Investigation on the Production Potential of Energy Content from Solid Waste

UNIVERSITY OF NAIROBI

INVESTIGATION ON THE PRODUCTION POTENTIAL OF ENERGY CONTENT FROM SOLID WASTE

BY

RUNGURUA NDERITU JOHN

F16/2326/2009

A research project submitted in partial fulfillment of the requirements for the award of degree of Bachelor of Science degree in the Department of Civil and Construction Engineering School of Engineering

MAY, 2015

DECLARATION

I, RUNGURUA NDERITU JOHN, hereby declare that this project is my original work and has not been presented for a degree in any other university.

Signed………………………………Date………………………………………………..

RUNGURUA NDERITU JOHN

DECLARATION OF SUPERVISOR

This research project has been submitted for examination with my approval as a University Supervisor in the Department of Civil and Construction Engineering.

Signed…………………………………Date………………………………………………..

DR.P.K NDIBA

ACKNOWLEDGEMENT

May the Almighty God receive all the glory and honour for it is Him who has taken me this far. Indeed no eye has seen, no ear has heard and no heart has perceived what God has in store for His children whom He loves. (1 Corinthians 2:9)Ebenezer!

I am greatly indebted to my supervisor DR.P.K. NDIBA under whose counsel, guidance and advice I have successfully completed my project.

Abstract

Daily human activities inevitably generated and accumulated Solid waste. The waste may bring about severe environmental degradation unless an appropriate solid waste management system is in place. The solid waste management method sought should deal with the waste efficiently. It will be more advantageous if not beneficial if energy can be harnessed through a variety of processes such as incineration, pyrolysis, gasification etc. In the design of these solid waste management processes, it is necessary to estimate the energy content of municipal solid waste in order to achieve the required optimal system performance.

This project evaluated the energy content and viability of energy derived from solid waste from Dandora dumpsite in Nairobi. Heat energy was calculated from municipal solid waste composition and their heating values per unit mass. The potential electricity production of waste is calculated using the net calorific value of 1400 k-Cal/kg at efficiency of 80%.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS……………………………………………………………………………………………..………….1

