Influence of the Inclusion of Ignition Stage Emissions in the

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Influence of the Inclusion of Ignition Stage Emissions in the Development of Emission Factors for Coal Cookstoves Used in India Darpan Das,*,† Upendra Bhandarkar,‡ and Virendra Sethi† †

Centre for Environmental Science and Engineering, IIT Bombay, Mumbai 400076, India Department of Mechanical Engineering, IIT Bombay, Mumbai 400076, India

‡

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S Supporting Information *

ABSTRACT: Coal is used widely for domestic cooking in many regions of India, which contributes significantly to the particulate matter (PM < 2.5 μm) and CO levels in ambient and indoor air. Modeling and inventorization require the use of emission factors (EFs) for cookstoves, which are specific to fuel type and cookstove design. These are usually not available or are available for emissions under steady state combustion conditions following some protocols that are end-use-specific. In this study, two types of cookstoves are deployed, and PM < 2.5 μm and CO emissions are measured for a combustion cycle that includes an initial ignition stage, a flaming stage, and a smoldering stage. EFs are estimated for PM < 2.5 μm and CO for each of these stages of the combustion cycle and indicate a 5−9-fold increase for PM < 2.5 μm when emissions from the ignition stage are included. Elemental carbon and organic carbon analyses are presented for PM < 2.5 μm using two protocols, namely, IMPROVE_A and DIN-19539. The EFs developed for the complete combustion cycle may be used to better represent the impact of coal cookstoves on the ambient air quality and for a more realistic assessment of health effects for exposure in kitchens.

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INTRODUCTION Air pollution issues in India have been under review over the past two decades, and it is becoming apparent that the sources and characteristics of emissions are uniquely linked with the socio-economic status of subcommunities as well as the regionspecific availability of fuels for domestic cooking. Traditional cookstoves or “chulhas” are known to be a significant source of carbon monoxide (CO) and PM < 2.5 μm for both indoor and ambient air pollution. Emissions from household cooking and space heating are reported to be a leading risk factor for disease in the developing world, accounting for approximately 4% of all lost healthy life years and ∼2 million premature deaths in lowand middle-income groups.1 Shen and co-workers2 report that 21.4% of primary PM < 2.5 μm, 63% of polyaromatic hydrocarbons (PAHs), and 28.9% of black carbon (BC) of the global inventory are contributed by residential solid fuel combustion. Coal is predominantly used in cookstoves in several parts of India and China, especially in coal mining areas where coal is © XXXX American Chemical Society

locally accessible (Figure SI 1). Almost 4 million households in India use coal as their primary cooking fuel.3 Several studies report measurements of pollutants from coal-based cookstoves from China;4−8 however, there is limited literature about coal cookstove emissions in India. In addition, the traditional coal cookstoves used in India are quite distinct in design from those reported in the literature. The International Panel on Climate Change report9 highlights the need for better data and control measures. There have been several studies of emissions from the use of coal briquettes6,8,10 for domestic applications, and substantial reductions in PM < 2.5 μm, elemental carbon (EC), and organic carbon (OC) have been reported. Air quality models are routinely used for estimating the impact of emissions from industries, vehicles, mines, and other Received: Revised: Accepted: Published: A

December 2, 2018 February 15, 2019 February 19, 2019 February 19, 2019 DOI: 10.1021/acs.est.8b06775 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Figure 1. Identification of different stages of the combustion cycle using the modified combustion efficiency [CO2/(CO2 + CO)] for the Varanasi stove with combined data of the two coals, CL1 and CL2.

