Emission characteristics of harmful air pollutants from cremators in Beijing, China
Emission characteristics of harmful air pollutants from cremators in Beijing, China
Yifeng Xue 0 1 2
Linglong Cheng 0 1 2
Xi Chen 0 2
Xiaoman Zhai 0 2
Wei Wang 0 2
Wenjie Zhang 0 2
Yan Bai 0 2
Hezhong Tian 0 2
Lei Nie 0 1 2
Shihao Zhang 0 1 2
Tong Wei 0 2
0 Science and Technology Support Program of the Ministry of Science and Technology of China (2014BAC23B02), the National Key Research and Development Program of China (2016YFC0201106), the Science Foundation of Beijing Municipal Research Institute of Environmental Protection (2017B01), and the Beijing Excellent Personnel Training Project
1 National Engineering Research Center of Urban Environmental Pollution Control, Beijing Municipal Research Institute of Environmental Protection , Beijing , China , 2 Key Laboratory of Pollution Control of Ministry of Civil Affairs, 101 Institute of Ministry of Civil Affairs , Beijing , China , 3 Chinese Research Academy of Environmental Sciences , Beijing, China, 4 Babaoshan funeral parlor, Beijing , China , 5 State Key Joint Laboratory of Environmental Simulation & Pollution Control, School of Environment, Beijing Normal University , Beijing , China , 6 College of Resource Environment and Tourism, Capital Normal University , Beijing , China
2 Editor: Chon-Lin Lee, National Sun Yat-sen University , TAIWAN
The process of corpse cremation generates numerous harmful air pollutants, including particulate matter (PM), sulfur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), and heavy metals. These pollutants could have severe effects on the surrounding environment and human health. Currently, the awareness of the emission levels of harmful air pollutants from cremators and their emission characteristics is insufficient. In this study, we obtained the emission characteristics of flue gas from cremators in Beijing and determined the localized emission factors and emission levels of harmful air pollutants based on actual monitoring data from nine typical cremators. The results show that the emissions of air pollutants from the cremators that directly discharge flue gas exceed the emission standards of China and Beijing. The installation of a flue gas post-treatment system could effectively reduce gaseous pollutants and the emission levels of PM. After being equipped with a flue gas post-treatment system, the emission concentrations of PM10, PM2.5, CO, SO2 and VOCs from the cremators are reduced by 97.6, 99.2, 19.6, 85.2 and 70.7%, respectively. Moreover, the emission factors of TSP, PM10, PM2.5, CO, SO2 and VOCs are also reduced to 12.5, 9.3, 3.0, 164.1, 8.8 and 19.8 g/body. Although the emission concentration of VOCs from the cremators is not high, they are one of major sources of ªodorº in the crematories and demand more attention. Benzene, a chemical that can seriously harm human health, constitutes the largest proportion (~50%) of the chemical components of VOCs in the flue gas from the cremators.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
China has the highest annual number of deaths in the world. According to the ªChina Civil
Affairs Statistical Yearbook 2015º, China's national death toll was 9.77 million, and its corpse
cremation rate was 47% in 2014. The process of corpse cremation generates numerous harmful
(2017000021733G105). The funders had no role in
study design, data collection and analysis, decision
to publish, or preparation of the manuscript.
air pollutants [1±3], including particulate matter (PM), SO2, NOx, CO, HCl, HF, NH3, VOCs,
heavy metals, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) [4±8]. Due to
the characteristics of the funeral sector, the chimney heights are usually low, and the air
pollutants disperse close to the ground, thus severely affecting the surrounding air quality and
human health [9±17]. The problem of the emissions of harmful air pollutants from cremators
is causing increasing social concern.
