Present and Future Emissions of HAPs from Crematories in China

Yifeng Xue1，2 ，Hezhong Tian1 ，Jing Yan2 ，Chengcheng Xiong3 ，Tao Pan2 ，Lei Nie1 ，Xiaoqing Wu1 ，Jing Li1 ，Wei Wang3 ，Jiajia Gao1 ，Chuanyong Zhu1 ，and Kun Wang1

1. State Key Joint Laboratory of Environmental Simulation & Pollution Control，School of Environment，Beijing Normal University，Beijing 100875，China

2. National Engineering Research Center of Urban Environmental Pollution Control，Beijing Municipal Research Institute of Environmental Protection，Beijing 100037，China

3. Key Laboratory of Pollution Control of Ministry of Civil Affairs，101 Institute of Ministry of Civil Affairs，Beijing 100070，China

Graphical Abstract

Abstract：China is the most populous country in the world.The amount of death population has reached 9.65 million and 49.5% of human corpses are cremated by about 1700 crematories spread throughout the country in 2012，leading to considerable discharge of various hazardous air pollutants（HAPs）into the atmosphere and great concerns on regional air quality and health risks for surrounding residents.By using the practicable or best available emission factors，for the first time，a multiple-year emission inventory of typical hazardous air pollutants discharged from crematories in the Chinese mainland，has been established for the historical period of 1990 to 2012，and the future trends of HAPs emissions until 2030 are forecasted based on three scenarios analysis.Our results show that the total emissions have gradually increased to 906t of NOX ，443 t of SO2 ，2713t of CO，477.7t of PM，377t of HCl，36t of H2 S，25 t of NH3 ，62t of NMHC，592kg of Hg，48kg of Pb，14kg of Cd，53kg of As，40kg of Cr，37kg of Cu，51kg of Ni，and 96g of PCDD/Fs as TEQ（toxic equivalent quantity）by the year 2012.Under the business-as-usual（BAU）scenario，various HAPs emitted from cremators would continuously increase with an average growth rate of 3% till to 2030；whereas the emissions will peak at around 2015 and then decline gradually with varied speed under the two improved control scenarios.To mitigate the associated air pollution and health risks caused by crematories，it is of great necessary for implementing more strict emission standards，applying combustion optimization and requiring installation of best available flue gas purification system，as well as powerful supervision for sound operation of crematories.

Key words：Crematory；Hazardous Air Pollutants（HAPs）；PCDD/Fs；Emission inventory；Scenario analysis；China

1　Introduction

Chinais the largest country with respect to population throughout the world，which is also featured with the largest annual death population and the highest cremation rate.According to the official statistics，the amount of death population has reached 9.65 million and 49.5% of human corpses are cremated in 2012（China Statistical Yearbook and China Civil Affairs’ Statistical Yearbook，2013）.During the high temperature cremation process，various hazardous air pollutants（HAPs）will be produced and released into the atmosphere through the stack（Liu et al.，2013；Mari and Domingo，2010）.（HAPs）emitted by cremation mainly include particulate matters（PM），gaseous pollutants（SO2 ，NOX ，CO，HCl，HF，NH3 ，NMVOCs，etc.），heavy metals（Hg，Pb，As，Cd，etc.），and the more dangerous polychlorinated dibenzo-p-dioxins and dibenzofurans（PCDD/Fs），as well as other persistent organic pollutants（POPs）（Chen，2004；Kim et al.，2008；Nriagu and Pacyna，1988）.During the past decades，along with the rapid growth of urbanization process and due to lack of suitable sites for establishing new crematoria sittings，more and more existing crematoria plants that were originally located in the outskirts of the downtown area in the cities，have now happened to be encircled in urban areas，and even some are very close to residential communities（Santarsiero et al.，2005a）.Consequently，risks to local air quality and public health effects imposed by the emissions of various HAPs and especially the PCDD/Fs from crematories are emerging concerns in more and more cities of China（Green et al.，2014；Llobet et al.，2008；Tian et al.，2012a）.

