BIO-FUEL FROM GREEN SOLID WASTE

A report submitted to the Department of Mechanical Engineering, Khulna University of

Engineering & Technology in partial fulfillment of the requirements for the

“Course of ME 3100”

Supervised by Submitted by

Dr. Khandkar Aftab Hossain Md. Shariful Islam

Professor Roll: 1205004

Department of Mechanical Engineering Section: A

Khulna University of Engineering & Technology

August 2015

Department of Mechanical Engineering

Khulna University of Engineering & Technology

Khulna 9203, Bangladesh

i

Acknowledgements

All the praises to the almighty who makes author capable to complete this Special

work successfully. The author is very much indebted to his course Dr. Khandkar Aftab

Hossain , professor of Department of Mechanical Engineering, Khulna University of

Engineering & Technology, Bangladesh, for his wise inspiration to do such extraordinary

special work. The author expresses the heart- felt respect to him for his proper guidance and

all kind of support to perform and complete this special study.

The author is extremely grateful to Prof. Dr. Nawsher Ali Moral ,Head of the department of

Mechanical Engineering Khulna University of Engineering & Technology, Bangladesh,

to provide such a good opportunity to do the special work and for providing all other

supports.

May ALLAH bless the course teacher.

“Author”

ii

Abstract

Demand for energy is increasing in an alarming rate. This is due to the rapid outgrowth of

population and urbanization. Conventional energy sources are not sufficient to face the

phenomena of energy shortage. In this condition renewable energy can be a substitute of

conventional energy. Such as Bio- fuel can be a substitute general fuel diesel. Bio- fuel can

be used in boilers, furnaces, engines and turbines for electricity generation.

Pyrolysis process can successfully be applied for converting biomass (solid green waste) into

bio-energy (bio-fuel). Pyrolysis is a thermo-chemical decomposition of organic material at

prescribed temperatures. Among various types of pyrolysis process Fast pyrolysis process

can be used to produce bio- fuel. The Bio- fuel produced through Pyrolysis process is not

stable as conventional fuels. It has High density, High viscosity, Low pH, Low heating value,

highly oxygenated compounds etc.

iii

CONTENTS

Page

Acknowledgement………………………………………………………….…………….…i

Abstract……………………………………………………………………….….….………ii

List of Figures………………………………………………………………………………..v

List of Tables………………………………………………………………………………...vi

CHAPTER-І: INTRODUCTION

1.1 Introduction……………………………………………………………………………..2

1.2 Objectives……………………………………………………….……………………….2

CHAPTER-ІІ: LITERATURE REVIEW

2.1 Historical Background………………………………………………………...................4

2.2 Biomass …………………….………….…….…….…………………………………….4

2.2.1 Constituents of biomass…………….…….…………………………………….4

2.2.2 Sources of Biomass ………….….……………………………………………..6

2.3 Bio-diesel ……………….……………………………………………………………….9

2.3.1 Why Bio-diesel…………………………………………………………………9

2.4 Green Waste ………………………………………………………………..…………..10

2.5 Waste Disposal ………………….……. …………………………………………..……10

iv

2.6

Pyrolysis……………………………………………………………………………………..10

2.6.1 Types of pyrolysis……………………………………………………………...11

2.6.1 .1 Fast pyrolysis……………………………………………………….11

2.6.1 .2 Slow pyrolysis ……………………………………………………..12

2.6.1 .3 Flash Pyrolysis………………………………………….…………..12

2.7 Characteristics of pyrolysis oil …………………………………………..………….......13

2.8 Comparison of pyrolysis liquid and conventional fuel oil characteristics……………….13

2.9 Application of pyrolysis oil………………………………………...……………………14

2.10 Pyrolysis Economics ……………….…………………………………………………..15

2.11 Disadvantages of Bio-fuels…………………..…………………………………………15

CHAPTER-ІІІ

3.1 Pyrolysis Principle…………...………….………………………………………………18

3.2 Pyrolysis Process steps ………………..………….………….…………………………19

CHAPTER- ІV

4.1 Conclusion ……………………………………………………………………….……..21

4.2 Recommendations ………………………………………………………………………21

References………………………………………………………………………….………..22

v

LIST OF FIGURES

Figure Title Page

Figure-2.1 Biomass composition in percentage………………………………………....5

Figure-2.2 A typical view of forest residue ……………….…………………………….6

Figure-2.3 A typical view of Industrial green Waste…………….………………….…..7

Figure-2.4 A typical view of Agricultural Residues………………….……………….…7

Figure-2.5 A typical view of Energy Crops……………………………….………….….8

Figure-2.6 Some biomass conversion processes………………………………………....10

Figure-2.7 Schematic diagram showing simple pyrolysis system……………………….11

Figure-2.8 Schematic diagram showing Fast pyrolysis product distribution…………....12

