- Email: [email protected]
Test Kitchen studies of indoor air pollution from biomass cookstoves
Energy for Sustainable Development 17 (2013) 458–462
Contents lists available at ScienceDirect
Energy for Sustainable Development
Test Kitchen studies of indoor air pollution from biomass cookstoves Kelley Grabow, Dean Still ⁎, Sam Bentson Aprovecho Research Center, 79093 Highway 99, Cottage Grove, OR 97424, USA
a r t i c l e
i n f o
Article history: Received 8 May 2013 Accepted 9 May 2013 Available online 28 May 2013 Keywords: Air exchange rate Biomass fuel Indoor air pollution Ventilation Cookstoves Test Kitchen Water boiling test
a b s t r a c t Indoor air pollution from biomass cookstoves seriously affects human health worldwide. This study investigated the effect of increasing air exchange rates in a Test Kitchen. Opening the door and window in a Test Kitchen lowered the particulate matter (PM) 1-hour concentrations between 93 and 98% compared to the closed kitchen, and the carbon monoxide (CO) 1-hour concentrations were 83 to 95% lower. © 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved.
Introduction Approximately 3 billion people worldwide rely on the combustion of solid biomass fuels for heat and cooking (Rehfuess et al., 2006). It is well established that the incomplete combustion of biomass can emit high levels of PM and CO (Bhattacharya et al., 2002; Naeher et al., 2007). These pollutants are known to contribute to adverse health effects (USEPA, 2009; WHO, 2000). Moreover, when activities such as cooking are performed inside the home, high levels of indoor air pollution (IAP), which contains CO and PM, can accumulate in frequently occupied spaces including the kitchen. Women and children are especially vulnerable to the dangers of IAP due to time spent indoors and age-related susceptibility (Smith et al., 2009). A review of the literature reveals that a great deal of attention has been devoted to solving the problem of IAP through the introduction of more efficient and cleaner improved cook stoves (ICSs) (Adkins et al., 2010; Li et al., 2011; Smith et al., 2009). However, only some attention has been paid to lower-cost interventions such as ventilation (Barnes et al., 2006; Bates, 2005; Bhangar, 2006; Dasgupta et al., 2004), and often ventilation is only considered in conjunction with ICSs. This study examines the effect of changes in kitchen ventilation arrangements on lowering levels of CO and PM in a Test Kitchen. Air exchange rates were calculated using a method similar to that used in Bhangar et al. for 10 homes using traditional stoves in Kaldari,
⁎ Corresponding author. Tel.: +1 541 767 0287. E-mail address: [email protected] (D. Still). URL: http://www.aprovecho.org (D. Still).
India. Mean Air Exchange Rate (AER) was found to be 15.8 ± 4.04 h−1 and mean 1-hour CO concentration was 23.8 ± 11.87 ppm.1 Material and methods Equipment All emissions data were acquired using the Aprovecho Research Center manufactured Indoor Air Pollution Meter (IAP Meter), which uses a light scattering-based PM sensor and an electrochemical cell based CO sensor (Aprovecho Research Center, 2011). The CO sensor is calibrated against a reference gas of a known concentration. The PM sensor is calibrated against an identical Aprovecho IAP meter, which is treated as a reference. The reference meter is calibrated against a Radiance Research Nephelometer. Work is ongoing at Aprovecho to complete a gravimetric calibration of the PM sensor using wood smoke as the standard aerosol. Either a Fluke 52 II or a UEI DT-150 thermometer was used. An Acculab digital balance measured pot, stove, and water masses. Testing location Tests were performed in the 24.6 m3 Aprovecho Research Center Test Kitchen (Diagram 1). The door, window, and hole in the roof could all be opened and closed. The mesh vent to the right of the door remained open at all times. All stoves were tested under the 1
C.I., 95% was calculated for consistency with the data presented in this paper.
