**2.4 Pyrolysism**

For the production of bio oil from biomass, process of pyrolysis is used. Pyrolysis is a thermal degradation of lignocellulosic biomass at very high temperature without the presence of oxidizing agent. At temperature ranging between 500 and 800°C, pyrolysis was performed. Rapid decomposition of cellulose resulted in the formation of products like pyrolysis oil and charcoal [36]. Based on temperature, pyrolysis pretreatment process is divided into fast and low pyrolysis. Certain factors affect the end products like biomass characteristics, reaction parameters, and type of pyrolysis. Due to high-value energy-rich product formation, easy transport management retrofitting, combustion, storage, and flexibility in utilization and marketing, thermal industries are adapting to the process of pyrolysis. Presence of oxygen and less temperature increase the efficiency of this process. A study on the bond cleavage rate of cellulose was carried out in the presence of nitrogen and oxygen. During the process of pyrolysis, breakage of 7.8 × 109 bonds/min/g cellulose

**21**

*Different Pretreatment Methods of Lignocellulosic Biomass for Use in Biofuel Production*

presence of nitrogen at 25°C were observed. In order to obtain more efficiency and results, microwave-assisted pyrolysis is preferred due to the microwave dielectric heating [37]. Thermochemical conversion of biomass into biofuels can be performed via three technologies, gasification, pyrolysis, and direct combustion [38]. Different yields of products from pyrolysis are due to different modes of pyrolysis. Bio oil is a mixture of polar organics and water. Pyrolysis is used where bio oil production is required. Fast pyrolysis in a controlled environment leads to the formation of liquid products (fuels). Torrefaction is an emerging technique which is also known as mild pyrolysis. It differs from pyrolysis with reference to thermochemical process that is carried out at temperature range between 200 and 300°C. Partial decomposition of biomass occurs in this process, and ultimate product obtained is terrified biomass. Whereas, in the process of pyrolysis, plant biomass is decomposed into vapor, aerosols, and char. Torrefaction has been categorized into two

Dry torrefaction needs an inert environment and completely dry biomass and normal atmospheric pressure. Biochar is the major product in this type of biomass pretreatment. Hydrothermal carbonization and hydrothermal torrefaction are other terminologies used for wet torrefaction. Unlike dry torrefaction, pressurized vessel of water is used to carry out the pretreatment. Biomass used for wet torrefaction contains moisture content, but after torrefaction, a drying process is necessary in this type of torrefaction. A pressure between 1 and 250 MPa is required to carry out wet torrefaction. Biomass used during wet torrefaction pretreatment produces

In this method, pores are created in the cell membrane due to which cellulose exposes to such agents that cause its breakdown by entering into the cell. High voltage ranging between 5.0 and 20.0 kV/cm is applied in a sudden burst to biomass for nano- to milliseconds. Sample was placed between two parallel plate electrodes, and the strength of electric field is given as *E = V*/*d*, where *V* and *d* are voltage and distance, respectively, between plate electrodes. Dramatic increase in mass permeability and tissue rapture occurred on the application of electric field. Electric pulses are applied, generally in the form of square waves or exponential decay. Setup of pulse electric field consisted of pulse generator, control system, data acquisition system, and material handling equipment [40, 41]. At ambient temperatures, the treatment can be performed at low energy. Another advantage of this treatment is the simple design of the instrument. Short duration of pulse time saves the effort and energy [42, 43]. Pulse electric field pretreatment was applied to pig manure and waste activated sludge by Author et al. [44]. As compared to untreated

bonds/min/g cellulose in the

*DOI: http://dx.doi.org/10.5772/intechopen.84995*

*Twin screw extruder (Researchgate.net).*

**Figure 4.**

in the presence of oxygen and breakdown of 1.7 × 108

categories based on dry and wet torrefaction.

hydro-char as a main product [39].

