COMPARING PYROLYSIS AND CO-PYROLYSIS VIA ANALYSIS OF IMPACT ON PRODUCT YIELD AND QUALITY

COMPARING PYROLYSIS AND CO-PYROLYSIS VIA ANALYSIS OF IMPACT ON
PRODUCT YIELD AND QUALITY.

BY


HILARY NZUBE DAVID



�ABSTRACT

Reduction of conventional fuel has encouraged to find new sources of renewable energy. Oil
produced from the pyrolysis method using biomass is considered as an emerging source of
renewable energy. Pyrolytic oil produced in pyrolysis needs to be upgraded to produce bio-oil that
can be used with conventional fuel. However, pyrolytic oil contains high amounts of oxygen that
lower the calorific value of fuel, creates corrosion, and makes the operation unstable. On the other
hand, the up-gradation process of pyrolytic oil involves solvent and catalyst material that requires
a high cost. In this regard, the co-pyrolysis method can be used to upgrade the pyrolytic oil where
two or more feedstock materials are involved. The calorific value and oil yield in the co-pyrolysis
method are higher than pyrolytic oil. Also, the upgraded oil in the co-pyrolysis method contains
low water that can improve the fuel property. Therefore, the co-pyrolysis of biomass waste is an
emerging source of energy. Among different biomasses, solid waste and plants are significantly
used as feedstock in the co-pyrolysis method. As a consequence, pressure on conventional fuel can
be reduced to fulfill the demand for global energy. Moreover, the associated operating and
production cost of the co-pyrolysis method is comparatively low. This method also reduces
environmental pollution.




�TABLE OF CONTENTS
CERTIFICATION

ii

DEDICATION

iii

ACKNOWLEDGEMENTS

iv

ABSTRACT

v

TABLE OF CONTENTS

vi

LIST OF TABLES

vii

LIST OF FIGURES

viii

CHAPTER ONE

1

INTRODUCTION

1

1.1.

Background of the study

1

1.2

Statement of the problem

4

1.3

Purpose of the Study

5

1.4

Significance of the Study

6

1.5

Scope of the Study

7
vi

�CHAPTER TWO
8
LITERATURE REVIEW

8

2.1

Conceptual framework

8

2.2

Theoretical Framework

13

2.3

Empirical review

18

2.4

Summary of literature review

21

CHAPTER THREE

22

MATERIALS AND METHODS

22

3.1

Present materials and methods used to achieve Objectives

LIST OF TABLES
Table 1. Kinetic parameters, used by (Thurner & Mann, 1981)

16

Table 2. Kinetic parameters, (Koufopanos et al., 1989)

17

Table 3. Optimum operating conditions of co-pyrolysis method

26

Table 4. The characteristics of different biomass materials

27

Table 5. Calorific value of product yield of co-pyrolysis process

29

LIST OF FIGURES
Figure. 1. Schematic diagram of the experimental set-up of slow pyrolysis

9

Figure 2. The Broido – Shafizadeh mechanism

14

Figure 3. Biomass kinetic reaction scheme

15

Figure 4. Reaction scheme of Biomass Pyrolysis

17

Figure 5. Biomass conversion process technologies

23

Figure 6 .Upgradation methods of pyrolytic oil.

24
vii

�Figure 7. Overall process of co-pyrolysis

29

viii

�CHAPTER ONE
INTRODUCTION
1.1 Background to the study
The increasing global fuel consumption and growing environmental concerns has made many
researchers to explore alternative energy that is clean and renewable for fuel production.
Converting biomass and plastic waste into high-value fuel and chemicals via pyrolysis and copyrolysis technique may provide a sustainable remediation to this problem. However, the
incessant growth of plastics demands has resulted in the increase of plastic solid waste (PSW)
deposit every year. Municipal solid waste (MSW) accounts for around 30–35 % of the total
plastic wastes in industrialized country, Wu et al., (2020).


At present, the traditional recycling methods, including incineration and landfills pose a serious
threat to the environment via water resource pollution, air pollution and damages to marine
ecosystems and terrestrial habitats, Salvilla et al., (2019). In addition, the natural degradation
of plastic needs 400 to 1000 years, causing a major negative impact to the environment.
Therefore, an alternative approach that can convert the abundant plastic waste into a more
value-added product and protect the environment and human health needs to be explored.
Furthermore, the fluctuation of fossil fuels prices and the heavy reliance of energy and
chemical sectors on fossil fuels have caused a dramatic increase in demand for alternative,
renewable and sustainable energy.

Biomasses stand out as a suitable renewable energy source to produce liquid fuels due to their
environmental benefits, such as abundant availability, renewability, low cost and carbon
neutral, Zulkafli et al., (2023). About 220 billion metric tons of lignocellulosic biomass are
generated annually worldwide, making biomass the world’s largest renewable source of
energy, Maqsood et al., (2021). Biomass-derived bio-oil can be an alternative to fossil fuels
to produce value-added chemical, heat, electricity, and energy. (Sarangi et al., 2018)

1

�Co-feeding hydrogen-rich materials to the oxygen-rich biomass has recently paved the way to
upgrade bio-oil quality. The co-pyrolysis process is highly similar to pyrolysis because it can
deliver high quality bio-oil, but it involves the combination of two or more feed materials. This
technique can compensate the flaws of biomass-derived bio-oil, and provide safe and effective
waste treatment, (Pawar et al., 2020). Hydrogen-rich materials such as plastics, tires and
lubricant oil can act as hydrogen donor, increase the hydrogen-to-carbon ratio of feedstock and
induce positive synergistic interaction with biomass to enhance the oil quality. The interactions
between the intermediates of lignocellulosic biomass and synthetic polymers during copyrolysis can produce bio-oil with high carbon yields, high calorific value, aromatic selectivity
and hydrocarbon , Vibhakar et al., (2022).

Thus, pyrolysis and co-pyrolysis process are a thermo-chemical degradation reaction
performed at high temperatures ranging from 400 to 900 °C in an inert atmosphere. Upon
heating above the degradation temperature, the high-molecular-weight chains are fractured to
form more stable, low-molecular-weight products and solid residue .(Sarangi et al., 2018).
Char, oil/wax, and gas are the products of the thermal conversion process, the composition and
yield of which depend on the plastic type, reactor type, and the process conditions, particularly
the reaction temperature and heating rate , Maqsood et al., (2021). Pyrolysis and co-pyrolysis
can both be used to convert biomass and other organic materials into valuable products.
However, there are some key differences between the two processes that can have a significant
impact on product yield and quality.