area sources for regulatory and abatement purposes.11 While EFs are well documented for industrial and vehicle sources, they are highly variable in nature for cookstoves using solid fuels. The literature also indicates several studies of biomassbased cookstoves in the context of the use of renewable energy, while studies of coal-based cookstoves are sparse. Jetter and coworkers1 report EFs for a wide variety of biomass-based cookstoves. In a previous air quality modeling study in the coal mining area of Chandrapur,12 EFs were used from the literature. It was found that the contribution of PM emissions from coal cookstoves to ambient PM < 2.5 μm had been grossly underestimated. The underlying cause for underestimation of emissions by using the EFs reported in literature needs to be investigated by studying user practices. The laboratory cookstove standard test protocol is reported in ISO 19867-1:2018.13 Lombardi and co-workers14 have reviewed several protocols for testing cookstoves, leading to the development of protocol-specific EFs, and concluded that there is a need to improve the existing protocols to represent field conditions adequately. Field surveys in the Chandrapur region allowed us to understand the user practices for cooking. Cooking takes place twice a day, with the cookstove left outside the house for the initial high-smoke (ignition) stage (∼30 min) and then brought indoors when the visible smoke has subsided, for a cooking cycle of ∼60 min. The focus of this study was to develop EFs for two types of cookstoves prevalent in India, using coals from two different mining areas, and one type of commercially available coalbased briquette. Three stages are identified in the overall combustion cycle, namely, ignition, flaming, and smoldering. PM < 2.5 μm, CO, and EC−OC measurements were taken, and the respective EFs were developed for each of these stages. EC−OC analyses were carried out for particulate emissions (PM < 2.5 μm) using IMPROVE_A and DIN-19539 methods, and a comparison of the two protocols is presented.

from an online commercial vendor. The volatile matter levels of the CL1, CL2, and CB coal samples are 26.77, 27.60, and 24.70%, respectively, and the moisture contents are 6.64, 5.18, and 4.00%, respectively. The values of fixed carbon for CL1, CL2, and CB are 42.49, 44.72, and 44.28%, respectively, while those for ash are 24.10, 22.50, and 27.02%, respectively. The coals used from the two regions are both of sub-bituminous type (Table SI 1). Two types of natural draft domestic cookstoves are procured locally and are representative of the cooking practices prevalent in the respective regions (Figure SI 2). The Chandrapur stove, labeled as CS, is obtained from the coal mining city of Chandrapur, Maharashtra, where raw coal from the mines is used widely for cooking. It has a height of 18.5 cm and inner and outer diameters of 22 and 23 cm, respectively. The Varanasi stove, labeled as VS, is made locally in Varanasi and has a height of 22 cm, inner and outer diameters of 20 and 24 cm, respectively, a grate at a depth of 8 cm, and a 6 cm diameter hole for air supply near the bottom of the stove. It has an insulating ceramic liner that is 2 cm thick; the fuel is loaded from the top of the stove into the combustion cavity, and the ash falls through a grate into the bottom chamber of the stove. The Chandrapur stove, however, does not have such a division of spaces. Both types of cookstoves can take a batch of approximately 1 kg of coal. A summary of the stoves studied in the literature is included in Table SI 2. Design and Development of an Emission Measurement Setup. An emission measurement setup is developed as a part of this study. A schematic of it is included as Figure SI 3 and consists of a hooded duct system with a sampling configuration for PM < 2.5 μm, CO, and CO2 using sampling probes, two PM2.5 single-stage impactors, filter holders, rotameters, and a pump. Gaseous emissions are recorded in real time every minute using an electrochemical sensor for CO and a NDIR-based gas sensor for CO2. The dilution ratio in the hood is estimated to be ∼10. Emissions are well mixed within the pipe; the flow is turbulent (Re > 105), and samples are taken 12−15 duct diameters downstream of the combustion zone. The fuel charges in the VS and CS are kept as 1.1−1.2 kg. Coal is broken to a size that is typical of user practice, and a

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MATERIALS AND METHODS Fuel and Stove Type. Raw coal (fossil coal) samples are collected from two different mining areas, namely, CL1 from Western Coalfield Limited (WCL) and CL2 from Eastern Coalfield Limited (ECL). Coal briquettes (CB) are procured B

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Figure 2. PM2.5 and CO concentration measurements for different stages of the combustion cycle (ignition, flaming, and smoldering) for different fuels (CL1, CL2, and CB) and two stoves (CS and VS): (a and b) PM2.5 concentrations and (c and d) CO concentrations.