To strengthen the control and management of pollutant emissions from cremators and
incinerators, China and Beijing have issued emission standards of air pollutants for
crematories (GB13801-2015 and DB1203-2015). These standards have enhanced the emission limits of
air pollutants from cremators and incinerators and clarified relevant requirements on
pollution control, which are promoting the implementation of prevention and control measures in
the crematories to reduce pollutant emission levels. However, the standards have not specified
the emission limits of PM10, PM2.5 and VOCs from cremators. Previous studies on air
pollutants from cremators have typically focused on the problem of emissions of PCDD/Fs and
other persistent pollutants in China and other countries [5,18±20]. The emission
characteristics of PM10, PM2.5 and VOCs in flue gas from cremators have seldom been reported. These
pollutants have provoked increasing attention for their severe impacts on air quality, visibility
and human health. The EU EMEP/EEA guidebook (2016) [
] provided the emission factors
of pollutants such as PM10, PM2.5 and VOCs from cremators, but this guidance did not
distinguish the cremators with and without flue gas purification systems, and the collected data were
not timely enough to accurately represent the current emission levels from cremators. In
China, relevant studies have primarily focused on quantifying conventional pollutants such as
total suspended particulates (TSP), SO2, NOx, CO and persistent organic pollutants from
]. Research into the emission concentrations and emission factors of fine
particulate matter and VOCs from cremators is relatively scant.
To better understand the emissions of flue gas from cremators after the implementation of
the standards in China, we examined the emission levels and emission characteristics of PM
(TSP, PM10 and PM2.5) and air pollutants (SO2, NOx, CO and VOCs) from different types of
cremators with and without flue gas post-treatment systems by practical monitoring of nine
crematories in Beijing. We determined the localized emission factors and analyzed the
chemical components of VOCs in the flue gas from these crematories. This study was the first in
China to monitor and analyze PM10, PM2.5, VOCs and their chemical components as well as
quantify the pollutant emission levels from the cremators. The result could provide a reference
for the subsequent assessment and revision of national or local standards and serve as a
reference providing support for the current civil administration and environmental management.
Materials and methods
Beijing, the capital of China, is located in the northern part of the North China Plain, covering
an area of 16,410.54 km2. It is characterized by high residential density, with a resident
population of 21.516 million. Limited in land resources, cremation is implemented as a fundamental
national policy. Beijing has achieved a cremation rate of nearly 100% for many years. There
are currently 12 funeral parlors in Beijing; two of them are located in the urban area, i.e.,
Babaoshan funeral parlor and Dongjiao funeral parlor, and the others are located in the
suburbs. Each funeral parlor is for corpse cremation.
Based on the site survey and data collection at 12 funeral parlors in Beijing, we present the
following findings. Regarding fuel type, the cremators in Beijing were mainly oil-fired, and the
fuel conversion from oil to gas was performed for only 15 cremators in the Babaoshan funeral
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parlor. In terms of furnace structure, Beijing's cremators were predominantly car-bottom type
with a percentage of ~70%. Considering end-of-pipe control, 59.8% of the cremators in Beijing
were equipped with a flue gas purification system, which mainly included flue gas cooling,
deacidification, deodorization and dedusting devices. The flue gas containing various harmful
air pollutants emitted from combustion has a high temperature. To prevent the re-synthesis of
dioxins, the flue gas is rapidly cooled to avoid recombination. Moreover, to remove the acid
gases such as SO2 and H2S in the flue gas, alkali liquor is used to neutralize the acid gas, and
the activated carbon is used to adsorb VOCs and odor components. Finally, the particulate
matter in the flue gas is removed by a dust collector, thereby reducing the concentration of
harmful air pollutants in the flue gas. Based on the control measure equipment for pollutants
emitted from the cremators, the furnace type and fuel type, one typical cremator was selected
from each of nine selected funeral parlors (geographical coordinates information in S1 Table)
for monitoring the actual flue gas emissions. The emission concentrations of air pollutants
were sampled, and the emission factors were determined. The configuration of the nine
cremators is depicted in Table 1. Four cremators post-processed the flue gas, and five discharged
the flue gas directly. There was one gas-fired cremator and eight oil-fired cremators.
The sampling and monitoring of PM and air pollutants were conducted from the nine selected
cremators during the winter from November 2016 to January 2017. The sampling location was
on the exhaust stack, which can be seen in Fig 1. Dust samples (TSP, PM10 and PM2.5) were
Fig 1. Typical flue gas post-treatment system of a cremator.