Pyrolysis is a closed-system process that involves heating biomass in the absence of oxygen to
temperatures of 400-600°C. This process breaks down the complex molecules in biomass into
simpler ones, which can then be condensed into bio-oil, a liquid fuel that can be used as an
alternative to petroleum. Pyrolysis also produces char, a solid residue that can be used for
energy generation or as a soil amendment. Co-pyrolysis is a similar process to pyrolysis, but it
involves heating two or more different materials together. This can be done with any
combination of biomass, plastics, or other organic materials. The synergistic effects of co2

�pyrolysis can lead to improved product yields and qualities. Nevertheless, this positive
synergistic interaction due to the mixing of feedstocks during co-pyrolysis has led to efficient
oil content in combination with a secure and alternate way to handle non-biodegradable waste,
such as plastic, tire, etc. (Chang et al., 2023).

Co-pyrolysis can generally produce a higher yield of bio-oil than pyrolysis. This is because the
different feedstocks in co-pyrolysis can interact with each other in a way that promotes the
production of bio-oil. For example, the addition of plastics to biomass can increase the yield
of bio-oil by up to 50%, (TaÅŸar, 2022). In addition, the yield of char is generally lower in copyrolysis than in pyrolysis. This is because the co-pyrolysis process breaks down the biomass
more completely, leaving less residue. According to (Wu et al., 2020b), the yield of gas is
generally higher in co-pyrolysis than in pyrolysis. This is because the co-pyrolysis process
produces more volatile compounds that can be condensed into gas. Many studies have shown
that the use of co-pyrolysis is able to improve the characteristics of pyrolysis oil, For instance,
Co-pyrolysis can produce bio-oil with higher heating values and lower oxygen content than
bio-oil produced from pyrolysis. This makes co-pyrolysis-derived bio-oil a more promising
fuel source (Román, 2010).

The char produced from co-pyrolysis is generally more reactive than the char produced from
pyrolysis. This makes co-pyrolysis-derived char a better material for energy generation or soil
amendment , Iribarren et al., (2012). The gas produced from co-pyrolysis is generally more
complex than the gas produced from pyrolysis. This makes co-pyrolysis-derived gas a more
valuable source of chemicals, (Mariyam et al., 2022). Overall, co-pyrolysis is a more promising
technology for the production of bio-oil and other biofuels than pyrolysis. Co-pyrolysis can
produce higher yields of higher-quality products, making it a more sustainable and costeffective alternative to traditional fossil fuels. The main difference between pyrolysis and copyrolysis is the number of feedstocks used.

Generically, a process based on pyrolysis has two main mechanisms, primary and secondary.
The primary reactions involve bond breaking that results in the synthesis of biochar


�Ramanathan et al.,( 2022), bio-oils through the process of de-polymerization (Moldoveanu,
2019), and gaseous products in a fragmentation step, (Guran, 2018).The leading technique
comprises chemical bonds that break down reactions and emit light components inside the
reactor subjected to heat. Furthermore, more reactions are developed and considered part of
the side mechanism. On the other hand, the subsequent reactions of these products, like
cracking and re-polymerization, are classified as secondary reactions, Lam et al., (2022). The
first stage of thermal degradation forms benzene that bonds to create solid biochar residue with
organic matter proceeding to decompose up to 800 °C. When decomposed, organic matter is
comprised of long polymeric chains, which de-polymerize organic matter into monomers.

There are three forms of pyrolysis: slow, fast, and flash. Flash pyrolysis operates with a higher
heating rate and shorter reaction time than fast pyrolysis, and the main product formed is biooil. Whereas slow pyrolysis is done at low temperature, a low heating rate, and longer vapour
residence time. The main product formed from slow pyrolysis is biochar, (Basu, 2018).
Li et al., (2021) opine that fast pyrolysis is commonly used and operates at controlled
temperatures (~500 °C) for a short residence period (<2 s) and high heating speed
(>200 °C s−1) and its main product is bio-oil. Martínez et al., (2014) investigated the effects
of slow pyrolysis of biomass and polymers and discovered that the viscosity and acidity of the
pyrolysis oil reduced; however, the energy content of the oil increased when compared to
pyrolysis oil derived only from biomass. It has also been stated that when biomass and plastics
are co-paralysed, the production of oil is significantly larger than the total amount of individual
oil products obtained from biomass and plastics, (Brebu et al., 2010). The study conducted by
many researchers concluded that the co-pyrolysis of biomass and plastics has a stronger
synergistic effect compared to individual pyrolysis , (Mohapatra & Singh, 2021).

1.2 Statement of the problem
The oil produced by the pyrolysis of biomass has potential for use as a substitute for fossil fuel.
The oil needs to be upgraded since it contains high levels of oxygen, which causes low calorific
value, corrosion problems, and instability. Generally, upgrading the pyrolysis oil involves the
addition of a catalyst, solvent and large amount of hydrogen which can cost more than the oil
�itself. According to Sarangi et al., (2018), co-feeding hydrogen-rich materials to the oxygenrich biomass has recently paved the way to upgrade bio-oil quality. The co-pyrolysis process
is highly similar to pyrolysis because it can deliver high quality bio-oil, but it involves the
combination of two or more feed materials. This technique can compensate the flaws of
biomass-derived bio-oil, and provide safe and effective waste treatment, (Pawar et al., 2020).
In this regard, the co-pyrolysis technique offers simplicity and effectiveness in higher product
yield and quality. The main difference between pyrolysis and co-pyrolysis is the number of
feedstocks used. In pyrolysis, single feedstock is used, while in co-pyrolysis, two or more
feedstocks are used. Pyrolysis and co-pyrolysis are basically the same.

However, there is need to obtain a clearer difference between pyrolysis and co-pyrolysis
process. Thus, this research aims at addressing the impact both processes have on product yield
and quality. This will help to providing a better understanding on the quantity and quality of
products that can be obtained when a single feedstock is use compared to when two or more
feedstocks are used.

1.3 Purpose of the Study
The general purpose of this study is to analyse the impact on product yield and quality by
the comparison of pyrolysis and co-pyrolysis process. Specifically, the study sought to;
➢ To evaluate the quantity of products that can be obtained from pyrolysis and copyrolysis
➢ To evaluate the quality of products that can be obtained from both pyrolysis & copyrolysis process
➢ To assess the product properties of pyrolytic and co-pyrolytic process.
➢ To evaluate the factors that governs the yield of pyrolytic products, as well as copyrolytic products.
➢ To understand how the quality of pyrolytic products can be improve or upgraded
through co-pyrolysis.