atures.17 Prior to the tests for each fuel−stove combination, several trial runs are conducted and a satisfactorily repeatable protocol is developed. Each test is started with a cold stove and is ignited with locally available wood (preweighed 0.25 kg, dimensions of 25−30 cm, sprinkled with a few drops of kerosene). The wood is ignited, and then coal and/or coal briquettes are placed on the burning wood. Combustion in a packed bed with a cold start goes through at least three distinct stages, namely, ignition, flaming, and smoldering,18 as described below. The duration of each of the combustion stages is ∼30 min as illustrated in Figure 1. After a 1.5 h combustion cycle, the unburned coal is removed and quenched with water. The unburned coal and ash are air-dried for ∼12 h and then weighed. Results are reported for each condition as an average for three successful tests, and bars are used to indicate the standard deviations.

size analysis is carried out using an image analyzer (Figure SI 4). The volume average diameter is determined to be 45 mm. The size of the coal briquettes is approximately 50 mm × 50 mm. PM is collected on 47 mm diameter glass fiber filter paper (Whatman, GF/C, catalog no. 1822047) and a quartz filter (Whatman, QMA, catalog no. 1851037) using two PM2.5 single-stage impactors (one online and the other on standby) as shown in Figure SI 3. Filters are weighed by a microbalance (resolution of 1 μg) in a clean room maintained at 25 °C and a relative humidity of 40% after desiccation for at least 48 h before and after sampling. The weight of every filter is taken as the average of three consecutive weighings if they agree within ±10 μg. EFs are determined as the mass of particulate matter emitted per unit mass of fuel used. PM samples on quartz filters are used to analyze OC and EC in the PM. The organic and elemental carbon (OC−EC) concentrations are analyzed using two protocols, (A) IMPROVE_A protocol15 and (B) DIN-19539 method,16 by a PRIMACS SNC100‑IC‑E Analyzer. An EC−OC analyzer (DRI model 2001) is used for the IMPROVE_A protocol, where a 0.5 cm2 punch from a quartz filter is submitted to volatilization at temperatures of 140 °C for OC1, 280 °C for OC2, 480 °C for OC3, and 580 °C for OC4 in a helium carrier gas and 580 °C for EC1, 740 °C for EC2, and 840 °C for EC3 in a 98% He/2% oxygen carrier gas. For the DIN-19539 analysis, the sample is heated by increasing the temperatures to 400, 600, and 900 °C, at which OC, EC, and IC are expected to combust, respectively. Emission rates and PM characteristics are influenced by many factors such as the fuel itself, the ignition method, fuel feeding practices, stove design, and combustion temper-

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RESULTS AND DISCUSSION Quantification of Emissions from Different Combustion Stages. Field observations were used to understand the cookstove user practices. Cookstoves are kept outside the house during the initial ignition stage (0.5 h), and once the smoke has subsided, this visual clue is used to bring the cookstove inside the kitchen for cooking. After the ignition stage, the flaming stage is observed, followed by the smoldering stage where the coal bed is found to be glowing with no visible flames. Several literature studies report different ignition methods, including the use of propane gas, 19 wood chips, 4,20 charcoal,21,22 electric wire,5 and paper,4 and indicate a 45− 50 min duration for ignition. In other studies, pre-ignited coal C

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Figure 3. Comparison of emission factors of carbon monoxide (CO) and PM < 2.5 μm (represented in grams per kilogram, grams indicates the grams of pollutant emitted and kilograms indicates the kilograms of fuel consumed in the entire combustion cycle) for the total combustion cycle (with ignition) and the cooking cycle. The inset box represents the range of emission factors for PM < 2.5 μm and CO reported for coal under steady state combustion conditions.

