8
(ⴗC)
20
62
92
99
82
N/A
11
45
4
14
29
32
16
26
35
10
18
34
6
22
46
52
45
46
41
39
50
54
72
56
18
45
37
45
51
50
66
(ⴗC)
Max
(ⴗC)
Avg.
TC Max
TC Avg.
(ⴗC)
Hut TC
Hut TC
Over Barrel
Over Barrel
TC6
Max
TC6
Avg.
TC5
Max
TC5
Avg.
TC4
Max
TC4
Avg.
TC3
Max
TC3
Avg.
TC2
Max
TC2
Avg.
TC1
Max
TC1
Avg.
Lemieux et al.
Volume 53 May 2003
Lemieux et al.
Table 4. Other measured and calculated parameters
Test
Description
A
B
C
K
D
L
M
O
P
E
S
T
Baseline
Baseline
Baseline
0% PVC
Baseline
1% PVC
1% PVC
7.5% PVC
7.5% PVC
Baseline
0% PVC
CaCL2
U
Q
W
G
X
Z
AA
Y
AC
AD
AH
AF
AE
CaCl2
High Cu
Wetted
Compressed
Baseline
Double
Compressed
High Cu
Baseline
Wetted
Open
Double
Double
MAXBURN
(kg/min)
MAXTIME
(min)
TS1
TS2
TS3
TS4
0.34
0.23
0.23
0.23
0.25
0.27
0.20
0.25
0.30
0.16
0.16
34
42
34
40
27
18
2
14
16
21
35
102
119
112
93
84
87
133
80
91
91
79
84
59
70
67
70
47
60
37
65
33
47
51
62
63
37
33
29
75
14
41
49
31
44
26
43
25
28
24
32
13
27
19
19
0.18
0.18
0.14
0.23
0.18
0.16
0.34
0.18
0.25
0.23
0.32
0.18
0.27
0.34
26
26
22
26
40
9
6
1
9
6
6
1
3
17
107
70
71
73
116
104
90
140
84
71
74
87
104
143
39
45
44
54
43
31
88
53
50
39
43
0
41
81
55
31
27
33
45
53
64
69
51
40
38
86
74
71
21
22
17
25
18
14
63
18
27
18
29
0
21
34
Note: NM ⫽ not measured.
Effect of Exhaust Gas Constituents:
Statistical Analysis
Comparison of the 14 runs in which burn condition factors (Double, Compress, Wetted, Baseline) were changed
but the composition was held constant resulted in
PCCD/F emissions that ranged from 9 to 992 ng TEQ/kg.
Excluding the one high TEQ (and total) value for the Wet
run, analysis of variance testing on the mean TEQs and
totals for these factors shows no statistically significant
differences, likely because of the limited number of runs
and the wide variability in emissions. To determine
whether this variability could be accounted for by combustion characteristics, the normally distributed log(TEQ)
data were modeled using an SAS STEPWISE regression to
choose among various parameters that were suspected of
possibly having a statistically significant effect on the
emissions of PCDD/Fs, including waste Cl concentration
[Cl]; continuously measured parameters of average and
maximum TC temperatures (TC1–TC6 AVG and MAX);
sampled HCl and Cu (particle-bound) emissions; average
CEM values including CO, CO2, and O2; the time (MAXTIME) and mass loss rate (MAXBURN) when the waste is
at maximum burn rate; and the duration (in minutes)
Volume 53 May 2003
that in-barrel TC temperatures were
within the common formation winCu
HCl
dow temperature (TS2 ⫽ 250 – 450 °C
(mg/m3)
(mg/m3)
[excluding TC1 and TC2] and TS3 ⫽
300 – 400 °C). An optimal model (R2
NM
23.98
⫽ 0.83) for log(TEQ) of these 14 baseNM
2.66
line composition runs consisted of
NM
2.98
three significant (␣ ⬍ 0.06) linear preNM
1.26
dictors: log([HCl]), MAXBURN, and
2.88
1.51
log([Cu]). Selection of these predic5.56
5.07
tors suggests that byproduct emis1.05
3.08
27.98
23.52
sions and burn rate parameters pro36.32
10.04
vided the best predictive capability of
2.36
1.63
TEQ emissions. It is interesting to
0.27
3.87
note that the gas-phase [HCl] was a
2.96
4.97
more important predictor than the
4.53
9.78
[Cl] in the waste. Because [HCl]
0.93
13.62
should be closely correlated with [Cl],
1.87
12.01
it suggests that the nonhomogeneity
1.83
7.59
of the waste resulted in an uneven
0.34
3.30
distribution of the [Cl] within the
0.05
10.67
barrel and therefore within the flame
NM
1.02
zone, leading to [HCl] showing more
NM
2.74
0.04
7.94
statistical significance as a predictor
NM
0.94
than [Cl]. This further suggests the
2.21
2.73
importance of the combustion condi3.85
16.27
tions and possibly the distribution of
4.42
15.71
the waste components in the barrel
to PCDD/F emissions.