�1.4 Significance of the Study

The essence of this study is to obtain a clearer difference between pyrolysis and co-pyrolysis
process by analysing the impact both processes have on product yield and quality. However,
this study is meant to provide information on how pyrolytic products can be upgraded through
co-pyrolysis process. Nevertheless, this study would help to provide information on the factors
that influences the pyrolytic and co-pyrolytic product yield and quality. This research attempts
to provide a distinct understanding of pyrolysis and co-pyrolysis products.

Furthermore, this study could provide valuable insights on how pyrolytic oil can be upgraded
through co-pyrolysis. This knowledge could be applied to other renewable energy sources,
potentially benefiting a wide range of research areas and industries.

Finally, by comparing the impact pyrolysis and co-pyrolysis has on product yield and quality,
this research could also lead to an alternative energy source to fossil fuels. This would not only
benefit oil producing companies, but will also protect the environment and human health
In conclusion, this study is expected to contribute significantly to existing literature in the
subject under consideration. The findings from this research work could advance our
understanding of how bio-oil products can be improved both in quantity and quality for
commercial purposes.



�1.5 Scope of the Study
This work is strictly limited to evaluating and studying the impact pyrolysis and co-pyrolysis
has on product yield and quality. The scope of this study is defined primarily by evaluating;
The yield and quality of bio-oil that can be obtained from a single feedstock like biomass and
from two or more feedstocks like co-feeding plastics and biomass. However, the specific
experiments, tests, examinations and analyses conducted in this research are limited to the
impact on product yield and quality.
Hence, this study seeks to examine how pyrolysis and co-pyrolysis can impact the quality and
the quantity of products (bio-fuels). Both experimental and analytical methods are employed
in this research in order to achieve the above-stated objectives. The experimental component
involves pyrolysing different feedstocks separately. After that, they are co-pyrolysed by
blending waste plastics with biomass materials at the ratios of 20%, 40%, 60%, and 80% by
weight. The analytical component involves interpreting the experimental results and drawing
conclusions about the yielding rate and product quality obtained.
In addition, it is important to note that further research may be required to evaluate more on
the quality value of the products and the specific quantity yield of the products.



�CHAPTER TWO
LITERATURE REVIEW
2.1 Conceptual Review
Pyrolysis is the process of thermally degrading or decomposing long chain polymer molecules and
organic materials into smaller, less complex molecules through heat and pressure. The process
requires intense heat with shorter duration and in absence of oxygen. The three major products that
are produced during pyrolysis are oil, gas and char which are valuable for industries especially
production and refineries. Pyrolysis was chosen by many researchers since the process enable to
produce high amount of liquid oil up to 80 wt% at moderate temperature around 500 °C (Eimontas
et al., 2024). In addition, pyrolysis is also very flexible since the process parameters can be
manipulated to optimize the product yield based on preferences. The liquid oil produced can be
used in multiple applications such as furnaces, boilers, turbines and diesel engines without the
needs of upgrading or treatment, Praveenkumar et al., (2024).
Unlike recycling, pyrolysis does not cause water contamination and is considered as green
technology when even the pyrolysis by-product which is gaseous has substantial calorific value
that it can be reused to compensate the overall energy requirement of the pyrolysis plant, (Xiang
et al., 2024). The process handling is also much easier and flexible than the common recycling
method since it does not need an intense sorting process, thus less labour intensive. However,
pyrolysis is an irreversible chemical process and is due to heat supplied in the absence of oxygen.
It is widely used in the chemical industry to produce methanol, activated carbon, charcoal, bio char
and other substances from wood. Synthetic gas produced from the conversion of waste using
pyrolysis can be used in gas or steam turbines for producing electricity. Pyrolysis process can also
be carried out by supplying small amount of oxygen (gasification), water (steam gasification), or
hydrogen (Hydrogenation) in the reactor. The device used for Pyrolysis process is called Pyrolyser.
Igliński et al., (2023) critically reviewed the various research works done by authors for pyrolysing
wood and biomass to produce bio-oil. Ye et al., (2020), presented the effects of temperature,


�particle size and heating rate on the production of bio-oil. They proved the production was
maximum (75.74 wt%) when the temperature, heating rate and particle sizes are 575 °C, 20 °C
/min and 5 mm respectively. The various by products, their production and performances of agro
industrial bio masses were analysed by Auxilio et al.,( 2017). The aim of biomass conversion
through pyrolysis could be maximizing either the bio-oil or the bio-char yields, thereby adjusting
operating parameters to achieve this. This justifies the three main biomass pyrolysis types, namely
slow (conventional), fast, and flash pyrolysis, (Babu, 2008). They differ in heating rate, process
temperature, residence time, biomass particle size, etc.
Slow (conventional) pyrolysis, also known as carbonization, occurs at a relatively low temperature
with a slow heating rate and long solids residence time, thereby favouring solid, liquid, and gaseous
pyrolysis products significant proportions (Babu, 2008). However, this process favours about 15%
higher bio-char yield compared to bio-oil due to the longer retention time and relatively lower
heating rates causing the formation of more carbonaceous solids, Banadda et al.,( 2018).
Azeta et al., (2021) used an experimental set-up for the slow pyrolysis of coconut shell waste (Fig.
2). The set up included pyrolyzing the condensing parts with an additional nitrogen gas system to
maintain the pyrolyzer's inert atmosphere. The pyrolysis process was conducted at temperatures
ranging from 350°C to 600 °C. Other parameters indicating slow pyrolysis were the heating rate
of 5 °C/min and an hour's holding time, Mohamed Noor et al., (2019).


