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Emissions from the combustion of peat: an experimental study
Atmospheric Environment 34 (2000) 3033}3035
Short communication
Emissions from the combustion of peat: an experimental study T.R. Muraleedharan , Miroslav Radojevic *, Allan Waugh, Anthony Caruana Brunei Shell Petroleum Co. Sdn Bhd, Seria 7082, Brunei Darussalam, Brunei Department of Chemistry, University of Brunei Darussalam, Bandar Seri Begawan BE 1410, Brunei Darussalam, Brunei Watson Hawksley Asia, P.O. Box 63, MPC, Bandar Seri Begawan BB3577, Brunei Darussalam, Brunei Consil-Global Environment Group, 34 Norfolk Court, Coburg 3058, Australia Received 23 February 1999; received in revised form 2 October 1999; accepted 15 November 1999
Abstract The "rst-ever experimental study of gaseous emissions from tropical biomass in southeast Asia is reported. Forest "res have been responsible for regional haze episodes in recent years, and most of the "res were in areas where peat is the dominant biomass fuel. Samples of peat were combusted at temperatures typical of smouldering combustion (500}6003C) and the combustion products were analysed for CO, CO , CH , C H , C H , C H , C H , HCHO, CH CHCHO, and PAHs. The most abundant carbon-containing species was CO , followed by CO, and CH . Emission factors were quanti"ed for the gases that were detected. No aldehydes nor PAHs were detected in the combustion products, however, these may have been present at levels below the method detection limits. Aldehydes and PAHs identi"ed in "eld studies during biomass "res and haze episodes may also result from atmospheric reactions of primary emissions. 2000 Elsevier Science Ltd. All rights reserved. Keywords: Peat; Haze; Combustion; CO; CO ; CH ; PAH
1. Introduction The diverse e!ects of the haze caused by biomass "res in SE Asia have been widely recognised, and of these, the potential threat to human health is of greatest concern (Radojevic, 1997, 1998). In a separate paper (Muraleedharan et al., 1999) we have reported the "rst-ever "eld study of the chemical components present in the haze in southeast Asia with special emphasis on those substances with potential health impacts. The study was carried out during a severe haze episode caused mainly by local peat "res. We also identi"ed and quanti"ed the combustion products of local peat in an experimental study in an
* Corresponding author. Fax: #673-2-249502. E-mail address: [email protected] (M. Radojevic). Present address: Corporate Environmental Advisor (CSM/22), PDO, PO Box C81, Muscat 113, Oman. Present address: ERM Mitchell McCotter Pty Ltd, 151 Clarendon Street, South Melbourne, Victoria 3205, Australia.
attempt to further explain the observations of the "eld study. Results of the experimental study are reported in this paper. Several experimental studies of biomass combustion have been reported in the literature (see review by Ward and Radke, 1993) and most of these have involved biomass from temperate regions (e.g. US). Two types of laboratory systems have been used to study emissions from biomass "res: `combustion laboratorya and `microcombustiona in which kg or mg quantities of biomass are burned, respectively. Most experiments conducted so far have studied emissions of total hydrocarbons, CO, CO , NO, NO , N O, NH , CH O, CH Cl, volatile organic compounds (VOCs), polynuclear aromatic hydrocarbons (PAHs) and particles from burning biomass, mainly pine needles. Only one combustion experiment seems to have been reported for tropical biomass; this involved the quanti"cation of the emission of particulate matter which could act as cloud condensation nuclei (CCN) and ice nuclei (IN) from burning savanna species (Lacaux et al., 1993). All previously reported
1352-2310/00/$ - see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 5 1 2 - 9
3034
T.R. Muraleedharan et al. / Atmospheric Environment 34 (2000) 3033}3035
combustion studies were carried out with the aim of quantifying emissions of trace species which could be used in global budgets and biogeochemical cycles, or improving our understanding of the processes of biomass combustion. We report the "rst-ever experimental study of the emissions of volatile compounds from tropical biomass, namely peat, which has been largely responsible for the haze in SE Asia. Our main goal was to identify and quantify those components which could have potential impacts on health (e.g. CO, aldehydes, PAHs), and these are somewhat di!erent from those components studied in some of the previously reported experiments.