Driven by the rapid economic development and intensive energy use，emissions of atmospheric pollutants from various sources have caused severe complex air pollution in China （Chan and Yao，2008；Fu et al.，2007；Streets and Waldhoff，2000；Zhao et al.，2013b）.The Chinese government has taken aggressive steps to improve energy efficiency and reduce emissions of primary aerosols and gaseous pollutants to tackle with the serious regional PM2.5 and haze pollution（Zhao et al.，2013a）.However，most control measures have been focused on the major pollution sources such as power plants，industrial sectors and the conventional air pollutants including PM，SO2 ，NOX and so on （Fu et al.，2013；Wang et al.，2014；Zheng et al.，2009）.However，the contribution of crematories to the national and city-scale emissions cannot be ignored especially for mercury（Hg），dioxins and furans，which have been proved to be dangerous for human health.In addition，crematoria have the potential to emit polycyclic aromatic hydrocarbons（PAHs）.

Several studies（Maloney et al.，1998；Panyametheekul et al.，1999；Petzoldt，2012；Santarsiero et al.，2005b；Schetter，2009，2012；Wang et al.，2003；Wiechmann and Gleis，2012；Xiong et al.，2013）have investigated the emission characteristics of Hg and PCDD/Fs from crematories in varied countries.For example，PCDD/Fs and Hg emissions from crematories in Japan were estimated，and the relationship between PCDD/Fs and several factors such as structure，equipment，and operational state of the crematory were assessed，for better understanding the pollution characteristic by crematories in Japan.（Takaoka et al.，2010；Takeda et al.，2014）；.As for China，the health risk arose by crematories have been concerned，some scholars have carried some measurements on the concentration of PCDD/Fs from crematories，for knowing about the emission level，and proposed the strategy for the process of cremation in China.（Wei et al.，2006；Yue et al.，2009）.Nevertheless，there are few studies on the temporal trend and spatial distribution characteristics of various HAPs emissions from crematories and lack of systematic understanding on possible future trends and control options in China.

In this study，a comprehensive emissioninventory on key HAPs emitted from crematories in China for the historical period of 1990 to 2012 has been established and their future emissions till 2030 are predicted through scenario analysis.The temporal variation trends and spatial distribution characteristics by provinces are analyzed in detail.

2　MATERIALS AND METHODS

2.1　Study domain and methods

The study domain under the Lambert conformal projection covers the Chinese mainland，including 22 provinces，5 autonomous regions and 4 municipalities（exclusive of Hong Kong，Macau and Taiwan）（Chen et al.，2014）.As shown in Fig.1，the maximum density of crematories is associated with eastern China such as the Yangtze River Delta，the North China Plain，and the Pearl River Delta（exclusive of Hong Kong and Macau），which partly can be explained by the dense populations，intensive available land use and the relatively developed regional economy.

In this study，atmospheric emissions of key HAPs are calculated based on unit-specific energy and materials consumption and the best available emission factors for specified HAPs with control technologies，which are sub-grouped by taking account of different patterns of combustion facilities and the equipped PM collection and flue gas purification devices.The algorithm of a bottom-up emission inventory of HAPs emission for crematoria can be expressed by the following equation：

　　（1）

Where E denotes the emission of various HAPs；A is the annual activity level，representing the number of cremated corpses；CEFrepresents the comprehensive emission factor of HAPs for a cremator；j is the cremator type；i is the province；and t is the calendar year.

2.2　Cremators

Nowadays，there are more than 1700 crematories in the Chinese mainland（China civil affairs’ statistical yearbook，2013），and the majority type of cremators is oil-fired.The atmospheric emission concentrations of several hazardous air pollutants from cremators are restricted by the emission limit values of air pollutants for fuel oil cremator（GB13801-2009）.For other fuel-fired cremators there are no specific emission standards but they are required to comply with the Integrated Emission Standards of Air Pollutants（GB16297-1996）.Therein，the emission limit value of PCDD/Fs is regulated at 1.0ng TEQ/m3 （@11% O2 ，secondary air quality distinct）in the standard GB13801-2009，10 times higher than the relevant EU emission standard（0.1ng TEQ/m3）.Table 1 shows the comparison emission limits for crematories among different countries or districts.It can be inferred that the emission ceilings of these HAPs are still rather loose under the existing control technology in China.