has also been used to study emissions and precludes the emissions during the ignition stage. Real time measurements for CO and CO2 were taken at 1 min resolution. Jetter and co-workers1 report the use of the modified combustion efficiency [MCE = CO2/(CO2 + CO)] as a proxy for combustion efficiency. The real time CO and CO2 data in this work were used to estimate the MCE for the VS with two coals (CL1 and CL2) and are presented in Figure 1. MCE values for other stove−fuel combinations are shown in Figure SI 5. On the basis of visual observations and the MCE for VS, three stages of the complete combustion cycle were defined for this work: (a) ignition stage, (b) flaming stage, and (c) smoldering stage. The duration of each is 30 min. Previous studies have addressed the time required for cooking of different foods. Several studies report the typical time for cooking to be 60 min.23−25 On the basis of these observations and the results for the VS in this study, two additional terms are defined as the combustion cycle (which includes all three stages) and the cooking cycle (which includes the flaming and smoldering stages), so named because the cooking activity starts after the ignition stage is complete and the cookstove is brought indoors (Figure 1). Emission characteristics from cookstoves are known to be affected by the size and temperature of the pots used for cooking.26,27 In this work, the heaped loading of coal in the cookstoves prevents placement of a pot during the ignition stage. Thus, all measurements in all three stages are taken without using a pot. Another important aspect of the cooking practice is the reuse of unburned coal, which could be as much as 35% of a single charge. The characteristics of unburned coal are different from those of raw coal and could affect the emissions in each of the three stages. For this study, however, a fresh charge of only raw coal is used, and unburned coal is not reused.

Concentration measurements for the two stoves with three fuels are presented in Figure 2. Particulate matter (PM < 2.5 μm) measurements are carried out separately for each of the three stages to quantify the relative contributions of each. The highest emissions are observed during the initial ignition stage, followed by the flaming stage and then the smoldering stage. Total emissions are calculated by summing the emissions from all three stages (30 min duration for each stage). A comparison between the emissions from the total combustion cycle and the emissions from the cooking cycle (flaming and smoldering) for all stove−fuel combinations is included in Figure SI 6. We observe that in the VS, the particulate matter emissions for the cooking cycle alone under-represent the emissions from the complete combustion cycle by a factor of 3−4. The case is similar for the CS with a factor of 4−8. Briquettes used in this study are found to have lower PM < 2.5 μm emissions than the two types of coal, while CO emissions are higher (Figure 2). However, even for the briquettes, the PM < 2.5 μm emissions are higher by a factor of 3−6 when the ignition stage is included (Figure SI 6). No such stage-specific distinction can be made for CO concentrations. Development of PM2.5 and CO Emission Factors. In this work, the particulate matter EFs for the cooking cycle are estimated to be 0.69, 1.12, and 0.90 g/kg for CL1, CL2, and CB in the CS and 2.48, 4.39, and 2.03 g/kg in the VS, respectively. The EFs for CO are estimated to be 34.97, 42.37, and 96.32 g/kg for CL1, CL2, and CB in the VS and 72.53, 88.40, and 148.29 g/kg in the CS, respectively. The PM < 2.5 μm EFs for the complete combustion cycle for CS using CL1, CL2, and CB are found to be 6.52, 8.03, and 5.08 g/kg, respectively, and for the VS for CL1, CL2, and CB, they are found to be 13.64, 10.82, and 5.70 g/kg, respectively. CO EFs for the complete combustion cycle for CL1, CL2, and CB are estimated to be 72.82, 80.53, and 145.42 for the CS and 46.08, D

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Figure 4. We observed that OC is the more dominant fraction during the initial stage of the combustion cycle in all stove−