0973-0826/$ – see front matter © 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.esd.2013.05.003
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462
459
Fig. 1. Mean PM concentrations by stove in Test Kitchen.
hole in the roof on a bench raised 62 cm from the ground. The room was built using construction techniques commonly found in the United States: a square frame of dimensionally cut lumber, both sides of which are covered in sheets of oriented strand board (OSB), with spun fiberglass insulation between the two sheets. The distance between the two sheets of wood was 3.5″.
The initial and ending times were selected during the region of exponential decay in the concentration graph. The Basic Room Purge Equation is
Calculations
where
Air exchange rates were determined by burning a set amount of charcoal in the Test Kitchen for each ventilation arrangement. The charcoal was burned in a pile on a flat tray. Charcoal was used instead of wood because it has a more consistent emissions profile that does not require user control. The IAP Meter collected 10 min of background before the charcoal was placed in the kitchen. After 20 min, the charcoal was quickly removed, and the meter was run for 60 more minutes. The Basic Room Purge Equation was applied to CO concentrations to calculate air exchange rates (reported in air changes per hour, or ACHs).
Dt V Q Cinitial Cending
# " V C initial Dt ¼ ⋅ ln Q C ending
Time elapsed (h) Volume of room (m3) Flow rate of air through room (m3/h) Initial CO concentration in room (ppm) Ending CO concentration in room (ppm)
which is solved for the quotient V / Q to determine ACH. Firepower, which was reported as a parameter of stove operation, was calculated using the method found in WBT4.2.1 (2013).
Fig. 2. Mean CO concentrations by stove in Test Kitchen.
Fig. 3. Mean firepower (Watts).
460
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462
Photograph 2. StoveTec two door rocket stove with pot skirt.
Diagram 1. Test Kitchen interior dimensions.
Results and analysis
Three stoves were tested: the three stone fire (TSF), a rocket stove, and a top-lit updraft (TLUD) stove (Photographs 1–3). The TSF is the most common household stove among the poorest people worldwide. It is the baseline stove. The rocket stove is an improved stove type that is in widespread use around the world. A StoveTec rocket stove was used in these tests. The TLUD is a promising new technology from an air quality perspective, but one that has not been heavily marketed. At the start of each test, the IAP meter was suspended in the Test Kitchen 0.6 m vertically and 0.6 m horizontally from the center of the stove. This position was chosen to approximate the location of a cook's nose and mouth relative to the stove. Both the TSF and the rocket stove were fueled by Douglas-fir sticks. The TLUD used Douglas-fir wood pellets. Further information on fuel and lighting may be seen in Table A1 in the Appendix A. All stoves were lit inside the Test Kitchen. The water was brought to a boil as quickly as possible, and then the water was simmered for 30 min. A pot skirt included with the stove was used with the rocket stove. The modified water boiling test (WBT) was used instead of a more realistic controlled cooking test (CCT) to achieve less variation in the results so that reporting could be done at a higher degree of confidence.
Table 1 presents the air exchange rates of the Test Kitchen. Fig. 1 shows the average recorded PM concentrations, measured in μg/m3, for each stove and ventilation setup, and Fig. 2 shows CO in ppm. Fig. 3 shows average firepower for each stove. Opening the hole in the roof caused an insignificant change in measurable air exchanges, but that change in ventilation significantly lowered the pollution concentrations at 95% confidence. All figures and tables show the data with a 95% confidence interval. Data were analyzed using the software package Statistical Analysis Systems (SAS®) version 9.2. Two-way analyses of variance were conducted separately for PM and CO levels, with three stoves (TSF, rocket stove, and TLUD) and four ventilation conditions (closed kitchen, hole in roof open, door open, and door and window open) as the two factors. The Scheffé test was used first, as opposed to a series of t-tests, to analyze the data simultaneously since for multiple comparisons the Scheffé test conservatively deals with compounding Type I errors (Cohen et al., 2003). The t-test was used in cases where the Scheffé test was suspected to be too conservative, the results of which are shown in Table 3. Table 2 shows the results of the Scheffé test. Post hoc analyses using the Scheffé test found that the open fire operated in a closed room emitted the highest levels of PM. the rocket stove in a closed room and the TSF with a hole in the roof emitted significantly less PM, but did not differ significantly from each other.
