**4. Methods of generating electricity using biomass**

#### **4.1 Biomass in the Brazilian energy matrix**

Global energy demand is still largely satisfied by non-renewable energy sources. According to the International Energy Agency [46], in the world, of the nearly 14 million toe (tons of oil equivalent) of the total primary energy supply in 2019, oil, coal, and natural gas together represented more than 80% of this demand, where each one corresponded to 32, 27, and 22% respectively, on the other hand, biomassderived energy supplied only 10% of this amount [46].

The domestic energy supply in Brazil in 2019 reached 294 million toes, corresponding to a total of approximately 1.4 tons per inhabitant, an increase of 1.4% over the previous year [47].

Of this total, renewable sources corresponded to 46.1% of the total energy generation in the country, divided into biomass from sugarcane (18%), hydraulic (12.4%), firewood, and charcoal (8.7%) and other renewables (7%) [47]. Only biomass from sugarcane and firewood with charcoal were responsible for 26.7% of the domestic energy supply, however, it is known that among others renewables there are more biomass-derived energy sources such as leachate, biogas, biodiesel, and others, which still increase the share of biomass in the Brazilian energy matrix [47].

The current Brazilian electric scenario is even more centered on renewable energies, since of the domestic supply of electric energy in the country, approximately 651.3 TWh, during 2019, 83% was composed of renewable energy sources, with the generation of electricity through hydroelectric (64.9%), wind (8.6%), biomass (8.4) and solar (1%) [47].

#### **4.2 Electricity production and cogeneration using biomass**

The power production by biomass can be carried out through different technological routes, commonly the process consists of converting the feedstock into an intermediate product, which will be used for the operation of generating mechanical energy in a machine to drive an electric generator, which will produce electricity [48].

Traditionally, the industrial sectors that generate electricity by biomass also choose to have a cogeneration system, where two or more energy forms are produced from a single process for generating energy, such as heat and electricity [48].

Among the main technological routes, stands out the steam cycle with back pressure turbines, steam cycle with extraction condensing turbines, and the biomass integrated gasification combined cycle [48].

#### **4.3 Steam cycle with back pressure turbines**

In this process for generating power, the steam produced by the direct burning of biomass in the boilers is used in turbines coupled with generators, for the production of electrical energy or in turbines for the production of mechanical work and also the fraction that would be released into the atmosphere can be reused directly to meet the thermal needs of the process [48]. In general, the back-pressure steam turbines provide not only electricity but also steam to be used in the plant facilities [49].

**87**

*Agroenergy from Residual Biomass: Energy Perspective DOI: http://dx.doi.org/10.5772/intechopen.93644*

**4.4 Steam cycle with extraction condensing turbines**

specific levels for heating the feedwater boiler supply [48].

**4.5 Biomass integrated gasification combined cycle**

**4.6 Biomass thermoelectric plants in Brazil**

acts to complement the electrical demand, **Figure 2** [50, 51].

exported to the network about in mean 2.6 GW [51].

condensing systems [48].

The advantage of this process is that the back pressure turbines have few stages

with simple structure and small exhaust parts, which results in low cost of the equipment [49], currently this route is the most used and is already well developed

This process is similar to the previous one, however, the steam is totally or partially condensed, after its use in the production process, therefore, its main difference is found in the presence of a condenser in the exhaust of the turbine and

In addition, extraction condensing turbines can independently change the production of electricity and process steam, through the control of valves [49], thus, this type of cycle has greater operational flexibility for power generation, concerning with the back pressure turbines [48, 49], also having higher global energy

However, the disadvantage of this type of process is the higher investments for its implementation in relation to the use of back pressure turbines [49] and simple

By biomass gasification, the fuel gas is obtained and can be used in thermoelectric plants operating on gas for power generation, and applied on a large scale, transforms biomass into an important feedstock for the large thermoelectric plants and through the use of combined cycles of gas and steam, increases the system efficiency [48].

However, it is still a technological route that is not yet commercially competitive, since its greatest difficulty for its application is the production of quality fuel gas, with reliability and safety, adapted to the parameters of biomass and operation [48].

