A Review on Bio Methane Production using Kitchen Waste

A Review on Bio Methane Production using Kitchen Waste

Ashutosh Pathak1, Harshad Patil2, Sandesh Patil3, Varun Patil4, Prof. Firdos Khan5

1234Student, 5Project Guide, Department of Mechanical Engineering, Bharati Vidyapeeth College of Engineering, Navi Mumbai, India

Abstract Increasing population has led to increase in energy demand and waste production hence it is of great need to provide alternative to fuelling. This review paper contains the deciding parameters for increasing the efficiency of a biogas plant. In this paper municipal kitchen waste has been used as substrate for biogas production which not only produces more biogas as compared to traditional substrate but also solves the problem of municipal wet waste disposal. The parameters discussed in the paper are temperature, pH, particle size, CN ratio, total solid and volatile matter of the kitchen waste slurry and operating conditions of biogas plant like organic loading waste, retention time, agitation, filtration, and storage of biogas. The methodology proposed processing of the kitchen waste through shredder mechanism via hopper, into bio-digester, storage of biogas and filtration before utilisation. Keywords biogas, kitchen waste, methane, wet waste, carbon neutral, LPG, digester, gas storage tank, shredder, etc.

INTRODUCTION

Todays growing community has led into generation of municipal solid waste on a large scale and has led to an ever-increasing demand of energy. Waste generation has led to various problems of pollution and is a cause of nuisance. Even after applying the concept of four Rs which stands for Reduce, Reuse, Recycle, and Renewable energy, no proper solution for disposal of municipal solid waste is achieved. Dry and solid waste is processable using various methods to recycle it. But wet waste including kitchen and garden waste is the area of major concern. Wet waste cause land pollution, leaching of leachate into ground water, scarcity of land due to generation of landfills, breeding of rodents and insects causing diseases and air pollution. Increased population has led to increase in demand for cooking gas which led to inflation of prices. LPG on burning releases ample amount of carbon dioxide as compared to methane. It possesses numerous hazards while working with as being heavier tends to sink. Biogas being renewable source of energy generated from wet waste provides sustainable development and clean fuel which is eco-friendly. Biogas is the way possible to solve this being carbon neutral i.e., it doesnt add up carbon in atmosphere but recycles it.

Biogas is a mixture of primarily methane (CH4) 55 60 % and carbon dioxide (CO2) 30 40 % and traceable gases [1]. Anaerobic digestion is a microbial process used for production of biogas; whereby organic matter is broken down by microbiological activity in absence of oxygen. Biomethane is one of the main constituents of biogas which is used as fuel. Biomethane being odourless, blue burning flame is used for cooking and heating purposes. 28 m3 of biogas is equivalent to one domestic LPG cylinder. Organic waste of 200 kgs can contribute one LPG cylinder daily [2].

Traditional biogas plants were prone to various problems like no portability, low quality biomethane production, less efficient, high cost, no filtration equipment and robust design. Hence compact design and more efficient biogas plant is need of future. Anaerobic Digestion

It is a simple process in which micro-organism break down complex organic matter into simple by-products in absence of oxygen. It is further subdivided into 4 steps as follows:-

1. Hydrolysis : being the prime step of anaerobic digestion involves breaking of macromolecules into micro molecules. It involves conversion of organic polymers into monomers using enzymes and bacteria. The macromolecules include polysaccharides, proteins and complex fatty acids which are converted into soluble sugars, amino acids, and simpler fatty acids respectively. Carbohydrates are converted into sugars within few hours whereas proteins and lipids require few days to beak down [3].

2. Acidogenesis : it involves formation of volatile fatty acids from substrate obtained from hydrolysis. It involves conversion of sugars, amino acids, fatty acids into short chain organic acids, alcohols, hydrogen. etc [3].

3. Acetogenesis : it is fermentation process that involves conversion of volatile fatty acids into acetic acid, carbon dioxide and hydrogen with help of specific group of fermenting bacteria called as acetogenic bacteria.

4. Methanogenesis : this is the last stage of anaerobic digestion where the main by-product methane is obtained. In this process microbes known as methanogens are responsible for production of biomethane in suitable conditions. The end products of acetogenesis are converted into methane, carbon dioxide and hydrogen. pH level between 5.5 8.5 and temperature between 30 60 oC must be maintained for higher rate of digestion [3]. At the end of methanogenesis reduction between carbon dioxide and hydrogen takes place resulting in formation of one-third of total biomethane produced [4, 5].