Photograph 1. Three stone fire (TSF).
Photograph 3. Aprovecho Patio TLUD stove.
Method
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462 Table 1 Air exchange rates.
Closed kitchen Hole in roof open Door open Door & window open
Average ACHs (1/h)
CI, 95%
N
3.2 3.9 8.6 12.8
1.3 0.6 1.0 1.2
6 3 3 3
These three conditions emitted significantly more PM than all other conditions, which did not differ significantly among themselves. From the t-tests it was determined that the TLUD with the door open resulted in significantly less PM than the rocket stove with the door open, and that the TLUD with the door opened had lower emissions than the TLUD with only the roof open. In general increasing the ventilation from the closed condition to the door and window open condition resulted in a 98% reduction in PM concentration for each stove type. From the Scheffé test it was determined that three of the test conditions had the highest CO emissions, not differing from one another. These included the open fire in either the closed room or with the ceiling hole open, and the rocket stove with the hole in the roof open. Again, these three conditions resulted in significantly more CO than the remaining conditions, which did not differ significantly with each other. From the t-tests it was determined that, similar to the PM results, the TLUD with the door open created significantly less CO than the rocket stove with the door open, and that the TLUD in the room with the door open also performed significantly better than the TLUD in the room with only the roof hole open. The rocket stove with the door open performed significantly better than the TLUD with the roof open. In general increasing the ventilation from the closed condition to the door and window open condition resulted in an 89% reduction in CO concentrations for the TSF, and a 96% reduction for the rocket stove and TLUD. Discussion The IAP meter uses a light scattering based PM sensor. Aprovecho is conducting research to calibrate the meter against a gravimetric system. In general light scattering sensors respond similarly to similar types of smoke, but are thought to mask differences when differing types of smoke are emitted. A follow-up study will be carried out in which PM concentrations in the room are measured simultaneously with gravimetric and light scattering based methods. One could expect the relationship between the ventilation conditions found here
461
Table 3 Comparison of mean PM & CO concentrations by stove and ventilation that pass t-test at 95% confidence. PM (μg/m3) TLUD door open TLUD door open
CO (ppm) TLUD door open TLUD door open Rocket door open
54 (N 54 (N
± 44 = 3) ± 44 = 3)
TLUD hole in roof open
4 ± 0.3 (N = 3) 4 ± 0.3 (N = 3) 31 ± 10 (N = 3)
TLUD hole in roof open
Rocket door open
Rocket door open TLUD hole in roof open
1988 ± 1502 (N = 9) 973 ± 116 (N = 3)
67 (N 31 (N 67 (N
± 23 = 9) ± 10 = 3) ± 23 = 9)
to be the same for the gravimetric study, but it may be that the gravimetric relationship for the levels of PM between the three types of stoves will be different. It is important to note that pollutant concentrations do not equate to levels of personal exposure. However, the IAP meter was placed at a position that approximates where a cook might be while cooking food. It is hoped that the data can be used to approximate personal exposure.
Conclusion Increasing ventilation by opening a window or door was found to have a dramatic impact on lowering the levels of CO and PM in a Test Kitchen. For any of the three stoves tested, opening the door and window in the Test Kitchen increased the ACH and contributed to a decrease in 1-hour PM concentrations of 97 to 98% and a decrease in 1-hour CO concentrations of 89 to 96% compared to the closed Test Kitchen condition. Increasing ACH seems to be a successful method for cooks using biomass fires to experience cleaner room air benefits. The cleaner combustion in the TLUD coupled with opening the door and window in the Test Kitchen resulted in a combination that reduced IAP by 90%, which is the aspirational requirement used currently by the United States Department of Energy.
