Thermal Degradation Analysis of Plastic Waste for Conversion into Liquid Fuel Using Catalytic Pyrolysis

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Plastic waste has become one of the most pressing environmental challenges worldwide. Communities generate millions of tonnes of plastic every year, and most of it ends up in open dumps, landfills and water bodies. Because plastics degrade very slowly, they remain in the environment for decades and continue to accumulate. Consequently, they harm aquatic life, contaminate soil and contribute to long-term pollution (Smith, 2019). Researchers have emphasized that rapid population growth, urbanization and increased consumption worsen the scale of this problem (Olorunfemi, 2021).

Converting plastic waste into useful products has therefore gained global attention. One promising approach is catalytic pyrolysis. During pyrolysis, plastic materials are heated in the absence of oxygen, which breaks them down into smaller molecules that can condense into liquid fuel (Zhang & Li, 2020). This process reduces pollution, decreases the volume of waste and produces valuable energy. Moreover, pyrolysis is flexible because it can process mixed or contaminated plastics (Ajayi, 2022).

Thermal degradation plays a crucial role in pyrolysis. Understanding how plastics break down at various temperatures helps determine the best operating conditions for fuel production. Factors such as heating rate, catalyst type and reactor design influence the yield and quality of the resulting fuel (Kumar et al., 2021). Catalysts such as zeolites, silica–alumina and activated carbon often improve the process by lowering reaction temperatures and enhancing fuel quality (Rahman, 2020). Therefore, thermal degradation analysis remains essential for optimizing conversion.

Liquid fuel produced from pyrolysis contains hydrocarbons similar to conventional fuels. Because fossil fuels continue to rise in price, pyrolysis presents a sustainable alternative (Adekunle, 2023). It supports energy diversification and promotes environmental sustainability. Although many developed countries have advanced research on pyrolysis, several developing nations still lack detailed studies that focus on locally generated plastic waste (Mohammed, 2022).

This study investigates the thermal degradation of plastic waste and evaluates its conversion into liquid fuel using catalytic pyrolysis. It provides scientific insights that support improved waste management and renewable energy development.

1.2 Statement of the Problem

Plastic pollution has reached alarming levels. Many cities face serious waste management challenges because plastic waste accumulates faster than it can be removed. Open burning remains common, but it releases toxic gases that affect human health and contribute to climate change (Danladi, 2020). Landfilling is not a sustainable long-term solution either, since plastics degrade slowly and require large storage areas (Okeke, 2019).

At the same time, many communities face energy shortages. Fuels such as diesel, kerosene and petrol have become increasingly expensive. This situation places extra pressure on households and small businesses. Therefore, there is a strong need for affordable alternative energy sources.

Although pyrolysis provides a promising solution, its effectiveness depends on a clear understanding of thermal degradation behavior. Several studies have addressed pyrolysis but have not focused enough on thermal analysis, especially for plastics commonly found in developing countries (Eze & Chukwu, 2022). In addition, the influence of locally available catalysts on fuel yield has not been adequately explored (Bello, 2021).

This study addresses these gaps by analyzing thermal degradation patterns and evaluating catalytic pyrolysis performance using selected plastic waste.

1.3 Aim of the Study

The aim of this study is to analyze the thermal degradation of plastic waste and evaluate its conversion into liquid fuel through catalytic pyrolysis.

1.4 Objectives of the Study

The specific objectives are:

1. To collect and classify selected plastic waste materials for thermal analysis.

2. To examine the thermal degradation behavior of the plastics using appropriate analytical techniques.

3. To carry out catalytic pyrolysis under controlled operating conditions.

4. To measure the yield and properties of the liquid fuel produced.

5. To assess the influence of catalyst type on thermal degradation and fuel quality.

1.5 Research Questions

1. What thermal degradation patterns do the selected plastic wastes exhibit

2. How does catalytic pyrolysis influence the breakdown of the plastics

3. What volume and quality of liquid fuel does the process produce

4. How does the presence of a catalyst improve conversion efficiency

5. Which plastic type provides the best fuel yield under the selected conditions

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1.6 Research Hypotheses

H1: Catalytic pyrolysis significantly improves liquid fuel yield from plastic waste.
H0: Catalytic pyrolysis does not significantly improve liquid fuel yield from plastic waste.

1.7 Significance of the Study

This study is significant for several reasons. First, it supports environmental protection by offering a scientific approach to reducing plastic pollution. Converting waste into fuel helps divert plastics from landfills and water bodies (Ogundipe, 2022). Second, it promotes renewable energy development. Liquid fuel from waste offers an affordable alternative to petroleum-based fuels, especially in communities facing high fuel costs (Afolabi, 2020).

Third, thermal degradation and catalytic studies provide essential scientific data. They help determine optimal operating conditions and identify the catalysts that improve conversion efficiency (Wang & Chen, 2021). This information benefits engineers, researchers and students involved in sustainable energy research.

Fourth, the study supports local economic development. Communities can adopt pyrolysis technologies to reduce waste and generate energy at low cost. Finally, the research adds to academic literature by providing data on thermal behavior, catalyst performance and fuel characteristics.

1.8 Scope of the Study

The study examines thermal degradation and catalytic pyrolysis of selected plastic waste materials. It includes waste classification, thermal analysis, pyrolysis experiments and fuel characterization. The study does not include large-scale industrial production, economic feasibility analysis or pollutant emissions testing.

1.9 Limitations of the Study

Several limitations may affect the study. Plastic waste composition may vary across different sources, which may influence thermal behavior (Ibrahim, 2022). Laboratory equipment may also limit the range of temperatures and reaction conditions tested. Furthermore, laboratory results may not fully represent industrial scale operations. Despite these limitations, the study employs standard analytical methods to ensure accuracy.

1.10 Organization of the Study

The research is presented in five chapters. The first chapter introduces the study and outlines its purpose. The second chapter reviews literature on plastic waste, thermal degradation and catalytic pyrolysis. The third chapter explains the research methods and analytical procedures. The fourth chapter presents the results and discusses their significance. The final chapter concludes the study and offers recommendations for further research and practical applications.