Fig. 1 Anaerobic digestion process Types of Digestors

Based on design there are various types of digestors available. Type of digestor design to be selected is based on geographical condition, climatic condition and feedstock available.

1. Fixed dome digesters : these type of digestors is also known as Chinese digestors which is most common model used for biogas production. [5, 6]. In this type of digestors there is an inlet and outlet through which feedstock is fed and slurry obtained is removed respectively. The greatest advantage of these type of model is no external agent is required to develop pressure inside the digestor as difference between the slurry level and gas in the storage part creates optimum pressure required. The biogas produced is stored in the digestor in upper part itself. These types of digestors are most feasible. [7] . In India fixed dome digestor are further distinguished into Janta and Deenbandhu models.

   1. Janta biogas plant : These type of digesters were firstly introduced in 1978. The basic structure of this type of plant includes integrated structure of digester and gas holder as a whole brick masonry structure. The plant is provided with inlet and outlet shallow well and are connected to digester with help of chutes [8]. These type of plants do not use any steel components as a part of plant providing with less maintenance cost.

      Fig. 2 Janta model biogas plant [8]

   2. Deenbandhu biogas plant : These type of biogas plants was introduced in 1984 in India. As the name suggests these type of biogas plant is the cheapest model introduced among all available models. The main feature of this type is that to reduce installation cost the surface area of plant is minimized without reducing efficiency of plant. The design consists of two spheres of different diameters joined at their bases providing gas chamber as well as digester chamber [8].

      Fig. 3 Deenbandhu biogas plant [9]

2. Floating drum digester : these models was primarily developed in India. In this type of design there is a moveable inverted drum placed on bottom digestor that acts as storage tank and provides required pressure into biogas plant. This drum moves up and down based on amount of biogas accumulated into it and weight of the drum provides necessary constant pressure for the gas flow through pipeline for use. The drum helps to indicate the level of biogas stored into it. [8]

Paramters for digesters operation

Fig. 4 Floating drum biogas plant [11, 12]

1. Feedstock : Kitchen waste provides with more biogas production as it contains carbohydrates, proteins and fats. 1 Kg of kitchen waste produces around 0.3 m3 of gas [13]. At same HRT 1 kg of kitchen produces same amount of biogas which 40 kg of cow dung could produce. Hence 400 times more efficiency can be achieved. The total solid concentration of kitchen waste ranges between 14 25% best suited for biogas production. Hopper could be used is the inlet of the biogas plant which is used to collect the feedstock. Based on the feeding rate of the feedstock hopper capacity could be designed. Experimental feedstock of kitchen waste includes cooked rice, vegetable leftover of tomatoes, carrots, onions, banana peels, etc. were brought from canteen and poured into digestor. The temperature of digester was constant between 38 45 oC during the day and 35 40 oC during the night. [14].

2. Particle size: Particle size highly affects the biogas production. Smaller the particle size more the biogas production and lesser the HRT required. Hence smaller particle size would lead into better optimization of plant design. Particle size less than 5 mm gives more biogas production [15]. In order to achieve smaller particle size shredder mechanism

   could be incorporated. HRT is largely influenced by particle size of the feed. Smaller the size of feed, lesser the HRT. Hence, it is essential to use some mechanism such as grinder or shredder to convert waste into smaller particle to improve overall efficiency of plant. Size and material optimization are done [13]. Five particles were taken as sample of following sizes 0.088, 0.40, 1.0, 6.0 and 30.0 mm. Maximum biogas was produced from 0.088 and 0.40 mm sized particle. The physical pre-treatment like grinding also leads to increased biogas production. It was concluded that the smaller the particle size more degradation of feed and more biogas production. [16].

3. Feeding rate: Organic loading rate highly depends on availability of feedstock and amount of biogas to be produced. For household and small canteen purpose 3 25 kg/day feeding rate is observed. In order to provide liquified inflow to the feed 20 % water of total feedings is added to make kitchen waste slurry [17]. For example, considering college canteen if 10 kg/day of kitchen waste is fed then 2 litres (approx.) of water is needed to provide required liquified inflow. 1 kg of kitchen waste when digested properly yields 0.3 m3 of biogas. The gas produced by kitchen waste feeding of 80 kg/day gives 24 m3/day of biogas. HRT is selected as 30 days. Sufficient biogas of 2.4 m3 can be obtained by loading rate of 10 kg/day [18].