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collected using a two-stage PM10 and PM2.5 virtual impactor (Model IV501, China) according
to the method of ISO 13271:2012. Before sampling, we measured the temperature, water
content, oxygen content, pressure, flow rate and other parameters at the sampling point to
calculate the flow rate and the PM2.5 main flow, PM2.5 secondary flow and PM10 secondary flow
required for estimating the sample nozzle diameter. The sampling period started from the
beginning of corpse incineration in the main combustion chamber and ended when ashes
were emptied from the main combustion chamber after the completion of the cremation
process. Each cremator was sampled three times; unfortunately, due to pump failure during the
sampling, 22 groups of available PM samples were obtained. Before sampling, a Teflon
membrane was placed in a constant temperature and humidity chamber for 24 h of equilibration
and then weighed with a precision electronic balance (0.00001 g resolution). After sampling,
the Teflon membrane was held at constant temperature and humidity for 24 h and then
weighed and stored. VOCs were sampled in air bags (10 L) from the flue gas of the cremators
via a vacuum box and suction pump (set at 0.2 L/min) following the standard for emissions
from stationary sources of volatile organic compounds using the Bags method (HJ 732±2014);
the sampling time covered the time to cremate an entire body, which was approximately 45
minutes. Every cremator was sampled three times. In total, 27 groups of VOC samples were
obtained from the cremators. The samples were stored in the dark and analyzed as soon as
possible. Simultaneously, a microcomputer dust parallel sampler (TH880F, Tianhong, Wuhan)
was applied to monitor the concentrations of CO, SO2 and NOx and record the information of
other parameters including flue gas temperature, humidity, oxygen content and flow rate. The
trace gases (e.g., CO, SO2 and NOX) were determined by the fixed potential electrolysis
method (HJ 693±2014 and HJ/T 57±2010).
Concentration and chemical composition analysis of VOCs
The VOC samples were subjected to non-methane hydrocarbon (NMHC) analysis using a gas
chromatograph (Beifen SP-3420A, China). The composition of the collected VOC samples was
analyzed by a pre-concentrator (Entech 7100A, USA) and a gas chromatograph-mass
spectrometer (Agilent 7890A-5975C, USA). The GC-MS enables qualitative and quantitative
analysis of more than 100 types of VOCs according to the standard of stationary source emission
determination of VOCs based on the sorbent adsorption and thermal desorption gas
chromatography-mass spectrometry method (HJ 734±2014).
VOCs were identified based on their retention times and mass spectra and quantified by
external calibration. The calibration standards were prepared by dynamically diluting the
100 ppbv Photochemical Assessment Monitoring Station (PAMS) standard mixture (57
NMHCs) and TO-15 standard mixture (65 compounds, from Spectra Gases Inc., NJ, USA) to
2.5, 5, 10, and 20 ppbv, with pure nitrogen as the mixing medium in a chamber after passing
mass flow controllers. The calibration curves were obtained by running the four diluted
standards plus humidified zero air in the same way as the field samples [
Quality assurance and quality control (QA/QC)
The collected filter samples of particulate matter were collected on aluminum foil paper as
soon as possible after sampling and stored in a refrigerator before analysis. The storage
temperature was approximately -18ÊC. Weighing, extraction and analysis of the sample filter were
performed in a closed and clean laboratory, which avoids errors introduced by the dust falling
into the sample film during the experiment.
As for VOCs, before sampling, all canisters were cleaned at least five times by repeatedly
filling and evacuating with humidified zero air. To check if there was any contamination in the
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canisters, after the cleaning procedure, all vacuumed canisters were re-filled with humidified
zero air and stored in the laboratory for at least 24 h. They were analyzed using the same
method as the field samples to ensure that none of the target VOC compounds were present in
The precision of the VOCs measurements was compound-specific and within 3% for
NMHCs and 6% for VOCs. The measurement accuracy was determined by treating the system
with the dynamically diluted authentic standards and calculating the differences between the
measured and true values. When running the samples, the system was challenged with a
standard each day. If the reported values were beyond +/−10% of the standard values, recalibration
of the system was performed [
Calculation of emission factors
The emission factors of harmful air pollutants from the cremators were calculated based on
their emission concentrations, flue gas amount and cremation time. The formulae are as
where E is the pollutant emission factor, g/body; C is the pollutant emission concentration,
mg/m3; T is the cremation time, min; V is the flue gas flow speed, m/s; S is the cross-sectional
area of the flue, m2; and D is the stack diameter, m.