Figure. 1. Schematic diagram of the experimental set-up of slow pyrolysis
Fast pyrolysis is an attractive technology for biomass conversion with bio-oil as the preferred
product having great potential in industrial fuel and transport fuel applications (Heo et al., 2010).
In this process development, technologies are employed to maximize the bio-oil yield of high
quality and quantity, Adjin-Tetteh et al., (2018). The advantages of fast pyrolysis are greater
combustion efficiency, the low cost associated with storage and transportation. Fast pyrolysis
technologies include reactors with varying configurations such as ablative pyrolysis reactors,
vacuum pyrolysis reactors, entrained flow reactors, circulating bed, fluidized bed, and fixed bed
reactors. A fast pyrolysis process main features are very high heat transfer and heating rates that
require a finely ground biomass feed, carefully controlled temperature (about 500 °C; and rapid
cooling of the pyrolysis vapour to give bio-oil (Heo et al., 2010).
Flash pyrolysis is carried out for small particle sizes of biomass at too high temperatures, high
heating rates, and very short contact times. It gives off mostly gaseous products (Babu, 2008). It
is characterized by feed particle sizes of not more than 200 µm, higher heating rates of 1000–
10000°C/s and shorter residence times (<0.5 s), resulting in very high bio-oil yields of up to 75–
80 wt%, Kan et al., (2016). Alias et al., (2014) studied the characteristics and thermal degradation
behaviour of coconut pulp alongside rice husk via flash pyrolysis. The effects of particle size,
heating rate and biomass properties on the pyrolysis products were studied. It was observed that
particle size has an insignificant effect on the pyrolysis of coconut pulp and rice husk. It was also
observed that the bio-gas yield of coconut pulp was higher than that of rice husk at the same
condition.
Pyrolysis has been used since ancient times to turn wood into charcoal. Today pyrolysis is being
developed as a waste to energy technology to convert biomass and plastic waste into liquid fuels
(Román, 2010). Pyrolysis does have higher costs associated with the machinery and heating and
is dependent on a supply of feedstock , (Ramanathan et al., 2022). The quality of the bio-oil is also
low grade and cannot be used in all applications where fossil fuels are used.
However, because pyrolysis has a low environmental impact, it takes a shorter process time and
can be operated independently. In an evaluation study (Bridgwater et al., 2002), noted that the fast
pyrolysis process is proven to be a better method of power production than gasification and
combustion. It was further highlighted that the fast pyrolysis step could be operated independently
with the biofuel's intermediate storage, hence increasing the overall reliability of the process. An
economic analysis of biomass pyrolysis, gasification, and biochemical conversion processes to
produce transportation fuels by Anex et al.,( 2010) also shows that biomass pyrolysis has a much
lower capital cost. An economic evaluation of the pyrolysis process for biofuel and electricity
generation by (Tursi, 2019), revealed that pyrolysis has higher conversion efficiency.
In addition, pyrolysis is not just an independent process; it is also the first step in the gasification
or combustion process. Production of liquid fuel via pyrolysis has garnered a lot of interest due to
its enormous advantages in transportation and versatility of application such as boilers, turbines,
and combustion engines (French & Czernik, 2010).
Co-pyrolysis on the other hand has the same process as that of the process of pyrolysis, except
this process involves two or more substances as raw materials. One of the raw materials is biobased waste, while the other material is fossil-based waste. Even this process requires inert
atmospheres and absence of oxygen. The process of co-pyrolysis is more profitable than the
process of pyrolysis of biomass alone. The basic steps involved in the co-pyrolysis process are: (1)
preparation of samples, (2) co-pyrolysis, and (3) condensation. Prior to the process of co-pyrolysis,
the sample should be dried and ground to remove the moisture content from the sample. Many
studies have shown that the use of co-pyrolysis is able to improve the characteristics of pyrolysis
oil, e.g., increase the oil yield, reduce the water content, and increase the caloric value of oil. When
oil from biomass is completely mixed with the oils from plastic or tyres, unstable mixture forms,
which breaks after a certain amount of time.
However, the co-pyrolysis of lignocellulosic residues like corn-stover with hydrogen-rich
feedstocks such as plastics is a promising conversion process to produce oil and gas products.
Having a high hydrogen content of about 14 % by mass, plastic could donate hydrogen during copyrolysis which leads to improvement in both oil yield and quality (Salvilla et al., 2019). The copyrolysis of biomass and plastics is considered to be a promising technology that can improve the
quality of oil, which also paves the way for a better utilization of municipal solid waste plastics
(Zulkafli et al., 2023). (Özsin & Pütün, 2018) studied the co-pyrolysis behavior of polystyrene
(PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC) and walnut shell, peach pit at
�500°C. The results showed that the co-pyrolysis of PET, PS and biomass could effectively improve
the liquid yield.
Pinto et al., (2016) studied the effect of co-pyrolysis of cellulose and PS at different mass ratios
on the composition of liquid products. The results revealed that the mass ratio of Cellulose/PS
would greatly affect the contents of oxygenated compounds and hydrocarbons in bio-oils.
Furthermore, co-pyrolysis offers economic advantages since it requires less energy than the
pyrolysis of biomass and plastic alone (Chen et al., 2020). Supelano et al., (2020) investigated the
synergistic effects between biomass (rice husk, groundnut shell, bagasse, mixed wood sawdust and
Prosopis juliflora) and hydrogen-rich plastics (Polyisoprene (PIP) and low-density polyethylene
(LDPE)). The study deduced that co-pyrolysis significantly boosted the calorific value of bio-oil.
The heating value of co-pyrolysis oil varied from 38 to 42 MJ/kg as compared to the heating value
of biomass pyrolysis oil of 20 to 28 MJ/kg. In addition, the deoxygenation degree also increased
due to the synergistic effects.