Cremation is one of basic national policies on human corpse disposal in China.A human crematory contains one or more combustion units known as cremators，and the process of cremation is to combust the corpse mandatory through maintaining high temperature and sufficient oxygen in the incineration chambers（see Fig.2）.

Along with the urbanization process and the growing demand for human corpse cremation，the number of cremators has been increased from 1990～2012 in China（Fig.3）.The average capacity of cremation in one cremator is about 913 corpses per year.The operation loads of usage for cremators are rather high and often fail to keep adequate maintenances，which reducing the life expectation of cremators and leading to elevated HAPs emissions.

2.3　Analysis of PCDD/Fs and other air pollutants

Sampling and analysis of PCDD/Fs in flue gas are based on the Chinese standard method（HJ 77.2-2008）.PCDD/Fs are analyzed by high-resolution gas chromatography（HP 6890，Agilent Technologies，Palo Alto，CA，USA）or high-resolution mass spectrometry（Auto Spec-Ultima，Waters/Micromass，Milford，MA，USA）with a DB 5MS column（60m×0.25mm×0.25μm，J&W）or a DB 17MS column（60m×0.25mm×0.25μm，J&W）.Sampling and analysis of PM，SO2 ，NOX ，CO，HCl，NH3 ，H2S，and Hg also comply with the Chinese standard methods including HJ/T 397-2007，HJ/T 57-2000，HJ 693-2014，HJ/T 27-1999，HJ/T 44-1999，HJ 533-2009，GB/T 14678-1993 and HJ 543-2009，respectively.All the measurements of these pollutants are according to the technical specifications of quality assurance（QA）and quality control（QC）for monitoring of stationary pollution source（HJ/T 373-2007）.

2.4　Emission factors of key hazardous air pollutants in flue gas

Considered that the combustion conditions in the cremator are discontinuous and intermittent，we choose some typical and representative cremators to conduct field monitoring experiments and collecting samples.For the conventional air pollutants such as PM，SO2 ，NOX ，CO，HCl，NH3 ，H2S，and Hg，totally 32 cremators which have installed no extra flue gas treatment system are adopted for determining the uncontrolled baseline emission factors，while 12 cremators which installed with flue gas treatment system including heat exchanger，bag filters，wet scrubber and activated carbon adsorption devices are investigated for calculating the controlled emission factors.

Whereas，6 cremators with post-treatment devices and 11 cremators without post-treatment devices are selected for PCDD/Fs field measurements partly because of the difficulties and expensive cost on monitoring and analyzing of PCDD/Fs emitted from cremators.Fig.4 summarizes the monitored concentration distribution of varied air pollutants from tested cremators in China.

Average emission factors of varied HAPs are calculated by using the following equation：

　　（2）

E：emission factor，g/corpse；C：average concentration of one pollutant in flue gas，mg/m3；Q：volume of dry flue gas，m3 /s；T：time period of cremation，minute；N：number of cremation（corpses）.

Except for the conventional air pollutants and mercury，the process of crematory

could release various VOCs and heavy metals such as Pb，Cd，As，Cr，Cu，Ni and others.However，owing to lack of adequate field measurements，the emission factors of these toxic pollutants are determined by referring the emission factors of crematory from the EU EMEP/EEA guidebook（2013）.Average emission factors of various HAPs are summarized in Table 2.

The average emission factors of HAPs in flue gas we used in this study are determined by combining domestic field tests which can be best represent for the practice emission level of TSP，SO2 ，NOx ，CO，HCl，H2S，NH3 ，Hg，PCDD/Fs and EEA emission factors for Pb，Cd，As，Cr，Cu，Ni and others in order to get more reliable and complete estimations.

2.5　Scenario analysis

The situations of pollution control are forecasted with three scenarios：Business-As-Usual（BAU）scenario and two Improved Pollution Control（IPC-1，IPC-2）scenarios.Under the BAU scenario，we assume that crematories will be still following the current emission standards，and environmental supervision and enforcement still do not have access to improve，most of flue gas cleaning system stays on the non-operation or poor operation for saving fuel and reducing operation cost；Under the IPC-1 scenarios，we assume that new revised air pollutant emission standard for cremation will be issued and implemented，and environmental supervision and enforcement have more access to improve，flue gas cleaning systems are widely installed and in well operation conditions and the emission levels of various air pollutants reach the standard of emission limitations.As for IPC-2，we presume that new revised air pollutant emission standards for cremation comparable with those of EU are issued and the best available control technology（BACT）will be adopted by the crematories，to further lower the emission levels of various HAPs，especially PCDD/Fs and heavy metals.

