Physico-Chemical Characterisation of Particulate Matter and Ash from Biomass Combustion in Rural Indian Kitchens

Gopika Indu; Saragur Nagendra; Richard Ball

doi:10.3390/air3030023

Physico-Chemical Characterisation of Particulate Matter and Ash from Biomass Combustion in Rural Indian Kitchens

Gopika Indu, Saragur Nagendra, Richard Ball

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Abstract

In developing countries, indoor air pollution in rural areas is often attributed to the use of solid biomass fuels for cooking. Such fuels generate particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO2), polyaromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs). PM created from biomass combustion is a pollutant particularly damaging to health. This rigorous study employed a personal sampling device and multi stage cascade impactor to collect airborne PM (including PM2.5) and deposited ash from 20 real-world kitchen microenvironments. A robust analysis of the PM was undertaken using a range of morphological, physical, and chemical techniques, the results of which were then compared to a controlled burn experiment. Results revealed that airborne PM was predominantly carbon (~85%), with the OC/EC ratio varying between 1.17 and 11.5. Particles were primarily spherical nanoparticles (50–100 nm) capable of deep penetration into the human respiratory tract (HRT). This is the first systematic characterisation of biomass cooking emissions in authentic rural kitchen settings, linking particle morphology, chemistry and toxicology at health-relevant scales. Toxic heavy metals like Cr, Pb, Cd, Zn, and Hg were detected in PM, while ash was dominated by crustal elements such as Ca, Mg and P. VOCs comprised benzene derivatives, esters, ethers, ketones, tetramethysilanes
(TMS), and nitrogen-, phosphorus- and sulphur-containing compounds. This research
showcases a unique collection technique that gathered particles indicative of their potential for penetration and deposition in the HRT. Impact stems from the close link between the physico-chemical properties of particle emissions and their environmental and epidemiological effects. By providing a critical evidence base for exposure modelling, risk assessment and clean cooking interventions, this study delivers internationally significant insights. Our methodological innovation, capturing respirable nanoparticles under real-world conditions, offers a transferable framework for indoor air quality research across low- and middle-income countries. The findings therefore advance both fundamental understanding of combustion-derived nanoparticle behaviour and practical knowledge to inform public health, environmental policy, and the UN Sustainable Development Goals.

Original language	English
Article number	23
Number of pages	24
Journal	Air
Volume	3
Issue number	3
DOIs	https://doi.org/10.3390/air3030023
Publication status	Published - 2 Sept 2025

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request. All relevant data have been summarized in the article through
tables and figures. Specific datasets can be made available upon request by contacting the corresponding author.

Acknowledgements

The authors thank Philip Fletcher, University of Bath, for his technical input and
guidance for Raman spectroscopy, electron imaging and EDX analysis. Support from the Sophisticated Analytical Instruments Facility (SAIF) at IIT Madras for their help with laboratory analyses is also acknowledged. We would also like to thank the people of Madahalli village for providing access to their kitchens to enable monitoring, and Mahesh PA and associates, JSS Medical College and Academy of Higher Education and Research, Mysuru, Karnataka, for supporting the field campaign and study.

Funding

Part of the study was supported by the Climate-Resilient Energy Secure and healthy built environmenTs (CREST) project. CREST is supported by a Going Global Partnerships—Collaborative Grant from the British Council’s Going Global Partnerships programme [grant number 877766384]. The program builds stronger, more inclusive, internationally connected higher education and TVET (Technical and Vocational Education and Training) systems.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 3 Good Health and Well-being

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2025 Indu MDPI AirFinal published version, 5.74 MBLicence: CC BY