Rahman et al., (2021) carried out pyrolysis for mixtures of pine and HDPE in a double-column
staged reactor and observed that the addition of HDPE to pine could increase the pyrolysis oil yield
up to threefold compared to pyrolysis oil of pine alone. In addition, the oil produced was rich in
hydrocarbon with 99 % selectivity. Adding the catalyst to the co-pyrolysis process could facilitate
the cracking of pyrolysis vapour and deoxygenate the oxygenated compounds via dehydration,
decarboxylation and decarboxylation reactions, improving selectivity towards the desired
compounds, such as hydrocarbon(Dyer et al., 2021). Co-pyrolysis offers simplicity in design and
operation, and in many cases has successfully produced oil with a high quantity and quality. Copyrolysis reduces the need for post-modification of bio-oil, unlike pyrolysis of a single feedstock.
Co-pyrolysis is governed by numerous factors, such as biomass variety, type of reactor, and
operating parameters, such as temperature, heating speed, reaction period, and particle dimensions
of feed Ghai et al., (2022). In addition, the interaction of radicals during the co-pyrolysis reaction
can promote the formation of a stable pyrolysis oil that avoids phase separation Martínez et al.,
(2014).Prior to co-pyrolysis, feedstocks must be prepared and pre-treated. Pre-treatment is another
approach to improving the synergistic interactions between biodegradable wastes and nonbiodegradable wastes. Pre-treatment is an essential step for the generation of bio-oil with higher
quality and quantity from co-pyrolysis. Pre-treatment of biomass is necessary due to the
coincidence of alkali and alkaline earth metals that negatively influence the performance of
co-pyrolysis, Ansari et al., (2021). In comparison to normal pyrolysis, co-pyrolysis could lower
the temperature and time required to produce high-quality biofuels. Some researchers have also
reported synergistic effects among the substrates used in co-pyrolysis, enhancing bio-oil yield as
well as improving its applicability as a liquid biofuel.
2.2 Theoretical Review
The word “pyrolysis” is coined from two Ancient Greek words pyro (πυρο) meaning fire and lysis
(λύσις) meaning separating (or solution), so pyrolysis means separation by fire or heat. In
photolysis, by contrast, the chemical substances are treated with light rather than heat. Pyrolysis
process converts biomass into liquid, gaseous and solid fuels. Chemical kinetics play a key role in
explaining the characteristics of pyrolysis reactions and developing mathematical models. Many
studies have been undertaken to understand the kinetics of biomass pyrolysis; however, due to the
heterogeneity of biomass and the complexity of the chemical and physical changes that occur
during pyrolysis, it is difficult to develop a simple kinetic model that is applicable in every case.
Pyrolysis involves numerous extremely complex reactions and end up with large number of
intermediates and end products, devising an exact reaction mechanism and kinetic modelling for
pyrolysis is extremely difficult, hence, pyrolysis models are modelled on the basis of visible
kinetics (Hu & Gholizadeh, 2019). From a theoretical point of view, an endless variety and
complexity of reactions forming a network can be assumed in pyrolysis. Hence, even today it is
difficult to develop a precise kinetic model taking into account all the parameters concerned.
Numerous models exist for the primary and secondary pyrolysis, each with their advantages and
disadvantages. They range in complexity from simplest models to more mathematically complex
models incorporating various factors which influence the kinetics of pyrolysis.
�The semi-global models are used to describe primary and secondary solid degradation by means
of experimentally measured rates of weight loss. Though one step models can predict the
characteristic time of the pyrolysis process, for the formulation of engineering models with a view
of reactor optimization and design, semi-global mechanisms appear to be more promising, because
competitive chemical pathways are described, which allow product distribution to be predicted on
dependence of reaction conditions (Di Blasi, 1998). The degradation of the three main biomass
components is described through a kinetic mechanism, which deviates from the original
Broido – Shafizadeh mechanism for the introduction of a linked tar and gas formation, Figure 2
(Di Blasi, 1998). Then the degradation rate of biomass is considered as the sum of the contribution
of its main components, cellulose, hemicelluloses and lignin (Di Blasi, 1998). The extrapolation
of the thermal behaviour of main biomass components to describe the kinetics of complex fuels is
however, only a rough approximation because it has not been possible to establish exact
correlations (Scotia & Ellis, 1978). This is probably due to: the presence of inorganic matter in the
biomass structure, which acts as a catalyst or an inhibitor for the degradation of cellulose, purity
and physical properties of cellulose, which play an important role in the degradation process,
noticeable differences in the hemicellulose and lignin, depending on the biomass type
(Di Blasi, 1998).

Cellulose

K1

KV

Volatile

Kc

Charcoal + Gases

Active Cellulose

Figure 2. The Broido – Shafizadeh mechanism (Di Blasi, 1998)
In addition, as it is impossible to isolate biomass components without affecting to varying extents
their chemistry and structure, differences can be expected in the degradation mechanisms on
dependence of the separation technique (Di Blasi, 1998). As well as for cellulose, wide interest in
the primary pyrolysis of whole biomass has appeared in the literature (the pyrolysis of
hemicelluloses and lignin).
�(Thurner & Mann, 1981), investigated the kinetics of wood (oak sawdust) pyrolysis into gas, tar,
and charcoal, to determine the reaction rate parameters, and to identify the composition of the
pyrolysis products. It has been found that, in the range investigated, wood decomposition into gas,
tar, and charcoal can be described by three parallel first-order reactions as suggested by
Broido-Shafizadeh. They proposed the model which is an upgrade of the Broido-Shafizadeh
model, Figure 3.
According to the model, wood is pyrolyzed into gas, tar, and charcoal according to three parallel
reactions (reaction k1, k2, k3), called primary reactions, and the tar decomposes into gas and
charcoal according to two parallel reactions (reaction k4, k5), called secondary reactions
(Thurner & Mann, 1981). Each product in Figure 2 represents a sum of numerous components
which are lumped together to simplify the analysis. The composition of each product, especially
the distribution between the gas and the tar, depends, among other things, on the conditions under
which the products are collected (Thurner & Mann, 1981). In principle, the reaction rate constants
of these five reactions can be determined by measuring the amount of each product as a function
of time. When the tar is removed from the reaction zone the secondary reactions are avoided and
the reaction rate constants of the primary reactions can be determined directly from these
measurements (Thurner & Mann, 1981). Table 1 presents evaluated kinetic parameters

Gas
K1

K4
K2

Biomass

Tar
K5

K3

Charcoal

Figure 3. Biomass kinetic reaction scheme (Thurner & Mann, 1981)

Table 1. Kinetic parameters used by (Thurner & Mann, 1981).
Reaction rate constant

A

E

S-1

(S-1)

(KJ/mol)

K1

1.43.104

88.6

K2

4.12.106

112.7

K3

7.37.105

106.5

Koufopanos et al., (1989), attempted to correlate the pyrolysis rate of the biomass with its
composition. Koufopanos et al., (1989), proposed kinetic model based on experimental results
preformed experiment of pyrolysis of fine particles of lignocellulosic materials (below 1 mm) in
size. In this case, the possible effects of heat and mass transfer phenomena are drastically decreased
and the process is controlled by kinetics. The good fit of the kinetic model to experimental data
obtained under different heating conditions and over a wide temperature range suggests that the
pyrolysis rate of fine particles can be interpreted in terms of pyrolysis temperature and solid
residence time, Koufopanos et al., (1989). This model is presented in Figure 4. This model uses an
intermediate step (initial reaction k1) to get an activated sample. This initial reaction (k1) describes
the overall results of the reactions prevailing at lower pyrolysis temperatures (below 473 K)
Ji et al., (2022).
This first step is considered to be of zero-order and is not associated with any weight loss. The
intermediate formed further decomposes through two competitive reactions, to charcoal (reaction
k3) and to gaseous/volatile products (reaction k2). This model is relatively simple and can predict
the final charcoal yield in different heating conditions.

�Kb

Ka

Biomass

Volatile +tar

Intermediate
Kc
Charcoal +gases

Figure 4. Reaction scheme of Biomass Pyrolysis suggested by Koufopanos et al., (1989), a, b, c –
share of biomass components.
Kinetic parameters used by Koufopanos et al., (1989) are presented in Table 2. The proposed
kinetic model for the pyrolysis of lignocellulosic materials is relatively simple and predicts with
sufficient accuracy both the reaction rate (expressed in terms of weight-loss) and the charcoal
yield, also model can be used for the interpretation of experimental data and for the design of
biomass thermochemical conversion apparatus, (Koufopanos et al., 1989). Another set of
conclusions emerging from this work relates to the relationship between the biomass pyrolysis rate
and the biomass composition; it was found to be possible to analyse biomass pyrolysis by
considering the biomass as the sum of its main components: cellulose, lignin and hemicellulose
(Koufopanos et al., 1989).
Table 2. Kinetic parameters, (Koufopanos et al., 1989).

