Torrefaction of Biomass for Energy Applications: From Fundamentals to Industrial Scale

By Leonel JR Nunes, Joao Carlos De Oliveira Matias and Joao Paulo Da Silva Catalao

Torrefaction of Biomass for Energy Applications: From Fundamentals to Industrial Scale explores the processes, technology, end-use, and economics involved in torrefaction at the industrial scale for heat and power generation. Its authors combine their industry experience with their academic expertise to provide a thorough overview of the topic. Starting at feedstock pretreatment, followed by torrefaction processes, the book includes plant design and operation, safety aspects, and case studies focusing on the needs and challenges of the industrial scale. Commercially available technologies are examined and compared, and their economical evaluation and life cycle assessment are covered as well.

Attention is also given to non-woody feedstock, alternative applications, derived fuels, recent advances, and expected future developments. For its practical approach, this book is ideal for professionals in the biomass industry, including those in heat and power generation. It is also a useful reference for researchers and graduate students in the area of biomass and biofuels, and for decision makers, policy makers, and analysts in the energy field.

• Compares efficiency and performance of different commercially available technologies from the practical aspects of daily operation in an industrial scale plant
• Presents a cost analysis of the production, logistics, and storage of torrefied biomass
• Includes case studies addressing challenges that may occur in the daily operation in an industrial scale plant
• Covers other associated technologies, the densification of torrefied biomass, and non-woody feedstock

• Language: English
• Publisher: Academic Press
• Release date: Nov 21, 2017
• ISBN: 9780128096970

Leonel JR Nunes

Leonel Jorge Ribeiro Nunes holds two B.Sc. in Geology (1995 and 2008), two M.Sc. in Hydraulics and Water Resources (1999) and Geological Engineering (2011), a PhD degree in Industrial Engineering and Management (2015), and concluded two Post Doctoral research projects about thermochemical conversion technologies at the University of Beira Interior (2016) and at theUniversity of Aveiro (2017). His professional background is supported by more than 20 years of professional experience in industry. Also developed an academic career and presently supervises or co-supervises several M.Sc. and Ph.D. students at DEGEIT – Department of Economics, Management, Industrial Engineering and Tourism of the University of Aveiro (Portugal) where is Invited Assistant Professor and Researcher at GOVCOPP. Also teach subjects related with biomass energy, environment engineering and sustainability at ISMAI - Instituto Superior da Maia (Portugal) and at Agrarian Higher School of the Polytechnic Institute of Viana do Castelo. His areas of research focus mainly in Biomass Energy in general and in Thermochemical Conversion Technologies and Biomass for Energy Supply Chains in particular. He is involved in several research projects in Portugal, Vietnam and USA and has collaborated as reviewer with many journals. He is author or co-author of more than 50 articles published in several international journals and conference proceedings.