2. Experimental Peat was sampled in the Belait district of Brunei Darussalam. Peat "res were burning in other areas in the vicinity of where peat was sampled. A representative sample of peat (28}54 mg) was combusted in a closed pyrex (20 ml) or silica tube (30 ml) at 480 and 6003C, and the combustion products were investigated by instrumental methods. The closed tubes were not evacuated and contained ambient air when sealed. The experiments were performed in this way to try and duplicate peat combustion as observed in Brunei during the "eld study; in the "eld, most of the peat appeared to smoulder from deep within the peat heaps. A sample of peat was weighed into the tubes. The tubes were then sealed and heated in a mu%e furnace until the required temperature was reached. The evolved gases were either injected into the gas chromatograph or adsorbed onto appropriate absorption tubes. Sampling was achieved by breaking a seal on the tubes and extracting the gases by means of a syringe. Hydrocarbons (C }C ) were determined by gas chro matography with #ame ionisation detection (GC/FID), CO and O were analysed by gas chromatography with thermal conductivity detection (GC/TCD), and CO was determined by gas chromatography with electron capture detection (GC/ECD). Aldehydes and polynuclear aromatic hydrocarbons (PAHs) were determined by gas chromatography with mass spectrometric determination (GC/MS) following standard NIOSH methods as described in another publication (Muraleedharan et al., 1999).
3. Results and discussion Results of the experimental study are summarised in Table 1. During the #aming stage of combustion temperatures can be as high as 1800 K while during smouldering temperatures are generally (850 K (Lobert and Warnatz, 1993). Therefore, temperatures employed in the present study (750}870 K) are characteristic of the
Table 1 Emissions form the combustion of peat Temperature (3C) 480
600
Component
% vol/vol mg kg\ % vol/vol mg kg\ peat peat
Moisture Loss-on-ignition Ash CH C H C H C H C H CO CO O HCHO CH CHCHO Other aldehydes PAHs
51.4 75 25 1.134 0.148 0.146 0.049 0.087 4.159 16.36 6.52 ND ND ND ND
* * * 5785 1320 1960 875 721 37134 185000 * * * * *
51.4 77 23 2.761 0.434 0.001 0.014 0.017 2.122 13.216 5.81 (dl (dl (dl (dl
* * * 11338 3122 11 203 113 15279 149591 * * * * *
wt/wt. Includes residual oxygen from ambient air. Acrolein. Pyrex tube (20 ml) 28 mg peat. Silica tube (30 ml) 53.8 mg, except aldehydes and PAHs, 51.8 mg. ND"not determined. (dl"not detected (below detection limit).
smouldering stage of combustion. The smouldering stage is expected to release large amounts of incompletely oxidised compounds (e.g. CO, VOCs, PAHs) which are potentially more harmful than substances emitted during the high temperature #aming stage of combustion (Lobert and Warnatz, 1993). The most abundant C-containing combustion product is CO , followed by CO in the second place, and CH in the third place. The con centration of the alkanes generally decreases with increasing molecular mass. The proportion of the alkanes of lower molecular mass (methane, ethane) increases as the temperature is increased and the concentration of long chain alkanes decreases. The concentrations of CO and C H decrease signi"cantly at higher temperature. The emission factors of CH agree well with those of between 5.7 and 19.4 g kg\ reported by Ward and Hardy (1984) for smouldering combustion. Emission factors of between 1 and 4.2 g kg\ were reported for #aming combustion. Aldehydes and PAHs were not detectable in the emission products. The presence of benzo(a)pyrene was reported in particulate matter emitted from the combustion of pine needles in one experimental study
T.R. Muraleedharan et al. / Atmospheric Environment 34 (2000) 3033}3035