3　RESULTS AND DISCUSSION

3.1　Temporal trends of hazardous air pollutant emissions from crematories in China

According to the annual volume of corpses cremated and the historical transition of cremators constitution and the equipped control devices，the temporal trends of provincial and national total emissions of HAPs from cremators in China during the period 1990～2012 are calculated by combining the specific emission factors for various HAPs，as illustrated in Fig.5.As can be seen，the emissions of key HAPs have increased rapidly，with annual growth rates of about 6% since 1990.By 2012，the national total emissions are estimated at 672t of PM，443t of SO2 ，906t of NOX ，2713t of CO，377t of HCl，36t of H2S，25t of NH3 ，62t NMHC，592kg of Hg，48kg of Pb，14kg of Cd，53kg of As，40kg of Cr，37kg of Cu，51kg of Ni，96g-TEQ of PCDD/Fs，respectively.

China possesses the largest population in the world，for feeding the citizens and ensuring food supply safety，the Chinese government has regulated strict regulations of land use and the cultivatable land is saved to use for planting and living.Under this circumstance，Chinese government has launched a series of cremation reform policies since 1956，such as dividing the cremation districts and non-cremation districts，supplying economics subsidy to encourage cremation.Except for some of the minority nationality habitation districts，the majority of Chinese mainland where characterized with larger population destiny，less planting land，and convenient traffic is normally defined as cremation district，and the corpses dead in these areas are requested to be cremated by the central and local governments.With the progress of urbanization and the promotion by relevant policies，the national rate of cremation has greatly increased from about 31.5% in 1990 to about 49.5% in 2012，and more and more crematories are built to meet the growing cremation demand.However，due to the emission standards for cremator are still rather loose compared to EU and lacking of effective supervision and maintenance，though some of cremators have been equipped with flue gas treatment system，most of these flue gas treatment devices are in poor operation，even some of them are not really put into operation for saving operating cost，causing various air pollutants produced by the cremators are discharged into the atmosphere directly.The gradually growing emissions of various HAPs from cremators implies that more rigorous control and management are in great needed，especially when considering the exposure risks on human health for some dangerous species such as PCDD/Fs and Hg.

3.2　Distribution Characteristics of HAPs Emissions in 2012

Emissions of key HAPs by province in China for the year 2012 are summarized in Table 3.As can be seen，HAPs emissions from cremators in the Chinese mainland are distributed very unevenly，obviously with higher emission intensities in eastern provinces than the western provinces，which can be mainly explained by the obvious difference of population density and the ratio of cremation.Shandong，Jiangsu，and Guangdong rank as the top three largest emitting provinces.In general，the provincial emission inventories of HAPs from crematories coincide well with their economic development and population.All provinces emitting large amounts of HAPs are relatively developed economically or densely populated，which cause much higher numbers of cremations.

①more details about provincial emissions of HAPs from crematories in China in 2012 can be seen in Supplementary Table S1

②unit：g TEQ

Furthermore，we find that Qingdao，Jinin and Yantai rank as the top three cities with largest HAPs emissions in Shandong province；Nantong，Yancheng，and Xuzhou are the top three cities with largest emissions in Jiangsu province；and HAPs emissions in Guangzhou，Zhanjiang，and Jieyang cities are highest in Guangdong province.These cities are all located in the eastern and southern areas，especially some provincial capital and coastal cities where cremation practices are rigorously implemented.Heavy emissions are mainly driven by these areas with more developed local economy，denser population，and lack of land resource for traditional burial.