**2.5 Pulse electric field (PEF)**

*Different Pretreatment Methods of Lignocellulosic Biomass for Use in Biofuel Production DOI: http://dx.doi.org/10.5772/intechopen.84995*

**Figure 4.** *Twin screw extruder (Researchgate.net).*

*Biomass for Bioenergy - Recent Trends and Future Challenges*

hydrolysis rates are achieved by the use of single and twin screw extruders. Different parameters like speed of screw, temperature of barrel, and compression ratio can significantly affect recovery of sugars. Short-time extruders provide fast heat transfer, proper mixing, and increased shear. When material passed through the extruder barrel, structure of biomass is disturbed, exposing more surface for enzymatic hydrolysis [31–33]. During extrusion process, lignocellulosic material can be treated with alkali or acid in order to increase sugar recovery. Acidic treatment is less preferred than alkali because of the corrosion caused by acid to the extruder material. Corrosion problem can be solved by the use of AL6XN alloy for barrel fabrication and screws of extruder. With less carbohydrate degradation and role in the delignification, alkali treatment is suitable for lignocellulosic material. Sodium hydroxide is most commonly used to break ester linkages and solubilization of lignins and hemicelluloses. Alkali treatment can be applied by addition of alkali using volumetric pump into the extruder or by soaking the lignocellulosic material

For the production of bio oil from biomass, process of pyrolysis is used. Pyrolysis is a thermal degradation of lignocellulosic biomass at very high temperature without the presence of oxidizing agent. At temperature ranging between 500 and 800°C, pyrolysis was performed. Rapid decomposition of cellulose resulted in the formation of products like pyrolysis oil and charcoal [36]. Based on temperature, pyrolysis pretreatment process is divided into fast and low pyrolysis. Certain factors affect the end products like biomass characteristics, reaction parameters, and type of pyrolysis. Due to high-value energy-rich product formation, easy transport management retrofitting, combustion, storage, and flexibility in utilization and marketing, thermal industries are adapting to the process of pyrolysis. Presence of oxygen and less temperature increase the efficiency of this process. A study on the bond cleavage rate of cellulose was carried out in the presence of nitrogen and

bonds/min/g cellulose

in alkali at room temperature [31, 34, 35] (**Figure 4**).

oxygen. During the process of pyrolysis, breakage of 7.8 × 109

**20**

**2.4 Pyrolysism**

**Figure 3.**

*Microwave irradiation (Researchgate.net).*

in the presence of oxygen and breakdown of 1.7 × 108 bonds/min/g cellulose in the presence of nitrogen at 25°C were observed. In order to obtain more efficiency and results, microwave-assisted pyrolysis is preferred due to the microwave dielectric heating [37]. Thermochemical conversion of biomass into biofuels can be performed via three technologies, gasification, pyrolysis, and direct combustion [38]. Different yields of products from pyrolysis are due to different modes of pyrolysis. Bio oil is a mixture of polar organics and water. Pyrolysis is used where bio oil production is required. Fast pyrolysis in a controlled environment leads to the formation of liquid products (fuels). Torrefaction is an emerging technique which is also known as mild pyrolysis. It differs from pyrolysis with reference to thermochemical process that is carried out at temperature range between 200 and 300°C. Partial decomposition of biomass occurs in this process, and ultimate product obtained is terrified biomass. Whereas, in the process of pyrolysis, plant biomass is decomposed into vapor, aerosols, and char. Torrefaction has been categorized into two categories based on dry and wet torrefaction.

Dry torrefaction needs an inert environment and completely dry biomass and normal atmospheric pressure. Biochar is the major product in this type of biomass pretreatment. Hydrothermal carbonization and hydrothermal torrefaction are other terminologies used for wet torrefaction. Unlike dry torrefaction, pressurized vessel of water is used to carry out the pretreatment. Biomass used for wet torrefaction contains moisture content, but after torrefaction, a drying process is necessary in this type of torrefaction. A pressure between 1 and 250 MPa is required to carry out wet torrefaction. Biomass used during wet torrefaction pretreatment produces hydro-char as a main product [39].