Acknowledgments The authors wish to thank Dr. George Howe, and Dr. James Schaper for their assistance with statistical analysis.
Table 2 Mean PM & CO concentrations by stove and ventilation, with Scheffé test results.
PM (μg/m3) TSF Rocket TLUD
CO (ppm) TSF Rocket TLUD
Closed
Scheffé test grouping
Hole in roof open
Scheffé test grouping
Door open
Scheffé test grouping
Door & window open
Scheffé test grouping
24,922 ± 1900 (N = 9) 13,041 ± 7061 (N = 4) 2806 ± 2501 (N = 5)
3
7866 ± 292 (N = 3) 3439 ± 5753 (N = 3) 1988 ± 1502 (N = 9)
2
1145 ± 2030 (N = 3) 973 ± 116 (N = 3) 54 ± 44 (N = 3)
1
631 ± 520 (N = 3) 349 ± 827 (N = 3) 46 ± 24 (N = 3)
1
256 ± 10 (N = 9) 177 ± 63 (N = 5) 79 ± 56 (N = 5)
2 1
2 2 1
182 ± 50 (N = 3) 61 ± 56 (N = 3) 67 ± 23 (N = 9)
1 1
2 1 1
43 ± 71 (N = 3) 31 ± 10 (N = 3) 4 ± 0.3 (N = 3)
1 1
1 1 1
27 ± 26 (N = 3) 8 ± 21 (N = 3) 3±2 (N = 3)
1 1
1 1 1
Note: Means with different Scheffé test groupings differ significantly on Scheffé tests. Confidence intervals are with p = 0.05. In some cases the confidence interval is so large that the minimum value appears negative. In these cases the negative values should be interpreted as zero.
462
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462
Appendix A
Table A1 Fuel and cookstove characteristics. Fuel
Douglas-fir sticks
Dimensions
1 cm × 2 cm, various lengths 10% 20,634 kJ/kg Newspaper and Douglas-fir splinters TSF & rocket stove
Moisture content Gross calorific value Kindling Cookstove
Golden Fire Douglas-fir pellets 0.5 cm diameter × 1 cm length 10% 19,832 kJ/kg Sunnyside brand kerosene TLUD stove
References Adkins E, Tyler E, Wang J, Siriri D, Modi V. Field testing and survey evaluation of household biomass cookstoves in rural sub-Saharan Africa. Energy Sustain Dev 2010;14(3):172–85. Aprovecho Research Center. http://www.aprovecho.org/lab/emissionsequip/iap-meter. [accessed 17 October 2011]. Barnes B, Mathee A, Bruce N, Bates L. Protecting children from indoor air pollution exposure through outdoor cooking in rural South Africa. Boiling Point 2006;52: 11–3.