Figure-2.9 Schematic diagram showing slow pyrolysis product distribution……………12

Figure-2.10 Applications of pyrolysis product (pyrolysis oil)……………………………15

Figure-3.1 Schematic diagram showing fluid bed pyrolysis processes ………………….18

vi

LIST OF TABLES

Table Title Page

Table-2.1 Biomass composition of different sources of biomass …….…….…………8

Table-2.2 comparison of pyrolysis liquid and conventional oil ………….…………...13

1

Chapter I

Introduction

Objectives

2

1.1 Introduction:

Demand for energy and its resources, is increasing day by day. This is due to the rapid

outgrowth of population and urbanization. Present sources of energy are not sufficient to

overcome the increasing needs. The major energy demand is fulfilled from the conventional

energy resources like coal, petroleum and natural gas. The huge amount usage of fossil fuels

creates environmental threads.

Renewable energy can be a solution at this situation. A renewable energy system converts the

nature energy into usable form such as heat or electricity. Renewable energy sources offer

sustainable living due to being pollution free and economically feasible. There are various

forms of renewable energy such as Biomass, Geo­energy, Hydroelectric, solar, wind and

wave etc. Biomass is one of the promising environment friendly renewable energy options.

Different thermo­chemical conversion processes that include combustion, gasification,

liquefaction, hydrogenation and pyrolysis, have been used to convert the biomass into

various energy products. Pyrolysis can convert biomass directly into solid, liquid and gaseous

products by thermal decomposition of biomass in absence of oxygen. To obtain bio­fuel from

green solid waste the Pyrolysis process is preferred mostly. Fast pyrolysis is used to produce

Bio­Oil.

1.2 Objectives:

The objectives of this special study is to

i. Study about a selected topic that is “Bio­fuel from green solid waste”.

ii. Present that selected topic.

3

Chapter II : Literature Review

Historical Background

Biomass

Bio-diesel

Green Waste

Waste Disposal

Pyrolysis

Characteristics of pyrolysis oil

Comparison of pyrolysis liquid and conventional fuel oil

characteristics

Application of pyrolysis oil

Pyrolysis Economics

Disadvantages of pyrolysis oil

4

2.1 Historical Background:

Biodiesel is a renewable fuel which is in use throughout the world. Biodiesel is made

commercially from soybeans and other oilseeds in an industrial process, but it is also

commonly made in home shops from waste fryer grease.

Dr. Rudolf Diesel first demonstrated his diesel engine to the world running on peanut oil in

the early 1900’s. The high compression of diesel engines creates heat in the combustion

cylinder, and thus does not require a highly flammable fuel such as that used in gasoline

engines. The diesel engine was originally promoted to farmers as one for which they could

“grow their own fuel”. Diesels, with their high torque, excellent fuel efficiency, and long

engine life are now the engine of choice for large trucks, tractors, machinery, and some

passenger vehicles. Diesel passenger vehicles are not presently common in the United States

due to engine noise, smoky exhaust, and cold weather starting challenges. However, their

use is quite normal in Europe and Latin America, and more diesels are starting to appear in

the US market.

Over time, the practice of running the engines on vegetable oil became less common as

petroleum diesel fuel became cheap and readily available. Today, people are rediscovering

the environmental and economic benefits of making fuel from raw and used vegetable oils

[1].

2.2 Biomass:

Biomass is defined as organic materials which are derived from plants or animals sources. In

general it is difficult to find out the actual definition. Biomass is formed by the interaction of

CO2, water and sunlight. When a living being dies, microorganisms and bacteria break down

the constituents into elementary components like H2O, CO2, and energy. Since, plants use the

same the carbon dioxide at the time of photosynthesis, the amount of CO2 does not increase

in the earth. Biomass is a green house gas (GHG) emission neutral energy source.

2.2.1 Constituents of biomass:

5

The major constituents of biomass are cellulose, hemicelluloses and lignin [3].