Book preview

Torrefaction of Biomass for Energy Applications

From Fundamentals to Industrial Scale

Leonel Jorge Ribeiro Nunes

João Carlos De Oliveira Matias

João Paulo Da Silva Catalão

Table of Contents

Cover image

Title page

Copyright

Biographies of the Authors

Chapter 1. Introduction

1.1. Background

1.2. Composition of Biomass

1.3. Wood Properties

1.4. Biomass Thermochemical Conversion Technologies

1.5. Origin of Torrefaction Process

1.6. Applications for Torrefied Biomass

1.7. Pyrolysis Behavior and Characterization of Torrefied Wood Chips

Chapter 2. Physical Pretreatment of Biomass

2.1. Background

2.2. Biomass Pretreatment Assumptions

2.3. Potential of Biomass as an Energy Resource

2.4. Valorization of Biomass Waste

2.5. Prospects for the Use of Biomass

2.6. Conditioning Processes

2.7. Current Situation in Portugal

2.8. Future Trends for the Use of Biomass

Chapter 3. Biomass Torrefaction Process

3.1. Background

3.2. Mass and Energy Balance

3.3. Operation Conditions

3.4. Characteristics of Solid Products

3.5. Molecular Composition and Its Changes

3.6. Produced Gases

3.7. Modeling of the Torrefaction Process

Chapter 4. Additional Processes

4.1. Washing

4.2. Densification

4.3. Transportation

4.4. Management and Storage Characteristics

4.5. Grinding

Chapter 5. Plant Design and Operation

5.1. Background

5.2. Biomass Pellets Production

5.3. Production of Torrefied Biomass Pellets

Chapter 6. Torrefaction Technologies

6.1. Initial Experiments

6.2. Technologies in Development

Chapter 7. Final Users Experiments and Trials

7.1. Torrefaction Units in Operation

7.2. Large-Scale End-Users Trials

7.3. Project Advanced Fuel Solutions (AFS) SA (Portugal)

Chapter 8. Torrefied Biomass Safety Aspects

8.1. Introduction

8.2. Product Safety

8.3. Material Safety Data Sheet for Torrefied Biomass

8.4. Determination of the Hazard Potential

8.5. Logistics and Utilization of Torrefied Biomass

Chapter 9. Economical Evaluation of Torrefaction: Case Study Analysis

9.1. Economics of a Torrefaction Plant Project

9.2. Production Plant Lifetime

9.3. Scaling Factor of Torrefaction Production Plants

9.4. Torrefaction Costs Analysis

9.5. A Comparative Cost Analysis Between Wood Pellets and Torrefied Biomass Pellets

Chapter 10. Biomass Torrefaction for Energy Life Cycle Assessment

10.1. Introduction

10.2. Quality of the Biomass and the Air

10.3. Life-Cycle Assessment

Chapter 11. Applications for Torrefied Biomass

11.1. Introduction

11.2. Materials and Methods

11.3. Results and Discussion

Chapter 12. Torrefaction of Nonwoody Feedstocks

12.1. The Behavior of Lignocellulosic Materials in Pyrolysis

12.2. Torrefaction Mechanisms

12.3. Differences Found in Deciduous, Coniferous, and Herbaceous Biomass

12.4. Kinetic Rate

Chapter 13. Future Developments and Derived Fuels

13.1. Background

13.2. Technologies Characterization

13.3. Applications of Torrefied Biomass

13.4. Advantages of Torrefied Biomass

Chapter 14. Conclusions

Index

Copyright

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Biographies of the Authors

Leonel Jorge Ribeiro Nunes holds two BSc in Geology (1995 and 2008), two MSc in Hydraulics and Water Resources (1999) and Geological Engineering (2011), a PhD degree in Industrial Engineering and Management (2015), and concluded two Postdoctoral research projects about thermochemical conversion technologies at the University of Beira Interior (2016) and at the University of Aveiro (2017). His professional background is supported by more than 20  years of professional experience in industry. Also developed an academic career and presently supervises or cosupervises several MSc and PhD students at the Department of Economics, Management, Industrial Engineering, and Tourism (DEGEIT) of the University of Aveiro (Portugal), where he is Invited Assistant Professor and Researcher at GOVCOPP. He also teaches subjects related to biomass energy, environment engineering, and sustainability at Instituto Superior da Maia (ISMAI) and at Agrarian Higher School of the Polytechnic Institute of Viana do Castelo. His areas of research focus mainly in Biomass Energy in general and in Thermochemical Conversion Technologies and Biomass for Energy Supply Chains in particular. He is involved in several research projects in Portugal, Vietnam, and the United States and has collaborated as a reviewer for many journals. He is author or coauthor of more than 50 articles published in several international journals and conference proceedings.

João C. O. Matias holds a BSc in Mechanical Engineering (1994) from University of Coimbra, a PhD degree in Production Engineering (2003), and Habilitation for Full Professor Agregação (2014) from University of Beira Interior (UBI). He is Full Professor at the Department of Economics, Management, Industrial Engineering, and Tourism (DEGEIT), University of Aveiro (UA), Researcher at C-MAST/UBI and GOVCOPP/UA, and member of the Industrial Engineering and Management and Sustainable Energy Research Groups. He is Coordinator of Scientific Areas and a director of PhD courses in Industrial Engineering and Management at DEGEIT/UA. His areas of research focus in Industrial Engineering and Management in general and in Sustainability, Sustainable Energy Systems, Sustainable Design, and Management Systems in particular. He is also involved in several research projects, the editor-in-chief in a scientific journal, member of the editorial board of several scientific journals, and has collaborated as reviewer with many journals and also international conferences. He is author or coauthor of more than 200 articles published in several international journals and conference proceedings.