Bates L, Bates L. Smoke-reduction technologies in developing countries. Proc Inst Civ Eng Munic Eng 2005;158(ME2):137–43. Bhangar S. Indoor air quality of households with improved and traditional stoves in Kaldari, India. Health, environment and development. Berkeley: University of California; 2006. Bhattacharya S, Albina D, Abdul Salam P. Emission factors of wood and charcoal-fired cookstoves. Biomass Bioenergy 2002;23(6):453–69. Cohen J, Cohen P, West S, Aiken L. Applied multiple regression/correlation analysis for the behavioral sciences. 3rd ed. New Jersey: Lawrence Erlbaum Associates, Inc.; 2003184–5. Dasgupta S, Huq M, Khaliquzzaman M, Pandey K, Wheeler D. Indoor air quality for poor families: new evidence from Bangladesh. World Bank policy research working paper; 2004. Li Z, Sjödin A, Romanoff L, Horton K, Fitzgerald C, Eppler A, et al. Evaluation of exposure reduction to indoor air pollution in stove intervention projects in Peru by urinary biomonitoring of polycyclic aromatic hydrocarbon metabolites. Environ Int 2011. Naeher L, Brauer M, Lipsett M, Zelikoff J, Simpson C, Koenig J, et al. Woodsmoke health effects: a review. Inhal Toxicol 2007;19(1):67–106. Rehfuess E, Mehta S, Prüss-Üstün A. Assessing household solid fuel use: multiple implications for the millennium development goals. Environ Health Perspect 2006;114: 373–8. Smith K, McCracken J, Thompson L, Edwards R, Shields K, Canuz E, et al. Personal child and mother carbon monoxide exposures and kitchen levels: methods and results from a randomized trial of woodfired chimney cookstoves in Guatemala (RESPIRE). J Expo Sci Environ Epidemiol 2009:1–11. U.S. EPA. Integrated science assessment for particulate matter (final report). Washington, DC: U.S. Environmental Protection Agency; 2009 [EPA/600/R-08/139F]. WBT 4.2.1. Global alliance for clean cookstoves. http://community.cleancookstoves. org/files/357, 2013. [accessed April 3, 2013]. World Health Organization. Air quality guidelines for Europe. WHO regional publications, European series2nd ed. ; 20001–273.
Contents lists available at ScienceDirect
Energy for Sustainable Development
Test Kitchen studies of indoor air pollution from biomass cookstoves Kelley Grabow, Dean Still ⁎, Sam Bentson Aprovecho Research Center, 79093 Highway 99, Cottage Grove, OR 97424, USA
a r t i c l e
i n f o
Article history: Received 8 May 2013 Accepted 9 May 2013 Available online 28 May 2013 Keywords: Air exchange rate Biomass fuel Indoor air pollution Ventilation Cookstoves Test Kitchen Water boiling test
a b s t r a c t Indoor air pollution from biomass cookstoves seriously affects human health worldwide. This study investigated the effect of increasing air exchange rates in a Test Kitchen. Opening the door and window in a Test Kitchen lowered the particulate matter (PM) 1-hour concentrations between 93 and 98% compared to the closed kitchen, and the carbon monoxide (CO) 1-hour concentrations were 83 to 95% lower. © 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved.
Introduction Approximately 3 billion people worldwide rely on the combustion of solid biomass fuels for heat and cooking (Rehfuess et al., 2006). It is well established that the incomplete combustion of biomass can emit high levels of PM and CO (Bhattacharya et al., 2002; Naeher et al., 2007). These pollutants are known to contribute to adverse health effects (USEPA, 2009; WHO, 2000). Moreover, when activities such as cooking are performed inside the home, high levels of indoor air pollution (IAP), which contains CO and PM, can accumulate in frequently occupied spaces including the kitchen. Women and children are especially vulnerable to the dangers of IAP due to time spent indoors and age-related susceptibility (Smith et al., 2009). A review of the literature reveals that a great deal of attention has been devoted to solving the problem of IAP through the introduction of more efficient and cleaner improved cook stoves (ICSs) (Adkins et al., 2010; Li et al., 2011; Smith et al., 2009). However, only some attention has been paid to lower-cost interventions such as ventilation (Barnes et al., 2006; Bates, 2005; Bhangar, 2006; Dasgupta et al., 2004), and often ventilation is only considered in conjunction with ICSs. This study examines the effect of changes in kitchen ventilation arrangements on lowering levels of CO and PM in a Test Kitchen. Air exchange rates were calculated using a method similar to that used in Bhangar et al. for 10 homes using traditional stoves in Kaldari,
⁎ Corresponding author. Tel.: +1 541 767 0287. E-mail address: [email protected] (D. Still). URL: http://www.aprovecho.org (D. Still).
