2f2 -
ANALYSIS AND DEVELOPMENT OF HIGH RATE 
COMPOSTING SYSTEM USING MUNICIPAL 
SOLID WASTE IN SRI LANKA 
By 
W.M.J.A.S.B. Manipura 
A thesis submitted in partial fulfillment of the requirements 
for the Degree of 
Master of Engineering (Research) 
Research work supervised 
By 
Dr. Ajith De Abvis 
Dr. Sumith Pilapitiya 
Mr. S. Pathinathar 
JJWIVERSITVLLSSA.SRIlAfiIfCil 
M O R A T U W A * 
DEPARTMENT OF CIVIL ENGINEERING 
UNIVERSITY OF MORATUWA 
MORATUWA 
SRI LANKA 
1 5 1 3 8 
University of Moratuwa 
75138 
July 2002 
7 5 1 3 8 
Abstract 
Municipal solid waste has become a major problem in every country in terms of 
public health and environmental damage. As a developing country, Sri Lanka too 
faces the same challenge not only by public health and environmental damage, but 
also in finding an affordable yet effective technology, which is socially and 
economically acceptable. Municipal Solid Waste (MSW) is qualitatively 
heterogeneous. Therefore, it is difficult to find a unique solution for proper treatment. 
I.e. The solution is always an integrated one, which consists of sorting, 
biological/thermal/chemical treatment, recycling and land filling. However 
quantification and characterization of solid waste in a given area are important factors 
prior to selecting suitable technology. Therefore, it is required to find waste quantity, 
composition, density, moisture content, annual rate of waste generation and calorific 
value of waste etc in a given area. In Sri Lanka, moisture content and organic fraction 
are reasonably high and lack of high thermal value materials in solid waste stream, 
have lead to an overall low calorific value of MSW. The general practice for handling 
the M S W is low rate composting systems. Most have been failed due to poor process 
management, lack of knowledge of proper operation (feedstock formulation, process 
control, end point indicators), poor product quality, long lead-time, weaker 
community participation and lack of public awareness. In all systems existing at 
present bad odor and leachate are unsolved issues. These systems have largely been 
controlled by default rather than by design. Thus, losing the public confidence on 
composting is inevitable. 
Properly engineered composting systems require to monitor and control of key 
parameters such as aeration, C/N ratio of feedstock, pile temperature, moisture content 
and particle size. The broad objectives of the research were, a detailed review of solid 
waste management practices in Sri Lanka and process of composting, Identification of 
composting strategies & evaluation of systems, and design of a high rate in-vessel 
composting system. During the design, it was considered to maintain the opt imum 
environmental conditions for higher rate of decomposition by microbial activities, 
aeration demands, and required moisture content throughout the process. The main 
component of the model is a rotating drum reactor, which is operated under the 
thermophilic temperature conditions. The rate of decomposition at thermophilic 
temperatures is much higher (low residence time) than the mesophilic temperatures. A 
shredder could be used for size reduction of incoming feed in order to determine the 
optimum particle size. As source separation is very poor in Sri Lanka, this research 
addresses the possibility of using a semi-mechanized waste segregation device at the 
secondary stage. Special care was taken to control the odor and leachate of the system. 
On the other hand, the confidence on low rate windrow / static pile composting among 
the people have been lost due to the process mismanagement. Therefore, the design 
offers to have an energy optimized semi mechanized system in which minimum labor 
contact with the waste occurs. 
The reactor is operated by a feedback control system, in which real-time monitoring of 
critical parameters are done. Based on the existing value and the set point (opt imum 
value for each parameter: moisture and aeration), the control action is taken. Further, 
intermittent rotation of the reactor facilitates the proper temperature distribution 
inside, particle size reduction and uniform porosity throughout the mixture while 
reducing the energy consumption faced by the continuous operated system. Sensor 
II 
setup at different heights of the reactor monitors the temperature and moisture content 
along the axis of the system. It has been observed that moisture is the limiting factor, 
when the temperature feedback control system is used in the composting. However, 
real-time monitoring of the moisture content avoids this difficulty. Further, weak 
pathogen inactivation is a major drawback found in most of the manually turned 
systems. Intermittent rotation and temperature feedback control system ensure the 
proper temperature distribution across the reactor and mixes the matrix properly in 
order to subject to uniform temperature throughout the mass. The modular basis helps 
for easy movement and it consumes less space compared to the windrow system. 