Fig 2.1: Biomass composition in percentage

1. Cellulose: The primary organic component of cell wall is cellulose. It is represented by

generic formula (C6H10O5)n. It is crystalline in nature, resistant to hydrolysis, a large

molecular weight (∼500,000) due to the presence of a long chain polymer having high

degree of polymerization (∼10,000). Cellulose is primarily composed of d­glucose, which is

made of six carbons.

2. Hemicellulose: Hemi cellulose is also one of the constituent of cell wall. It is represented

by the generic formula (C5H8O4)n. It has branched chain structure with groups of

carbohydrates and a lower degree of polymerization (∼100–200). The composition and

structure of hemicelluloses varies from biomass to biomass.

3. Lignin: The third important constituent of woody biomass is lignin, which is complex in

nature, highly branch polymer of phenyl propane. It is a three dimensional polymer. Lignin

is the binding agent for cellulose. It is highly insoluble; it does not even dissolve in sulphuric

acid.

6

2.2.2 Sources of Biomass:

The common biomass sources are agricultural, forest, Industrial green Waste and Energy

Crops. The examples of sources are discussed below [2].

1. Forest Residues: Forest residues are defined as the biomass material remaining in

forests that have been harvested. for timber, and are almost identical in composition

to forest thinnings. Because only timber of a certain.

Forest residues consist of Cotton seed hairs, Tree branches, tops of trunks, stumps, branches,

and Leaves etc.

Fig 2.2: A typical view of forest residue

2. Industrial green Waste: Industrial waste is the waste produced by industrial

activity which includes any material that is rendered useless during a manufacturing process

such as that of factories, mills, and mining operations. It has existed since the start of

the Revolution.

Some examples of industrial waste are Citrus peels, sugarcane bagasse, milling residues,

olive husks.

7

Fig 2.3: A typical view of Industrial green Waste

3. Agricultural Residues: Field residues are materials left in an agricultural field or orchard

after the crop has been harvested. These residues include stalks and stubble (stems), leaves,

and seed pods. The residue can be sloughed directly into the ground, or burned first.

Includes corn stover, wheat husk and rice straw.

Fig 2.4: A typical view of Agricultural Residues

4. Energy Crops: An energy crop is a plant grown as a low­cost and low­maintenance

harvest used to make biofuels, such as bioethanol, or combusted for itsenergy content to

generate electricity or heat. Energy crops are generally categorized as woody or herbaceous

plants; many of the latter are grasses (Graminaceae).

8

Examples are Sunflower shell, Switch grass, miscanthus, bamboo, sweet sorghum, tall

fescue, kochia, wheatgrass, and others.

Fig 2.5: A typical view of Energy Crops

Table 2.1: Biomass composition of different sources of biomass [7­12]:

9

2.3 Bio-diesel:

Biodiesel is a form of diesel fuel manufactured from vegetable oils, animal fats, or recycled

restaurant greases. It is safe, biodegradable, and produces less air pollutants than petroleum­

based diesel. Biodiesel can be used in its pure form (B100) or blended with petroleum diesel.

Bio­fuels are obtained from living organisms. The fuel should consist of more than 80%

renewable materials to be considered as a bio­fuel.

In Europe, biodiesel is widely available in both its neat form (100% biodiesel, also known as

B100) and in blends with petroleum diesel. Most European biodiesel is made from rapeseed

oil (a cousin of canola oil). In the United States, initial interest in producing and using

biodiesel has focused on the use of soybean oil as the primary feedstock, mainly because this

country is the world’s largest producer of soybean oil.

2.3.1 Why Bio-diesel:

There are various advantages of substituting diesel fuel by Bio­Diesel. Such as­ [4]

i. It can reduce our dependence on foreign petroleum.

ii. It can leverage limited supplies of fossil fuels.

iii. It can help reduce greenhouse gas emissions.

iv. It can help reduce air pollution and related public health risks.

10

2.4 Green Waste:

Basically the “Green waste” is produced from regular maintenance of gardens and parks. It

consists of all plant materials: branches, logs, leaves, stumps, grass, sticks, paper, cardboard,

and other woody materials. It also contains large quantities of waste paper and cardboard,

waste timber, old wooden pallets and sawmills wastes. The largest single component of

municipal waste is green waste and traditionally it takes up a significant quantity of landfill

volumes. All of those wastes are suitable for bio­diesel and energy production [5].