India. Mean Air Exchange Rate (AER) was found to be 15.8 ± 4.04 h−1 and mean 1-hour CO concentration was 23.8 ± 11.87 ppm.1 Material and methods Equipment All emissions data were acquired using the Aprovecho Research Center manufactured Indoor Air Pollution Meter (IAP Meter), which uses a light scattering-based PM sensor and an electrochemical cell based CO sensor (Aprovecho Research Center, 2011). The CO sensor is calibrated against a reference gas of a known concentration. The PM sensor is calibrated against an identical Aprovecho IAP meter, which is treated as a reference. The reference meter is calibrated against a Radiance Research Nephelometer. Work is ongoing at Aprovecho to complete a gravimetric calibration of the PM sensor using wood smoke as the standard aerosol. Either a Fluke 52 II or a UEI DT-150 thermometer was used. An Acculab digital balance measured pot, stove, and water masses. Testing location Tests were performed in the 24.6 m3 Aprovecho Research Center Test Kitchen (Diagram 1). The door, window, and hole in the roof could all be opened and closed. The mesh vent to the right of the door remained open at all times. All stoves were tested under the 1
C.I., 95% was calculated for consistency with the data presented in this paper.
0973-0826/$ – see front matter © 2013 International Energy Initiative. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.esd.2013.05.003
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462
459
Fig. 1. Mean PM concentrations by stove in Test Kitchen.
hole in the roof on a bench raised 62 cm from the ground. The room was built using construction techniques commonly found in the United States: a square frame of dimensionally cut lumber, both sides of which are covered in sheets of oriented strand board (OSB), with spun fiberglass insulation between the two sheets. The distance between the two sheets of wood was 3.5″.
The initial and ending times were selected during the region of exponential decay in the concentration graph. The Basic Room Purge Equation is
Calculations
where
Air exchange rates were determined by burning a set amount of charcoal in the Test Kitchen for each ventilation arrangement. The charcoal was burned in a pile on a flat tray. Charcoal was used instead of wood because it has a more consistent emissions profile that does not require user control. The IAP Meter collected 10 min of background before the charcoal was placed in the kitchen. After 20 min, the charcoal was quickly removed, and the meter was run for 60 more minutes. The Basic Room Purge Equation was applied to CO concentrations to calculate air exchange rates (reported in air changes per hour, or ACHs).
Dt V Q Cinitial Cending
# " V C initial Dt ¼ ⋅ ln Q C ending
Time elapsed (h) Volume of room (m3) Flow rate of air through room (m3/h) Initial CO concentration in room (ppm) Ending CO concentration in room (ppm)
which is solved for the quotient V / Q to determine ACH. Firepower, which was reported as a parameter of stove operation, was calculated using the method found in WBT4.2.1 (2013).
Fig. 2. Mean CO concentrations by stove in Test Kitchen.
Fig. 3. Mean firepower (Watts).
460
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462
Photograph 2. StoveTec two door rocket stove with pot skirt.
Diagram 1. Test Kitchen interior dimensions.
Results and analysis
Three stoves were tested: the three stone fire (TSF), a rocket stove, and a top-lit updraft (TLUD) stove (Photographs 1–3). The TSF is the most common household stove among the poorest people worldwide. It is the baseline stove. The rocket stove is an improved stove type that is in widespread use around the world. A StoveTec rocket stove was used in these tests. The TLUD is a promising new technology from an air quality perspective, but one that has not been heavily marketed. At the start of each test, the IAP meter was suspended in the Test Kitchen 0.6 m vertically and 0.6 m horizontally from the center of the stove. This position was chosen to approximate the location of a cook's nose and mouth relative to the stove. Both the TSF and the rocket stove were fueled by Douglas-fir sticks. The TLUD used Douglas-fir wood pellets. Further information on fuel and lighting may be seen in Table A1 in the Appendix A. All stoves were lit inside the Test Kitchen. The water was brought to a boil as quickly as possible, and then the water was simmered for 30 min. A pot skirt included with the stove was used with the rocket stove. The modified water boiling test (WBT) was used instead of a more realistic controlled cooking test (CCT) to achieve less variation in the results so that reporting could be done at a higher degree of confidence.