Results and discussion
Emission concentrations of flue gas from cremators
The emission concentrations of harmful air pollutants from cremators are affected by various
factors, such as fuel type, cremator type, flue gas post-treatment system and operational
maintenance. In this study, monitoring was conducted for the concentrations of PM (TSP, PM10
and PM2.5) and gaseous pollutants (SO2, NOx, CO and VOCs) emitted from nine typical
cremators (four with flue gas post-treatment devices) in Beijing as well as the related parameters
(flue gas oxygen content, temperature, humidity and flow rate). The results (data in S2 Table)
are presented in Fig 2.
PM from cremators is predominantly generated as a result of the incomplete combustion of
the fuel or corpse. At the initial stage of combustion, the furnace temperature is relatively low
and there is no guarantee for the retention time of the flue gas in the secondary combustion
chamber, thus resulting in a relatively high concentration of dust discharged directly from the
cremator without a dust removal treatment system. The emission concentration of TSP from
those cremators without flue gas post-treatment systems ranged from 104.8 to 1,323.5 mg
Nm3 (@ 11% O2; the same as below), with an average concentration of 393.7 mg Nm-3, which
greatly exceeded the emission limit for PM specified by local standards (30 mg Nm-3).
Remarkably, the emission concentrations of TSP from the cremators with a flue gas
post-treatment system ranged from 0.5 to 70.3 mg Nm-3, with an average concentration of 11.0 mg
Nm3. The emission concentrations of PM10 and PM2.5 from the cremators without a flue gas
posttreatment system ranged from 76.6 to 1,084.6 and 47.5 to 1,069.9 mg Nm-3, with average
concentrations of 350.6 and 300.9 mg Nm-3, respectively. After being processed with a flue gas
post-treatment system, these concentrations were efficiently reduced, ranging from 0.2 to 54.8
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Fig 2. Emission concentration of harmful air pollutants from cremators.
and 0.1 to 13.0 mg Nm-3, with average concentrations of 8.4 and 2.4 mg Nm-3, respectively.
The removal rates of TSP, PM10 and PM2.5 were 97.2, 97.6 and 99.2%, respectively. These
results demonstrate that dust concentrations were markedly reduced for the cremators with a
flue gas post-treatment system. The reduction in PM is an effective measure to coordinate
controlling the emission of PCDD/Fs [
CO is a product of incomplete combustion in the cremators. At furnace start-up or the
initial cremation stage, a low furnace temperature can easily result in incomplete combustion.
The emission concentrations of CO in the flue gas from the cremators with and without flue
gas purification systems were 0.4±750.8 and 42.3±1,378.6 mg Nm-3, with average
concentrations of 369.8 and 460.2 mg Nm-3, respectively. The emission concentrations of CO from the
cremators with and without flue gas purification devices were 3.7 and 4.6 times the emission
limits of the local standards. Because CO is predominantly regulated by the furnace
temperature and the retention time of the flue gas, at the beginning of cremation, the temperature was
low, incomplete combustion occurred, and the CO concentration was high. As combustion
continued, the furnace temperature increased, combustion became increasingly complete, and
the concentration of CO emissions decreased. Cremators with a secondary combustion
chamber have a relatively low CO emission concentration. Compared to oil-fired cremators,
gasfired cremators have lower CO emissions.
SO2 principally originates from the combustion of sulfur in the fuel source. A CO
interference experiment was performed prior to the determination of SO2, which was performed at
the highest SO2 concentration and highest CO concentration. For flue gas purification
systems, the deacidification device with an alkaline solution can neutralize and remove SO2. In
this study, the emission concentrations of SO2 from the cremators without flue gas purification
devices ranged from 3.8 to 350.2 mg Nm-3, with an average of 65.0 mg Nm-3. This level
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exceeded the standard limit by 116.7%, and it was also higher than the emission concentration
of SO2 from the cremators with flue gas purification devices.