2.5 Waste Disposal:

Green waste can be disposed in many ways: Burying in landfills, using as mulch, composting

and then used in crop production, vermin­composting and used in plant production, used as a

landscape mix in landscaping, bio­char and bio­oil preparation (pyrolysis)etc[5].

Biomass can be converted into heat and electricity in a number of ways. Depending on its

source, these processes include: combustion, pyrolysis, gasification, liquefaction, anaerobic

digestion or fermentation.

Fig 2.6: Some biomass conversion processes

To obtain bio­diesel from green solid waste the Pyrolysis process is preferred mostly.

2.6 Pyrolysis:

11

Pyrolysis is a thermo­chemical decomposition of organic material at temperatures

between 400 ° C and 900 °C without the presence of oxygen or other reagents. The

pyrolytic breakdown of wood produces a large number of chemical substances. Some of

these chemicals can be used as substitutes for conventional fuels. The distribution of the

products varies with the chemical composition of the biomass and the operating conditions

[2].

Fig 2.7: Schematic diagram showing simple pyrolysis system

2.6.1 Types of pyrolysis:

The process pyrolysis occurs in three different ways, namely fast pyrolysis, slow pyrolysis

and flash pyrolysis.

2.6.1 .1 Fast pyrolysis :

In fast pyrolysis process the feed stock is rapidly heated (high rate of heating) in absence of

oxygen at high temperature. During the decomposition, vapours and char are formed.

After condensation of the vapours, a dark brown liquid is obtained. Fast pyrolysis is an

advanced process which can be controlled to produce higher yields of liquid products.

Fast pyrolysis process produces 60­75% liquid bio­oil, 15­25% char and 10­20% non­

condensable gases. The bio­oil and char can be used as source of fuel and the non­

condensable gases can be recycled back in the process [3].

12

Fig 2.8: Schematic diagram showing Fast pyrolysis product distribution

2.6.1 .2 Slow pyrolysis

In slow pyrolysis, pyrolysis is carried out at a slow heating rate of 5­10 oC/min. Product

yields from slow pyrolysis are approximately 35% biochar,30% bio­oil, and 35% gaseous

products.

Fig 2.9: Schematic diagram showing slow pyrolysis product distribution

2.6.1 .3 Flash Pyrolysis:

In flash pyrolysis the reaction time is in the range of 30 – 1500 ms. This process increases the

amount of liquid product decreasing the char amount. Upon cooling, the condensable vapor

13

is then condensed into a liquid fuel known as bio­oil. Such an operation increases the liquid

yield (70–75%) while reducing the char production. There are four different methods

of flash pyrolysis viz, flash hydro­pyrolysis, solar flash pyrolysis, vacuum flash

pyrolysis and rapid thermal process [3].

2.7 Characteristics of pyrolysis oil:

Bio­Oil or Bio­Diesel is not stable as conventional fuels [2].

Highly oxygenated compounds

High density

High viscosity

Low pH

Low heating value

CO2 neutral

No SOx and low NOx

Bio­Oil can be combusted directly in boilers, gas turbines and slow and medium

speed diesels for heat and power applications.

2.8 Comparison of pyrolysis liquid and conventional fuel oil characteristics:

Table 2.2: comparison of pyrolysis liquid and conventional oil: [2]

14

2.9 Application of pyrolysis oil:

The bio­oil obtained from pyrolysis can have the following industrial applications:

Combustion of fuel

power generation

extraction of chemicals and resins

production of laevoglucose

binding agents

blending with diesel

bio­oils can be used in making adhesives

15

Fig 2.10: Applications of pyrolysis product (pyrolysis oil)

2.10 Pyrolysis Economics:

Economic viability is the key factor in the development of commercial pyrolysis processes.

Currently, pyrolysis products are unable to compete economically with fossil fuels due to

high production costs. The pyrolysis technology has to overcome a number of technical and

non­technical barriers before industry can implement their commercialization and usage.

Production cost of pyrolysis product is higher compared to production of fossil fuel. The

main component of pyrolysis plants are the reactor, although it represents only 10%–15% of

the total capital cost. The rest of the cost consists of biomass collection, storage and handling,

biomass cutting, dying and grinding, product collection and storage, etc [7].

2.11 Disadvantages of Bio-fuels: [6]

1. High Cost of Production: Even with all the benefits associated with biofuels, they are quite

expensive to produce in the current market. As of now, the interest and capital investment

being put into biofuel production is fairly low but it can match demand.