João P. S. Catalão received an MSc degree from the Instituto Superior Técnico (IST), Lisbon, Portugal, in 2003, and a PhD degree and Habilitation for Full Professor (Agregação) from the University of Beira Interior (UBI), Covilha, Portugal, in 2007 and 2013, respectively. Currently, he is a professor at the Faculty of Engineering of the University of Porto (FEUP), Porto, Portugal, and Researcher at INESC TEC, INESC-ID/IST-UL, and C-MAST/UBI. He was the Primary Coordinator of the EU-funded FP7 project SiNGULAR, a 5.2-million-euro project involving 11 industry partners. He has authored or coauthored more than 570 publications, including 195 journal papers (more than 50 IEEE Transactions/Journal papers), 330 conference proceedings papers, 31 book chapters, and 14 technical reports, with an h-index of 34 and over 4900 citations (according to Google Scholar), having supervised more than 50 post-docs, PhD and MSc students. He is also an editor of the IEEE Transactions On Smart Grid, an editor of the IEEE Transactions on Sustainable Energy, an editor of the IEEE Transactions on Power Systems, and an associate editor of the IET Renewable Power Generation. Since May 2017, he is the corresponding guest editor for a special section of the IEEE Transactions on Industrial Informatics. He was the recipient of the 2011 Scientific Merit Award UBI-FE/Santander Universities and the 2012 Scientific Award UTL/Santander Totta, in addition to an Honorable Mention in the 2017 Scientific Awards ULisboa/Santander Universities. Moreover, he has won four Best Paper Awards at IEEE Conferences.

Chapter 1

Introduction

Abstract

This chapter presents an overview of the definitions and concepts used in this book. It gives particular emphasis to the concept of thermochemical conversion of biomass, biomass chemical composition, and biomass properties with the objective of supporting further developments in the upcoming chapters. It also makes a brief analysis of the different types and technologies of thermochemical conversion of biomass, such as combustion, gasification, liquefaction, pyrolisys, torrefaction, hydrothermal carbonization, and steam explosion, where the processes are described and presented. It also revisits the history of the torrefaction process and research developments, as well are presented the main possible uses for torrefied biomass.

Keywords

Biomass; Biomass properties; Chemical composition; Thermochemical conversion; Torrefaction

1.1. Background

1.1.1. Energy

Nonrenewable raw materials are considered those whose consumption rate is much higher than their regeneration rate, and therefore can provoke its exhaustion. This is the case of fossil fuels such as coal, oil, or natural gas. Over time nonrenewable resources were the main sources of energy, coming to calculate the reserves of fossil fuels will be depleted within 50–100  years. Among the common alternatives to the use of traditional fossil fuels is one that is currently one of the most used for the production of electricity, which are the nuclear power plants. Countries such as France and Belgium among others use this technology to produce approximately 50% of the required electricity [1].

Nuclear power is an alternative to fossil fuels because it decreases the effect of global warming due to the reduction of CO2 emissions produced primarily by burning fossil fuels. However, due to accidents such as Fukushima, and the radiation exposure that is generated in a nuclear accident of this nature, fears have become more prevalent and the image of nuclear power plants has been seriously undermined. Furthermore, it is only favorable from an environmental point of view by the fact that the main source of CO2 is road transport, and nuclear power is hardly used as fuel for vehicles. Moreover, although results are profitable because of the relationship between energy obtained and the amount of fuel consumed, which is positive, the costs of constructing a nuclear power plant and its commissioning are very high, and its lifetime is reduced. So it should be resorted to renewable natural resources that can generate energy in a more environmentally friendly way, whose production processes are more favorable [2].

Renewable natural resources are those who keep steadily in nature, since they are cyclic, as long as they are capable of their regeneration. That is, even if humans consume natural resources it is possible to restore them thereby maintaining a continuous flow. The plants and animals, water, and arable land, among others, are renewable resources if always operated in such a way that allows their regeneration, either naturally or induced by humans. Other features, like air, sunlight, or wind, are available on an ongoing basis regardless of consumption [3].

Today, renewable alternatives as sources of energy are needed for the development of the society. The energy consumption of an ordinary person is very high, just considering the energy that is consumed per person in everyday processes. Although the reserve energy source may last many years, the processing of these features results currently more costly due, for example, to extract oil because the wells must be drilled deeper, increasing costs. Moreover, the quality is also lower, as the best quality fuels are spent resulting in lower costs for the oil companies. It will therefore be necessary to ensure the achievement of alternative energy that reduce the environmental impact on the biosphere. In this respect, the biomass can be very useful because in its processing, the carbon footprint is neutral [4].

The energy is present in everything and in every moment of life. However, it is difficult to define, perhaps because it is something abstract, not palpable. The most common physical concept is energy as the ability of a system to do work. Work is the product of a force applied to a body (system) of a known mass by its consequent displacement. In a simplified way, a system is a set of elements in interaction [5].

