**1. Introduction**

Sustainable development is a multi-aspect concept which demands a variety of decision makers from different sectors to play a role in saving the resources for future generations. Environment, Economy and Society are three key elements in Sustainable development. There are a variety of environmental issues, such as air pollution, water pollution, waste and land contamination and climate change, which threaten both the natural resources and the human.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

To a great extent, fossil fuels consumption is the cause of the environmental issues. The context of sustainability, as it relates to energy, requires considering potential replacements for the fossil fuels. Renewable resources of energy are the solution for solving this problem. The renewable resources do not interfere the carbon balance and therefore are so-called "carbon neutral" resources (**Figure 1**).

Biofuels have emerged as one of the most strategically important sustainable fuel sources and are considered an important way of progress for limiting greenhouse gas emissions, improving air quality and finding new energy resources. Advanced biofuels are referred to as liquid, gas and solid fuels predominantly produced from biomass, which are not in conflict with food security. A variety of fuels can be produced from biomass such as ethanol, methanol, biodiesel, Fischer-Tropsch diesel, hydrogen and methane. Renewable and carbon neutral biofuels are necessary for environmental and economic sustainability. Gasification is an environmentally friendly method which enables producing a wider range of products depending on

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There has been a great deal of attention from different authorities devoted to enhancing the share of advanced biofuels in the next decade. For instance, the Renewable Energy Directive (RED) stablished overall policy for the advancement of energy from renewable sources in the European Union (EU) which requires deployment of renewable energy for the share of 20% of the total energy needs of the union. RED also requires that all the members of the union to ensure use of renewable sources in the transport sector upward of 10% by 2020 which is twice of its share in 2009 [3]. Moreover, the U.S. Environment Protection Agency (EPA) mandates the increment in the share of biofuels in transportation sector from 41.9 (in 2009) to 136 billion

There are two major processes which can be served for converting biomass into useful forms of energy. The choice of conversion process could be performed by considering different parameters such as type and quantity of feedstock, the end-use applications, the local and national environmental regulations and the financial and economic conditions. Thermochemical and biochemical conversion pathways are categorized as the most well-known techniques for producing the desired form of the energy from biomass feedstocks [6, 7]. An overview of different technologies which falls under thermochemical and biochemical conversion pathways is

Gasification technology represents an effective thermochemical conversion method which converts carbonaceous into synthetic feedstock. Gasification technology has been receiving a great deal of attention in the past few decades. Gasification converts carbon-based materials into gaseous products using a gasifying agent such as air, oxygen, steam and carbon dioxide. When air is used as the oxidant, the gaseous product is usually called producer gas, and when oxygen or steam is used, the product is termed synthesis gas (syngas). Syngas is an important feedstock for the chemical and energy industries, along with hydrocarbons traditionally produced from petroleum oil that can also be produced from syngas [1, 8]. During gasification, feedstock is partially oxidized. A gas medium air, pure oxygen, steam or a mixture of these gases—is required to maintain the process. Biomass feedstock and gasification reactants, which accelerate ignition of the feedstock, typically enter the gasifier at the top and travel in the same direction down the gasifier. It should be noted that feeding points for biomass gasifiers can be from the top or from the

Compared to combustion, gasification has higher efficiency due to exergy (i.e. the energy that is available to be used) losses, mainly from lower internal thermal energy exchange of expended exergy. The losses due to internal thermal energy exchange may be lowered by changing the

liters (in 2022) under Renewable Fuel Standard (RFS2) [4, 5].

the ultimate application.

presented in **Figure 2**.

side depending on the process.

Owing to the depletion of fossil resources and the increasing demand on fuels, it is important to develop renewable resources to produce fuels and chemicals for energy security. Biobased materials, including biomass and wood pellets, are one of the most promising sustainable energy resources to replace expensive fossil fuels, which are threatening our environment and global climate. Biobased residues and waste, as renewable multifunctional resources, can not only be used for heating and power generation but also for greenhouse carbon dioxide enrichment and the improvement of soil structure or soil aeration via biochar production.

Bio-based materials have been introduced as one of the energy resources for producing advanced biofuels. Advanced biofuels are technically referred to non-food biomass materials which can potentially be used for producing bioenergy. Advanced biofuels derived from biomass feedstock, such as agroforestry, municipal and industrial residues, each of which has the biological source for bioenergy production purposes [1]. The definition of advanced biofuels as defined in European Union (EU) Commission is "every type of biomass typically derived from plant material which does not have an alternative use as food; they can be based on waste biomass, cereal stalks, other dry plant matter, or crops grown especially for fermentation into biofuels (algae, Miscanthus)" [2].

**Figure 1.** A developmental perspective on the transition from unsustainable era to sustainable era and sustainable development.

Biofuels have emerged as one of the most strategically important sustainable fuel sources and are considered an important way of progress for limiting greenhouse gas emissions, improving air quality and finding new energy resources. Advanced biofuels are referred to as liquid, gas and solid fuels predominantly produced from biomass, which are not in conflict with food security. A variety of fuels can be produced from biomass such as ethanol, methanol, biodiesel, Fischer-Tropsch diesel, hydrogen and methane. Renewable and carbon neutral biofuels are necessary for environmental and economic sustainability. Gasification is an environmentally friendly method which enables producing a wider range of products depending on the ultimate application.

