Methane Emission and Carbon Sequestration Potential from Municipal Solid Waste Landfill, India

Round 1

Reviewer 1 Report

1. Comment on how the quality of experimental research was ensured. 2. Specify the measurement limits and errors of the devices used in experimental studies. 3. Comment on how samples were prepared for analysis, what was mass of sample, how much time passed from collection to analysis, how samples were transported, etc. 4. To cite literature uniformly in the text - change Lester 2002 to a number. 5. In 14 Fig. change NMOC to NMVOC. 6. Use Si units of measurement and change acres to hectares. 7. To update the literature list and supplement it with at least 6 new literature sources, as well as to update statistical data on the amount of generated waste.

Author Response

Reviewer 1

 

1. Comment on how the quality of experimental research was ensured.

       Ans: You can test reliability through repetition. The more similar repeated measurements are, the more reliable the results.  For example, if I repeat an experiment 5 times and get similar results each time, then I can be confident that my results are reliable.

 

2. Specify the measurement limits and errors of the devices used in experimental studies.

       Ans: If you find that your percent difference is more than 10%, there is likely something wrong with your experiment and you should figure out what the problem is and take new data.

 

3. Comment on how samples were prepared for analysis, what was the mass of the sample was, how much time passed from collection to analysis, how samples were transported, etc.

     Ans: A disturbed sample does not retain the in-situ structure of the soil. These types of samples can be used for classification tests such as the grain size analysis.

8 number of disturbed samples can be retrieved from the auger in any soil or waste sample. 5kg of mass of sample collected from each borehole. 10 days time taken to drill the 8 boreholes (because it is loose material and the auger can strike inside the landfill or the borehole stand can topple).  Grab samples shall be placed in large air-tight plastic bags to prevent moisture loss and leakage of fine material from the bag.

 

4. To cite literature uniformly in the text - change Lester 2002 to a number.

          Ans:

• Naveen BP, Mehran Karimpour-Farda (2022) Estimation of Methane Emission and Electricity Generation Potential from Mavallipura Landfill Site, Iranian Journal of Science and Technology, Transactions of Civil Engineering, Springer, 46(2),1-11, https://doi.org/10.1007/s40996-022-00857-2,ISSN: 22286160

 

 

 

 

 

 

 

5. In 14 Fig. change NMOC to NMVOC.

       Ans: Incorporated

 

6. Use Si units of measurement and change acres to hectares

      Ans: Incorporated

              40.46 hectares

7. To update the literature list and supplement it with at least 6 new literature sources, as well as to update statistical data on the amount of generated waste.

       Ans: Incorporated

• Naveen BP, Mehran Karimpour-Farda (2022) Estimation of Methane Emission and Electricity Generation Potential from Mavallipura Landfill Site, Iranian Journal of Science and Technology, Transactions of Civil Engineering, Springer, 46(2),1-11, https://doi.org/10.1007/s40996-022-00857-2,ISSN: 22286160
• Wu S, Hu Z, Hu T, Chen J, Yu K, Zou J, Liu S (2018) Annual methane and nitrous oxide emissions from rice paddies and inland fish aquaculture wetlands in southeast China. Atmos Environ 175:135–144.

 

• Ganesan AL, Rigby M, Lunt MF, Parker RJ, Boesch H, Goulding N, Umezawa T, Zahn A, Chatterjee A, Prinn RG, Tiwari YK (2017) Atmospheric observations show accurate reporting and little growth in India’s methane emissions. Nat Commun 8(1):836.

 

• Du M, Peng C, Wang X, Chen H, Wang M, Zhu Q (2017) Quantification of methane emissions from municipal solid waste landfills in China during the past decade. Renew Sustain Energy Rev 78:272–279.

 

• Garg A, Bordoloi S, Ni J, Cai W, Maddibiona PG, Mei G, Poulsen TG, Lin P (2019) Influence of biochar addition on gas permeability in unsaturated soil. Géotech Lett 9(1):66–71.