4. C/N ratio: C/N ratio is ratio of carbon to nitrogen in any substrate. C/N ratio of feedstock for biogas plant ranges from 10:1 to 30:1. For kitchen waste the range lies from 15:1 to 25:1 [18]. C/N ratio from 15 to 25 is best suited for different physical and chemical pretreatment like fungi activation. Increased temperature makes it more effective and provides with rapid digestion with lower retention time. To maintain higher temperature of digester tank, energy consumption for heater arrangement increases and also inhibition of ammonia formation is large [19].

5. Temperature: Optimum temperature for mesophilic bacteria culture to develop is between 35 45 oC [5]. In the mesophilic range, the activity and growth rate of bacteria decrease by 50% for each 10 oC drop. Fall in biogas production starts, when temperatures decrease to 20 oC and the production even stops at 10 oC. Heating system based on solar water tubes increases the digester chamber temperature. It is seen that 35 oC is optimum temperature required for faster digestion and particle size was taken 0.05 mm. It was noted that biogas yield and degradation efficiency were substantially higher for the substrate of pH 7 compared to other pH values. Heating element could be provided in order to maintain the temperature of digester for all weather conditions. Solar based water tubing arrangement which is non- direct method of heating could be replaced by direct heater arrangement [20].

6. Retention time: Hydraulic Retention Time (detention period) ranges between 15 days to 100 days [5]. HRT is highly affected by temperature of the digester. Low temperature requires higher HRT and larger digester size whereas high temperature requires lower HRT and lower digester size. Very low HRT leads to wash out of reactor which means all the microorganism escape out of reactor. It is highly recommended to consider minimum 30 40 days as HRT, best suited for most of areas of India for operating temp of 35 40 oC. Use of kitchen waste improves production of biogas as kitchen waste has more nutrients compared to cow dung [21].

7. pH: Mesophilic bacteria are more efficient to work with neutral pH. Hence considering pH of 7.5 8.5 as operational pH of the digester in order to achieve more biogas production [22].

8. Agitation: Since HRT of a biogas plant could be long which leads to scum and crust formation on top layer leading to stop further biodegradation and stoppage of biogas production thus hampering the efficiency of the plant. Therefore, agitation i.e., mixing of whole slurry could be incorporated. Using automated mechanism will greatly enhance efficiency of the plant.

9. Filtration: Along with production of CH4 other gases like CO2, H2S, water vapours and other trace elements are produced which reduces the efficiency of biogas plant. In order to increase efficiency these impurities must be removed. For these purposes filtration system has to be used. 10 % NaOH in water or else 40 % KOH solution could be used for CO2 filtration i.e., when biogas passed through the solution CO2 is removed [23]. H2S could be highly dangerous to inhale and corrosive in nature so must be removed. When biogas passed through iron wool reacts with it to remove it, if considered rusted would give better results. Filtration of biogas could provide with up to 99 % pure bio-methane that could be used for cooking purpose, [23, 24]. CO2 has no heat value i.e.; they don't take part in combustion hence must be removed. Raw Methane i.e., methane with other impurities has heat value of 7.2 kWh/m3 and after filtration we gets

   9.94 kWh/m3 hence efficiency increases by 27.5 % [23].

10. Material: Traditional biogas plants were made of bricks and cement provide with a good self-life but having the greatest disadvantage of leakage of biogas and robust design made is less suitable in use. Organic acids produced during anaerobic reaction may corrode the digester body if made of steel of any metal making its self-life shorter although it provides with no leakage of gas. FRP material developed offers with more tensile strength and is thermally and chemically resistant, hence provide with longer life span than steel. If FRP material is used for biogas plant, it offers most economical body of plant having longer lifespan along.

    Table 1. Comparison of mechanical properties of FRP and steel [25]

    Proposed Design

    The proposed design of biogas plant is fixed dome model comprising with agitator mechanism.

    1. Digester volume: Digester volume can be calculated based on feeding rate and HRT. For feeding rate of 3 kg (kitchen waste), 0.6 litres of water (20% of total waste) is required to provide inflow for the waste [16]. Considering HRT = 30 days recommended for weather conditions of Maharashtra.

       Inflow = 3 kg waste + 0.6 L water = 3.6 litres/day (considering kg = litre).

       Volume of digester = daily inflow x HRT = 3.6 x 30 = 108 L + 10% (due to formation of bubbles) = 120 L (approx.).