To a great extent, fossil fuels consumption is the cause of the environmental issues. The context of sustainability, as it relates to energy, requires considering potential replacements for the fossil fuels. Renewable resources of energy are the solution for solving this problem. The renewable resources do not interfere the carbon balance and therefore are so-called "carbon

Owing to the depletion of fossil resources and the increasing demand on fuels, it is important to develop renewable resources to produce fuels and chemicals for energy security. Biobased materials, including biomass and wood pellets, are one of the most promising sustainable energy resources to replace expensive fossil fuels, which are threatening our environment and global climate. Biobased residues and waste, as renewable multifunctional resources, can not only be used for heating and power generation but also for greenhouse carbon dioxide enrich-

Bio-based materials have been introduced as one of the energy resources for producing advanced biofuels. Advanced biofuels are technically referred to non-food biomass materials which can potentially be used for producing bioenergy. Advanced biofuels derived from biomass feedstock, such as agroforestry, municipal and industrial residues, each of which has the biological source for bioenergy production purposes [1]. The definition of advanced biofuels as defined in European Union (EU) Commission is "every type of biomass typically derived from plant material which does not have an alternative use as food; they can be based on waste biomass, cereal stalks, other dry plant matter, or crops grown especially for fermen-

**Figure 1.** A developmental perspective on the transition from unsustainable era to sustainable era and sustainable

ment and the improvement of soil structure or soil aeration via biochar production.

neutral" resources (**Figure 1**).

80 Gasification for Low-grade Feedstock

tation into biofuels (algae, Miscanthus)" [2].

development.

There has been a great deal of attention from different authorities devoted to enhancing the share of advanced biofuels in the next decade. For instance, the Renewable Energy Directive (RED) stablished overall policy for the advancement of energy from renewable sources in the European Union (EU) which requires deployment of renewable energy for the share of 20% of the total energy needs of the union. RED also requires that all the members of the union to ensure use of renewable sources in the transport sector upward of 10% by 2020 which is twice of its share in 2009 [3]. Moreover, the U.S. Environment Protection Agency (EPA) mandates the increment in the share of biofuels in transportation sector from 41.9 (in 2009) to 136 billion liters (in 2022) under Renewable Fuel Standard (RFS2) [4, 5].

There are two major processes which can be served for converting biomass into useful forms of energy. The choice of conversion process could be performed by considering different parameters such as type and quantity of feedstock, the end-use applications, the local and national environmental regulations and the financial and economic conditions. Thermochemical and biochemical conversion pathways are categorized as the most well-known techniques for producing the desired form of the energy from biomass feedstocks [6, 7]. An overview of different technologies which falls under thermochemical and biochemical conversion pathways is presented in **Figure 2**.

Gasification technology represents an effective thermochemical conversion method which converts carbonaceous into synthetic feedstock. Gasification technology has been receiving a great deal of attention in the past few decades. Gasification converts carbon-based materials into gaseous products using a gasifying agent such as air, oxygen, steam and carbon dioxide. When air is used as the oxidant, the gaseous product is usually called producer gas, and when oxygen or steam is used, the product is termed synthesis gas (syngas). Syngas is an important feedstock for the chemical and energy industries, along with hydrocarbons traditionally produced from petroleum oil that can also be produced from syngas [1, 8]. During gasification, feedstock is partially oxidized. A gas medium air, pure oxygen, steam or a mixture of these gases—is required to maintain the process. Biomass feedstock and gasification reactants, which accelerate ignition of the feedstock, typically enter the gasifier at the top and travel in the same direction down the gasifier. It should be noted that feeding points for biomass gasifiers can be from the top or from the side depending on the process.

Compared to combustion, gasification has higher efficiency due to exergy (i.e. the energy that is available to be used) losses, mainly from lower internal thermal energy exchange of expended exergy. The losses due to internal thermal energy exchange may be lowered by changing the

**Figure 2.** Biomass conversion pathways for producing bioenergy.

gasifying agent [9]. The gas composition evolved from biomass gasification strongly depends on the gasification process, the gasifying agent, and the feedstock composition [9].

The production of renewable energy from biomass using a gasification system is an environmentally friendly method that helps reduce dependence on fossil fuels. Biomass gasification offers advantages over the direct burning of biomass in a boiler. The sustainability of biomass utilization will greatly increase the overall sustainability of biomass management. In this chapter, the technical aspects of sustainable biomass management, with specific focus on recycling and energy recovery via gasification technology, are investigated. The Chapter is consisting of four interconnected studies to examine the basics towards advancements in the gasification process.

to reduce the moisture content of the biomass that will enter the main reactor. The drying bucket is a double layer container with the biomass feedstock in the middle and hot syngas coming from the cyclone in a separate compartment surrounding the feedstock. From feeding point of view, the capacity of the employed mini-scale gasification system ranges averagely between 2.45 and 3.75 kg hr−1 of biomass. However, this range may change depending on the

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**Figure 3.** A downdraft gasification unit for producing advanced biofuels (McGill University, Canada).

The main reactor, which is a cylinder-shaped vessel, receives the gasifying medium (i.e. air, oxygen, steam or carbon dioxide) using internal pipes rolled around the reactor. These pipes are used to preheat the air prior the injection at the top of the reduction bell allowing a more stable gasification. Thermocouples are installed at different heights into the reactor to monitor the gasification process. An ignition port provides an access to introduce a flame directly at the top of the reduction bell to start the gasification process. The pressure into the reactor is maintained at atmospheric pressure by an ejector venturi located prior the swirl burner. This negative pressure siphons the syngas produced at the bottom of the reduction bell into the air particulate cyclone. There is a reticular grate under the reduction bell that allows the ash to be separated from the unprocessed feedstock. The ash accumulates under the grate and can be removed from the reactor by the ash trap. The compartment comprised between the reduction bell and the grate is filled with wood charcoal. A bed of pyrolysis materials facilitates the ignition of the system. The compartment between the lid and the reduction bed is filled with the biomass that will be gasified. A manometer is connected to the reactor frame to measure the

conditions of the reactor as well as the biomass feedstock.