According to the national database on solid waste in Sri Lanka, 8 8 % of Local 
Authorities collects less than 10 Tons per day. This shows the possibility of use of 
modular units in areas, where space is limited. Close monitoring of the critical 
parameters of the system helps to maintain optimal decomposition rates while 
ensuring consisted product quality during the decomposition. 
Since organic farming is a growing area in export-oriented agriculture (Tea, 
vegetables) in our country, this research helps to produce a good soil conditioner (with 
consistent finished product) using M S W while solving a major environmental 
problem. Tea plantation companies put special attention to identify the requirements 
of quality standards for the production of famous 'Ceylon Tea ' . Hence as a part of this 
work, analysis of the critical parameters of the compost, manufactured by different 
organizations in the country that use solid waste as the substrate was carried out. It is 
important to match composting quality and the particular plantation requirement to 
develop a sustainable market for the compost produced using MSW. This has been 
particularly lacking in the Sri Lankan market with the compost producer hoping to 
realize a good price for anything that is produced; an expectation that had not been 
realized. 
Ill 
Acknowledgement 
The author wishes to express his sincere gratitude to Dr. Ajith De Alwis, Dr. Sumith 
Pilapitiya, Prof. Malik Ranasinghe, Dr. Mrs. Indrika Abeygunawardhana and Mr. S. 
Pathinathar for their valuable advices, guidance, encouragement and the extended 
support through out the research. It was really a privilege to work under them and 
their kind directions, which helped me to understand the art of researches. The whole 
research was beyond the imagination, unless otherwise the necessary funding 
arrangements were done by Dr. Ajith de Alwis, Dr. Sumith Pilapitiya and Prof. Malik 
Ranasinghe. 
Author extremely grateful to Miss L. C. Jayawardhana for the generous support and 
keep of team spirit all the time giving useful comments and necessary coordination 
with all relevant organizations in order to make reality of BIOCOM - M S W and the 
field studies done. 
Appreciation is also extended to Dr. Frank Warnakulasooriya, Mr. Nimal Riligala, Mr. 
Prabath and Mr. Thushan of Jinasena Engineering Technologies at Ekala for 
fabricating the reactor and giving useful comments with modifications as necessary 
and delivering it on time. 
Author grateful to Dr. Ben Basnayake of Dept. of Agricultural Engineering, 
University of Peradeniya for giving useful comments during the design of reactor. 
The author grateful to Dr. Ananda Mallawatantri of USAEP for donating a Data 
logger and necessary accessories to the Dept. of Chemical and Process Engineering, 
University of Moratuwa. This is very much useful for the characterization studies of 
the reactor. 
Appreciation is also extended to Dr. Arulia Anandacumaraswamy of Tea Research 
Institute of Sri Lanka, Talawakele for giving advises and necessary information in 
selecting the data logger and its accessories. 
Author wishes to thank Dr. Lateef and Mrs. Marikkar of Horticulture Research and 
Development Institute at Gannoruwa for giving the necessary assistance to analyze the 
compost samples. 
Author wishes to thank Dr. Mahesh Jayaweera and Ms. Priyanka Dissanayake for 
giving the necessary assistance for the heavy metal analysis of compost at the 
Environmental Engineering laboratory of the Dept. of Civil Engineering. 
Appreciation should also go to Prof. Kovoor, Mrs. Maneesha Rajapaksha and Mr. 
Nishantha of National Research Council for giving the necessary administrative 
support during the transactions related to N R C funds and the coordination with the 
NRC. 
Author wishes to extremely thank Prof. Malik Ranasinghe, Dr. Asoka Perera, Dr. 
Gamini Kidikara and Dr. Niranjan Gunawardhana of Construction Management 
Division of the Dept. of Civil Engineering for giving the freedom to use the lab freely, 
exceeding the country 's norm of only in office hours concept! 