DEDICATION…………………………………………………………………………………………………………………………2

ABSTRACT………………………………………………………………………………………………………………………….…3

Table of contents………………………………………………………………………………………………………… ….…4

LIST OF TABLES………………………………………………………………………………………………………….……… ...7

LIST OF PLATES……………………………………………………………………………………………………………………..8

ABBREVIATIONS, ACRONYMS AND MEASUREMENTS……………………………………………..……………9

CHAPTER 1………………………………………………………………………………..…………………………..….…….….. 10

INTRODUCTION…………………………………………………………………………………………………………………….10

1.1 Background information………………………………………………..………………………………………………………10

1.2 PROBLEM STATEMENT…………………………………………………………………………………….….………...... 11

1.3Objective of the Project…………………………………………………………………………………………………………12

CHAPTER 2……………………………………..………………………………………………………………...... …………... 13

LITERATURE REVIEW……………………………………………………………………………………………………………... 13

2.1 Definitions……………………………………………………………………………………………………………...... 13

2.2 Types of Solid Wastes……………………………………………….…………………………………………………………....13

2.2.1 Municipal Solid Waste(MWS)………………………………………………………………………………………….....13

2.3 Waste Collection and Transportation……………………………………….……………………………………………..15

2.4 Solid Waste Management……………………………………………………………………………………………...... .. 15

2.5 Methods of Solid Waste Management………………………………………………..……………………………….….16

2.5.1 Composting / Biological Treatment………………………………………………………………………………………16

2.5.2 Landfilling………………………………………………………………………………………………………………… ………. 17

2.5.3 Incineration of Solid Waste…………………………………………………………………….…………………… ………18

2.5.4 Comparison of Incineration with Other Methods of Waste Management….……….…………… 18

2.5.5 Basic Objectives of Incineration………………………………………..……………………………………………….19

2.5.6 Description of Incineration………………………………………………………………………………………………. 19

2.6 Combustion Conditions………………………………………….…………………………………………………………... 23

2.7 Energy Recovery…………………………………………………………………………………………………………………. 23

2.7.1 Assessment of Energy Recovery Potential……………………………………………….………………………..24

2.8 Environmental Impacts……………………………………………………………………..………………………………....24

2.8.1 Air Emissions………………………………………………………………………………………………………..…………….24

2.8.2 Control of Air Emission………………………………………………………………………………………….…………...28

2.9 Disposal of Ash……………………………………………………………………………………………………………………...29

2.9.1 Processing…………………………………………………………………………………………………………………………..30

2.9.2 Treatment…………………………………………………………………………………………………………………………..30

2.10 Economic Costs of Thermal Treatment………………………………………………………………………………..31

2.11 Advantages and Disadvantages of Incineration……………………………………………………………………31

CHAPTER 3……………………………………………………………………………………………………………………………. 32

RESEARCH METHODOLOGY…………………………………………………………………………………………………….32

3.1 Location and Description of Area of Study…………………………………………………………….……………..32

3.2 Sources of Solid Waste on Dandora dumpsite…………………………………………………………………….. 32

3.3 Management of Solid Waste in Dandora area…………………………………………………………………….. 32

3.4 Types and Sources of Data………………………………………………………………………………………………….. 37

3.5 Laboratory Analysis…………………………………………………………………………………..……………………….. 37

CHAPTER 4……………………………………………………………………………………………………………………..……….38

RESULTS AND DATA ANALSIS…………………………………………………………………………………………………. 38

4.1 Composition of the Solid Waste…………………………………………………………………………………..……….. 38

4.2 Moisture Content of theWaste……………………………………………………………………….……………………...39

4.3 Heat content of the Waste……………………………………………………………..………………………………….. 39

4.4 Potential Electricity Production from the Waste……………………………………………..………………….. 45

4.5 Total Energy from dandora dumpsite…………………………………………………………….……………………..46

4.6 DISCUSSION…………………………………………………………………………………………….…………………………….48

CHAPTER 5………………………………………………………………………………..…………………………………………..50

CONCLUSION AND RECOMMENDATIONS……………………………………………….……………………….…….50

5.1 Conclusion………………………………………………………………………………..……………………………………………50

5.2 Recommendation……………………………………………………………………………………………………..……………50

REFERENCES……………………………………………………………………………………………………………….………….52

LIST OF TABLES

Table 2.1 Higher (Gross)Heat values (HHV)of selected materials (Kiser ,J,V,L et al,1992)

………………………………………………………………………………………………………………………………….13

Table 2.2 Typical proximate Analysis of selected combustible components of

Municipal solid waste Niessen 1997…………………………………………………………………………………14

Table 4.1 Waste Composition of the sample…………………………………………………………………….30

Table 4.2 proximate Analysis of components of MSW(%weight); Tchobanoglous et al,:

1993)……………………………………………………………………………………………………………………………………32

Table 4.3 wet and adjusted Dry weight of the sample……………………………………………………………..33

Table 4.4 Energy content of the combustibles……………………………………………………………………….35

Table4.5 population growth rate in Kenya(CIA world factbook,jan,2011)…………………………………….36