Comparison of the 15 runs in
which only Cl levels were changed shows significant (␣ ⫽
0.05) differences in log(TEQ) values between the 7.5%
PVC runs and all other runs, except for CaCl2. Distinctions in these runs are clearly related to the Cl content of
the waste: log(TEQ) can be modeled with log(Cl) alone (R2
⫽ 0.74, Q2 ⫽ 0.64). This is not surprising because [Cl] was
varied over a wide and unrepresentative range. Even with
a more rigorous statistical algorithm, no distinction is
observed in log(TEQ) for inorganic (7% Cl in CaCl2) versus organic (7% Cl in PVC) Cl sources. These 15 runs were
well modeled for log(TEQ) (R2 ⫽ 0.90, Q2 ⫽ 0.80) by
log([Cl]), TC6MAX, and CO. Selection of these parameters
indicates the importance of byproduct emissions and
temperature trends in predicting PCDD/F emissions, supporting earlier results. Comparison of log(total) suggests
significant differences for 7.5% PVC versus all conditions
(1% PVC, baseline, and 0% PVC) except for CaCl2. A
model of log(total) for this group results in a single predictor model (R2 ⫽ 0.76, Q2 ⫽ 0.68) using log([Cl]). In
summary, although Cl in the waste does appear to influence emissions of PCDD/Fs from burn barrels, this effect
can be observed only at high levels of Cl, atypical of
household trash, and is independent of the source of the
Journal of the Air & Waste Management Association 529
Lemieux et al.
Cl (organic or inorganic). At moderate levels of Cl, a
statistically significant effect of waste Cl concentration
is not observed, because other more important variables have a much greater influence on the emissions of
PCDD/Fs.
The results indicate that a high degree of PCDD/F
emission variation can be expected because of factors not
wholly related to waste composition or burning practice.
Random factors, such as waste orientation and its subsequent impact on the path of the combustion air through
the barrel, possibly play a significant role in affecting
combustion conditions (e.g., as observed by TC variations) and, hence, emissions. Statistical modeling of the
results supports this possibility through selection of temperature-related predictors. While the wide variation in
PCDD/F emissions and the limited number of runs preclude unambiguous determinations of differences caused
by composition and burn condition factors, several trends
seem apparent. PCDD/F emissions increased for the runs
with very large amounts of Cl, whether organic or inorganic, and higher amounts of Cu catalyst. Test runs at
alternative burn conditions (Compress, Wet, Double) resulted in higher mean PCDD/F emissions (203 ng TEQ/kg)
and a 6-fold increase in the SD of the TEQ value (260 ng
TEQ/kg) from that of the baseline runs. These results
suggest widely variant PCDD/F emissions from uncontrolled domestic waste burning. These emissions are partially dependent on practice- and composition-related
factors as well as random waste orientation.
CONCLUSIONS
Experiments were performed to evaluate emissions of
PCDD/Fs and other organic pollutants from uncontrolled
combustion of household waste in barrels. The main goals
of the research described in this paper were to develop a
more representative emission factor that could be used to
calculate the overall contribution of burn barrels to the
national dioxin source inventory and to identify the variables that most affect burn barrel emissions. The experiments were performed nominally at full scale, although
there are a host of variables likely implemented in practice that were not addressed at all in this research. Based
on the experiments, the following conclusions can be
made:
• Emissions from the replicate baseline runs showed
approximately an order of magnitude in variability.
The average emissions from the replicate baseline
runs was 76.8 ng TEQDF/kg waste burned.
• Because of the wide variability in the baseline emissions, many of the attempted perturbations in burn
condition and waste composition were not able to
achieve a statistically significant effect on PCDD/F
emissions. Thus, it is likely that most barrel burning
530 Journal of the Air & Waste Management Association
practices would result in emissions that would fall
within or near the bounds of the baseline composition runs (i.e., between 9 and 308 ng TEQ/kg waste
combusted, which equals the 10 and 90% quantiles of
the emissions from tests using the baseline composition).
• Organic and inorganic Cl sources showed similar propensities to form PCDD/Fs.
• PCDD/F emissions increased for the runs with very
large amounts of Cl, whether organic or inorganic,
and higher amounts of Cu catalyst.
• Test runs at alternative burn conditions (Compress,
Wet, Double) resulted in higher mean PCDD/F emissions from that of the baseline runs.