 

• Ayodele TR, Ogunjuyigbe ASO, Alao MA (2017) Life Cycle Assessment of Waste-to-Energy (WtE) Technologies for Electricity Generation Using Municipal Solid Waste in Nigeria. Appl Energy 201:200–218

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Good manuscript and here are a few comments to improve the quality of the manuscript:

1. The article has a clear objective, which is to estimate the amount of carbon stored in MSW burial in landfills and to quantify methane gas production from the ward levels and the Mavallipura landfill site in India. However, the introduction could be more informative and provide more background information on the issue of waste management, GHG emissions, and landfill sites, particularly in developing countries.
2. The article presents a crucial point that most of the waste is disposed of through open dump and landfilling, leading to the production of major GHGs such as methane, carbon dioxide, and nitrous oxide. However, the article could benefit from providing more information on the impact of GHGs and landfill sites on climate change and the environment.
3. The article highlights the composition of MSW in developing countries, which has a higher percentage of biodegradable waste than the developed world. This is an essential point to consider, particularly in terms of GHG emissions, and the article could benefit from discussing the factors that contribute to this difference.
4. The methodology used in the study is well explained, particularly the sample collection process, and the results are presented in a clear and concise manner. However, the article could benefit from providing more information on the equipment used for the tests and the potential limitations of the methodology.
5. The article concludes that the carbon sequestration from MSW burial in the Mavallipura landfill is estimated to be at least 10 million metric tons per year, based on the carbon storage factor and data on MSW generation. However, the article could benefit from discussing the potential implications of this finding and how it could contribute to reducing GHG emissions.
6. The article aims to quantify methane gas production from the ward levels and the Mavallipura landfill site in India. This is an important aspect to consider, particularly in terms of understanding the impact of landfill sites on GHG emissions. However, the article could benefit from providing more information on the results of this analysis and how it could inform future waste management practices.
7. Overall, the article presents a valuable contribution to the understanding of carbon sequestration from MSW burial in landfill sites and the production of methane gas. However, the article could benefit from providing more information on the broader implications of the findings and how they could inform future waste management policies and practices.

Author Response

 

Reviewer 2

Good manuscript and here are a few comments to improve the quality of the manuscript:

1. The article has a clear objective, which is to estimate the amount of carbon stored in MSW burial in landfills and to quantify methane gas production from the ward levels and the Mavallipura landfill site in India. However, the introduction could be more informative and provide more background information on the issue of waste management, GHG emissions, and landfill sites, particularly in developing countries.

 

 

Ans:    The landfills have the potential to emit around 15-25 l/kg of gas per year over its operational period. This LFG can be used as a good fuel for power generation and the gas collected can be supplied to appropriate industries located in the vicinity for direct use in areas like internal combustion engines, gas turbines, micro turbines, steam boilers, and other facilities (Sayak Sinha, 2013). The major cities in India are working hard to bridge the gap to achieve 100 per cent waste processing efficiency. But still, it is a work in progress and cities like Gangtok, Bengaluru, Gurugram, Kumbakonam and North Delhi are in the process of improving their processing efficiency (Atin Biswas, Subhasish Parida et al. 2021). High population growth and waste generation per capita have resulted in a 50% increase in waste generation by Indian cities. A declining trend in solid waste landfilled has been observed during the last six years where landfilled waste decreased from 54% in 2015-16 to 18.4% in 2020-21. On the other hand, an increasing percentage of solid waste processed has been seen during the last five years wherein percentage of solid waste processed has increased from 19% in 2015-16 to 49.96% in 2020-21 (CPCB Delhi, 2020).

Methane is a primary constituent of GHGs having a Global Warming Potential of about 21 times that of carbon dioxide (IPCC 2007). Anaerobic decomposition of wastes due to microorganisms present in landfills leads to methane emissions, carbon dioxide emissions and gases such as H₂S and NOx in lower amounts (ATSDR 1998). Methane has a high thermal and calorific value which is comparable to that of a litre of kerosene (Aydi 2012). This high heating capacity of methane makes this gas reasonable and alarming. However, policies have been implemented over the world to minimize the emissions of methane from waste (Naveen et al. 2021). The negative impacts of LFG can be remediated by making use of eco-friendly technologies and adequate solid waste management techniques. Sustainable means of waste management are reduced, reuse, recycle, recover and the finally landfilling. Methane mitigation provides substantial benefits by reducing greenhouse warming and air pollution. Due to its short atmospheric lifetime, reductions in CH4 emissions lead to visible climate impacts within a few short decades of policy implementation (IPCC 2007).

Modeling and estimation of landfill gas in waste landfills play a primary role in its designing and tapping of energy. In fact, quantitative assessment of the landfill gas emissions will help in evaluating India's contribution to the global emission of GHGs. The behavior of MSW landfill can be evaluated over the years using various mathematical models available in literature to avoid the disastrous effects. These models can predict precise estimation of LFG emission and settlement rates over the years according the rate of biodegradation and thereby helping in maintenance of landfill sites. Moreover, prediction of methane emissions can help in extracting out information on global warming potentials and designing adequate methane control and accumulation systems for harnessing energy.  