IV 
Appreciation is extended to Mr. Sanjaya Sooriyarachchi and Miss Champika 
Jayawardhna at the Construction Management Division of the Dept. of Civil 
Engineering for the assistance given during the research. 
Author wishes to acknowledge the National Research Council (NRC), University of 
Moratuwa and Environment Action 1 Plan (EA1P) and United States - Asia 
Environmental Partnership (USAEP) for providing the funds for this research 
otherwise it is just an imagination. 
At last, but not least, author thanks his parents, brothers and sister for their constant 
encouragement and support given with understanding during the studies at all the 
time. 
v 
This thesis is dedicated to my parents for caring & making me to see the world as a 
better place and to Dr. Ajith de Alwis and Dr. Sumith Pilapitiya who paved the way 
for graduate studies and insight into the research making the life more meaningful. 
VI 
Contents 
Abstract 
Acknowledgements 
Dedication 
Content 
List of Figures 
List of Tables 
Chapter One: Introduction 
1.1 Garbage - Urban waste management issue 
1.2 Problems of mismanagement of solid waste 
1.3 The need analysis for ISWM 
1.4 Waste as a Resource 
1.5 Objectives and the scope of the research 
1.6 Thesis Structure 
Chapter Two: Municipal Solid Waste in Sri Lanka 
2.1 Characteristics and Generation of MSW in Sri Lanka 
2.2 Review of solid waste management efforts 
2.3 Lessons to be learnt 
2.4 Role of Composting in ISMW in Sri Lanka 
Chapter Three: Literature Review 
3.1 Basic Science of Composting 
3.1.1 What is composting? 
3.1.2 Critical Parameters 
a. Microorganisms 
b. Raw Materials and Particle Size 
c. Moisture 
d. Aeration (Oxygen) 
e. Temperature 
3.1.3 Compost Maturity 
a. Pathogen Inactivation 
b. Temperature 
3.2 Technology of Composting 
3.2.1 Process configuration and control strategy 
3.2.2 Different Control Strategies 
a. The Beltsville Control Strategy 
b. The Rutgers Control Strategy 
c. Oxygen Feedback Control Strategy 
d. The Linear Temperature Feedback (modified Rutgi 
3.2.3 Comparison of Different Control Strategies 
3.3 Review of Composting Technologies 
3.3.1 Vertical Reactors 
3.3.2 Horizontal Reactors 
3.3.3 Rotating drum Reactors 
3.4 Review of composting applications 
3.5 Compost as a resource for soil enhancement and limitations 
VII 
3.6 Further Research Needs 37 
Chapter Four: Composting System Design and Utilization 38 
4.1 Selection of the composting technology 38 
4.2 Feedstock Characterization and Preparation 41 
4.3 Basic design of the composting system 42 
4.4 Process Control 45 
4.5 Typical compost analysis from Sri Lankan 46 
Chapter Five: BIOCOM-MSW System 47 
4. 5.1 Principles of the system design 47 
5.2 System characteristics 57 
5.3 Operational Characteristics 60 
5.4 Fabrication, installation and daily operation 60 
5.5 Different stages of BIOCOM - MSW development 62 
Chapter Six: Results and Conclusion 63 
6.1 Review of Solid Waste Management practices in Sri Lanka. 63 
6.2 Compilation of visited existing composting practices 62 
6.3 Design of high rate composting system 68 
Chapter seven: Recommendations for future studies 71 
References 72 
Appendix A 76 
VIII 
List of Tables 
Table 1.1 :Typical waste composition in Sri Lanka 4 
Table 2.1 :District wise waste percentage composition of biodegradable 9 
Materials 
Table 2.2:Waste Composit ion Atakalanpanna Pradeshiya Sabha 10 
Table 2.3:Waste Composition of Vauniya Urban Council 11 
Table 2.4:Waste Composit ion Hambantota Urban Council 12 
Table 2.5:Comparison of biodegradable waste composition 13 
Table 2.6:Solid waste composition in the Colombo city 13 
Table 2.7:Waste densities in Vauniya Urban Area 14 
Table 2.8:Daily waste collection by district 14 
Table 2.9: Waste collection according to the TPD by Province in 15 
Sri Lanka 
Table 2.10: Land use by types in Sri Lanka 19 
Table 2 .11: Soil Erosion rates under different Crops in Nuwaraeliya District 19 
Table 3.1 Maximum recommended moisture content for various composting 24 
materials 
Table 3.2: Thermal death points of some common pathogen & parasites 26 
Table 3.3: Comparison of different technologies 30 
Table 3.4: Ranges of Users, Form Distribution, and Final User Group 36 
Table 4 .1 : Approximate nitrogen content and C/N ratio in various waste 41 
materials 
Table 4.2: Important design considerations for aerobic composting process 44 
Table 5.1: Reactor sizing for BIOCOM - M S W 
Table 6.1: Comparison of Biodegradable organic fraction in different areas 62 
Table 6.2: Waste density comparison of residential vs. commercial in 62 
Vauniya. 
