**2. Types of biomass conversion technologies**

Biomass can be converted into several useful products for energy generation and chemicals. There are some factors that influence the choice of a conversion technology to be applied on the biomass. These factors include quality and quantity of the biomass feedstock, availability, choice of end-products, process economics and environmental issues (**Figure 1**) [9].

#### **2.1 Thermochemical methods**

The major options within thermochemical biomass conversion processes include combustion, gasification, pyrolysis, and liquefaction (**Figure 2**). The most practiced thermochemical conversion of biomass industrially is combustion process, which is used for heat and electricity generation. Most of biomass thermochemical conversions were carried out with or without the use of catalysts, though the use of catalyst has distinct effects on the end-products [10].

#### *2.1.1 Gasification*

The process of biomass gasification was discovered independently in France and England by the year 1798. The technology did not come into its limelight until 60 years later. The gasification process continued flourishing until 30 years later when natural gas from oil fields was discovered. Until 1970, the use of natural gas for cooking and lighting was substituted with liquid fuels due to discovery of oil. Generally, biomass gasification is an endothermic thermochemical conversion of solid biomass fuel using gasifying agents such as air, steam or CO2 to form a mixture of combustible gases which may include H2, CH4, CO and CO2. The process is carried out at temperatures between 800 and 1300°C. Nowadays, flexibility of the

**5**

**Figure 2.**

**Figure 1.**

*Main biomass conversion routes [8].*

*Biomass Conversion Technologies for Bioenergy Generation: An Introduction*

gasification technology coupled with the different uses of the produced syngas, allows for the integration of biomass gasification with many industrial processes

heating value, carbon content and ash content significantly affect the gasifier performance. However, knowledge on feedstock parameters such as volatility, elemental analysis, heat content and biomass potential for fouling or slagging is essential for evaluation of gasification process [11]. Therefore, feedstock with low volatile contents are preferred for partial oxidation gasification, while those with high volatile content are more suitable for indirect gasification process [12].

Biomass feedstock characteristics such as particle size, moisture content, shape,

and as well with power generation systems [7].

*Thermochemical conversion processes and end products [10].*

*DOI: http://dx.doi.org/10.5772/intechopen.93669*

*Biomass Conversion Technologies for Bioenergy Generation: An Introduction DOI: http://dx.doi.org/10.5772/intechopen.93669*

*Biotechnological Applications of Biomass*

gas, biomass was the main source of energy for heating and cooking [2]. Biomass is the term used to describe all materials that contain carbon in an organic form. This organic form of carbon can be transformed into inorganic through photosynthesis by forming bonds with other elements such as hydrogen, and oxygen using solar energy. The demolishing of these bonds (molecules) through physical or biological means, causes a closure in the cycle and making CO2 to be regenerated. During the regeneration process, energy is released which can be converted into other forms of energy. Therefore, as long as these equilibrium is maintained between use and regeneration, biomass is a renewable or inexhaustible source of energy [3]. Biomass is expected to be the leading form of energy with a significant global energy load of about 10–15%. However, biomass has a share of about 90% of total energy requirements for remote and rural areas of the developing countries. Therefore, it is likely to remain the future leading source of energy feedstock for the developing countries since about 90% of the world population is expected to live in the developing world by 2050 [4–6].

Biomass accumulates chemical energy in form of carbohydrates through combination of solar power and carbon dioxide during the process of photosynthesis. This has made it to be a potential energy source since the carbon dioxide captured during photosynthesis could be released when it burns. It is cheap and available in all forms such as forest and agricultural residues, wood, by-products of biological materials, organic components of municipal and sludge wastes, etc. There are several ways to convert biomass into useful products which largely depends on biomass characteristics and the end product [7]. The technologies applied in the conversion of biomass are mainly

Biomass can be converted into several useful products for energy generation and chemicals. There are some factors that influence the choice of a conversion technology to be applied on the biomass. These factors include quality and quantity of the biomass feedstock, availability, choice of end-products, process economics

The major options within thermochemical biomass conversion processes include combustion, gasification, pyrolysis, and liquefaction (**Figure 2**). The most practiced thermochemical conversion of biomass industrially is combustion process, which is used for heat and electricity generation. Most of biomass thermochemical conversions were carried out with or without the use of catalysts, though

The process of biomass gasification was discovered independently in France and England by the year 1798. The technology did not come into its limelight until 60 years later. The gasification process continued flourishing until 30 years later when natural gas from oil fields was discovered. Until 1970, the use of natural gas for cooking and lighting was substituted with liquid fuels due to discovery of oil. Generally, biomass gasification is an endothermic thermochemical conversion of solid biomass fuel using gasifying agents such as air, steam or CO2 to form a mixture of combustible gases which may include H2, CH4, CO and CO2. The process is carried out at temperatures between 800 and 1300°C. Nowadays, flexibility of the

the use of catalyst has distinct effects on the end-products [10].

categorized under thermochemical or biological methods.

**2. Types of biomass conversion technologies**

and environmental issues (**Figure 1**) [9].

**2.1 Thermochemical methods**

*2.1.1 Gasification*

**4**

**Figure 2.** *Thermochemical conversion processes and end products [10].*

gasification technology coupled with the different uses of the produced syngas, allows for the integration of biomass gasification with many industrial processes and as well with power generation systems [7].

Biomass feedstock characteristics such as particle size, moisture content, shape, heating value, carbon content and ash content significantly affect the gasifier performance. However, knowledge on feedstock parameters such as volatility, elemental analysis, heat content and biomass potential for fouling or slagging is essential for evaluation of gasification process [11]. Therefore, feedstock with low volatile contents are preferred for partial oxidation gasification, while those with high volatile content are more suitable for indirect gasification process [12].

Feedstocks for biomass gasification exists in different forms with each type having peculiar issues. Therefore, it is vital to predict suitable type of biomass for a specific gasifier type under defined conditions. Although, characteristics within specific biomass feedstock species is identical, the shape and size of the feedstock particles are useful in determining the difficulties that may arise during movement, delivery and as well as the feedstock behavior in the gasifier. The size and size distribution of the feedstock affect the gasification zone thickness, pressure drop in the bed and the maximum hearth load. To overcome some of this problems, biomass feedstock of uniform size were utilized [7].

Gasifier operation depends on moisture content of the biomass feed used. The use of feedstock with high moisture content reduces biomass conversion efficiency and as well the production rate. This is because the process discharges more fuel or heat in order to vapourize the excess moisture to the temperature of the syngas [13]. During the pyrolysis/gasification process, water need about 2.3 MJ/kg to vapourize and as well 1.5 MJ/kg to raise it to 700°C. Also, high moisture content in a biomass reduces the achieved temperature in the oxidation zone which results in incomplete cracking of the products released in the pyrolysis zone. Consequently, high moisture content in the biomass feedstock affect the syngas composition or quality due to production of CO2 from reaction between the moisture. Furthermore, using feedstock that has high moisture content results in the production of syngas with high moisture, which subsequently course additional stress on downstream cooling and filtering equipment [14].