NOx consists primarily of fuel-type and thermal-type gases, particularly the latter; the
production of thermal-type NOx increases with furnace temperature. The combustion
temperature in the cremators can be up to 900~1100ÊC, and about 700ÊC in secondary chamber. In
the present study, the average NOx concentrations from the cremators with and without
posttreatment systems were 435.5 and 280.2 mg Nm-3, respectively. The former value is 55% higher
than the latter, which is mainly because cremators with a post-treatment system were set to a
higher temperature for more complete burning and to further reduce the emission of PM and
dioxins, although the side effect is more NOX emissions.
Under high-temperature conditions, the strong oxidation process of combustible materials
such as fuel and corpses is associated with decomposition and combination reactions of the
materials. This process produces VOCs, leading to environmental pollution. The emission
concentrations of VOCs from the cremators with and without flue gas post-treatment systems
were in the ranges of 0.1±23.9 and 0.1±162.7 mg Nm-3, with average concentrations of 7.1 and
24.4 mg Nm-3, respectively. The former value is 70.7% less than the latter, suggesting that flue
gas post-treatment systems have a particular effect on the removal of VOCs emitted by
According to the Beijing emission standard of air pollutants from crematories
(DB11/12032015), the compliance rates of TSP, CO, SO2 and NOx of flue gas in the monitoring samples
with a post-treatment system are 87.5%, 33.3%, 87.5% and 25%, respectively, and they are 0%,
28.6%, 55.6% and 33.3% without a post-treatment system. Additionally, as shown in Fig 2, the
compliance rates of the average emission concentrations for these four pollutants are higher
for the cremators with a post-processing device than those without a post-treatment system.
Chemical composition analysis of VOCs
The chemical components of VOC samples from the cremators were analyzed by GC-MS.
Totals of 32 and 42 components were detected in the VOCs emitted from the cremators with
and without flue gas purification systems, respectively. Fig 3 displays the percentages of every
chemical component in the VOCs. The top 10 components in the flue gas from the cremators
without post-treatment were benzene, acrolein, acetone, ethanol, toluene, methyl chloride,
propylene, 1,2-dichloroethane, 2-butanone and naphthalene, accounting for 45.1%, 13.6%,
10.3%, 8.1%, 5.5%, 3.3%, 3.2%, 1.7%, 1.6% and 1.6% of the detected VOCs samples,
respectively. The top 10 components in the flue gas from the cremators with post-treatment were
benzene, propylene, acetone, acrolein, toluene, 1-butene, acetonitrile, n-dodecane, n-undecane
Fig 3. Percentage of compounds in VOCs from cremators.
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and n-hexane, which accounted for 49.0%, 8.1%, 7.4%, 6.7%, 5.7%, 2.9%, 2.6%, 1.6%, 1.2% and
1.1% of the detected concentrations, respectively. Based on the percentage distribution of the
chemical components with and without flue gas post-treatment systems, aromatics accounted
for more than 50% of the two VOC samples, and benzene, presenting high photochemical
activities and severe effects on human health, accounted for approximately half of the
aromatics. As shown in Fig 3, flue gas post-treatment systems are particularly effective at reducing the
levels of aldehydes, ketones and alcohols in VOCs. The percentages of acrolein, acetone and
ethanol in the VOCs of flue gas were lower for the cremators with a post-treatment system,
indicating an observable removal effect of post-treatment systems for these components.
Emission factors of flue gas from cremators
The EFs of harmful air pollutants for the studied cremators were calculated based on practical
monitoring data (data in S3 Table). Fig 4 exhibits the characteristics of pollutant emission
factors for the cremators with and without post-treatment systems based on the obtained
emission factors of PM10, PM2.5 and VOCs. For the cremators with a flue gas post-treatment
system, the emission factors of TSP, PM10, PM2.5, CO, SO2, NOx and VOCs were 12.5, 9.3, 3.0,
164.1, 26.4, 627.8 and 19.8 g/body, respectively. For comparison, the emission factors of the
aforementioned pollutants without a flue gas post-treatment system were 545.8, 498.7, 440.1,
909.5, 70.6, 501.6 and 41.6 g/body, respectively. Except for NOx, the remaining six pollutants
in the post-processed flue gas were characterized by significantly lower emission factors than
those in the untreated flue gas. The emission factors of TSP, PM10, PM2.5, CO, SO2 and VOCs
were reduced by 97.7, 98.1, 99.3, 82.4, 62.6 and 52.4%, respectively. The dust removal device in
the flue gas post-treatment system had a significant impact on limiting PM, and SO2 levels
were also reduced by the deodorization spray tower with alkaline solution. The cremators with
a flue gas post-treatment system were characterized by better operation management, with
lower emission levels of CO than those without a flue gas post-treatment system.