Table 6.3: Some Solid Waste Management projects in Sri Lanka 63 
Table 6.4: Composit ion analysis of random compost samples 66 
Table 6.5: Heavy metal content random compost samples 66 
Table 6.7: Operational characteristics of the BIOCOM - M S W 67 
IX 
List of Figures 
Figure 1.1: Garbage Beaches 1 
Figure 1.2: Mixed waste 1 
Figure 1.3: Waste disposal along streams 3 
Figure 1.4: Poultry waste along the Salten 3 
Figure 1.5: Biological treatment options 5 
Figure 1.6: Integrated solid waste treatment 5 
Figure 1.7: Plastic and polythene 6 
Figure 1.8: Waste paper 6 
Figure 2 .1 : Coconut shells and husks 8 
Figure 2.2: Slaughterhouse waste 9 
Figure 2.3: Biodegradable Waste Composition by District 10 
Figure 2.4: Biodegradable Waste Composition of Atakalanpanna Pradeshiya 11 
Sabha 
Figure 2.5: Biodegradable Waste Composition of Vauniya Town 12 
Figure 2.6: Bio - degradable Waste Composition of Hambantota Town 12 
Figure 2.7: Comparison of Biodegradable Waste Composition with National 13 
Average 
Figure 3 .1 : Temperature profile and organic matter loss during composting 21 
Figure 3.2: A. fumigatus Common fungus in compost 22 
Figure 3.3: H lanuginosus Grows at 30o to 52o-55oC 22 
Figure 3.4: Blower Control Logic of Beltsville Strategy 28 
Figure 3.5: Blower Control Logic of Rutgers Strategy 28 
Figure 3.6: Categorization of composting technologies 31 
Figure 3.7: New Zealand Vertical Unit 32 
Figure 3.8: Japanese Vertical Unit 32 
Figure 3.9: Inclined Step-Grate Unit 33 
Figure 3.10: Containerized composting unit 34 
Figure 3.11: Moving by a skip truck 34 
Figure 3.12: Rotating Drum in farm scale 34 
Figure 3.13: Rotating Drum in large scale 34 
Figure 4 .1 : Selection of the composting technology 39 
Figure 5.1: Reactor Sizing 48 
Figure 5.2: Engineering drawing of BIOCOM - M S W reactor 49 
Figure 5.3: Power calculation parameters 51 
Figure 5.4: Power transmission efficiency 51 
Figure 5.5: Instrumentation setup of the reactor 53 
Figure 5.6: B IOCOM - M S W Control strategy formation 55 
Figure 5.7: B IOCOM - M S W Control Algorithm 56 
Figure 5.8: Isometric view of the BIOCOM - MSW 57 
Figure 5.9: Block diagram of wiring, sensor setup, actuators and datalogging 59 
Figure 5.10: Site view from Gate end 61 
Figure 5.11: Site view from opposite end 61 
Figure 5.12: Reactor under construction 61 
Figure 5.13: Frame and the Drum 61 
Figure 5.14: Feeding point 61 
Figure 5.15: Driving motor and gearbox 61 
Figure 5.16: Completed Reactor 61 
Figure 5.17: Reactor placed under the structure behind the pavilion 61 
X