 

2. The article presents a crucial point that most of the waste is disposed of through open dump and landfilling, leading to the production of major GHGs such as methane, carbon dioxide, and nitrous oxide. However, the article could benefit from providing more information on the impact of GHGs and landfill sites on climate change and the environment.

 

Ans:  Deforestation and human activities that emit large volumes of carbon dioxide are to blame for climate change. However, a lot of people are unaware that solid waste is a component of the climate change feedback loop. Greenhouse gas (GHG) emissions are the primary cause of climate change. Solid waste and some of these emissions are directly related. GHG emissions are caused by the production, distribution, and consumption of goods as well as the formation of waste, which have an impact on the climate of the planet.

 

 

 

1. The article highlights the composition of MSW in developing countries, which has a higher percentage of biodegradable waste than the developed world. This is an essential point to consider, particularly in terms of GHG emissions, and the article could benefit from discussing the factors that contribute to this difference.

 

 

         Ans:  Factors Affecting Landfill Gas Generation and Emission: The major drivers of generation of landfill gas (LFG) are: (1) amount of organic material deposited in landfills, (2) degree (%) of anaerobic decomposition of organic matter in MSW, (3) thickness and physical and chemical properties of cover materials in the landfill, (4) seasonal variation in methane oxidation rates, 5) moisture and bacterial concentration in landfill.

The driving factors for the trends in material landfilled and landfill gas are:(1) growing populations, (2) increases in personal incomes, (3) expanding industrialization.

The emissions of landfill methane to the atmosphere depend on: (1) the operation of landfill (e.g., thickness of daily deposition, provision of daily cover, etc.), (2) the effort made to capture landfill gas (e.g., placement and timing of gas collection piping; horizontal collection pipes are placed in early days of landfill, vertical pipes are placed after filling a landfill cell); (3) use of LFG to operate electricity generators and/or gas flaring systems.

 

1. The methodology used in the study is well explained, particularly the sample collection process, and the results are presented in a clear and concise manner. However, the article could benefit from providing more information on the equipment used for the tests and the potential limitations of the methodology.

 

       Ans: SPT is performed in accordance with ASTM D 1586. (ASTM, 2005). The SPT test provides details about the MSW's strength. During a tedious procedure, it is completed at regular intervals of approximately 1.5 m. The drill rods are lowered to the bottom of the borehole, fitted with a split-spoon sampler, and driven repeatedly into the earth with a 65 kg standard hammer through a hole that is 75 centimetres deep. For driving the sampler, three depths of 15 cm (a total of 45 cm) were measured consecutively. Due to the aftereffects and the disturbance at the bottom of the borehole, the first 15 centimetres of penetration is disregarded. The blow count, penetration number, or N-value is the total of the last 30 centimetres and is represented by N.

 

1. The article concludes that the carbon sequestration from MSW burial in the Mavallipura landfill is estimated to be at least 10 million metric tons per year, based on the carbon storage factor and data on MSW generation. However, the article could benefit from discussing the potential implications of this finding and how it could contribute to reducing GHG emissions.

 

Ans:  A wide range of mature, environmentally effective waste-management strategies can minimize GHG emissions from this sector and provide public health, environmental protection, and sustainable development co-benefits. These technologies can directly reduce GHG emissions (landfill gas recovery, improved landfill practices, engineered wastewater management) or avoid significant GHG generation (controlled composting of organic waste, modern incineration, and expanded sanitation coverage) (high evidence, high agreement). Waste minimization, recycling, and reuse have a growing potential to indirectly reduce GHG emissions through raw material conservation, energy and resource efficiency, and fossil fuel avoidance (medium evidence, high agreement).  

 

      Waste management decisions are often undertaken locally without quantification of GHG mitigation, underestimating the waste sector's role in decreasing global GHG emissions (medium evidence, high agreement). Flexible strategies and financial incentives can expand waste management options to achieve GHG mitigation goals. In integrated waste management, local technology decisions depend on many competing variables, including waste quantity and characteristics, cost and financing issues, infrastructure requirements, including land area, collection and transport considerations, and regulatory constraints. LCA provides decision-support tools (strong evidence, high agreement).

 

1. The article aims to quantify methane gas production from the ward levels and the Mavallipura landfill site in India. This is an important aspect to consider, particularly in terms of understanding the impact of landfill sites on GHG emissions. However, the article could benefit from providing more information on the results of this analysis and how it could inform future waste management practices.