• In most cases, the majority of the PCDD/F emissions
were produced during the smoldering stages of the
burn.
• Total PCBs were approximately a factor of 200 greater
than total PCDD/Fs; however, TEQPCB is approximately 5% of TEQDF.
• The single open-pile burning test was within the
bounds of the baseline emissions, so it is not possible
to generalize whether the estimated emissions from
burn barrels could be used to approximate emissions
from this practice.
The September 2000 draft of the EPA Dioxin Reassessment17 estimates 1995 PCDD/F emissions from backyard
barrel burning to be 628 g TEQ (based on the WHO
TEFs14). The reassessment also upgraded the uncertainty
status of the estimate from a preliminary estimate to an
estimate reliable enough to be included in the quantitative inventory. Barrel burning is now identified as the
second largest quantifiable source for 1995, making up
23% of the total release estimate. One implication of this
research is that based on the fact that most of the emissions of PCDD/Fs occurred during the later, smoldering
stage of the burn, emissions could be high from other
potentially important open burning sources such as burning dumps and landfills, where smoldering combustion
may constitute a major portion of the total burn time.
ACKNOWLEDGMENTS
The authors thank Steve Terll and Richie Perry of ARCADIS
Geraghty & Miller for their sampling support.
REFERENCES
1. Emission Characteristics of Burn Barrels; Report prepared for U.S. Environmental Protection Agency Region 5 by Two Rivers Regional Council of Public Officials and Patrick Engineering Inc.: Chicago, IL, June
1994.
2. Burn Barrel Dioxin Test; Western Lake Superior Sanitary District: Duluth, MN, August 1992.
3. Lemieux, P.M. Evaluation of Emissions from the Open Burning of Household Waste in Barrels; Volume 1, Technical Report; EPA-600/R-97–134a
(NTIS PB98 –127343); Air Pollution Prevention and Control Division:
Research Triangle Park, NC, November 1997.
Volume 53 May 2003
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4. Lemieux, P.M.; Lutes, C.C.; Abbott, J.A.; Aldous, K.M. Emissions of
Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofurans from the Open Burning of Household Waste in Barrels; Environ.
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D.L. PCDD/F Emissions from Uncontrolled Domestic Waste Burning;
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D.L. PCDD/F Emissions from Uncontrolled Domestic Waste Burning;
Chemosphere 2001, 43 (4-7), 721-725.
8. Lemieux, P.; Gullett, B.; Lutes, C.; Winterrowd, C.; Winters, D. Parameters Influencing Emissions of PCDDs/Fs from Open Burning of
Household Waste in Barrels. In Proceedings of AWMA/Environment Canada Specialty Conference Recent Advances in the Science and Management
of Air Toxics, Banff, Alberta, Canada, April 2000.
9. Lemieux, P.; Gullett, B.; Lutes, C.; Winterrowd, C.; Winters, D. Dioxin
Formation: The Barrel Burn Study. In Proceedings of the Eighth Annual
North American Waste-to-Energy Conference (NAWTEC VIII), Nashville,
TN, May 2000.
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the United States; External Review Draft; EPA-600/P-98/002Aa (NTIS
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11. Rigo, G.H.; Chandler, A.J.; Lanier, W.S. The Relationship between Chlorine in Waste Streams and Dioxin Emissions from Waste Combustor Stacks;
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12. Winberry, W.T.; Murphy, N.T.; Riggan, R.M. Compendium Method
TO-9: Method for the Determination of Polychlorinated Dibenzo-pDioxins (PCDDs) in Ambient Air Using High-Resolution Gas Chromatography/High Resolution Mass Spectrometry (HRGC/HRMS). In Compendium of Methods for the Determination of Toxic Organic Compounds in
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About the Authors
Paul M. Lemieux (corresponding author) is a senior research engineer with EPA. He may be reached at Office of
Research and Development, National Risk Management
Research Laboratory, Research Triangle Park, NC 27711;
e-mail: [email protected]. He is working on formation
of products of incomplete combustion from stationary
combustion sources and is currently assigned to EPA’s
Center for Homeland Security Research. Brian K. Gullett is
a senior research engineer with EPA. He is working on trace
air toxics monitoring technologies and source characterization. Dwain L. Winters is a senior scientist working for EPA’s
Dioxin Policy Project. Christopher C. Lutes is a principal
scientist and business practice manager with ARCADIS,
Inc. He works in the areas of open-burning process assessment as well as development and implementation of innovative remediation technologies for soil and groundwater.
Chris K. Winterrowd has 10 years of experience in the
air-emissions monitoring industry. He serves as a staff research engineer for ARCADIS, Inc.
Journal of the Air & Waste Management Association 531