    2. Gas storage volume: Gas produced is stored in the upper part of digester and is used as per requirement. COD of kitchen waste = 242 g/L [24].

       Total COD of feed = COD x waste inflow = 242 x 3 = 726 g.

       4 g COD = 1.4 L CH4 [16]. Therefore, CH4 roduced = (726 x 1.4) / 4 = 254.1 L/day. Total biogas produced = 254.1 /

       0.65 = 390 L/day (approx.)

    3. Total volume:

       Total volume of plant = 120 + 390 + agitator volume + tolerances = 550 L (approx.)

    4. Dimensions of plant:

       Cylindrical biogas plant having radius = 0.4 m, height = 1.1 m provides with the required volume i.e., 550 L.

       Fig. 5 Prospective and section view of proposed model

       METHODOLOGY

       Based on the trends observed the following steps could be followed in order to achieve better biogas production along with applying parameters suggested in to this review paper. This would surely lead in more production of biogas having higher biomethane compositions.

       Mesophilic bacteria culture (inoculum) is developed to the digestor

       Biogas produced is stored in the gas storage part of the plant

       As per requirement of biogas, gas valve is opened

       As per optimal conditions waste is

       Mixing blades mix the composition in order

       Biogas passes through various filters which

       collected and put into

       to avoid formation of

       filters out

       carbon

       hopper

       crust on the top layer (scum layer)

       dioxide, hydrogen sulphide and moisture

       The waste is crushed

       The crushed waste is

       into fine particles shredder.

       sized using

       fed into digestor where anaerobic digestion takes place

       Effluent generated is removed periodically and used as fertiliser

       Fig. 6 Flow chart of methodology

       APPLICATIONS

       1. Cooking and heating: Biogas produced is mainly used for cooking purposes [26, 27]. The value of biogas needed for cooking purpose for family of four varies from 30 to 45 m3 per month which is equivalent to 1 LPG cylinder per month. The calorific value of biogas and LPG are 5000 kcal per m3 and 10800 kcal per kg respectively which when compared on monthly scale is equivalent.

       2. Fertiliser: the left over slurry is rich in nitrogen, phosphorus and potassium which can be used as fertilizer. This slurry increased potato cultivation by 27.5% compared to no fertilizer. [28, 29]. Biogas slurry could be helpful in growing algae and fish food. The fertilizer obtained is organic in nature and no chemicals are involved which is rich in biomass.

       3. Other applications: they include electricity and power generation; livestock bedding and helps maintaining nutrient of soil along with wet waste reduction.

CONCLUSION

Biogas could be alternative source for fuelling option. This ensures proper handling and disposal of wet waste in cities. Digestate obtained is highly rich in N:P:K ratio which increases the growth of plant by greater percentage as compared to chemical fertilizer. Kitchen waste has the best suited C/N ratio of 25:1 for biogas production. As per study by incorporating the proposed parameters and substrate parameters would produce more biogas having higher biomethane composition, this also increases efficiency of biogas plant. Biogas also helps to maintain carbon neutrality. By applying all studied parameters biogas containing 75 85 % biomethane could be obtained. Biogas is a promising technology which provides sustainable fuelling option along with economic benefits. Further study on efficiency and cost of biogas plant would surely make it most affordable and easy to use technology leading towards greener environment.

REFERENCES:

BOOKS

1. Anna Karlsson, Annika Björn, Sepehr Shakeri Yekta, Bo H. Svensson, Improvement of the biogas production process, Linköping University, Biogas Research Centre, SE 581 83, 2014.

2. Akanksha Agrawal, Parmesh Kumar Chaudhari, Prabir Ghosh, Hydrolysis of the kitchen waste through dry anaerobic digestion – a sustainable environmental practice for its effective management, Research square, 2021.

3. Teodorita Al Seadi, Dominik Rutz, Heinz Prassl, Michael Köttner, Tobias Finsterwalder, Silke Volk, Rainer Janssen, Biogas handbook, University of Southern Denmark Esbjerg, ISBN 978-87-992962-0-0, 2008.

4. Hamed El Mashad, Ruihong Zhang, Biogas energy from organic wastes, Introduction to Biosystems Engineering, ISBN 978 1 949373 97 4, 2020.

Journal papers

1. Adiotomre, K. and Ukrakpor E. F., "Production of biogas from kitchen waste and cow dung", IJISETR, ISSN 2360 896x, 2015.