Thermodynamics, the energy science, has other classifications for systems. A thermodynamic system can be isolated when it suffers no interference from the outside environment; closed when there is no mass transfer, but there may be transfer of energy to the environment; and open when there is mass transfer and energy with the environment [6].

The understanding of the thermodynamic systems helps in the understanding of the laws of thermodynamics. The first law, the Law of Energy Conservation,states that energy can neither be created nor destroyed, but transformed, thus clarifying the energy transfer at the boundaries of systems. However, it is unclear the energy transformation process. The second law, the Law of Energy Dissipation, states that the loss of energy at the border of a system is irreversible and contributes to the increase of entropy or the state of maximum disorder that causes the death of a thermal system [7].

Thermodynamics then requires a broader definition of energy. Heat, for example, is the energy in transit, but in certain cases it represents an energy dissipation process of a system, and their recovery is impossible. Thus, no work has 100% efficiency, and there will always be an energy loss. Several studies highlight the definition of Maxwell (1872), as the right one, energy is that which allows a change in the configuration of a system, as opposed to a force that resists to this change [8]. Other studies reached a simpler concept in defining energy as what to provide to a material system, or remove from, to change or modify it [9].

Energy can be further divided into two parts: exergy, or available energy, and anergy or nonavailable energy. The exergy can be converted into work, unlike anergy [10]. The exergy can be understood as the work and anergy is an energy loss in the conversion process. Energy sources can be primary when coming from nature (sun, wind, rivers, tides, etc.) or secondary when suffered some conversion process (alcohol, charcoal, oil products, etc.). The energy conversion takes place to have a final energy form that meets a specific demand as heat or light, which is defined as the useful energy [11].

Energy sources may be categorized as being renewable or nonrenewable. The difference between these two sources is the consumption rate relative to the rate of replacement by nature. Nonrenewables are consumed more quickly because the replacement requires processes lasting millions of years, as in the case of oil, natural gas, coal or radioactive elements. The replacement of renewables is relatively short, for example, biomass can take 7  years in eucalyptus plantations, or even be constant and permanent, like rivers and winds in certain regions [12].

Energy conversions express the ways in which energy is presented in nature. Therefore, energy can be found as [13]:

• Nuclear energy: Energy of the atoms that can be released by fusion or fission, but difficult to control;

• Chemical energy: Energy stored in the bonds between atoms and molecules and which is released by the breakdown of these links;

• Electricity: The movement of electric charges in a potential electric field, perhaps the most widely used form, being the primary purpose of energy conversion processes;

• Thermal energy: The energy in form of heat being transferred by the processes of conducting, convection, or radiation;

• Mechanical energy: Divided into potential and kinetic energy. The potential energy is related to the position, and may be elastic or gravitational. The kinetic energy relates the mass and velocity of a body;

• Magnetic Energy: Accumulated in magnetic fields, it is used in the transport and processing of electrical power in transformers.

1.1.2. Energy Matrix

Fossil fuels such as oil, coal, and natural gas have dominated the world energy matrix since the industrial revolution, when a set of changes, particularly technological and social, allowed the establishment of a mass culture [14]. Until then humanity based its energy consumption mainly on biomass, because energy generation was located in homes for cooking and heating, and very little in production processes as in the case of windmills and water wheels.

The invention of the steam engine was the great technological leap that allowed the paradigm shift on a global scale. The new production processes required an energy intake never generated and the fuel should be abundant and efficient. At first, coal was the primary source, thanks to the exploitation of wood that caused shortages and high prices and the consequent search for alternative fuels. Since then, oil has become the basis of energy use. Still, millions of people living in forests and rural areas depend primarily from biomass for subsistence [15].

The world energy matrix remains relatively stable for several decades since the energy revolution expressed in the change of renewable energy sources from fossil fuels, particularly oil and mineral coal. What has changed significantly is the amount of energy supplied. While in 1973 were offered 6128  million tons of oil equivalent (toe), in 2005 the world energy supply was 11,435  million toe. This 32-year range the share of nonrenewable sources has changed little, there was a drop of oil participation and increase of coal, nuclear, and natural gas. Renewable sources also hardly changed, where biomass is the most representative and others as the direct use of solar, wind, and geothermal energy are almost insignificant in the global context [16].

In simulated scenarios by the International Energy Agency, considering the levels of consumption and no change of current policies, the supply will reach 17,100  million toe in 2030 and the proportion will change little [17]. But the energy mix is much more complex. These amounts do not relate to access to energy. Worldwide, one out of every four people has no access to modern energy, i.e., their relationship with the energy comes from primitive forms to ensure their livelihood as firewood used for heating and cooking [18].

