Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems: A Systematic Review of Published Literature

Prativa Poudel; Anish Ghimire; Guy Howard; Barbara Evans; Miller Carmargo-Valero; Freya Mills; Olivia Reddy; Subodh Sharma; Sarana Tuladhar; Abraham Geremew; Kenan Okorut; Baba Ngom; Manish Baidya; Sheila Dangol

doi:10.1016/j.heliyon.2023.e19947

Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems: A Systematic Review of Published Literature

Prativa Poudel, Anish Ghimire^*, Guy Howard, Barbara Evans, Miller Carmargo-Valero, Freya Mills, Olivia Reddy, Subodh Sharma, Sarana Tuladhar, Abraham Geremew, Kenan Okorut, Baba Ngom, Manish Baidya, Sheila Dangol

^*Corresponding author for this work

Research output: Contribution to journal › Review article (Academic Journal) › peer-review

7 Citations (Scopus)

Abstract

On-site sanitation systems (OSS) are a source of greenhouse gas (GHG) emissions. Although efforts have been made recently to measure and quantify emissions from septic tanks using various field-based methods, the vast majority of published literature reporting GHG emissions from OSS units (e.g., pits and tanks) is based on non-empirical evidence. This systematic review presents an overview and limitations of field-based methods used for the quantification of GHG emissions from OSS. Papers published in English were searched in three databases: Google Scholar, PubMed, and Directory of Articles and Journals. Peer-reviewed papers that reported field-based methods applied to containment units in OSS were included in this study. Only eight out of 2085 papers met the inclusion criteria with septic tanks as the sole technology reported and were thus, considered for the review. Most of the studies have been conducted in middle- and high-income countries. Field-based measurements of GHGs are conducted using a flux chamber (FC) and the most commonly used FC methods are (a) the modified simple static FC, (b) automated static FC, and (c) floating FC. Data reported in published studies do not provide sufficient information on the calibration and validation of the results from the FCs used. The complex FC designs, laborious fieldwork operations, and reliance on expensive, specialist equipment, suggest that such methods may not be suitable in Low and Middle-Income countries (LMICs), where resources and access to laboratory facilities are limited. Also, the complexity of pits and tank typology in LMICs (i.e., unstandardised designs and sizes) may be a challenge to the use of FCs with fixed dimensions and set operational conditions. The variation in the quantification methods and resulting emission rates among the studies indicates that gaps prevail in the use of existing methods. Therefore, there is still a need for a simple field-based, easily adaptable FC method with adequate calibration and validation that can help in reliably quantifying the emissions from different OSS in any LMICs.

Original language	English
Article number	e19947
Journal	Heliyon
Volume	9
Issue number	9
DOIs	https://doi.org/10.1016/j.heliyon.2023.e19947
Publication status	Published - 14 Sept 2023

Bibliographical note

Funding Information:
We would like to acknowledge the support from the Sanitation and Climate: Assessing Resilience and Emissions (SCARE) project, led by the University of Bristol . We would also like to thank the Aquatic Ecology Centre, Kathmandu University, for providing the necessary resources for this review. We would also like to acknowledge Dr. Khagendra Acharya for the English editing of this review paper.

Funding Information:
This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation under grant No: INV-015713 . Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.

Funding Information:
The FC method is found the most prominent field-based method, for measuring GHG emissions from STs. However, this method was critically assessed to determine the limitations. Limitations to the method including from collection of the gas and analysis of the samples were observed. Comparison was made between the calculated mass emission rate of gases reported in previous studies. The consistency in the emission rate was lacking in similar kinds of containments. One of the probable causes of this inconsistency in the emission rate obtained may be due to variations in the design and operation of the FC in each study. For instance, Winneberger in 1984 performed an experiment that consisted of a simple inverted bowl that allowed the CO2 to dissolve back to the liquid surface which undervalued the emissions made from the tank (i.e., 5–6 g CO2 capita−1 day−1) [28]. Similarly, Huynh et al. [29] inserted 5 mm of the bottom of the FC into the septage which may not have been enough to avoid the dispersion of the gases. For these reasons and drawbacks, obtained emissions may have been underestimated. Limited insertion of FC to the septage or longer contact with the surface liquid might have reduced the concentration of the gases inside FC through leakage or dissolving back to the septage. Along with this, there might be several other factors that limit the results. The detection of the leakage either in the cover/cap of the FC or the connectors is not mentioned in any of the studies. Most of the flux chambers were fitted with a fan with a power supply [18,29,30]. The fitting of the fan must have led to multiple holes in the flux chambers that increase the chances of leakage. Such fans not only can cause leakages but the requirement of heavy power backup may cause less feasibility in geographically challenging areas, this can reduce the adaptability of the FC in all geographical areas. Diaz-Valbuena et al. [18] used some PVC legs to support the inserts and the FC. These legs were designed for fixed-depth septic tanks. Containments in LMICs are diverse in size and design. This would again lead to lower adaptability in LMICs.This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation under grant No: INV-015713. Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.We would like to acknowledge the support from the Sanitation and Climate: Assessing Resilience and Emissions (SCARE) project, led by the University of Bristol. We would also like to thank the Aquatic Ecology Centre, Kathmandu University, for providing the necessary resources for this review. We would also like to acknowledge Dr. Khagendra Acharya for the English editing of this review paper.