Cite this

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title = "Physico-Chemical Characterisation of Particulate Matter and Ash from Biomass Combustion in Rural Indian Kitchens",

abstract = "In developing countries, indoor air pollution in rural areas is often attributed to the use of solid biomass fuels for cooking. Such fuels generate particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO2), polyaromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs). PM created from biomass combustion is a pollutant particularly damaging to health. This rigorous study employed a personal sampling device and multi stage cascade impactor to collect airborne PM (including PM2.5) and deposited ash from 20 real-world kitchen microenvironments. A robust analysis of the PM was undertaken using a range of morphological, physical, and chemical techniques, the results of which were then compared to a controlled burn experiment. Results revealed that airborne PM was predominantly carbon (\textasciitilde{}85\%), with the OC/EC ratio varying between 1.17 and 11.5. Particles were primarily spherical nanoparticles (50–100 nm) capable of deep penetration into the human respiratory tract (HRT). This is the first systematic characterisation of biomass cooking emissions in authentic rural kitchen settings, linking particle morphology, chemistry and toxicology at health-relevant scales. Toxic heavy metals like Cr, Pb, Cd, Zn, and Hg were detected in PM, while ash was dominated by crustal elements such as Ca, Mg and P. VOCs comprised benzene derivatives, esters, ethers, ketones, tetramethysilanes (TMS), and nitrogen-, phosphorus- and sulphur-containing compounds. This research showcases a unique collection technique that gathered particles indicative of their potential for penetration and deposition in the HRT. Impact stems from the close link between the physico-chemical properties of particle emissions and their environmental and epidemiological effects. By providing a critical evidence base for exposure modelling, risk assessment and clean cooking interventions, this study delivers internationally significant insights. Our methodological innovation, capturing respirable nanoparticles under real-world conditions, offers a transferable framework for indoor air quality research across low- and middle-income countries. The findings therefore advance both fundamental understanding of combustion-derived nanoparticle behaviour and practical knowledge to inform public health, environmental policy, and the UN Sustainable Development Goals.",

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AB - In developing countries, indoor air pollution in rural areas is often attributed to the use of solid biomass fuels for cooking. Such fuels generate particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO2), polyaromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs). PM created from biomass combustion is a pollutant particularly damaging to health. This rigorous study employed a personal sampling device and multi stage cascade impactor to collect airborne PM (including PM2.5) and deposited ash from 20 real-world kitchen microenvironments. A robust analysis of the PM was undertaken using a range of morphological, physical, and chemical techniques, the results of which were then compared to a controlled burn experiment. Results revealed that airborne PM was predominantly carbon (~85%), with the OC/EC ratio varying between 1.17 and 11.5. Particles were primarily spherical nanoparticles (50–100 nm) capable of deep penetration into the human respiratory tract (HRT). This is the first systematic characterisation of biomass cooking emissions in authentic rural kitchen settings, linking particle morphology, chemistry and toxicology at health-relevant scales. Toxic heavy metals like Cr, Pb, Cd, Zn, and Hg were detected in PM, while ash was dominated by crustal elements such as Ca, Mg and P. VOCs comprised benzene derivatives, esters, ethers, ketones, tetramethysilanes (TMS), and nitrogen-, phosphorus- and sulphur-containing compounds. This research showcases a unique collection technique that gathered particles indicative of their potential for penetration and deposition in the HRT. Impact stems from the close link between the physico-chemical properties of particle emissions and their environmental and epidemiological effects. By providing a critical evidence base for exposure modelling, risk assessment and clean cooking interventions, this study delivers internationally significant insights. Our methodological innovation, capturing respirable nanoparticles under real-world conditions, offers a transferable framework for indoor air quality research across low- and middle-income countries. The findings therefore advance both fundamental understanding of combustion-derived nanoparticle behaviour and practical knowledge to inform public health, environmental policy, and the UN Sustainable Development Goals.

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DO - 10.3390/air3030023

M3 - Article

SN - 2813-4168

VL - 3

JO - Air

JF - Air

IS - 3

M1 - 23

ER -

Physico-Chemical Characterisation of Particulate Matter and Ash from Biomass Combustion in Rural Indian Kitchens

Abstract

Data Availability Statement

Acknowledgements

Funding

UN SDGs

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