 

Ans:    Carbon sequestration is one of the significant factors that should be considered in comparing the environmental benefits and liabilities associated with the MSW land-fills in specific and MSW management strategies in general. Other factors include gas-eous emissions from MSW decomposition and the equipment used for MSW landfill operation, energy consumed during MSW landfill construction and maintenance, and methane's potential recovery for energy. Hence, appropriate treatment options are necessary to treat the municipal solid waste's organic fractions to reduce Greenhouse Gas Emissions. Decentralized treatment options of converting to energy or composting would provide a better solution by converting the waste to wealth.

 

 

1. Overall, the article presents a valuable contribution to the understanding of carbon sequestration from MSW burial in landfill sites and the production of methane gas. However, the article could benefit from providing more information on the broader implications of the findings and how they could inform future waste management policies and practices.

 

Ans:

• Awareness campaigns should be employed to motivate community participation in the disposal of wastes and health. The economic wellbeing of the waste picking informal community should be taken care of.
• For achieving environmental sustainability, "reduce and reuse" for recyclables wastes (i.e., non-biodegradable wastes like paper, plastic) for further use and reduction of organic waste disposal.
• Appropriate legislation should be framed to delegate greater power and autonomy to urban local bodies, particularly in resource mobilization. The urban local bodies are the principal stakeholders in the waste management system in Bangalore. Yet, they suffer from a lack of adequate finance and appropriate government support at the central and state levels. A significant portion of the municipal expenditure on waste disposal and management goes into collecting and transportation waste, leaving very little finance to treat them effectively. In this respect, appropriate financial interventions on the centre and the state governments and providing suitable

subsidies for the promotion of more and more eco-friendly waste disposal measures will go a long way in addressing the issue of the garbage ‘pandemic’ in our country.

 

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Based on data on landfilled waste gathered from 2007 to 2013, the study determines the methane emission of the Mavallipura landfill in Bangalore. This data is ten years old, and the current contest research lacks information on the solid waste gathered during the COVID 19 era as well as the state of the current climate. Hence authors suggested to collect recent data and find out the present condition on methene emission. 

Author Response

Reviewer 3

Based on data on landfilled waste gathered from 2007 to 2013, the study determines the methane emission of the Mavallipura landfill in Bangalore. This data is ten years old, and the current contest research lacks information on the solid waste gathered during the COVID 19 era as well as the state of the current climate. Hence authors suggested to collect recent data and find out the present condition on methene emission. 

Ans: Thanks for the comments.  

 In my next article, I am working on the real data by conducting survey in entire Bangalore with help of Bruhat Bengaluru Mahanagara Palike (BBMP) then predicting the methane emission.

Reviewer 4 Report

A very interesting article showing the catastrophic impact of permanent landfill dumps on the natural environment. Waste dumps originating from cities were analysed. These waste are mixed and dominated by: plastic, paper and glass. It begs to use waste segregation and separate the main components and then dispose of them. The analyzed landfills produce large amounts of methane and CO2. Fortunately, according to the analysis, the period of the greatest pollution of greenhouse gases to the atmosphere is slowly passing. The mathematical models used to analyze the methane and CO2 content are interesting and give good results. Changes in the following parameters with the depth of the landfill were measured: temperature, moisture content, pH acidity scale,  and carbon content. The values of all measured parameters increase with depth. This phenomenon suggests the creation of dangerous chemically contaminated islands for future generations. The main conclusion resulting from this article is the need to segregate municipal waste, the amount of which will increase rapidly.

Author Response

Reviewer 4

A very interesting article showing the catastrophic impact of permanent landfill dumps on the natural environment. Waste dumps originating from cities were analysed. These wastes are mixed and dominated by: plastic, paper and glass. It begs to use waste segregation and separate the main components and then dispose of them. The analysed landfills produce large amounts of methane and CO2. Fortunately, according to the analysis, the period of the greatest pollution of greenhouse gases to the atmosphere is slowly passing. The mathematical models used to analyse the methane and CO2 content are interesting and give good results. Changes in the following parameters with the depth of the landfill were measured: temperature, moisture content, pH acidity scale, and carbon content. The values of all measured parameters increase with depth. This phenomenon suggests the creation of dangerous chemically contaminated islands for future generations. The main conclusion resulting from this article is the need to segregate municipal waste, the amount of which will increase rapidly.

 

Ans: Thanks for your motivation 

 

 

Reviewer 5 Report

Dear Authors

Congratulation for this interesting topic and also of pratical significance for landfill management researchers and companies. However, during my review, I identified (highlighted) issues that I recommend your attention to.

Comments for author File: Comments.pdf

Author Response

Incorporated 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors are analysing recent municipal solid waste (MSW) statistics; as a result of their research, a few interesting findings will emerge that will help to guide future steps.