Publisher Copyright:
© 2023 The Authors

Research Groups and Themes

Cabot Institute Water Research
Water and Environmental Engineering

Keywords

Greenhouse gas emissions Onsite sanitation Pit latrines Septic tanks

UN SDGs

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

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10.1016/j.heliyon.2023.e19947Licence: CC BY

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Methane from Onsite Sanitation: Empirical Model Development in Sub-Saharan Africa
Reddy, O. (Author), Howard, G. (Supervisor), Pregnolato, M. (Supervisor) & Ganesan, A. (Supervisor), 13 May 2025
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)

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Poudel, P., Ghimire, A., Howard, G., Evans, B., Carmargo-Valero, M., Mills, F., Reddy, O., Sharma, S., Tuladhar, S., Geremew, A., Okorut, K., Ngom, B., Baidya, M., & Dangol, S. (2023). Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems: A Systematic Review of Published Literature. Heliyon, 9(9), Article e19947. https://doi.org/10.1016/j.heliyon.2023.e19947

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title = "Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems: A Systematic Review of Published Literature",

abstract = "On-site sanitation systems (OSS) are a source of greenhouse gas (GHG) emissions. Although efforts have been made recently to measure and quantify emissions from septic tanks using various field-based methods, the vast majority of published literature reporting GHG emissions from OSS units (e.g., pits and tanks) is based on non-empirical evidence. This systematic review presents an overview and limitations of field-based methods used for the quantification of GHG emissions from OSS. Papers published in English were searched in three databases: Google Scholar, PubMed, and Directory of Articles and Journals. Peer-reviewed papers that reported field-based methods applied to containment units in OSS were included in this study. Only eight out of 2085 papers met the inclusion criteria with septic tanks as the sole technology reported and were thus, considered for the review. Most of the studies have been conducted in middle- and high-income countries. Field-based measurements of GHGs are conducted using a flux chamber (FC) and the most commonly used FC methods are (a) the modified simple static FC, (b) automated static FC, and (c) floating FC. Data reported in published studies do not provide sufficient information on the calibration and validation of the results from the FCs used. The complex FC designs, laborious fieldwork operations, and reliance on expensive, specialist equipment, suggest that such methods may not be suitable in Low and Middle-Income countries (LMICs), where resources and access to laboratory facilities are limited. Also, the complexity of pits and tank typology in LMICs (i.e., unstandardised designs and sizes) may be a challenge to the use of FCs with fixed dimensions and set operational conditions. The variation in the quantification methods and resulting emission rates among the studies indicates that gaps prevail in the use of existing methods. Therefore, there is still a need for a simple field-based, easily adaptable FC method with adequate calibration and validation that can help in reliably quantifying the emissions from different OSS in any LMICs.",

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author = "Prativa Poudel and Anish Ghimire and Guy Howard and Barbara Evans and Miller Carmargo-Valero and Freya Mills and Olivia Reddy and Subodh Sharma and Sarana Tuladhar and Abraham Geremew and Kenan Okorut and Baba Ngom and Manish Baidya and Sheila Dangol",