First reaction
Biomass

Second reaction

A

E

Third reaction

A

E
(KJ/mol)

A

E

(S-1)

(KJ/mol)

component

n

(S-1)

(KJ/mol)

n

(S-1)

cellulose

0

2.2.1014

167.5

1.5

94.1015

216.5

1.5

3.11013

196

hemicellulose

0

3.3.106

72.4

1.5

1.1.1014

174.1

1.5

2.51013

172

lignin

0

3.3.1012

147.7

1.5

8.6.108

137.1

1.5

4.4107

122



n


�Xiao et al., (2020) increased the information content of the experiments by involving successive
non-isothermal steps into their study. A wider range of the experimental conditions reveals more
of the chemical in homogeneities of the biomass components. Linear and stepwise heating
programs were employed to increase the amount of information in the series of experiments
(Trninić et al., 2012). Employing non isothermal experiments, not only identification of pseudo
components or zones were possible to made (hemi-cellulose, cellulose and lignin), but also, the
contribution of extractives or more than one reaction stage in the decomposition of components,
especially hemi- cellulose and lignin, could be also taken into pyrolysis kinetic analysis account.
Experimental measurements of the pyrolytic behaviour of biomass have been the focus of extraordinary interest in the research community, but practical problems associated with these
measurements have often been overlooked. The most important errors are connected to problems
of temperature measurements and to the self-cooling/self-heating of samples due to heat demand
by the chemical reaction, (Hameed et al., 2019). A consequence of these limitations is that the
single step activation energy measured at high heating rates is almost always lower than its true
value (Hameed et al., 2019). Another consequence is that weight loss is reported at temperatures
much higher than it actually occurs.
The concept of a distributed activation energy as originally proposed by (Vand, 1943) was adapted
to the problem of coal DE volatilization by de la Puente et al., (1998). (de la Puente et al., 1998),
first treated the coal as a mixture of a large number of species decomposing by parallel first order
reactions with different activation energies. The pyrolysis behaviour of coal is described as a
complex of first-order reactions, each with its own rate constants. Further work carried out by
ANTHONY et al., (1976), and (Braun & Burnham, 1987), modified the model developed by
(de la Puente et al., 1998) and extended its use to coal, biomass and even blends of the two.
2.3 Empirical studies
G. Ahmed & Kishore, (2023) in their study of Fuel phase extraction from pyrolytic liquid of
Azadirachta indica biomass followed by subsequent characterization of pyrolysis products
recorded that at the beginning of the 20th century, crude petroleum fuels covered only 4% of the
world's energy demand. However, nowadays, petroleum fuels are the most important energy


�source and covers about 40% of the world's energy demand. It also produces 96% of the
transportation fuels. Nevertheless, petroleum fuels are non-renewable and the reserves of fossil
fuel are depleting fast. In addition, the use of petroleum fuels influences environment by generating
huge amounts of net carbon dioxide emission and other pollutants such as NOx and SOx.
Therefore, there is an urgent need to find renewable and environmentally benign feedstocks for
sustainable supply of fuels and energy.
Baker, (1987) in his study of a review of pyrolysis studies to unravel reaction steps in burning
tobacco reported that a clear distinction between the processes of pyrolysis and combustion during
burning is extremely difficult because the formation of free radicals during the reaction with
oxygen can be involved in the pyrolytic decomposition of molecules. In addition, the term
pyrolysis should only be used to allude to chemical reactions taking place at temperature
significantly higher than the ambient temperature in order to differentiate between pyrolysis and
natural chemical decomposition.
Yuan et al., (2018) in his study of co-pyrolysis of cellulose and High density polyethylene (HDPE)
at different ratios, reported that the synergistic effects in the co-pyrolysis accelerated the
generation of small molecule volatiles, including H2O, CO/C2H4, and CO2. The decomposition
of HDPE via chain-end and random scission can transfer hydrogen for the decomposition of
cellulose derived anhydrosugars to aldehyde and ketone while cellulose-derived oxygenated
compounds, which act as acceptor, promote the scission of HDPE to alkane and alkene groups.
Suriapparao et al., (2020) examined the co-pyrolysis of Low Density Polyethylene (LDPE) with
five different biomass and found that the experimental bio-oil yield (13.2 – 32.3 wt. %) was less
than the theoretical value