50.98, and 88.22 for the VS, respectively. These results are summarized in Table SI 3. The results of this study are compared with those from previous studies of emission factors. Simultaneously estimated EFs for PM < 2.5 μm and CO have been reported for biomass and charcoal by Jetter and co-workers1 and are plotted in Figure 3. In the absence of data from any single study that reports both PM < 2.5 μm and CO for coal stoves, ranges of data from studies in which these are reported independently are plotted as an inset box in Figure 3. The carbon monoxide EFs are taken from Zhang and co-workers28 for various coal and/or coal-based fuels with different stove combinations and varied from 18 to 170 g/kg. The PM < 2.5 μm EFs are taken from studies using raw anthracite coal,10,19,20 bituminous coal,6,10,20 and coal briquettes.6,10,20 The range of PM < 2.5 μm varies from 0.098 to 4.25 g/kg. The CO emissions from charcoal are higher than the range reported for coal in the inset box, while PM < 2.5 μm emissions for both coal and biomass are found within the inset box. The PM < 2.5 μm and CO EFs are plotted in Figure 3 for two cases, namely, (a) the complete combustion cycle and (b) only the cooking cycle. The latter is comparable with the ranges within the inset box as well as the results presented by Jetter and co-workers,1 both of which are similar to case b, that is, they do not include emissions from the ignition stage. Comparison of EFs of the complete combustion cycle in this study with the EFs reported in the literature indicates that the ignition stage emissions may have not been included. The difference between the two is on the order of 5−9 times for PM < 2.5 μm, which is significant from the perspective of the impact of these cookstoves on ambient air pollution. Thus, adoption of emission factors that include emissions for the entire combustion cycle, that is, including the ignition stage instead of just the cooking cycle, is suggested for a better representation of emissions from coal cookstoves. In addition, specifically for the purpose of reducing emissions using CB as an alternative, this work indicates a reduction in PM < 2.5 μm emissions. By contrast, CO concentrations are observed to be relatively higher for briquettes for both the combustion cycle and the cooking cycle, for both stoves (Figure 3). Coal briquettes were found to be cleaner, with EFs for the entire combustion cycle for both stove combinations being 5.08−5.70 g/kg for PM < 2.5 μm. For the VS, a decrease in emissions of almost 50−60% via the use of coal briquettes was observed. However, in the case of the CS, this decrease was not as large and varied from 15 to 35%. Further work is required for the development of recipes and the possible utilization of coal wastes from mines locally, which could also aid in the alleviation of ambient air pollution. The methodology and outcomes of the study may be used for other regions of the country with region-specific fuels and local cookstove designs. Emission Factors for Elemental Carbon and Organic Carbon. The relative proportions of EC and OC in the total carbon (TC) in PM < 2.5 μm change with different stove−fuel combinations. Atiku and co-workers18 in their study reported that the values of the EC/TC ratios for wood logs, torrefied briquettes, coal, and smokeless fuel are highly dependent on burning conditions, namely, the flaming and smoldering stages. Zhang and co-workers25 reported 6.4/48.7 EC/OC ratio as a percentage of PM < 2.5. The results of our EC and OC analyses for PM < 2.5 μm samples using the IMPROVE_A protocol are presented in

Figure 4. EC and OC fractions of PM < 2.5 μm for the two cookstoves and three fuels: (a) CL1, (b) CL2, and (c) CB. The proportions of EC−OC in three stages of the complete combustion cycle are delineated to indicate relative contributions. The analysis is limited to only one sample set of the total triplicate sample. The total mass is indicated in milligrams above the respective bars: (spotted bars) organic carbon, (gray bars) elemental carbon, and (white bars) others.

fuel combinations. For CB, the OC fraction decreases after the ignition stage and EC becomes dominant during the flaming and smoldering stage in both stoves. For CB, the EC and OC fractions are 8 and 31% for the VS and 12 and 30% for the CS, respectively. This is comparable with the results of Zhang and co-workers.25 For CL1, the EC and OC for the VS are 22 and 49%, respectively, while the EC and OC for the CS are 30 and 40%, respectively. Similarly, for CL2 for the two stoves, the EC E

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Figure 5. Elemental and organic carbon emissions for all of the stove−fuel combinations determined for cooking and combustion cycles by the IMPROVE_A protocol. Data from ref 8 are included for comparison.

Figure 6. Comparison of IMPROVE_A and DIN protocols for (a) organic carbon (OC) and (b) elemental carbon (EC).