Although the offer is predominantly on fossil fuels, there are still several countries based on renewable sources, especially biomass. African countries such as Uganda, has 90% of its energy matrix based on biomass, or 45% in India, and 30% in China [19]. Another study reports that the fact these countries are underdeveloped or developing assigns a significance of poverty to biomass as a noncommercial fuel [20]. This study argues that this is a misperception because many developed countries obtain significant portion from biomass energy, such as Sweden (18%) and Finland (20%). Worldwide, 80% of the supply of renewable sources are biofuels and 75% of these are wood, charcoal, and black liquor from pulp and paper production process [21].

1.1.3. Heat

Heat is energy in transit and reflects the changes in a system, because it can be both from the surrounding, as from the intrinsic reactions in the system. The heat (q) is then a measure of the energetic dynamics of the systems, and together with the work (w) is a component of the internal energy (ΔE) of a system. The heat transfer from the surroundings into the system, and the work performed on it contributes to the increase of the internal energy [22], according to Eq. (1.1):

(1.1)

The direction of heat transfer on the system will determine if there is an endothermic or exothermic process. Endothermic process in the system absorbs heat from the surrounding, like the melting of ice. In the exothermic process, the system gives off heat to the surrounding as in the combustion of wood. The heat flows from an area of higher temperature to a lower, so the temperature is an indicator of the average kinetic energy of molecules of the body. Therefore, it is a measure of intensity, while heat is a measure of quantity [23].

To better understand the phenomenon of heat transfer, it is necessary to define specific heat, sensible heat, and latent heat. The specific heat is the quantity of heat required to raise the temperature of a mass unit of a material in 1°C. The sensible heat is the heat added or transferred into a substance which causes change in temperature without causing any phase change. The latent heat is the heat transferred by a substance which does not change its temperature but causes phase change [23].

Heat increased or owned by a system or even within it depends on the temperature difference, the geometry, and the physical properties of the materials involved. The heat may be transferred by conduction, convection, or radiation, which can occur individually or together depending on the process conditions.

Conduction takes place by molecular vibration and occurs in solids [24]. Therefore, heat transfer occurs by collision of molecules with increased kinetic energy (agitation) with slower molecules. Each material has its own thermal conductivity, which determines the rate at which heat flows through it.

Convection is the heat transfer in fluid materials. The fluid is induced by density differences caused by heat itself. The less dense zone of a fluid (hot) changes place with the densest (coldest) which, in contact with the heat source, becomes less dense and maintains the cycle [25].

Radiation is the way in which heat moves without the need for a material medium by means of electromagnetic waves. All bodies, regardless of the physical state, emit radiation [24]. It's the way solar energy reaches the planet, as between it and the sun there is no matter. The knowledge and control of the forms of heat transfer allow for more efficient heat treatment, but it is also necessary to know the properties of the material under treatment.

1.1.4. Biomass

According to the definitions and classifications already mentioned, biomass is a primary and renewable source of chemical energy able to be converted into other energy forms, both directly on the wood-burning for heat generation, and indirectly in the carbonization or in ethanol production. Biomass is the product of conversion of light energy into chemical energy through photosynthesis reaction [26]:

(1.2)

Photosynthesis is the fundamental process for energy conversion. This reaction provides power supply to a whole range of organisms. However, it is a process of low efficiency seen that the total solar energy absorbed by the leaves only 20% is converted into chemical energy, which determines a theoretical efficiency of 4% for photosynthesis [26].

The energy recovery of this reaction can be accomplished in four different ways according to the final chemical product. The energetic plant biomass is then divided into saccharides (C12H22O11), starch (C6H10O5), triglycerides (vegetable oils), and lignocellulosic materials [27].

1.1.5. Wood

Wood is the most widely used materials since the Neanderthal, who developed tools and weapons for hunting and the first energetic conversion process: fire [28]. During the evolution of humans, advances in technology have allowed the knowledge and full use of wood for various purposes, but still the energy use is one of the most expressive. Wood is still the major source of energy for cooking and heating in most parts of the world. The world consumption of wood as fuel amounted to over 1.8  billion  m³ in 2002, representing over 54% of world consumption of wood [29].

At first glance wood emphasizes its division into heartwood and sapwood. Such division shows the support functions of the heartwood dead cells and the crude sap conduction and storage function (water and mineral salts) in living cells of the sapwood. In certain types, there is a clear separation of the heartwood and sapwood by color difference, but other species do not exhibit this difference.