(42 47.5 wt. %). Excessive cracking of heavier molecules into lighter

gases contributed to low bio-oil yield. Although the yield of bio-oil was low, the heating value of
bio-oil (37.6–41 MJ/kg) was better than the theoretical value (32.6–37.8 MJ/kg) due to the
interaction between oxygen transfer from condensable phase to gas phase and hydrogen release
from LDPE vapours.
Özsin & Pütün, (2018) investigated the co-pyrolysis of PET blended with peach stones and walnut
shells using a fixed bed reactor, and observed increased ester and acid compounds and decreased
�phenolic compound. Maximum acid and ester yield of 65.87 % and 63.11 % were achieved in copyrolysis of PET with walnut shells and peach stones, respectively. The liquid was dominated by
benzene carboxylic acid with more than 40 % yield for both co-pyrolysis blend. Benzene
carboxylic acid and vinyl benzoate were formed when the ester link of carboxylic group was
broken via beta scission, initiating the decomposition of PET. One of the biggest challenges
regarding pyrolysis oil from PET is the high acid content such as benzoic acid. The acidic
characteristic of pyrolysis oil can lead to corrosiveness, depreciating the fuel quality. In addition,
benzoic acid can clog the pipelines and heat exchanger, triggering issues during operation at
industrial scale(Lee et al., 2021).
Ahmed et al., (2020) studied the co-pyrolysis of empty fruit bunch (EFB) and oil palm frond (PF)
with LDPE for bio-oil production. The results showed positive synergistic interaction on the
production of aliphatic hydrocarbons and inhibition of oxygenated compounds. The hydrogen
released from LDPE enhanced the decarboxylation of carbonyls and sugar, and decarboxylation
of acid to hydrocarbon due to oxygen removal via CO and CO2, respectively. In addition,
significant synergistic interaction between EFB and PF with LDPE on the production of bio-oil
has also been observed. The positive synergistic effect could be attributed to the secondary radical
reaction, leading to the condensation of non-condensable fragments. Furthermore, LDPE that acted
as the hydrogenation medium for biomass could inhibit the cross-linking reactions and
polymerization of biomass, leading to greater biomass weight loss (Aboulkas et al., 2012)
Rahman et al., (2021) and Dyer et al., (2021), carried out pyrolysis for mixtures of pine and High
density polyethylene (HDPE) in a double-column staged reactor and observed that the addition of
HDPE to pine could increase the pyrolysis oil yield up to threefold compared to pyrolysis oil of
pine alone. In addition, the oil produced was rich in hydrocarbon with 99 % selectivity. Adding
the catalyst to the co-pyrolysis process could facilitate the cracking of pyrolysis vapour and
deoxygenate the oxygenated compounds via dehydration, decarboxylation and decarboxylation
reactions, improving selectivity towards the desired compounds, such as hydrocarbon
Samal et al., (2021) examined the co-pyrolysis of eucalyptus biomass and polystyrene waste on
the physiochemical and thermal characteristic of the solid char. Two distinct physiochemical and
thermal characteristics of char have been observed basically at temperature below and above 450 °C. The char generated below 450°C has high heating value and volatile content with low
fixed carbon because of the polystyrene coating on the char surface. The melting polystyrene waste
could deposit over biomass at temperature below 450°C, go through volatilization with additional
increase in temperature, and be transformed to liquid oil and syngas. Solid fuels with high volatile
content and low fixed carbon generally possess low ignition and burnout temperatures and a higher
mass loss rate, making them unstable.
However, the increased high heating value due to the existence of waste plastic coating could ease
in enhancing the combustion efficiency of the fuel. In contrast, the produced chars at temperature
450°C and above possessed more high heating value and fixed carbon with low volatile content.
This kind of solid fuel demonstrates superior combustible behaviour with broader temperature
range and longer time for complete combustion, all of which signify an excellent solid fuel.
2.4 Summary of Literature/Research Gap
Generally, upgrading pyrolysis oil involves the addition of a catalyst solvent and large amount of
hydrogen which can cost more than the oil itself. Many researchers has suggested that co-pyrolysis
techniques offers simplicity and effectiveness in higher product yield and quality. However, form
the summary of all the reviewed literature, authors and researchers who have worked on the impact
pyrolysis and co-pyrolysis has on product yield and quality, did not clearly state how effective the
use of pyrolytic products can be for commercial use. Therefore, this research intend to provide a
better understanding on how efficient and effective pyrolytic products can be for commercial use.




�CHAPTER THREE
MATERIALS AND METHODS
This research work was conducted in Mechanical Engineering Department of Nnamdi Azikiwe
University, Awka. The research work was carried out to compare the impact pyrolysis and copyrolysis has on product yield and quality.

3.1. Evaluation of pyrolysis products
Pyrolytic oil generated from the pyrolysis method is less efficient on the basis of fuel combustion
when compared to conventional fuels, such as diesel, petrol, etc. This is due to the reason that
pyrolytic oil usually contains a high quantity of oxygen that creates unnecessary combustion
problems. In different previous research, it was found that pyrolytic oil contained approximately
30–60 wt. % of oxygen in the form of water molecules (Oasmaa & Czernik, 1999) . In addition,
high oxygen contents in pyrolytic oil cause lower calorific value and instability of operation. As a
consequence, it is required to upgrade and improve pyrolytic oil generated in the pyrolysis process.
To improve the quality of pyrolytic oil, it is required to reduce the quantity of dissolved oxygen.
It is possible to reduce the dissolved oxygen from pyrolytic oil by catalytic cracking, co-pyrolysis,
and hydro deoxygenation (HDO) process.
In the catalytic cracking and hydro deoxygenation (HDO) method, external catalysts are added in
the pyrolysis process. However, the addition of catalysts increases the operating cost of the
pyrolysis process. It also increases the number of solid materials at disposal Chen et al., (2020).
Overall, this process is costly, complex, and require higher pressure during operation. In contrast,
the co-pyrolysis method is an effective and efficient process that can improve the quality of
pyrolytic oil. In the pyrolysis method, produced combustible gases are condensed to a
combustible liquid called pyrolytic oil. The other products of the pyrolysis method are CO2, CO,
H2, and HC. Therefore, the pyrolysis method generates three types of products, such as solid
(charcoal), liquid (bio-oil/pyrolytic oil), and gas (synthetic gas). Figure 5 presents the overall
schematic diagram of the pyrolysis method that generates pyrolytic oil.



�Figure 5.
Biomass conversion process technologies Suriapparao et al., (2020).
Moreover, in pyrolysis method, biomass feedstock materials are decomposed in pyrolytic oil by
the following reaction mechanism Equations, Demirbas, (2004):

Biomass feedstocks→ H2O+residuematerials (unreacted)

Eq (1)

Residue materials (unreacted) →Volatilematters1+Charcoal1+Gases1

Eq (2)

Charcoal1→Volatilematters2+Gases2+Charcoal2

Eq (3)

Therefore, in the biomass pyrolysis method, firstly, moisture contents, and volatile matters are lost
as presents by Eq. (1). Secondly, unreacted residue materials are transformed into volatile matters,
as shown in Eq. (2). Finally, charcoal material is re-arranged at a slower step, as shown in Eq. (3).
Depending on the reaction temperature, residence time, and rate of heating, the pyrolysis process
can be classified as fast, slow, and flash pyrolysis. Pyrolysis process usually occurs in a fixed bed,
fluidized bed, moving bed, suspended bed reactors.


�However, the generated pyrolytic oil in the pyrolysis process contains a higher quantity of oxygen
that decreases internal combustion engines’ efficiency. Therefore, up-gradation of pyrolytic oil
generated from the pyrolysis method is necessary. The pyrolytic oil generated from the pyrolysis
method can be upgraded by esterification, emulsification, or catalytic cracking. All these upgradation methods include extra operating costs for the pyrolysis process and they are rather costly.
The other effective method of producing high-quality pyrolytic oil is the co-pyrolysis method that
can produce high-quality pyrolytic oil with less quantity of oxygen.
Figure 6 shows the upgradation methods of pyrolytic oil generated from biomass pyrolysis
method.

Figure 6.Upgradation methods of pyrolytic oil.



�3.2. Evaluation of Co-pyrolysis products
Co-pyrolysis is the process where two or more feedstock materials include to improve the quality
of pyrolytic oil in absence of oxygen at a moderate temperature (~500 °C). Effectiveness and
simplicity are two important characteristics of the co-pyrolysis process. Figure 7 shows the overall
process of co-pyrolysis.