Fig 4. EFs of harmful air pollutants for the studied cremators.
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According to the survey result, no activated carbon spray or adsorption occurred in the
crematories. The decrease in the emission factors of VOCs may be related to the
filtration-adsorption or condensation of VOCs. A combination of existing control techniques for VOC
pollution, such as activated carbon adsorption and catalytic combustion measures [
further reduce the emissions of VOCs. However, the drawback to a flue gas post-treatment
system is that the NOx emission levels of cremators increased by 25.1% relative to the levels from
cremators without a flue gas post-treatment system, which is likely due to the influence of
temperature regulation and other factors.
The emission factors for different fuel types were compared among cremators with and
without post-treatment systems (Fig 5). During the initial discharge of air pollutants, the emission
levels of various pollutants of the oil-fired cremators are higher than those of the gas-fired cremators.
Regardless of the type of fuel used in the cremator, the air pollutant emission levels for those
using a flue gas purification system were lower; however, due to the effect of temperature, NOX
emission levels were higher. The emission factors were considerably reduced for the oil-fired
cremators with flue gas purification systems than those without, and the removal rates of TSP, PM10,
PM2.5, CO, SO2 and VOCs were 97.2, 97.7, 99.2, 75.9, 56.3 and 43.4%, respectively. Similarly, the
emission factors of TSP, CO and SO2 were considerably reduced for the gas-fired cremators
equipped with a purification device. For the cremators fitted with a flue gas purification system,
the emission factors were much lower for gas-fired cremators than oil-fired cremators, and the
emission factors of TSP, PM10, PM2.5, CO, SO2 and VOCs were reduced by 68.8, 81.4, 80.1, 99.7,
58.7 and 63.4%, respectively. Therefore, a clean energy conversion of cremators from oil-fired to
gas-fired could improve the combustion efficiency and reduce the incomplete combustion of
corpses and fuel, effectively lowering the emission levels of pollutants such as PM, SO2 and CO.
Comparison of pollutant emission characteristics with other studies
In previous investigations [
], the analysis results of the EFs of harmful air pollutants from
cremators were 12.5±18.6 and 9.8~-4.6 mg Nm-3, with average concentrations of 15.6 and
Fig 5. Comparison of EFs of harmful air pollutants between gas-fired and oil-fired cremators.
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17.2 mg Nm-3, respectively. These values are similar to the emission concentration of TSP
in our study (11.0 mg Nm-3). However, previous studies did not report PM10 and PM2.5
levels. This is the first study in China to obtain the emission levels of PM10 and PM2.5.
According to the analysis results, the percentages of PM10 and PM2.5 in the TSP of the flue gas from
the studied cremators with a post-treatment system were 0.76 and 0.22, respectively, and
the values for cremators without a post-treatment system were 0.89 and 0.76, respectively.