2. Monoculture: Monoculture refers to practice of producing same crops year after year,

rather than producing various crops through a farmer’s fields over time.

16

3. Use of Fertilizers: Bio­fuels are produced from crops and these crops need fertilizers to

grow better. The downside of using fertilizers is that they can have harmful effects on

surrounding environment and may cause water pollution.

4. Shortage of Food: Bio­fuels are extracted from plants and crops that have high levels of

sugar in them. However, most of these crops are also used as food crops.

5. Industrial Pollution

6. Water Use: Large quantities of water are required to irrigate the bio­fuel crops and it may

impose strain on local and regional water resources, if not managed wisely resources.

17

Chapter III

Pyrolysis Principle

Pyrolysis Process steps

18

3.1 Pyrolysis Principle:

Pyrolsis is a thermo­chemical decomposition process which is found to be the best suited for

conversion of biomass to carbon­rich solid and liquid fuel. The process of pyrolysis of

organic matter is very complex and consists of both simultaneous and successive reactions

when organic material is heated in a non reactive atmosphere. In this process, thermal

decomposition of organic components in biomass starts at 350–550 0C and goes up to 700­

800 0C in the absence of air/oxygen suggested by Fisher et al. The long chains of carbon,

hydrogen and oxygen compounds in biomass break down into smaller molecules, in the form

of gases, condensable vapors (tars and oils), and solid charcoal under pyrolysis conditions.

Rate and amount of decomposition gases, tars and char depends on the process parameters of

the reactor (pyrolysis) temperature, heating rate, pressure, reactor configuration, feedstock’s

variation. Following figure shows schematic diagram for fast pyrolysis processes [5].

Fig 3.1: Schematic diagram showing fluid bed pyrolysis processes

19

3.2 Pyrolysis Process steps:

Pyrolysis process is a combination of some steps. All the steps simply categorise as feed

stock preparation, Feed stock drying, thermo­chemical conversion in the reactor, ash

separation and liquid collection. Different reactor needs different sizes particle, that is why

cutting and grinding is needed. Drying is essential to avoid adverse effects of water on

stability, viscosity, corrosiveness and other liquid properties in the pyrolysis product. After

drying and grinding, the biomass is fed into the reactor and the pyrolysis process takes place.

Char removal cyclones are used to separate char. Pyrolysis liquid is collected after quenching

the volatile material by the vapors liquid condensers [5].

20

Chapter IV

Conclusion

Recommendations

21

4.1 Conclusion:

Energy recovery from green waste through pyrolysis process has been discussed in this report.

Pyrolysis technology has strong adaptability to green waste to produce liquid fuels. It offers a

convenient solution for solid green waste management systems. In spite of comparatively low­grade

bio­fuels obtained from biomass; it has some promising properties to become a suitable substitute

of fossil fuel. In future successful research and improvement of bio­fuel quality can lead to huge

production of bio­energy from green waste commercially. It is important to optimize the process by

maximizing product quality and minimizing costs and environmental concerns.

4.2 Recommendations:

Bio­oil production through pyrolysis is still an immature technology and is not

commercially feasible yet. Pyrolysis bio­oil needs to overcome many technical,

economic and social barriers to compete with traditional fossil fuels.

Along with pyrolysis technology, proper biomass selection is also a critical issue to

achieve high bio­oil yields. Biomass with high cellulose content could be chosen, as

bio­oils are mainly derived from it. In addition, biomass with low water content is

desirable to reduce drying costs and improve oil quality.

22

References:

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[3]:ethesis.nitrkl.ac.in/5735/1/110CH0464­2.pdf

[4]:http://www.nrel.gov/docs/legosti/fy98/24772.pdf

[5]:www.wseas.us/e­library/conferences/2012/Kos/.../WEGECM­13.pdf

[6]:http://www.conserve­energy­future.com/advantages­and­disadvantages­of­biofuels.php

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its production and utilization. Renew. Sustain. Energy Rev.2010, 14, 919–937.

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434.

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[12]: Wang, J.; Wang, G.; Zhang, M.; Chen, M.; Li, D.; Min, F.; Chen, M.; Zhang, S.; Ren,

Z.; Yen, Y. A comparative study of thermolysis characteristic and kinetics of seaweeds and

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