Figure 7.
Overall process of co-pyrolysis, Anuar Sharuddin et al., (2016).
It is seen from Figure 5 that, in the co-pyrolysis method, two or more feedstock materials are dried
and ground to prepare feedstock material. After that inert gases are required to add to the reactor.
Inert gases use to speed up the sweeping vapours of feedstock materials from the pyrolysis region
to the condenser region. Nitrogen gas is used as an inert gas in the co-pyrolysis process due to its
low cost. Initially, charcoal and combustible gases are produced. After condensation, combustible
gases generate upgraded pyrolytic oil. Therefore, the co-pyrolysis method requires three steps for


�the generation of pyrolytic oil, such as preparation of feedstock materials, co-pyrolysis, and
condensation.
Drying of feedstock material can be done using the oven method at a higher temperature (~105
°C) for 1 day. The drying process is required to remove the moisture contents in the feedstock
material. However, for industrial purposes, the amount of required heat is higher than lab-scale.
Hence, process integration is used to heat feedstock materials Anuar Sharuddin et al., (2016). The
optimum temperature of the co-pyrolysis process is considered as 400 ~ 600 °C. At this
temperature, approximately 45 wt. % of pyrolytic oil is usually produced from feedstock material
Anuar Sharuddin et al., (2016). Table 3 presents the optimum operating conditions of co-pyrolysis
method for different feedstock materials.

Feedstock materials
Wood, plastic, rice husk ,rice straw,

Temperature(℃)
300~500

Inert gas

Pyrolytic oil (wt. %)

N2

45~75

water hyacinth

Table 3.
Optimum operating conditions of co-pyrolysis method, Anuar Sharuddin et al., (2016).
3.3 Reaction parameters of co-pyrolysis process
Reactions of the co-pyrolysis method are complex and it includes a number of different copyrolysis reactions. The biomass co-pyrolysis process and their reactions depend on different
parameters, such as the effect of feedstock materials, blending ratio, rate of heat, temperature,
reactor type, etc.
3.4 Effect of different feedstocks
Biomass feed materials consist of lignin, cellulose, and hemicellulose (Gates et al., 2008). These
components generate synergistic effects on the thermal behaviour of biomass. It is considered that


�the cracking of biomass depends on the H and OH radicals release during biomass pyrolysis
(Sonobe et al., 2008). On the other hand, hemicellulose components serve effects of promotion on
biomass conversion during co-pyrolysis process, S. Yuan et al., (2011).
Table 4 shows the characteristics of different biomass materials.
Feedstock materials

Lignin (wt. %) Cellulose (wt. %) Hemicellulose (wt. %)

Pinewood

24 [28]

42 [28]

23 [28]

Water hyacinth

3 ~ 28 [29]

~30 [30]

~25 [30]

Rice straw

16.5 [31]

29.8 [31]

33.3 [31]

Waste plastic (polystyrene)

10 ~ 15 [32]

35 ~ 55 [32]

20 ~ 40 [32]

Table 4.
Characteristics of different biomass materials.
3.5 Effect of blending ratio
The blending ratio is defined as the proportion of biomass in the blend of feedstock materials
during co-pyrolysis. In the co-pyrolysis method, the generated quantity of gas, liquid, and solid
materials depends on the blending ratio of feedstock material Aboyade et al., (2013). It was found
that increasing biomass blending ratio reduces the solid charcoal generation, while liquid and gas
production increases Quan et al., (2014). The blending ratio of biomass materials can also
influence the degree of synergistic effect.
3.6 Effect of rate of heat
The rate of heating is a significant factor that can affect the biomass co-pyrolysis process. The
biomass co-pyrolysis process can be distinguished if the rate of heat is low. At a low heating rate,
only additive behaviour of biomass materials occurs. On the other hand, the DE volatilization
process of biomass materials becomes slower with the increase in the heating rate. Synergism of
biomass feedstock materials is favoured by the increased heating rate of feedstock material



�(S. Yuan et al., 2011). It was found that low heating rate caused lack of synergies. Moreover, a
high rate of heat during co-pyrolysis generally produces higher volatile yields Demirbas, (2004).
3.7 Effect of temperature
The temperature in the co-pyrolysis process is an important factor for the generation of solid
(charcoal), liquid (pyrolytic oil), and gas. By increasing the temperature inside the co-pyrolysis
reactor, it is possible to decrease the production of charcoal from biomass co-pyrolysis. As a
consequence, the overall efficiency of the co-pyrolysis method can be increased by increasing the
temperature (Park et al., 2010).
3.8 Effect of types of reactor
Different types of reactors, such as fixed bed, fluidized bed, TG, drop style, auger are commonly
used in pyrolysis and co-pyrolysis process. In this chapter, the fixed bed reactor is considered for
biomass feedstock materials. However, the TG reactor is most commonly used during the copyrolysis method. In a fixed bed pyrolysis reactor, a large quantity of feedstock materials provides
intimate contact between fuel particles and their generated volatiles. Due to this phenomena,
synergistic effect is occurred for gas and pyrolysis product yield (Fei et al., 2012). Fluidized bed
and drop style type reactors are fast pyrolysis reactors that can be used to carry the co-pyrolysis
process. Auger reactor is more effective than fixed-bed reactor for co-pyrolysis process. Auger
type reactor usually generates higher liquid

product yield than fixed-bed reactor

Http://dx.doi.org/10.1016/j.fuproc.2013.11.015 et al., (2014).
Overall, the generation of liquid yield (pyrolytic oil) and solid yield (charcoal) in the co-pyrolysis
method increases with the increase of temperature of the pyrolysis reactor. However, the required
temperature of the co-pyrolysis process (300–450 °C) is lower than the temperature required for
the pyrolysis process (550–750 °C).
3.9 Characteristics analysis
In the co-pyrolysis process, the quality of the generated pyrolytic oil is better than the pyrolysis
process. As a consequence, the oxygen content in the pyrolytic oil generated from the co-pyrolysis
method is lower than the pyrolysis process. However, to improve or upgrade pyrolytic oil in the


�pyrolysis method requires an intermediate process that increases the complexity and cost. Hence,
this chapter considers only the co-pyrolysis process of biomass feedstock materials and their
related characteristics. However, the calorific value of pyrolytic oil and gas generated in the copyrolysis process for pinewood-waste plastic or rice straw-water hyacinth was higher than the
calorific value of product yield when used only pinewood or rice straw or water hyacinth feedstock
biomass. Table 6 presents the calorific value of different feedstock materials in pyrolysis and copyrolysis process.

Feedstock materials
Pinewood- plastic
(polystyrene) [47]
Rice straw-water
hyacinth [48]

Calorific value
(MJ/kg) of solids

Calorific value
(MJ/kg) of liquids

Calorific value
(MJ/kg) of Diesel

33 ~ 45

32 ~ 45

45.5

32 ~ 42

33 ~ 42

45.5

Table 5.
Calorific value of product yield of co-pyrolysis process.