This finding indicates that a PM removal device can effectively reduce the emission of
inhalable particle and fine particulate matter and reduce the impact on human health and the
The pollutant emission factors of the cremators obtained in this study were compared with
the research results within and outside China (Table 2). Compared with the results mentioned
in the EU EMEP/EEA guidebook (2016), the emission factors of PM, SO2 and NOx were
relatively low in the present study, which is perhaps related to the different contents of hazardous
components present in the fuel source. The relatively high emission level of CO may be
associated with the different control levels of combustion due to the differences among cremator
device types in China and other countries as well as the operational differences in the fuel
supply quantity and the fuel- and oxygen-supplying air time. Influenced by traditional customs,
corpse cremation in China may also include the incineration of burial objects. Moreover,
differences in flue gas treatment facilities and the standardization of their operational
management may result in higher emission levels of VOCs [
Compared with previous research results [
], the present monitoring results show that the
pollutant emission levels of cremators without a flue gas post-treatment system became
markedly higher, with TSP and CO increases of 288% and 60%, respectively. This is due in
part to the long-term use of cremators in addition to insufficient operational maintenance,
poor implementation of combustion controls and the incomplete combustion of fuel and
corpses. Additionally, previous studies have primarily been based on the supervisory
monitoring of cremators. To better represent the emission levels of flue gas directly discharged from
the cremators, our evaluation was conducted based on the implementation of emission
standards. For the cremators with a flue gas post-treatment system, the present monitoring results
were much lower than those of previous data except for NOx. This result also reflects that
adhering to stringent standardized limits and the oversight departments have strengthened the
operation and maintenance of flue gas post-treatment systems and enhanced the control of
combustion conditions in the cremators. By improving the combustion efficiency and
reducing incomplete combustion, the pollutant emission levels of cremators can be efficiently
reduced. Because of strengthened controls on combustion operating conditions, furnace
temperatures and thermal-type NOx generation have increased.
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In this study, we examined the emission characteristics of flue gas and determined the local
emission factors of pollutants from cremators in Beijing, China, based on the monitoring and
analysis of major air pollutants (TSP, PM10, PM2.5, SO2, CO, NOx, VOCs and their chemical
components) from nine cremators.
According to the monitoring results, the pollutant emission concentrations were
significantly lower for cremators with flue gas post-treatment system than those without. The
pollutant emission factors of TSP, PM10, PM2.5, CO, SO2 and VOCs were reduced in cremators with
flue gas post-treatment systems by 97.7, 98.1, 99.3, 82.4, 62.6 and 52.4, respectively. Dust
removal units can effectively remove PM. Additionally, deacidification spray towers are
available to remove a quantity of acidic gases and reduce SO2 emissions. Moreover, the operating
conditions of combustion were generally optimized and adjusted in the cremators with a flue
gas post-treatment system, which improved the combustion efficiency and reduced the
incomplete combustion of corpses and fuel, thereby reducing pollutant emission levels.
The emissions of VOCs from cremators have been a neglected issue in previous studies,
and no corresponding control requirements have been proposed for VOCs in emission
standards. Based on the monitoring of the parameters in this study, we found that the process of
corpse cremation produced certain emissions of VOCs, a significant source of odors emitted
from crematories. Benzene is the most significant VOC, with a percentage of ~50%, and it may
cause serious risks to human health. Moreover, benzene has high photochemical activity and
tends to cause the secondary transformation of PM2.5 and ozone, which may impact air
quality, meriting serious attention and concern.
Apart from the ability of flue gas post-treatment systems to reduce the emission of
pollutants, clean energy conversion of the fuel types used by cremators, such as the use of natural gas
in place of oil, can also effectively reduce the emissions of air fpollutants such as PM, CO and
SO2 from cremators. Among various pollution prevention measures, control over the content
of hazardous components in burial objects, the use of clean fuel and combustion optimization
should be implemented in crematories to match the current requirements of stringent
emission limits. Combining these measures with an efficient flue gas post-treatment system
(including dust removal, deacidification and odor removal) can further reduce the emission
levels of air pollutants from cremators.
S1 Table. Geographical coordinates for the funeral parlours sampled.
S2 Table. Emission concentration of harmful air pollutants from cremators (mg/m3).
S3 Table. Emission factors of harmful air pollutants from cremators (g/body).
This work was funded by the National Science and Technology Support Program of the
Ministry of Science and Technology of China (2014BAC23B02), the National Key Research and
Development Program of China (2016YFC0201106), the Science Foundation of Beijing
Municipal Research Institute of Environmental Protection (2017B01), and the Beijing
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Excellent Personnel Training Project (2017000021733G105). The funders had no role in study
design, data collection and analysis, decision to publish, or preparation of the manuscript.
Data curation: Xi Chen, Xiaoman Zhai, Lei Nie, Shihao Zhang.
Investigation: Linglong Cheng, Yan Bai, Tong Wei.
Methodology: Wenjie Zhang.
Validation: Lei Nie.
Writing ± original draft: Yifeng Xue.
Writing ± review & editing: Wei Wang, Hezhong Tian.
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