(McMahon and Tsoukalas, 1978). Formaldehyde was identi"ed in laboratory and "eld studies using Fourier transform infrared spectroscopy (FTIR) by Gri$th et al. (1991). Benzo(a)pyrene has so far not been identi"ed in "eld studies of tropical biomass "res reported by other workers (Lacaux et al., 1993) nor by ourselves (Muraleedharan et al., 1999). Some of the aldehydes and PAHs observed in the "eld studies may have resulted from atmospheric reactions of substances emitted by forest "res. The fact that aldehydes and PAHs were not identi"ed in laboratory studies does not imply that they were absent; they may have been present at levels below the method detection limits. Other gases which may be emitted by biomass combustion, such as O , NO, NO , N O, NH , CH Cl were not analysed in the present study. 4. Conclusions Biomass "res have been responsible for several regional haze episodes in SE Asia, and most of the "res were in areas where peat is the dominant biomass fuel. Samples of peat were burned at temperatures typical of smouldering combustion (500}6003C) and the combustion products were analysed for CO, CO , CH , C H , C H , C H , C H , HCHO, CH CHCHO, and PAHs. Emission factors were quanti"ed for the gases that were detected. The most abundant carboncontaining species was CO , followed by CO, and CH . No aldehydes nor PAHs were detected in the combustion products, however, these may have been present at levels below the method detection limits. Aldehydes and PAHs identi"ed in "eld studies during intense biomass "res may also have resulted from atmospheric reactions of primary emissions. The emission factors determined in this study provide a quantitative basis for assessing the impacts of biomass burning in SE Asia on the carbon cycle and they could be used as input parameters in computer models. The preliminary study reported here could be extended to investigate a greater variety of emission products over a wider temperature range.
3035
Acknowledgements This work was carried out on behalf of Brunei Shell Petroleum Company Sdn. Bhd. The authors gratefully acknowledge its support.
References Gri$th, D.W.T., Mankin, W.G., Co!ey, D.E., Ward, D.E., Riebau, A., 1991. FTIR remote sensing of biomass burning emissions of CO , CO, CH , CH O, NO, NO , NH , and N O. In: Levine, J.S. (Ed.), Global Biomass Burning: Atmo spheric Climate and Biospheric Implications. MIT Press, Cambridge MA, pp. 230}239. Lacaux, J.-P., Cachier, H., Delmas, R., 1993. Biomass burning in Africa: an overview of its impact on atmospheric chemistry. In: Crutzen, P.J., Goldammer (Eds.), Fire in the Environment: The Ecological, Atmospheric, and Climatic Importance of Vegetation Fires. Wiley, Chichester, UK, pp. 159}191. Lobert, J.M., Warnatz, J., 1993. Emissions from the combustion process in vegetation. In: Crutzen, P.J., Goldammer, (Eds.), Fire in the Environment: The Ecological, Atmospheric, and Climatic Importance of Vegetation Fires. Wiley, Chichester, UK, pp. 15}37. McMahon, C.K., Tsoukalas, S.N., 1978. Polynuclear aromatic hydrocarbons in forest "re smoke. In: Jones, P.W., Freudenthal, R.I. (Eds.), Polynuclear Aromatic Hydrocarbons, Carcinogenesis, Vol. 3. Raven Press, New York, pp. 61}73. Muraleedharan, T.R., Radojevic, M., Waugh, A., Caruana, A., 1999. Chemical characterisation of the haze in Brunei Darussalam during the 1998 episode. Atmospheric Environment, in press. Radojevic, M., 1997. The haze in South East Asia. Environmental Scientist 6(6), 1}3. Radojevic, M., 1998. Burning issues. Chemistry in Britain 34 (12), 38}42. Ward, D.E., Hardy, C.C., 1984. Advances in the characterisation and control of emissions from prescribed "res. Proceedings of the 78th Annual Meeting of the Air Pollution Control Association, 24}29 June 1984, San Francisco, CA, Paper no. 84}363. Ward, D.E., Radke, L.F., 1993. Emission measurements from vegetation "res: a comparative evaluation of methods and results. In: Crutzen, P.J., Goldammer (Eds.), Fire in the Environment: The Ecological, Atmospheric, and Climatic Importance of Vegetation Fires. Wiley, Chichester, UK, pp. 53}76.