note = "Funding Information: We would like to acknowledge the support from the Sanitation and Climate: Assessing Resilience and Emissions (SCARE) project, led by the University of Bristol . We would also like to thank the Aquatic Ecology Centre, Kathmandu University, for providing the necessary resources for this review. We would also like to acknowledge Dr. Khagendra Acharya for the English editing of this review paper. Funding Information: This work was supported, in whole or in part, by the Bill \& Melinda Gates Foundation under grant No: INV-015713 . Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission. Funding Information: The FC method is found the most prominent field-based method, for measuring GHG emissions from STs. However, this method was critically assessed to determine the limitations. Limitations to the method including from collection of the gas and analysis of the samples were observed. Comparison was made between the calculated mass emission rate of gases reported in previous studies. The consistency in the emission rate was lacking in similar kinds of containments. One of the probable causes of this inconsistency in the emission rate obtained may be due to variations in the design and operation of the FC in each study. For instance, Winneberger in 1984 performed an experiment that consisted of a simple inverted bowl that allowed the CO2 to dissolve back to the liquid surface which undervalued the emissions made from the tank (i.e., 5–6 g CO2 capita−1 day−1) [28]. Similarly, Huynh et al. [29] inserted 5 mm of the bottom of the FC into the septage which may not have been enough to avoid the dispersion of the gases. For these reasons and drawbacks, obtained emissions may have been underestimated. Limited insertion of FC to the septage or longer contact with the surface liquid might have reduced the concentration of the gases inside FC through leakage or dissolving back to the septage. Along with this, there might be several other factors that limit the results. The detection of the leakage either in the cover/cap of the FC or the connectors is not mentioned in any of the studies. Most of the flux chambers were fitted with a fan with a power supply [18,29,30]. The fitting of the fan must have led to multiple holes in the flux chambers that increase the chances of leakage. Such fans not only can cause leakages but the requirement of heavy power backup may cause less feasibility in geographically challenging areas, this can reduce the adaptability of the FC in all geographical areas. Diaz-Valbuena et al. [18] used some PVC legs to support the inserts and the FC. These legs were designed for fixed-depth septic tanks. Containments in LMICs are diverse in size and design. This would again lead to lower adaptability in LMICs.This work was supported, in whole or in part, by the Bill \& Melinda Gates Foundation under grant No: INV-015713. Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.We would like to acknowledge the support from the Sanitation and Climate: Assessing Resilience and Emissions (SCARE) project, led by the University of Bristol. We would also like to thank the Aquatic Ecology Centre, Kathmandu University, for providing the necessary resources for this review. We would also like to acknowledge Dr. Khagendra Acharya for the English editing of this review paper. Publisher Copyright: {\textcopyright} 2023 The Authors",

year = "2023",

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day = "14",

doi = "10.1016/j.heliyon.2023.e19947",

language = "English",

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Poudel, P, Ghimire, A, Howard, G, Evans, B, Carmargo-Valero, M, Mills, F, Reddy, O, Sharma, S, Tuladhar, S, Geremew, A, Okorut, K, Ngom, B, Baidya, M & Dangol, S 2023, 'Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems: A Systematic Review of Published Literature', Heliyon, vol. 9, no. 9, e19947. https://doi.org/10.1016/j.heliyon.2023.e19947

TY - JOUR

T1 - Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems

T2 - A Systematic Review of Published Literature

AU - Poudel, Prativa

AU - Ghimire, Anish

AU - Howard, Guy

AU - Evans, Barbara

AU - Carmargo-Valero, Miller

AU - Mills, Freya

AU - Reddy, Olivia

AU - Sharma, Subodh

AU - Tuladhar, Sarana

AU - Geremew, Abraham

AU - Okorut, Kenan

AU - Ngom, Baba

AU - Baidya, Manish

AU - Dangol, Sheila

N1 - Funding Information: We would like to acknowledge the support from the Sanitation and Climate: Assessing Resilience and Emissions (SCARE) project, led by the University of Bristol . We would also like to thank the Aquatic Ecology Centre, Kathmandu University, for providing the necessary resources for this review. We would also like to acknowledge Dr. Khagendra Acharya for the English editing of this review paper. Funding Information: This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation under grant No: INV-015713 . Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission. Funding Information: The FC method is found the most prominent field-based method, for measuring GHG emissions from STs. However, this method was critically assessed to determine the limitations. Limitations to the method including from collection of the gas and analysis of the samples were observed. Comparison was made between the calculated mass emission rate of gases reported in previous studies. The consistency in the emission rate was lacking in similar kinds of containments. One of the probable causes of this inconsistency in the emission rate obtained may be due to variations in the design and operation of the FC in each study. For instance, Winneberger in 1984 performed an experiment that consisted of a simple inverted bowl that allowed the CO2 to dissolve back to the liquid surface which undervalued the emissions made from the tank (i.e., 5–6 g CO2 capita−1 day−1) [28]. Similarly, Huynh et al. [29] inserted 5 mm of the bottom of the FC into the septage which may not have been enough to avoid the dispersion of the gases. For these reasons and drawbacks, obtained emissions may have been underestimated. Limited insertion of FC to the septage or longer contact with the surface liquid might have reduced the concentration of the gases inside FC through leakage or dissolving back to the septage. Along with this, there might be several other factors that limit the results. The detection of the leakage either in the cover/cap of the FC or the connectors is not mentioned in any of the studies. Most of the flux chambers were fitted with a fan with a power supply [18,29,30]. The fitting of the fan must have led to multiple holes in the flux chambers that increase the chances of leakage. Such fans not only can cause leakages but the requirement of heavy power backup may cause less feasibility in geographically challenging areas, this can reduce the adaptability of the FC in all geographical areas. Diaz-Valbuena et al. [18] used some PVC legs to support the inserts and the FC. These legs were designed for fixed-depth septic tanks. Containments in LMICs are diverse in size and design. This would again lead to lower adaptability in LMICs.This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation under grant No: INV-015713. Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.We would like to acknowledge the support from the Sanitation and Climate: Assessing Resilience and Emissions (SCARE) project, led by the University of Bristol. We would also like to thank the Aquatic Ecology Centre, Kathmandu University, for providing the necessary resources for this review. We would also like to acknowledge Dr. Khagendra Acharya for the English editing of this review paper. Publisher Copyright: © 2023 The Authors

