L f e / ^ O ^ /&1 /Ob 
In Vessel Composting of Urban Solid Waste 
A Thesis submitted in partial fulfi l lment of the requirement for the Degree of 
Master o f Science in Engineering 
Research work supervised by 
Dr. (Mrs.) Sanja Gunawardana 
Dr. Ajith de Alwis 
Dr. Sumith Pilapitiya 
Dr. (Mrs.) Indrika Abegunawardana 
Department of Chemical and Process Engineering 
University of Moratuwa 
Moratuwa 
Sri Lanka 
By 
V.I.S.C.K. Fernando 
6 6 - O ^ 
July 2004 
85400 
University of Moratuwa 
85400 
Declaration 
This thesis is a report of research work carried out in the Department of Chemical & 
Process Engineering, University of Moratuwa, Sri Lanka between September 2002 
and July 2004. The work included in this thesis is part or whole has not been 
submitted for any other academic qualification at any institution. 
V.I.S.C.K. Fernando 
Department of Chemical & Process Engineering 
University of Moratuwa 
Moratuwa 
Certified by 
•Department of Chemical & process Engineering 
University of Moratuwa 
Moratuwa 
Abstract 
Solid waste is the most critical and visible pollution stream in Sri Lanka. As many 
developing countries urban solid waste in Sri Lanka consists wi th high organic and wet solid 
waste. Studies on solid waste show that about 8 1 % o f the total waste consists o f organic solid 
waste. Organic waste can be composted and it is clear i f organic waste issue is addressed the 
major part of the sold waste component w i l l be automatically addressed. 
Above statistics show that the major component of any sustainable solid waste management 
plan should be organic waste treatment. 
However in Sri Lanka composting is not a popular option for solid waste. There are many 
reasons behind it. Some o f them are long lead composting time, low quality o f the final 
product, mixed solid waste, lack o f funds, technical problems in composting, less availability 
of expertise, etc. 
Under this background there is a need of sustainable composting system which is suitable 
for high organic urban solid waste while answering the drawbacks o f the present composting 
systems. This research aims to answer that timely and growing problem. 
Since composting is happened as a result of microbiological activities, by optimizing the 
factors for microbiological activities composting process can be optimized. This is the 
fundamental argument in this research. 
BIOCOM-MSW composting system(the method which is introduced by this research) 
consists of relevant equipment for semi automation system, wi th a major component o f drum 
reactor. The strategies are used to maintain a high composting process are controlling C:N 
ratio, moisture content, particle size, rotating speed and rotating time. It is aimed to maintain 
the thermophilic stage of the composting throughout the composting process. 
1 
Final outcome o f the research shows through this new attempt, after three days it is possible 
to obtain a stable product from organic solid waste. It can be identified that the waste has 
gone through a rapid stabilization. Result of this research shows that it can be introduced in 
two major practical implementations. They are as follows; 
1. Rapid organic waste stabilization 
2. Rapid pretreatment in sanitary land f i l l ing instead o f biological pretreatment 
In present back ground, export and local market consist wi th an increasing demand for 
organic foods, especially for fruits, vegetables and tea. According to that there is an 
increasing demand for organic fertilizers. 
It is a timely need o f the country to identify a solution for organic solid waste not only in the 
point o f environment and health but also in the point o f view o f economic and agricultural 
sector development. 
Out come of this research has already identified as a national priority by the ministry o f 
industries, tourism and investment promotion. Ministry has identified this research as one o f 
the project among the six for the implementation in next five years. Presently ministry seeks 
for foreign funding through the external resources department o f the ministry o f finance and 
planning. 
i i 
Acknowledgements 
To conduct my research in successful manner, I had inputs in various ways and various 
levels. I take this opportunity to remind them gratefully, who are part of this success. 
Firstly I wish to offer my gratefulness to my internal supervisors Dr. Ajith de Alwis and 
Dr.(Mrs.) Sanja Gunawardana, who encourage me all the time and provide valuable 
advises and inputs to conduct the work. In addition to the technical inputs, I would like to 
mention about the helps of them to fast track the procedures after my research when I was 
hurry to travel UK. 
At the same time I would thank my external supervisors Dr. Sumith Pilapitiya of the 
world bank, Dr. (Mrs.) Indika Abegunawardana of the University of Moratuwa. 
I would like to thank progress review committee of the research Dr. Suren and Dr.(Mrs.) 
Padma for their valuable comments and healp. Further more to Dr.(Mrs.) Padma 
Amarasingha for the support provided as the former head of the department. 
I like to remember Dr. Basnayaka, University of Peradeniya and Dr.(Miss) Manisha, 
University of Moratuwa of the viva committee for their support to conduct a quick viva 
when I was hurry to travel UK. 
Big thank to Lashan akka for the continuous help in many many ways. Thank to Aruna 
Manipura and Asanga. 
I like to thank Mr. Kuruppu, Director of Synergetics Lanka(pvt) Ltd; my previous 
employer who provided me leaves to carry out my research. 
I like to thank Mr. Sarath Gunathilake at Jinasena, environmental lab staff and the 
polymer lab staff of the chemical department, Mr. Leelarathna (ME), Mr. Karunarathna & 
staff of the maintenance department, Mr. Muralie at electro serve, Ms. Felisia at SLS 
institute, Mr. Priyantha at shawn engineers, all canteen and cleaning contractors, etc. 
Further more I like to remember National Research CouncilfNRC) and University 
Research Fund for the financial assistance. 