Short communication
Emissions from the combustion of peat: an experimental study T.R. Muraleedharan , Miroslav Radojevic *, Allan Waugh, Anthony Caruana Brunei Shell Petroleum Co. Sdn Bhd, Seria 7082, Brunei Darussalam, Brunei Department of Chemistry, University of Brunei Darussalam, Bandar Seri Begawan BE 1410, Brunei Darussalam, Brunei Watson Hawksley Asia, P.O. Box 63, MPC, Bandar Seri Begawan BB3577, Brunei Darussalam, Brunei Consil-Global Environment Group, 34 Norfolk Court, Coburg 3058, Australia Received 23 February 1999; received in revised form 2 October 1999; accepted 15 November 1999
Abstract The "rst-ever experimental study of gaseous emissions from tropical biomass in southeast Asia is reported. Forest "res have been responsible for regional haze episodes in recent years, and most of the "res were in areas where peat is the dominant biomass fuel. Samples of peat were combusted at temperatures typical of smouldering combustion (500}6003C) and the combustion products were analysed for CO, CO , CH , C H , C H , C H , C H , HCHO, CH CHCHO, and PAHs. The most abundant carbon-containing species was CO , followed by CO, and CH . Emission factors were quanti"ed for the gases that were detected. No aldehydes nor PAHs were detected in the combustion products, however, these may have been present at levels below the method detection limits. Aldehydes and PAHs identi"ed in "eld studies during biomass "res and haze episodes may also result from atmospheric reactions of primary emissions. 2000 Elsevier Science Ltd. All rights reserved. Keywords: Peat; Haze; Combustion; CO; CO ; CH ; PAH
1. Introduction The diverse e!ects of the haze caused by biomass "res in SE Asia have been widely recognised, and of these, the potential threat to human health is of greatest concern (Radojevic, 1997, 1998). In a separate paper (Muraleedharan et al., 1999) we have reported the "rst-ever "eld study of the chemical components present in the haze in southeast Asia with special emphasis on those substances with potential health impacts. The study was carried out during a severe haze episode caused mainly by local peat "res. We also identi"ed and quanti"ed the combustion products of local peat in an experimental study in an
* Corresponding author. Fax: #673-2-249502. E-mail address: [email protected] (M. Radojevic). Present address: Corporate Environmental Advisor (CSM/22), PDO, PO Box C81, Muscat 113, Oman. Present address: ERM Mitchell McCotter Pty Ltd, 151 Clarendon Street, South Melbourne, Victoria 3205, Australia.
attempt to further explain the observations of the "eld study. Results of the experimental study are reported in this paper. Several experimental studies of biomass combustion have been reported in the literature (see review by Ward and Radke, 1993) and most of these have involved biomass from temperate regions (e.g. US). Two types of laboratory systems have been used to study emissions from biomass "res: `combustion laboratorya and `microcombustiona in which kg or mg quantities of biomass are burned, respectively. Most experiments conducted so far have studied emissions of total hydrocarbons, CO, CO , NO, NO , N O, NH , CH O, CH Cl, volatile organic compounds (VOCs), polynuclear aromatic hydrocarbons (PAHs) and particles from burning biomass, mainly pine needles. Only one combustion experiment seems to have been reported for tropical biomass; this involved the quanti"cation of the emission of particulate matter which could act as cloud condensation nuclei (CCN) and ice nuclei (IN) from burning savanna species (Lacaux et al., 1993). All previously reported
1352-2310/00/$ - see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 5 1 2 - 9
3034
T.R. Muraleedharan et al. / Atmospheric Environment 34 (2000) 3033}3035
combustion studies were carried out with the aim of quantifying emissions of trace species which could be used in global budgets and biogeochemical cycles, or improving our understanding of the processes of biomass combustion. We report the "rst-ever experimental study of the emissions of volatile compounds from tropical biomass, namely peat, which has been largely responsible for the haze in SE Asia. Our main goal was to identify and quantify those components which could have potential impacts on health (e.g. CO, aldehydes, PAHs), and these are somewhat di!erent from those components studied in some of the previously reported experiments.