There are two large groups of trees: the coniferous or softwood, and broadleaved or hardwood. The first group is those producing the naked seeds (gymnosperms) and the second is those producing coated seeds (angiosperms). Conifers are concentrated more in temperate zones while the broadleaved are more in the tropics [30].

In general, it can be stated that wood essentially consists of 50% carbon, 44% oxygen, and 6% hydrogen, and trace inorganic elements [31]. The various combinations of these elements form, among others, the three main wood polymers: cellulose, hemicellulose, and lignin.

While macroscopically there are obvious differences between the different groups of trees and even between individuals of the same species, plant cells that comprise wood follow the same pattern. The wall of plant cells consists of the middle lamella, primary wall and the secondary wall. The secondary wall is formed of three layers (S1, S2, and S3) which are distinguished by the alignment of microfibrils that compose them. The microfibrils are formed by chains of cellulose and hemicellulose molecules, which in turn form the macrofibrils that constitute the cell walls. The lignin acts as a cementing agent which embeds and binds the cellulose and hemicellulose [32].

The main component of living wood is water, however, by analyzing this biopolymer dried with 0% moisture, there is the presence of 65%–75% of carbohydrates combined with 18%–35% of lignin. The conifers and broadleaved can be distinguished by the content of each polymer [32].

1.2. Composition of Biomass

The composition of biomass varies depending on factors such as geographical location, climate, soil type and part of the plant (roots, stems, branches) and is of fundamental importance for understanding the behavior of biomass across the different thermal treatments.

The composition of the biomass can be determined by proximate analysis (moisture, volatiles, ash content, fixed carbon content), the elemental chemical analysis (carbon, hydrogen, nitrogen and oxygen), and chemical analysis in terms of lignin, cellulose, hemicellulose and extractive [33].

Plants capture water and minerals from the soil salts and CO2 from the air to produce their food. In the presence of sunlight are able to perform photosynthesis obtaining carbohydrates and releasing oxygen to the atmosphere. Biomass is the result of processing the organic material during photosynthesis. Biomass can be obtained from natural or artificial manner, yielding products suitable for use as fuel.

According to Directive 2003/30/EC concerning the promotion of the use of biofuels or other renewable fuels for transport, biomass can be defined as the biodegradable fraction of products, waste and scrap coming from agriculture (including plant substances and animal), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste. Within the definition described may include up waste and animal waste, municipal solid waste, sludge from waste water purification plants or solid waste coming from agro industries, among others [34].

In Technical Specification CEN/TS 14588, concerning the use of solid fuels, biomass is defined as any material of biological origin excluding those who have been encompassed in geological formations undergoing a mineralization process. Therefore, should be excluded either coal as oil or natural gas, whose composition and formation cannot be included within the neutral balance of CO2 emissions [35].

Biomass can be used as fuel whenever several physical and chemical transformations are carried out, which can be employed both for the production of heat, electricity, or fuel for transportation. This type of raw material may come to replace petrochemical compounds and even fossil fuels in the future.

Waste can be produced both in industrial, forest, and urban activities, which in turn can be used for energy production. These lignocellulosic materials, unlike chemicals synthesized from fossil fuels, are renewable and are environmentally sustainable.

The lignocellulosic materials can be used in thermal applications such as acclimatization or other industrial applications, and they are also used for the production of more complex fuels such as wood chips and pellets, for producing electrical or thermal energy.

The key advantages of the use of lignocellulosic materials is that they are considerably more cheaper than petroleum, besides not directly competing with the demand for food. On the other hand, it is considered that the CO2 balance is neutral because during the combustion of coal for energy production, the carbon footprint does not increase beyond what would increase in the process of fermentation and decomposition, which was removed the atmosphere during the growth of plants [36].

Lignocellulosic biomass, commonly referred to as originating from trees and shrubs, is comprised primarily of cellulose, hemicellulose, and lignin.

1.2.1. Proximate Composition (Ash, Fixed Carbon, and Volatiles)

Proximate analysis of a fuel provides the percentage of the material that burns in a gaseous state (volatile matter), in the solid state (fixed carbon), and the percentage of inorganic waste material (ash), and is therefore of fundamental importance for biomass energy use [37].

There is a positive relationship between fixed carbon from biomass and charcoal yield while the volatile content and ash relate negatively with charcoal yield [38]. Thus, it is expected