Table 1 presents the air exchange rates of the Test Kitchen. Fig. 1 shows the average recorded PM concentrations, measured in μg/m3, for each stove and ventilation setup, and Fig. 2 shows CO in ppm. Fig. 3 shows average firepower for each stove. Opening the hole in the roof caused an insignificant change in measurable air exchanges, but that change in ventilation significantly lowered the pollution concentrations at 95% confidence. All figures and tables show the data with a 95% confidence interval. Data were analyzed using the software package Statistical Analysis Systems (SAS®) version 9.2. Two-way analyses of variance were conducted separately for PM and CO levels, with three stoves (TSF, rocket stove, and TLUD) and four ventilation conditions (closed kitchen, hole in roof open, door open, and door and window open) as the two factors. The Scheffé test was used first, as opposed to a series of t-tests, to analyze the data simultaneously since for multiple comparisons the Scheffé test conservatively deals with compounding Type I errors (Cohen et al., 2003). The t-test was used in cases where the Scheffé test was suspected to be too conservative, the results of which are shown in Table 3. Table 2 shows the results of the Scheffé test. Post hoc analyses using the Scheffé test found that the open fire operated in a closed room emitted the highest levels of PM. the rocket stove in a closed room and the TSF with a hole in the roof emitted significantly less PM, but did not differ significantly from each other.
Photograph 1. Three stone fire (TSF).
Photograph 3. Aprovecho Patio TLUD stove.
Method
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462 Table 1 Air exchange rates.
Closed kitchen Hole in roof open Door open Door & window open
Average ACHs (1/h)
CI, 95%
N
3.2 3.9 8.6 12.8
1.3 0.6 1.0 1.2
6 3 3 3
These three conditions emitted significantly more PM than all other conditions, which did not differ significantly among themselves. From the t-tests it was determined that the TLUD with the door open resulted in significantly less PM than the rocket stove with the door open, and that the TLUD with the door opened had lower emissions than the TLUD with only the roof open. In general increasing the ventilation from the closed condition to the door and window open condition resulted in a 98% reduction in PM concentration for each stove type. From the Scheffé test it was determined that three of the test conditions had the highest CO emissions, not differing from one another. These included the open fire in either the closed room or with the ceiling hole open, and the rocket stove with the hole in the roof open. Again, these three conditions resulted in significantly more CO than the remaining conditions, which did not differ significantly with each other. From the t-tests it was determined that, similar to the PM results, the TLUD with the door open created significantly less CO than the rocket stove with the door open, and that the TLUD in the room with the door open also performed significantly better than the TLUD in the room with only the roof hole open. The rocket stove with the door open performed significantly better than the TLUD with the roof open. In general increasing the ventilation from the closed condition to the door and window open condition resulted in an 89% reduction in CO concentrations for the TSF, and a 96% reduction for the rocket stove and TLUD. Discussion The IAP meter uses a light scattering based PM sensor. Aprovecho is conducting research to calibrate the meter against a gravimetric system. In general light scattering sensors respond similarly to similar types of smoke, but are thought to mask differences when differing types of smoke are emitted. A follow-up study will be carried out in which PM concentrations in the room are measured simultaneously with gravimetric and light scattering based methods. One could expect the relationship between the ventilation conditions found here
461
Table 3 Comparison of mean PM & CO concentrations by stove and ventilation that pass t-test at 95% confidence. PM (μg/m3) TLUD door open TLUD door open
CO (ppm) TLUD door open TLUD door open Rocket door open
54 (N 54 (N
± 44 = 3) ± 44 = 3)
TLUD hole in roof open
4 ± 0.3 (N = 3) 4 ± 0.3 (N = 3) 31 ± 10 (N = 3)
TLUD hole in roof open
Rocket door open
Rocket door open TLUD hole in roof open
1988 ± 1502 (N = 9) 973 ± 116 (N = 3)
67 (N 31 (N 67 (N
± 23 = 9) ± 10 = 3) ± 23 = 9)
to be the same for the gravimetric study, but it may be that the gravimetric relationship for the levels of PM between the three types of stoves will be different. It is important to note that pollutant concentrations do not equate to levels of personal exposure. However, the IAP meter was placed at a position that approximates where a cook might be while cooking food. It is hoped that the data can be used to approximate personal exposure.