2. Experimental Peat was sampled in the Belait district of Brunei Darussalam. Peat "res were burning in other areas in the vicinity of where peat was sampled. A representative sample of peat (28}54 mg) was combusted in a closed pyrex (20 ml) or silica tube (30 ml) at 480 and 6003C, and the combustion products were investigated by instrumental methods. The closed tubes were not evacuated and contained ambient air when sealed. The experiments were performed in this way to try and duplicate peat combustion as observed in Brunei during the "eld study; in the "eld, most of the peat appeared to smoulder from deep within the peat heaps. A sample of peat was weighed into the tubes. The tubes were then sealed and heated in a mu%e furnace until the required temperature was reached. The evolved gases were either injected into the gas chromatograph or adsorbed onto appropriate absorption tubes. Sampling was achieved by breaking a seal on the tubes and extracting the gases by means of a syringe. Hydrocarbons (C }C ) were determined by gas chro matography with #ame ionisation detection (GC/FID), CO and O were analysed by gas chromatography with thermal conductivity detection (GC/TCD), and CO was determined by gas chromatography with electron capture detection (GC/ECD). Aldehydes and polynuclear aromatic hydrocarbons (PAHs) were determined by gas chromatography with mass spectrometric determination (GC/MS) following standard NIOSH methods as described in another publication (Muraleedharan et al., 1999).
3. Results and discussion Results of the experimental study are summarised in Table 1. During the #aming stage of combustion temperatures can be as high as 1800 K while during smouldering temperatures are generally (850 K (Lobert and Warnatz, 1993). Therefore, temperatures employed in the present study (750}870 K) are characteristic of the
Table 1 Emissions form the combustion of peat Temperature (3C) 480
600
Component
% vol/vol mg kg\ % vol/vol mg kg\ peat peat
Moisture Loss-on-ignition Ash CH C H C H C H C H CO CO O HCHO CH CHCHO Other aldehydes PAHs
51.4 75 25 1.134 0.148 0.146 0.049 0.087 4.159 16.36 6.52 ND ND ND ND
* * * 5785 1320 1960 875 721 37134 185000 * * * * *
51.4 77 23 2.761 0.434 0.001 0.014 0.017 2.122 13.216 5.81 (dl (dl (dl (dl
* * * 11338 3122 11 203 113 15279 149591 * * * * *
wt/wt. Includes residual oxygen from ambient air. Acrolein. Pyrex tube (20 ml) 28 mg peat. Silica tube (30 ml) 53.8 mg, except aldehydes and PAHs, 51.8 mg. ND"not determined. (dl"not detected (below detection limit).
smouldering stage of combustion. The smouldering stage is expected to release large amounts of incompletely oxidised compounds (e.g. CO, VOCs, PAHs) which are potentially more harmful than substances emitted during the high temperature #aming stage of combustion (Lobert and Warnatz, 1993). The most abundant C-containing combustion product is CO , followed by CO in the second place, and CH in the third place. The con centration of the alkanes generally decreases with increasing molecular mass. The proportion of the alkanes of lower molecular mass (methane, ethane) increases as the temperature is increased and the concentration of long chain alkanes decreases. The concentrations of CO and C H decrease signi"cantly at higher temperature. The emission factors of CH agree well with those of between 5.7 and 19.4 g kg\ reported by Ward and Hardy (1984) for smouldering combustion. Emission factors of between 1 and 4.2 g kg\ were reported for #aming combustion. Aldehydes and PAHs were not detectable in the emission products. The presence of benzo(a)pyrene was reported in particulate matter emitted from the combustion of pine needles in one experimental study
T.R. Muraleedharan et al. / Atmospheric Environment 34 (2000) 3033}3035