PY - 2023/9/14

Y1 - 2023/9/14

N2 - On-site sanitation systems (OSS) are a source of greenhouse gas (GHG) emissions. Although efforts have been made recently to measure and quantify emissions from septic tanks using various field-based methods, the vast majority of published literature reporting GHG emissions from OSS units (e.g., pits and tanks) is based on non-empirical evidence. This systematic review presents an overview and limitations of field-based methods used for the quantification of GHG emissions from OSS. Papers published in English were searched in three databases: Google Scholar, PubMed, and Directory of Articles and Journals. Peer-reviewed papers that reported field-based methods applied to containment units in OSS were included in this study. Only eight out of 2085 papers met the inclusion criteria with septic tanks as the sole technology reported and were thus, considered for the review. Most of the studies have been conducted in middle- and high-income countries. Field-based measurements of GHGs are conducted using a flux chamber (FC) and the most commonly used FC methods are (a) the modified simple static FC, (b) automated static FC, and (c) floating FC. Data reported in published studies do not provide sufficient information on the calibration and validation of the results from the FCs used. The complex FC designs, laborious fieldwork operations, and reliance on expensive, specialist equipment, suggest that such methods may not be suitable in Low and Middle-Income countries (LMICs), where resources and access to laboratory facilities are limited. Also, the complexity of pits and tank typology in LMICs (i.e., unstandardised designs and sizes) may be a challenge to the use of FCs with fixed dimensions and set operational conditions. The variation in the quantification methods and resulting emission rates among the studies indicates that gaps prevail in the use of existing methods. Therefore, there is still a need for a simple field-based, easily adaptable FC method with adequate calibration and validation that can help in reliably quantifying the emissions from different OSS in any LMICs.

AB - On-site sanitation systems (OSS) are a source of greenhouse gas (GHG) emissions. Although efforts have been made recently to measure and quantify emissions from septic tanks using various field-based methods, the vast majority of published literature reporting GHG emissions from OSS units (e.g., pits and tanks) is based on non-empirical evidence. This systematic review presents an overview and limitations of field-based methods used for the quantification of GHG emissions from OSS. Papers published in English were searched in three databases: Google Scholar, PubMed, and Directory of Articles and Journals. Peer-reviewed papers that reported field-based methods applied to containment units in OSS were included in this study. Only eight out of 2085 papers met the inclusion criteria with septic tanks as the sole technology reported and were thus, considered for the review. Most of the studies have been conducted in middle- and high-income countries. Field-based measurements of GHGs are conducted using a flux chamber (FC) and the most commonly used FC methods are (a) the modified simple static FC, (b) automated static FC, and (c) floating FC. Data reported in published studies do not provide sufficient information on the calibration and validation of the results from the FCs used. The complex FC designs, laborious fieldwork operations, and reliance on expensive, specialist equipment, suggest that such methods may not be suitable in Low and Middle-Income countries (LMICs), where resources and access to laboratory facilities are limited. Also, the complexity of pits and tank typology in LMICs (i.e., unstandardised designs and sizes) may be a challenge to the use of FCs with fixed dimensions and set operational conditions. The variation in the quantification methods and resulting emission rates among the studies indicates that gaps prevail in the use of existing methods. Therefore, there is still a need for a simple field-based, easily adaptable FC method with adequate calibration and validation that can help in reliably quantifying the emissions from different OSS in any LMICs.

KW - Greenhouse gas emissions Onsite sanitation Pit latrines Septic tanks

U2 - 10.1016/j.heliyon.2023.e19947

DO - 10.1016/j.heliyon.2023.e19947

M3 - Review article (Academic Journal)

C2 - 37809600

SN - 2405-8440

VL - 9

JO - Heliyon

JF - Heliyon

IS - 9

M1 - e19947

ER -

Field-based Methods for Measuring Greenhouse Gases Emissions from On-Site Sanitation Systems: A Systematic Review of Published Literature

Abstract

Bibliographical note

Research Groups and Themes

Keywords

UN SDGs

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Student theses

Methane from Onsite Sanitation: Empirical Model Development in Sub-Saharan Africa

Cite this