Conclusion Increasing ventilation by opening a window or door was found to have a dramatic impact on lowering the levels of CO and PM in a Test Kitchen. For any of the three stoves tested, opening the door and window in the Test Kitchen increased the ACH and contributed to a decrease in 1-hour PM concentrations of 97 to 98% and a decrease in 1-hour CO concentrations of 89 to 96% compared to the closed Test Kitchen condition. Increasing ACH seems to be a successful method for cooks using biomass fires to experience cleaner room air benefits. The cleaner combustion in the TLUD coupled with opening the door and window in the Test Kitchen resulted in a combination that reduced IAP by 90%, which is the aspirational requirement used currently by the United States Department of Energy.
Acknowledgments The authors wish to thank Dr. George Howe, and Dr. James Schaper for their assistance with statistical analysis.
Table 2 Mean PM & CO concentrations by stove and ventilation, with Scheffé test results.
PM (μg/m3) TSF Rocket TLUD
CO (ppm) TSF Rocket TLUD
Closed
Scheffé test grouping
Hole in roof open
Scheffé test grouping
Door open
Scheffé test grouping
Door & window open
Scheffé test grouping
24,922 ± 1900 (N = 9) 13,041 ± 7061 (N = 4) 2806 ± 2501 (N = 5)
3
7866 ± 292 (N = 3) 3439 ± 5753 (N = 3) 1988 ± 1502 (N = 9)
2
1145 ± 2030 (N = 3) 973 ± 116 (N = 3) 54 ± 44 (N = 3)
1
631 ± 520 (N = 3) 349 ± 827 (N = 3) 46 ± 24 (N = 3)
1
256 ± 10 (N = 9) 177 ± 63 (N = 5) 79 ± 56 (N = 5)
2 1
2 2 1
182 ± 50 (N = 3) 61 ± 56 (N = 3) 67 ± 23 (N = 9)
1 1
2 1 1
43 ± 71 (N = 3) 31 ± 10 (N = 3) 4 ± 0.3 (N = 3)
1 1
1 1 1
27 ± 26 (N = 3) 8 ± 21 (N = 3) 3±2 (N = 3)
1 1
1 1 1
Note: Means with different Scheffé test groupings differ significantly on Scheffé tests. Confidence intervals are with p = 0.05. In some cases the confidence interval is so large that the minimum value appears negative. In these cases the negative values should be interpreted as zero.
462
K. Grabow et al. / Energy for Sustainable Development 17 (2013) 458–462
Appendix A
Table A1 Fuel and cookstove characteristics. Fuel
Douglas-fir sticks
Dimensions
1 cm × 2 cm, various lengths 10% 20,634 kJ/kg Newspaper and Douglas-fir splinters TSF & rocket stove
Moisture content Gross calorific value Kindling Cookstove
Golden Fire Douglas-fir pellets 0.5 cm diameter × 1 cm length 10% 19,832 kJ/kg Sunnyside brand kerosene TLUD stove
References Adkins E, Tyler E, Wang J, Siriri D, Modi V. Field testing and survey evaluation of household biomass cookstoves in rural sub-Saharan Africa. Energy Sustain Dev 2010;14(3):172–85. Aprovecho Research Center. http://www.aprovecho.org/lab/emissionsequip/iap-meter. [accessed 17 October 2011]. Barnes B, Mathee A, Bruce N, Bates L. Protecting children from indoor air pollution exposure through outdoor cooking in rural South Africa. Boiling Point 2006;52: 11–3.
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