LIST OF PLATES

Plate 3.1.1 plastic waste……………………………………………………………………………………………………….34

Plate 3.1.2 metal waste………………………………………………………………………………………………………..34

Plate 3.1.3 glass waste………………………………………………………………………………………………………….35

Plate 3.1.4 food waste………………………………………………………………………………………………………….35

Plate 3.1.5 paper waste………………………………………………………………………………………………………..36

Plate 3.1.6 ash and dust waste……………………………………………………………………………………………..36

ABBREVIATIONS, ACRONYMS AND MEASUREMENTS

ᵒC Degree Celsius

BTU British thermal unit

EfW Energy from Waste

Hawf ash and water free calorific value

Hinf Lower (inferior) calorific value

Hsup upper (superior) calorific value

HHV Higher Heating Value

IWM Integrated Waste Management

Kj Kilojoule

Kcal Kilocalories

lb. Pounds

LHV Lower Heating Value

MSW Municipal Solid Waste

NCV Net Calorific Value

PCB Polychlorinated biphenols

RDF Refuse Derived Fuel

SWM Solid Waste Management

WtE Waste-to- Energy

CHAPTER 1

INTRODUCTION

1.1 BACKGROUND INFORMATION

Solid water management is the process of control, collection, storage, and disposal of solid waste. The process includes the separation of waste materials and the processing, treatment, and recovery of some of the waste. Solid waste management also involves safe transport of this waste, and its ultimate disposal. Solid waste management is one of the vital services conducted by local governments.

Urbanization in many towns has resulted in high growth rate, which give rise to the problem of solid waste collection and disposal. The wastes resulting from daily human activities must eventually reach a designated area such as a dumpsite. When waste is left to accumulate unmonitored at the dumpsite, it leads to pollution of the environment which may be in form of unpleasant smell as well as leading to outbreak of diseases as was evidenced in 2004 when an epidemic of avian flu broke out and origins was credited to the dumping site. The uncensored continual disposal of wastes in the site creates unfavorable living conditions to the residents as well.

The Dandora dumpsite is destination of 850 tons of solid waste generated daily by around 3.5 million inhabitants of Nairobi. Being a low income residential area, poor collection and disposal is rampantly creating a serious issue that needs to be addressed. These large volumes of solid waste could serve as raw material for energy production.

Solid waste contains both organic and inorganic matter. The latent energy present in the organic matter can be harnessed for gainful utilization through adoption of suitable waste processing and treatment technologies. The recovery of energy from wastes also other benefits including reduction of the total quantity of wastes disposed, reduced demand for land for land filling, forgoing costs of transportation of waste to far away landfill sites and ease in environmental pollution

While every effort should be made to minimize generation, recycle, and reuse waste materials, the option of energy recovery from wastes should be properly examined and wherever viable should be reincorporated in the overall scheme of waste management.

1.2. PROBLEM STATEMENT

Economic growth and development are accompanied by the generation of large amounts of wastes that must be re-used in some way or disposed off in landfills. The generation of wastes can be reduced to some extent by improved design of product and packaging materials and by increasing intensity of service per unit mass of material used. Solid waste disposal and energy conservation are not usually considered to be related. However, a great deal of research has recently been focused on energy recovery from solid waste.

The energy sector in Kenya is largely dominated by petroleum and electricity, with wood fuel providing the basic energy needs of the rural communities, urban poor, and the informal sector. An analysis of the national energy shows heavy dependency on wood fuel and other biomass that account for 68% of the total energy consumption (petroleum 22%, electricity 9%, others account for 1%). Electricity access in Kenya is low despite the government’s ambitious target to increase electricity connectivity from the current 15% to at least 65% by the year 2022. Due to increased poverty, there is a significant shift to non-traded traditional biomass fuels. The proportion of households consuming biomass has risen to 83% from 73% in 1980.

Kenya has an installed capacity of 1.48 GW. Whilst about 57% is hydro power, about 32% is thermal and the rest comprises geothermal and emergency thermal power. Solar PV and Wind power play a minor role contributing less than 1%. However, hydropower has ranged from 38-76% of the generation mix due to poor rainfall. Thermal energy sources have been used to make up for these shortfalls, varying between 16-33% of the mix.

As a rapidly developing country, there is an increase in demand for energy that needs to be addressed hence paramount that alternative sources of energy be sought out to curtail this situation.

A potential source of energy in Kenya is incineration of solid waste which produces a relatively high energy through thermal treatment methods. The treatment uses solid waste beneficially as well reduces its volume.