EFs are 1.40−4.16 and 0.11−0.33 g/kg for the combustion and cooking cycles, respectively. Intercomparison of Two Thermo-Optical Instruments for EC−OC Analysis. In addition to the EC−OC analysis for PM < 2.5 μm carried out using the IMPROVE_A protocol, a parallel effort is made using the DIN-19539 protocol. The latter is known to be used for determination of carbon content in soil samples.31 A comparison of the results of EC−OC for the two protocols is shown in Figure 6. A strong correlation is observed between the two protocols for both OC and EC. In the absence of any available literature for the DIN-19539 protocol being used for particulate emissions, it is not possible to compare these results with those of any previous work. When compared with those for IMPROVE_A, facilities for the DIN-19539 method are often more readily available in soil

and OC are 17 and 48% for the VS and 28 and 44% for the CS, respectively. The noncarbonaceous component, labeled as “others” in Figure 4, is largely inorganic matter and ranges from levels that are negligible to as much as 93%. Detailed source profiles for cookstoves with biomass and coal have been reported in the literature.25,29,30 In addition, the EFs for EC and OC for this study are estimated and are shown in Figure 5. For the VS, EC varies from 0.43 to 1.94 g/kg for the complete combustion cycle. Cooking cycle EC EFs vary from 0.02 to 1.10 g/kg. Combustion cycle and cooking cycle EC EFs for the CS vary from 0.56 to 2.71 g/kg and from 0.001 to 0.49 g/kg, respectively. The OC EFs estimated for the complete and cooking cycles for the VS are 1.64−4.99 and 0.31−2.42 g/kg, respectively. Similarly, for the CS, the estimated values of OC F