2. Mohamad Y. Mustafa, Rajnish K. Calay and E. Romain, Biogas from organic waste a case study, Procedia Engineering 146, Elsevier, 310 317, 2016.

3. Deublein and D. Steinhauser, A Biogas from Waste and Renewable Resources. Wiley Online Library: Weinheim, Germany, 2008.

4. Karthik Rajendran, Solmaz Aslanzadeh and Mohammad J. Taherzadeh, Household biogas digesters a review, Energies, ISSN 1996 1073, 2012.

5. Santerre, M.T. and Smith, K.R., Measures of appropriateness: The resource requirements of anaerobic digestion (biogas) systems, World Dev., 10, 239 261, 1982.

6. Akinbami, J.F.K.; Ilori, M.O.; Oyebisi, T.O.; Akinwumi, I.O. and Adeoti, O.,

   Biogas energy use in Nigeria: Current status, future prospects and policy implications, Renew. Sustain. Energy, Rev. 5, 97 112, 2001.

7. K. Jatinder Singh and Sarbjit Singh Sooch, Comparative study of economics of different models of family size biogas plants for state of Punjab, India, Elsevier, Energy Conversion and Management 45, 1329 1341, 2004.

8. S. S. Sooch and A Gautam, PAU kutcha pucca model of biogas plant in Punjab

   a case study, Agricultural Energy Today, Vol 37 (3), 2013.

9. Deepinder Singh Aulakh, Jasvarinder Chalotra and S. S. Sooch, Survey report: performance evaluation of Deenbandhu biogas plants installed in various regions of Punjab, India, IJCMAS, ISSN 2319 7706, Vol 9, number 2, 2020.

10. Richard Arthur, Martina Francisca Baidoo and Edward Antwi, Biogas as a potential renewable energy source: a Ghanaian case study: Elsevier, Renewable Energy, Vol 36, Issue 5, 1510 1516, 2011.

11. M. Osei-Marfo, E. Awuah and N. K. de Vries, Biogas technology diffusion and shortfalls in the central and greater Accra regions of Ghana, Water Practice & Technology, Vol 13 4, 2018.

12. Ogur, E. O. and Mbatia, S. "Conversion of kitchen waste into biogas", IJES, ISSN 2319 1813, 2013.

13. VunduruNookaSaiVikram Kumar, The production of biogas using kitchen waste IJSER, ISSN 2229 5518, 2016.

14. Adiotomre, K. and Ukrakpor E. F., "Production of biogas from kitchen waste and cow dung", IJISETR, ISSN 2360 896x, 2015.

15. EK Orhorhoro, POB Ebunilo and EG Sadjere, Design of Bio-Waste Grinding Machine for Anaerobic Digestion (AD) System EJAET, ISSN 2394 658X, 2017.

16 .Dr Nitin W Ingole, Development and design of biogas plant for treatment of kitchen waste, IJRESTs, ISSN 2395-6453, 2016.

1. Gurinderpal Singh, V. K. Jain and Amanpreet Singh, Effect of temperature and other factors on anaerobic digestion process, responsible for biogas production, IJTAM, ISSN 0973 6085, 2017.

2. Ziana Ziauddin, Rajesh P., "Production and analysis of biogas from kitchen waste", IRJET, ISSN 2395 0056, 2015.

3. Sudhir K. Sharma, I. M. Mishra, M. P. Sharma, Effect of particle size on biogas generation from biomass residues, Elsevier, Biomass, Vol 17, Issue 4, 1988.

4. Ashwini M. V., Robinson P., Nithin P. S., Seella Charan Design of Automatic Organic Waste Shredder for Composting IJRTE, ISSN 2277 3878, 2020.

5. Ejiko S, Adewuyi R. A. and Filani O. A., Development of a household biogas digester, IJMSME, ISSN 2454 9711, 2019.

6. Smith Falco, Gokul Kunchumuthu, Rohan Bharate, Nishant Bhilare, Prof. Vishwas Palve, Portable biogas purification system using NaOH water scrubber, iron wool and silica gel, IJERT, ISSN 2278 0181, 2020.

   /li>

7. N. H. S. Ray, M. K. Mohanty, R. C. Mohanty, Biogas compression and storage system for cooking applications in rural households, IJRER, Vol.6, No.2, 2016.

8. Akanksha Agrawal, Parmesh Kumar Chaudhari and Prabir Ghosh, Hydrolysis of the kitchen waste through dry anaerobic digestion – a sustainable environmental practice for its effective management, Research Square, 2021.