There is need for energy sources that promote energy independence, avoid fossil fuel use and reduce greenhouse emissions. Research shows that for every ton of waste processed at a waste-to-energy facility, a nominal one ton of carbon dioxide is prevented from entering the atmosphere (L.P. Joseph et al 1975 use standard referencing

1.3 Objective of the project

The overall objective of the project is to investigate viability of energy recovery from solid waste from Dandora dump site, Nairobi. Specific objectives are to:

1. The moisture content of the samples
2. The heat energy of the samples
3. The potency of the energy recovered from the solid waste

CHAPTER 2

LITERATURE REVIEW

2.1 Definitions

Human activities generate waste materials that are often discarded because they are considered useless. These wastes are normally solids, and the word waste suggests that the material is useless and unwanted. However, many of these wastes materials can be reused, and thus they can become a resource for industrial production or energy generation, if managed properly.

2.2 Types of Solid Wastes

Wastes can be classified into physical forms (solids, liquids, gaseous); original use (packaging wastes, food wastes, etc.), material (glass, paper, etc.), origin (domestic, commercial, agricultural, industrial, etc.), physical properties (combustible, compostable, recyclable); orsafety (hazardous, non-hazardous).

2.2.1 Municipal Solid Wastes (MSW)

MSW is a waste arising from residential and commercial activities. With increasing urbanization and industrialization, millions of tones of MSW are generated. Domestic wastes by nature is one of the hardest wastes to manage effectively due to its diverse range of materials mixed together.

Different types of MSW include:

i. Domestic waste

Wastes from house hold activities, including food preparation and leftovers, cleaning, fuel burning, old clothes and furniture, obsolete utensils and equipments, packaging, newsprint, and garden wastes.

In low-income countries, domestic waste is dominated by food and ash. Middle-and higher-income countries have a larger proportion of paper, plastic, metal, glass, discarded items, and hazardous matter due to advanced industrialization.

ii. Commercial Waste

Waste from shops, offices, restaurants, hotels , and similar commercial establishments typically consisting of packaging materials, offices supplies, and food waste and bearing a close resemblance to domestic waste.

In low-income countries, food markets may contribute a large proportion of the commercial waste. Commercial waste may include hazardous components such as contaminated packaging materials.

iii. Institutional Waste

Waste from schools, hospitals, clinics, government offices, military bases, and so on is termed as institutional wastes. Institutional waste is similar to both domestic and commercial waste, although there are generally more packaging materials than food waste. Hospitals and clinical wastes include potentially infections and hazardous materials. It is important to separate the hazardous and non-hazardous components to reduce health risks.

iv. Industrial Waste

The composition of industrial waste depends on the kind of industries involved. Basically, industrial waste include components similar to domestic and commercial source waste, including wastes from kitchen and canteens, packaging materials, plastics, papers, and metal items. Some production processes, however, utilize or generate hazardous(chemicals or infectious) substances. Disposal routes for hazardous wastes are usually different from those for non- hazardous wastes and depend on the composition of actual waste type.

v. Street Sweepings

Wastes swept from the streets is dominated by dust and soil together with varying amounts of paper, metal, and other litter from the streets.

vi. Construction and Demolition Wastes

The composition of the construction wastes depend on the type of building materials, but typically includes soils, stones, brick, concrete and ceramic materials, wood, packaging materials and the like.

2.3Waste Collection and Transportation

Collecting municipal waste and transporting it to disposal sites is crucial activity in Solid Waste Management. Even though the government collects waste, private companies have bee formed which have their major businesses he collection and transport of solid waste. Such companies are responsible for collecting majority of commercial, institutional and industrial waste.

2.4 Solid Waste Management

Waste is inevitable product of the society; therefore it should be managed effectively. Solid waste management will include production of less and an effective system to waste produce.

Effective solid waste management systems need to ensure human health and safety. In addition to these, it should also be both environmentally and economically sustainable.

1. Environmentally sustainable:

The management must reduce as much as possible the environmental impacts of waste management, including energy consumption, pollution of land, air and water and lots of amenity.