(McMahon and Tsoukalas, 1978). Formaldehyde was identi"ed in laboratory and "eld studies using Fourier transform infrared spectroscopy (FTIR) by Gri$th et al. (1991). Benzo(a)pyrene has so far not been identi"ed in "eld studies of tropical biomass "res reported by other workers (Lacaux et al., 1993) nor by ourselves (Muraleedharan et al., 1999). Some of the aldehydes and PAHs observed in the "eld studies may have resulted from atmospheric reactions of substances emitted by forest "res. The fact that aldehydes and PAHs were not identi"ed in laboratory studies does not imply that they were absent; they may have been present at levels below the method detection limits. Other gases which may be emitted by biomass combustion, such as O , NO, NO , N O, NH , CH Cl were not analysed in the present study. 4. Conclusions Biomass "res have been responsible for several regional haze episodes in SE Asia, and most of the "res were in areas where peat is the dominant biomass fuel. Samples of peat were burned at temperatures typical of smouldering combustion (500}6003C) and the combustion products were analysed for CO, CO , CH , C H , C H , C H , C H , HCHO, CH CHCHO, and PAHs. Emission factors were quanti"ed for the gases that were detected. The most abundant carboncontaining species was CO , followed by CO, and CH . No aldehydes nor PAHs were detected in the combustion products, however, these may have been present at levels below the method detection limits. Aldehydes and PAHs identi"ed in "eld studies during intense biomass "res may also have resulted from atmospheric reactions of primary emissions. The emission factors determined in this study provide a quantitative basis for assessing the impacts of biomass burning in SE Asia on the carbon cycle and they could be used as input parameters in computer models. The preliminary study reported here could be extended to investigate a greater variety of emission products over a wider temperature range.
3035
Acknowledgements This work was carried out on behalf of Brunei Shell Petroleum Company Sdn. Bhd. The authors gratefully acknowledge its support.
References Gri$th, D.W.T., Mankin, W.G., Co!ey, D.E., Ward, D.E., Riebau, A., 1991. FTIR remote sensing of biomass burning emissions of CO , CO, CH , CH O, NO, NO , NH , and N O. In: Levine, J.S. (Ed.), Global Biomass Burning: Atmo spheric Climate and Biospheric Implications. MIT Press, Cambridge MA, pp. 230}239. Lacaux, J.-P., Cachier, H., Delmas, R., 1993. Biomass burning in Africa: an overview of its impact on atmospheric chemistry. In: Crutzen, P.J., Goldammer (Eds.), Fire in the Environment: The Ecological, Atmospheric, and Climatic Importance of Vegetation Fires. Wiley, Chichester, UK, pp. 159}191. Lobert, J.M., Warnatz, J., 1993. Emissions from the combustion process in vegetation. In: Crutzen, P.J., Goldammer, (Eds.), Fire in the Environment: The Ecological, Atmospheric, and Climatic Importance of Vegetation Fires. Wiley, Chichester, UK, pp. 15}37. McMahon, C.K., Tsoukalas, S.N., 1978. Polynuclear aromatic hydrocarbons in forest "re smoke. In: Jones, P.W., Freudenthal, R.I. (Eds.), Polynuclear Aromatic Hydrocarbons, Carcinogenesis, Vol. 3. Raven Press, New York, pp. 61}73. Muraleedharan, T.R., Radojevic, M., Waugh, A., Caruana, A., 1999. Chemical characterisation of the haze in Brunei Darussalam during the 1998 episode. Atmospheric Environment, in press. Radojevic, M., 1997. The haze in South East Asia. Environmental Scientist 6(6), 1}3. Radojevic, M., 1998. Burning issues. Chemistry in Britain 34 (12), 38}42. Ward, D.E., Hardy, C.C., 1984. Advances in the characterisation and control of emissions from prescribed "res. Proceedings of the 78th Annual Meeting of the Air Pollution Control Association, 24}29 June 1984, San Francisco, CA, Paper no. 84}363. Ward, D.E., Radke, L.F., 1993. Emission measurements from vegetation "res: a comparative evaluation of methods and results. In: Crutzen, P.J., Goldammer (Eds.), Fire in the Environment: The Ecological, Atmospheric, and Climatic Importance of Vegetation Fires. Wiley, Chichester, UK, pp. 53}76.