I like to give a special thank to my wife Melanthie who always encourage and help many 
ways to achieve this challenging work. 
Contents 
Abstract i 
Acknowledgement i i 
1.0 Background 1 
1.1 Impacts of SW 2 
1.1.1 Point of View of Environment 3 
1.1.2 Point of View of Health 4 
1.1.3 Impact on aesthetic beauty 4 
1.2 Options for Solid Waste 4 
1.2.1 Reduce 5 
1.2.2 Reuse 5 
1.2.3 Recycle 6 
1.2.3.1 Bio gas 6 
1.2.3.2 Composting 7 
1.2.3.3 Incineration 7 
1.2.3.4 Recycling 8 
1.3 Waste as an Assert 8 
2.0 Introduction to the SW Generation and Management Aspects 9 
2.1 History of SW 9 
2.2 SW of Sri Lanka 9 
2.2.1 SW Treatments in Sri Lanka 10 
2.2.2 SW Production in SL 12 
2.2.3 SW Composition in Sri Lanka 13 
2.2.4 Land Fill Sites 16 
2.2.5 Resource Involvement in SWM in Sri Lanka 18 
2.2.5.1 Human Resources 18 
2.2.5.2 Physical Resources 19 
2.2.6 Cost on SWM 19 
2.3 Objectives and the Scope of the Research 24 
3.0 Literature Review 25 
3.1 What is Waste? 25 
3.2 What is Solid Waste? 25 
3.3 Municipal Solid Waste 25 
3.4 Classification of Solid Waste 26 
3.5 What is Organic Waste? 26 
3.6 What is Composting? 27 
3.7 Why a controlled composting process is needed? 28 
3.8 What is Compost? 28 
3.9 What is Aerobic Composting? 29 
3.10 What is Anaerobic Composting? 30 
3.11 Phases of Composting 31 
3.11.1 Mesophilic Composting 32 
3.11.2 Thermophilic Composting 32 
3.11.3 Mesophilic Decomposting (Secondary) 33 
3.12 Differences between fresh and mature compost 33 
3.13 Factors affect the composting process 33 
3.14 Key Elements 44 
3.15 Nutrients 34 
3.16 C:N Ratio 35 
3.17 C:P Ratio 35 
3.18 Moisture Content 36 
3.19 Temperature 36 
3.20 Particle size 36 
4.0 Materials and Methods 37 
4.1 Waste Generation Characteristics and Analysis 37 
4.1.1 What is Solid Waste Analysis? 37 
4.1.2 Why is it Necessary to do a Solid Waste Analysis? 37 
4.1.3 How the Sources are Selected for Obtaining Samples for 
Analysis? 37 
4.1.4 Solid Waste in Urban Areas 38 
4.1.5 Identification of the Sources of Waste - 38 
4.1.6 Identification of the Waste Sample 39 
4.1.7 Sample Size 39 
4.1.7.1 Waste Analysis Anuradhapura Urban Council 39 
4.1.7.2 Waste Analysis Trincomalee Urban Council 41 
4.1.7.3 Waste Analysis University of Moratuwa 44 
4.2 Determination of Moisture Content, Carbon and Nitrogen 45 
4.2.1 Identification of waste categories 46 
4.2.2 Determination of Moisture Content 46 
4.2.3 Determination of the Nitrogen Content 49 
4.2.3.1 Dumas Method 49 
4.2.3.2 Persulfate Method 50 
4.2.3.3 Kjeldahl Method 50 
4.2.4 Carbon Content 54 
4.2.4.1 Walkley Black Method 54 
4.2.4.2 Fixed ash method 55 
4.3 C:N Ratio Calculation 59 
4.3.1 C:N Ratio 59 
4.3.2 Moisture Content 59 
4.4 BIOCOM-MSW Composting System 60 
4.4.1 Aims and Objectives of the BIOCOM-MSW 60 
4.4.2 Components of the BOICOM-MSW 60 
4.4.2.1 Unloading Ramp 60 
4.4.2.2 Conveyor Belt 1 - from the Unloading Point to the 
Shredder 60 
4.4.2.3 Shredder 60 
4.4.2.4 Conveyor Belt 2 - Shredder to the Rotating Drum 61 
4.4.2.5 Rotating Drum 61 
4.4.2.6 Variable Speed Controller 62 
4.4.3 Components Have to be Linked to the BIOCOM-MSW System 63 
4.4.3.1 Campbell CR 10 X Data Logger 63 
4.4.3.2 Campbell 108 Temperature Probe 64 
4.4.4 Future Development Needs 64 
4.4.5 Power Consumption of the BIOCOM-MSW 
4.5 Operational Conditions and Tests on the Research 
4.5.1 Operational Conditions 
4.5.2 Tests on the Research 
5.0 Observations and Results 
5.1 Observations 
5.2 Results 
5.2.1 Bulk Density Changes with Time 
5.2.2 Moisture Content Changes with Time 
5.2.3 Changes in Carbon Content 
5.2.4 Changes in Particle Size 
6.0 Analysis and Discussion of Results 
6.1 Composition of Waste 
6.2 Bulk Density Variation 
6.3 Moisture Content Variation 
6.4 Carbon Content Variation 
6.5 Particle Size Variation 
6.6 Conclusion 
7.0 Future Works 
7.1 Future Steps to Develop the Compost Industry in Sri Lanka 
7.2 Future Steps to Develop the BIOCOM-MSW System 
References 
Annexure