1. Economically sustainable

The management must operate at a cost acceptable to the community, which includes private citizens, businesses and government. The costs of operating an effective solid waste system will depend on local infrastructure, but ideally should be little or no more than existing local waste management costs.

There are different ways of managing solid waste including:

1. Material recycling
2. Biological treatment
3. Thermal treatment(incineration with solid and without energy recovery)
4. Compositing
5. Land filling

2.5Methods of solid waste management:

2.5.1 Composting/ biological treatment

Composting is the biological decomposition of the biodegradable organic fraction of MSW under controlled conditions to state sufficiently stable for nuisance-free storage and handling and for safe use in land applications (Goluekeet al, 1995; Golueke, 1972; Diaz et al, 1993). Biological treatment involves using naturally occurring micro-organisms to decompose the biodegradable components of waste. Aerobic organisms require molecular oxygen to use external electron acceptors in respiratory metabolism; this results in rapid growth rates and high cell yields. Anaerobic metabolism occurs in the absence of oxygen and does not involve an external electron acceptor. This fermentative metabolism is a less effective energy producing process than aerobic respiration and therefore results in lower growth rates and cell yields.

If left to go to completion, biological processes results in the production of gases (mainly carbon dioxide and water vapor from aerobic processes and carbon dioxide and methane from anaerobic processes) plus a mineralized residue. Normally the process is interrupted when the residue still contains organic materials, though in a more stable form, comprising a compost-like material.

There are many advantages to composting. First, it would reduce the amount of waste requiring ultimate disposal, extending the life of landfills. When doe correctly, the end result becomes a useful product, capable of being used at the household or farm level to augment soil nutrient levels and increase organic matter in soil, increasing soil stability. If the product is of high quality and markets exist, the product can be sold. Environmentally, the process by which composting organic waste is preferable to landfill processes. In a landfill, bacteria break down organics anaerobically in absence of oxygen, resulting in the release of methane gas. When properly composted, the organic matter is decomposed using an aerobic respiration process, which produces no methane by-product.

In reference to incineration, there are parameters that will limits composting as a disposal method. Nearly 20%-30% by weight, of municipal waste consists of non-compostable, non-recyclable waste hence another method has to be sought to dispose this waste most probably land filling. While one incineration plant can serve a large population, composting is limited to size of community it can serve. Land which is suitable for composting plants may be difficult to acquire in large metropolitan areas. Some wastes are better incinerated than composted. Wastes arising from construction e.g. timber will take a lot of time to decompose; instead it will produce a high calorific value in an incineration.

2.5.1.2 Advantages and Disadvantages of Composting/ Biological Treatment

Composting of the organic fraction of the waste leads to numerous advantages in the well overall waste treatment process:

1. Reduction of the amount of waste that has to be incinerated or put in landfills and therefore reduction of incinerator ash to be disposed off.
2. In general lower costs than incineration, although treatment costs are very sophisticated, completely enclosed composting systems are now near those for incineration.
3. Recycling of humus and nutrients into the soil.
4. Protecting and improving the microbiological diversity and quality of cultivated soils.
5. Beneficial role of composting micro-organisms in crop protection, in as much as they compete with plant pathogens.
6. Beneficial role of compost micro- organisms in biodegradation of toxic compounds and pollutants

If composting is not carried out properly, it can also have some disadvantages:

1. The most common complaint about composting instillation are odour nuisance, that’s why the tendency goes to completely enclosed systems where the outlet air is treated in a bio-filter before being emitted. The best way, though, to prevent malodor generation is a composting process with a high degradation rate, in order to remove the putrescible substances as quickly as possible.
2. Dispersion of potentially pathogenic and allergenic micro-organism.
3. Soil pollution is the heavy metal content of the compost is too high.
4. Ground water pollution if composting is carried out on a surface that is not made up properly or where the runoff water is not collected.

2.5.2 Land filling