3.3　Projection of future HAPs emissions

According to the statistical data in 2001～2013 China statistical yearbooks，along with an aging population occurred initially，the proportion of population aged 65 and over has increased from 6.96% in 2000 to 9.4% in 2012.Correspondingly，the death toll from 2000 to 2012 has been rising and the average annual growth rate is about 1.46%.It is anticipated that the death tolls in China will reach about 10.84 million and 12.52 million till 2020 and 2030，respectively.From 2000 to 2012，the cremation rate has increased with an average growth rate of 0.68% and it will steadily increase under the continuous implementation of cremation policies that benefit the public and constraint of land utilization.We assume that the cremation rate will increase with the current annual rate（0.68%）and reach about 52.3% and 55.9% by 2020 and 2030，respectively.Thus，the potential corpses of cremation are estimated at about 5.662 million and 7.002 million in 2020 and 2030，respectively.

Under BAU scenario，there is no significant change on the emission standard and environmental supervision，which lead to the emission levels of HAPs have no different from now，HAPs emission would keep rising followed by the increase of annual numbers of corpse cremation.Taking PM as an example，the emissions will reach at about 984 t by 2030，nearly 1.5 times than the emission at 2012，and the similar trend of other air pollutants can be seen in the Fig.6（a）.

Under the IPC-1 scenario，we assume the emission standard has been amended with more stringent emission limitations，and environmental supervision and enforcement have also been improved.According to the draft of national emission standard for crematories，the emission limits of various HAPs will reduce about 50%～60%.For example，TSP emission ceiling will be lowered from 80mg/m3 to 30mg/m3，while that of PCDD/Fs will be reduced from 1.0ng TEQ/m3 to 0.5 ng TEQ/m3.Considered that the wide concern of urban air quality and the severe PM2.5 pollution in key cities of China，we assume that the 74 major cities of China would take relevant control measures firstly，and then gradually spread in other cities，the rate of cremators which equipped with flue gas purification systems will be increased gradually，reaching about 30%，60%，90% in 2020，2025，2030，respectively.As a result，the emissions of various HAPs will have peak values at around the year 2015 and then decline gradually with an annual decline rate of about 1.3%.Therein，compared with that in 2012，PCDD/Fs emissions from crematories will be reduced about 31.3% in 2020 and 59.4% in 2030，respectively[see Fig.6（b）].

Under IPC-2 scenario（BACT），there is an obvious downward trend for various HAPs，with an annual decline rate of about 3.4% since 2015（see Fig.6（c））.Mainly because we assume that BACT technologies will be widely applied in the crematories，such as fabric filters（FFs）for removing PM，wet scrubber for removing SO2，activated carbon injection and catalytic degradation for removing PCDD/Fs，Hg and so on.The emission levels of HAPs will reduce about 80% on the basis of 2012.In this scenario，the emission of HAPs will also reach peak values at around 2015 and then decline with a much higher speed than that in IPC-1 scenario，and the HAPs emissions by 2030 would be almost equivalent to those of 1990.As for PCDD/Fs which the public more concerns about，after taking the BACT technologies including rapid quenching of flue gas，adsorption by activated carbon，catalytic oxidation，etc，even higher emission reduction would be acquired than in IPC-1 scenario.Nevertheless，implementation of amended emission standards and strong supervision are greatly important to the success of IPC-2 scenario.

3.4　Uncertainties

Several factors influence the estimation of atmospheric emissions from crematories in China，including the reliability of specific emission factors and activity levels.To better understand the uncertainties in our inventory，Monte Carlo simulation is adopted to quantify the potential uncertainties of key HAPs emissions from cremators.Here，we assume normal distributions with coefficient of variation（CV，the standard deviation divided by the mean）of 10% for activity levels of annual number of cremation and uniform distribution for comprehensive emission factors of HAPs（Tian et al.，2012b；Tian et al.，2014；Zhao et al.，2011）.

Table 4 summarizes the uncertainties（95% confidence interval around the arithmetic mean value）in Chinese atmospheric emission estimations of HAPs from cremators in 2012.

As mentioned above，the emission estimations of several pollutants，such as PM，SO2，NOX，CO，HCl，H2S，NH3 and Hg，whose emission factors are determined based on the practical monitoring experiments，show relative small uncertainties in the range of -35.6%～34.4%.For NHMC，Pb，Cd，As，Cr，Cu，Ni and other pollutants，the ranges of uncertainty are relatively large（-54.5%～57.1%）mainly due to lack of local emission factors which determined from adequate field measurements.It implies that much more field tests are necessary for better understanding the emission levels of various HAPs，especially for heavy metals，NHMC and PCDD/Fs.