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database for emission factors. Atmos. Environ. 2000, 34 (26), 4537− 4549. (8) Zhi, G.; Chen, Y.; Feng, Y.; Xiong, S.; Li, J.; Zhang, G.; Sheng, G.; Fu, J. Emission characteristics of carbonaceous particles from various residential coal-stoves in China. Environ. Sci. Technol. 2008, 42 (9), 3310−3315. (9) https://www.ipcc.ch/sr15/. (10) Zhang, Y.; Schauer, J. J.; Zhang, Y.; Zeng, L.; Wei, Y.; Liu, Y.; Shao, M. Characteristics of particulate carbon emissions from realworld Chinese coal combustion. Environ. Sci. Technol. 2008, 42 (14), 5068−5073. (11) Gibson, M. D.; Kundu, S.; Satish, M. Dispersion model evaluation of PM2.5, NOx and SO2 from point and major line sources in Nova Scotia, Canada using AERMOD Gaussian plume air dispersion model. Atmos. Pollut. Res. 2013, 4 (2), 157−167. (12) Bojjagani, S. Investigation towards a Pragmatic Approach for Air Quality Assessment in an Industrial Region: ChandrapurA Case Study. Ph.D. Thesis, IIT Bombay, Mumbai, India, 2016. (13) https://www.iso.org/obp/ui/#iso:std:iso:19867:-1:ed-1:v1:en. (14) Lombardi, F.; Riva, F.; Bonamini, G.; Barbieri, J.; Colombo, E. Laboratory protocols for testing of Improved Cooking Stoves (ICSs): A review of state-of-the-art and further developments. Biomass Bioenergy 2017, 98, 321−335. (15) http://vista.cira.colostate.edu/improve/publications/SOPs/ DRI_SOPs/2005/2-216r1_IMPROVEA_20051115.pdf. (16) https://www.skalar.com/news/determination-of-differentcarbon-species-according-to-din-19539-method-a-and-b. (17) Roden, C. A.; Bond, T. C.; Conway, S.; Pinel, A. B. O. Emission factors and real-time optical properties of particles emitted from traditional wood burning cookstoves. Environ. Sci. Technol. 2006, 40 (21), 6750−6757. (18) Atiku, F. A.; Mitchell, E. J. S.; Lea-Langton, A. R.; Jones, J. M.; Williams, A.; Bartle, K. D. The Impact of Fuel Properties on the Composition of Soot Produced by the Combustion of Residential Solid Fuels in a Domestic Stove. Fuel Process. Technol. 2016, 151, 117−125. (19) Qi, J.; Li, Q.; Wu, J.; Jiang, J.; Miao, Z.; Li, D. Biocoal briquettes combusted in a household cooking stove: improved thermal efficiencies and reduced pollutant emissions. Environ. Sci. Technol. 2017, 51 (3), 1886−1892. (20) Chen, Y.; Tian, C.; Feng, Y.; Zhi, G.; Li, J.; Zhang, G. Measurements of emission factors of PM2.5, OC, EC, and BC for household stoves of coal combustion in China. Atmos. Environ. 2015, 109, 190−196. (21) Chen, Y.; Sheng, G.; Bi, X.; Feng, Y.; Mai, B.; Fu, J. Emission factors for carbonaceous particles and polycyclic aromatic hydrocarbons from residential coal combustion in China. Environ. Sci. Technol. 2005, 39 (6), 1861−1867. (22) Chen, Y.; Zhi, G.; Feng, Y.; Liu, D.; Zhang, G.; Li, J.; Sheng, G.; Fu, J. Measurements of black and organic carbon emission factors for household coal combustion in China: implication for emission reduction. Environ. Sci. Technol. 2009, 43 (24), 9495−9500. (23) Arora, P.; Jain, S.; Sachdeva, K. Laboratory based assessment of cookstove performance using energy and emission parameters for North Indian cooking cycle. Biomass Bioenergy 2014, 69, 211−221. (24) Mukunda, H. S.; Dassapa, S.; Paul, P. J.; Rajan, N K S.; Yagnaraman, M.; Kumar, D. R.; Deogaonkar, M. Gasifier stoves: Science Technology and field outreach. Curr. Sci. 2010, 98 (5), 627− 638. (25) Zhang, H.; Wang, S.; Hao, J.; Wan, L.; Jiang, J.; Zhang, M.; Mestl, H. E.; Alnes, L. W.; Aunan, K.; Mellouki, A. W. Chemical and size characterization of particles emitted from the burning of coal and wood in rural households in Guizhou, China. Atmos. Environ. 2012, 51, 94−99. (26) L’Orange, C.; Volckens, J.; DeFoort, M. Influence of stove type and cooking pot temperature on particulate matter emissions from biomass cook stoves. Energy Sustainable Dev. 2012, 16 (4), 448−455. (27) https://cleancookstoves.org/binary-data/DOCUMENT/file/ 000/000/399-1.pdf.

analysis laboratories in India, and thus, similar quantification of EC−OC may be carried out in such laboratories.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.8b06775.

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Figures that provide further information about the geographical distribution of coal as a domestic fuel in India, photographs of the stoves and fuels, a schematic of the experimental setup, the size distribution of the coal used, and MCEs based on 1 min resolution measurements of CO and CO2 for all of the stove−fuel combinations and tables that include details of proximate analysis and ultimate analysis, a comparison of cookstoves reported in the literature with those used in this study, and compilations of emissions data (PDF)

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Darpan Das: 0000-0001-9830-7323 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge Professor Shireesh Kedare and Professor Srinivas Seethamraju for the use of the Kitchen Laboratory (Department of Energy Science and Engineering, IIT Bombay). The authors also acknowledge Dr. Rakesh Kumar, Er (Mrs.) Padma Rao, and Mr. Navneet Kumar from the National Environmental Engineering Research Institute and Dr. Sanjay Sahu and Mr. Tejas Rathod from the Bhabha Atomic Research Centre for their assistance with EC−OC analyses. Financial support for this project was provided by the Maharashtra Pollution Control Board.

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REFERENCES

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DOI: 10.1021/acs.est.8b06775 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.est.8b06775 Environ. Sci. Technol. XXXX, XXX, XXX−XXX