9. Imad Shakir Abbood, Sief aldeen Odaa, Kamalaldin F. Hasan and Mohammed A.

   Jasim, Properties evaluation of fibre reinforced polymers and their contituents materials used in structures a review, Materials Today: Proceeding 43, Elsevier, 1003 1008, 2021.

10. Gautam, R.; Baral, S. and Herat, S., Biogas as a sustainable energy source in Nepal: present status and future challenges, Renew. Sustain. Energy Rev. 13, 248 252, 2009.

11. Ferrer, I.; Gamiz, M.; Almeida, M. and Ruiz, A, Pilot project of biogas production from pig manure and urine mixture at ambient temperature in Ventanilla (Lima, Peru) Waste Manag. (Oxf.) 29, 168 173, 2009.

12. Garfí, M.; Gelman, P.; Comas, J.; Carrasco, W. and Ferrer, I., Agricultural reuse of the digestate from low-cost tubular digesters in rural Andean communities, Waste Manag. (Oxf.) 31, 2584 2589, 2011.

13. Garfí, M.; Ferrer-Martí, L.; Villegas, V. and Ferrer, I., Psychrophilic anaerobic digestion of guinea pig manure in low-cost tubular digesters at high altitude, Bioresour. Technol. 102, 6356 6359, 2011.

14. Shipra Arora, Developing Suitable Selection Technique of Organic Food Waste Shredder of Biogas Plant IJRSI, ISSN 2321 2705, 2016.

15. Anshu Kumar Singh, Varun Kumar Jha, Vijay Pratap Singh, Deep Goel, ChandraShekhar Singh, Fabrication and design of self- pressurised portable biogas plant for kitchen waste IJAER, ISSN 0973 4562, 2019.

16. E. Aravindaraj, Dr. R. Prabhu, S. Kalaimani, L. Natrayan, Experimental Analysis of Biogas from Kitchen Wastes IJIRSET, ISSN 2319

    8753, 2017.

17. Barinyima Nkoi, Barinadaa T. Lebele-Alawa, and Benedict Odobeatu, "Design and fabrication of a modified portable biogas digester for renewable cooking-gas production, EJERS, Vol 3, No 3, 2018.

18. S. Sharada, Mr. G. Surendra Babu, K. Hema Latha, Production of biogas from kitchen, IJSDR, ISSN 2455 2631, 2016.

19. Anaswara M. G., Design and fabrication of low-cost biogas digester using poultry waste and pig manure, IRJET, ISSN 2395-0056, 2015.

20. C. S. Agu and J. E. Igwe, Design and construction of an indigenous biogas plant, AJER, ISSN 2320 0847, 2016.

21. Jyothilakshmi R. and S. V. Prakash, Design, fabrication and experimentation of a small scale anaerobic biodigester for domestic biodegradable solid waste with energy recovery and sizing calculations, ELSEVIER, Procedia Environmental Sciences 35, 749 755, 2016.

22. Elasri O., Afilal M. E., Hafidi I., Boujibar O., Chafik T., Proposition of biogas filtration system, JMES, ISSN 2028 2508, 2015.

23. Irfan Abbas, Jizhan Liu, Rana Shahzad Noor, Muhammad Faheem, Muhammad

    Farhan, Muhammad Ameen, Sher Ali Shaikh, Development and performance evaluation of small size household potable biogas plant for domestic use, Springer, Biomass Conv. Bioref., 10, 1007, 2020.

24. T Younas, M Taha, S F Ehtesham, M F Siddiqui, Biogas generation using kitchen waste, ICACER, 51, 01002, 2018.

25. Sachin Kamboj, Jitender Maharshi, Neeladri Sekhar Kachari, Ajmal Saeed, Biogas from kitchen food waste: estimation, applications and economic analysis, IJREAM, ISSN 2454 9150, 2018.

26. S. Shrestha, N. P. Chaulagain, K. R. Shrestha, Biogas production for organic waste management: a case study of canteens organic waste in solid waste management technical support centre, Lalitpur, Nepal, Nep J Environ Sci, ISSN 2350 2901, 2017.

27. Firdos Jahan Khan, Sanket Haridas Ahire, Hrishikesh Suhas Bhagwat, Sarvesh

Shailesh Sanap, Pooja Sukhdev Lamkhade, Design and simulation of multipurpose waste processing unit, Journal of Huazhong University of Science and Technology, ISSN 1671 4512, 2021.