Particularly，it should be acknowledged that emission trends of HAPs are probably more uncertain than indicated.This is mainly because no dynamic emission factor curves are set from 1990 to 2012.Nevertheless，no data are available to improve the confidence presently，which merits further investigation in the future.

3.5　Possible control measures

Atmospheric emissions of HAPs from crematories mainly rely on the combustion optimization and the equipped flue gas purification system，as well as pollution prevention of feed fuels and others materials.Although it might not be an optimum solution，post-combustion emission control is still regarded as a useful way to limit the final atmospheric discharge.Effective HAPs emission reduction can be achieved through flue gas pollution control devices.In addition，make sure the feed materials and chemical components of clothes and other funeral objects should be met with relative standards to prevent and minimize the potential formation of HAPs，especially for PCDD/Fs.A stringent emission standard and a strong monitoring capacity can ensure the actual and steady reduction in HAP emissions （Kulkarni et al.，2008；Tian et al.，2012b；Zheng et al.，2004）.

By using advanced combustion control and effective flue gas purification systems，the emission of PM，SO2，NOX，CO，HCl，and PCDD/Fs from crematories can be effectively controlled （Fang et al.，2009；Hassanin et al.，2006；Yang et al.，2008；Zhao et al.，2013c）.During the process of cremation，improving burning conditions to ensure a stable and full burning environment can reduce the production of precursors，thereby avoiding much synthesis of PCDD/Fs.Activated carbon injection to absorb PCDD/Fs is an effective post-combustion emission control technology.Moreover，it is of great importance to establish laws，standards，and regulations that prohibit or restrict building of backward cremation processes and reliably management and disposal of residuals containing HAPs throughout their life cycles.

Additionally，compared with flue gas purification systems，pollution prevention in the feed materials is of equal importance （Cao et al.，2013；Tian et al.，2010）.Restricting the amount of dangerous chemical components such as chlorine containing plastics or heavy metal containing materials in the coffin，clothes and other funeral objects is a fundamental control measure for preventing HAPs emissions from crematories.Thus，the Chinese central and local authorities should actively plan and support programs for replacing the non-environmental friendly funeral objects in the cremation.

In a word，implementing the whole process control（Zhu et al.，2015），which simultaneously consider advanced combustion control，effective flue gas purification systems and pollution prevention in the feed materials can be regarded as reasonable and useful ways to limit HAPs emission from crematories and minimize their adverse effects in China.

4　CONCLUSIONS

In this study，in order to obtain the best available emission factors for calculating various HAPs emissions，we have selected representative types of cremators to test the real-world emission levels of various pollutants such as TSP，SO2，NOX，CO，HCl，H2S，NH3，Hg and PCDD/Fs.Then，by combining the calculated specific emission factors for various HAPs with the annual volume of corpses cremated，as well as considering the historical transition of cremators constitution and the equipped control devices，for the first time，a comprehensive emission inventory on key HAPs emitted from crematories in China for the historical period of 1990 to 2012 has been established and their future emission trends till 2030 are predicted through scenario analysis.In addition，some control proposals are raised for strengthening the HAPs emission control form crematories of China.

Our results show that the total emissions of key HAPs have increased rapidly with annual growth rates of about 6% since 1990.Further，we find that various HAPs emissions from cremators in the Chinese mainland are distributed very unevenly，obviously with higher emission intensities in eastern provinces than the western provinces，which can be mainly explained by the obvious difference of population density and the ratio of cremation.Under the business-as-usual（BAU）scenario，various HAPs emitted from cremators would continuously increase with an average growth rate of 3% till to 2030；whereas we predict that the emissions will peak at around 2015 and decline gradually with varied speed under the two improved control scenarios（IPC-Ⅰ，IPC-Ⅱ）.To mitigate the associated air pollution and health risks caused by crematories，it is of great necessary for implementing more strict emission standards，applying combustion optimization and requiring installation of best available flue gas purification system，as well as powerful supervision for sound operation of crematories.

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