Sugarcane bagasse is the most widely used biomass as fuel in Brazil for the production of electricity, corresponding to 82% of the electricity exported to the National Interconnected System (in Portuguese, Sistema Interligado Nacional or SIN), this is only possible, because its plants can be energetically self-sufficient [51]. As a result, the power generation costs are competitive with the conventional supply system, which makes the plants through cogeneration being energetic self-sufficient [50]. Sugarcane stands out among biomasses because its high productivity crops together with the gains from the transformation processes of sugar-alcohol biomass, make available an enormous amount of organic matter, mainly in the form of bagasse in the plants and distilleries, also, there is still an interesting complementary relationship between the electricity generated through sugarcane bagasse biomass and hydroelectric power plants, since the sugarcane harvest season coincides exactly in the dry months, thus, the generation of electricity through biomass

The share of electricity generated through sugarcane in Brazil's energy matrix in 2019 was 3.8%, of which, out of 366 sugar-energy plants in operation in 2019, 220

The participation of thermoelectric plants operating on biomass plays an increasingly important role for the national panorama concerning the supply of electricity. The immense Brazilian land surface located mainly in tropical and rainy regions favors the production and energy use of biomass on a large scale [50].

efficiency, allowing obtaining a larger volume of power produced [48].

commercially, having in Brazil several producers for most equipment [48].

*Biotechnological Applications of Biomass*

and result in increased operating costs.

**4.1 Biomass in the Brazilian energy matrix**

over the previous year [47].

and solar (1%) [47].

**4. Methods of generating electricity using biomass**

derived energy supplied only 10% of this amount [46].

**4.2 Electricity production and cogeneration using biomass**

integrated gasification combined cycle [48].

**4.3 Steam cycle with back pressure turbines**

chemical composition of the ash can present significant operational problems. This is especially true for combustion processes, where the ash can react to form a "slag," a liquid phase formed at elevated temperatures, which can reduce plant throughput

Global energy demand is still largely satisfied by non-renewable energy sources. According to the International Energy Agency [46], in the world, of the nearly 14 million toe (tons of oil equivalent) of the total primary energy supply in 2019, oil, coal, and natural gas together represented more than 80% of this demand, where each one corresponded to 32, 27, and 22% respectively, on the other hand, biomass-

The domestic energy supply in Brazil in 2019 reached 294 million toes, corresponding to a total of approximately 1.4 tons per inhabitant, an increase of 1.4%

Of this total, renewable sources corresponded to 46.1% of the total energy generation in the country, divided into biomass from sugarcane (18%), hydraulic (12.4%), firewood, and charcoal (8.7%) and other renewables (7%) [47]. Only biomass from sugarcane and firewood with charcoal were responsible for 26.7% of the domestic energy supply, however, it is known that among others renewables there are more biomass-derived energy sources such as leachate, biogas, biodiesel, and others, which still increase the share of biomass in the Brazilian energy matrix [47]. The current Brazilian electric scenario is even more centered on renewable energies, since of the domestic supply of electric energy in the country, approximately 651.3 TWh, during 2019, 83% was composed of renewable energy sources, with the generation of electricity through hydroelectric (64.9%), wind (8.6%), biomass (8.4)

The power production by biomass can be carried out through different technological routes, commonly the process consists of converting the feedstock into an intermediate product, which will be used for the operation of generating mechanical energy in a machine to drive an electric generator, which will produce electricity [48]. Traditionally, the industrial sectors that generate electricity by biomass also choose to have a cogeneration system, where two or more energy forms are produced from a single process for generating energy, such as heat and electricity [48]. Among the main technological routes, stands out the steam cycle with back pressure turbines, steam cycle with extraction condensing turbines, and the biomass

In this process for generating power, the steam produced by the direct burning of biomass in the boilers is used in turbines coupled with generators, for the production of electrical energy or in turbines for the production of mechanical work and also the fraction that would be released into the atmosphere can be reused directly to meet the thermal needs of the process [48]. In general, the back-pressure steam turbines provide not only electricity but also steam to be used in the plant facilities [49].

**86**

The advantage of this process is that the back pressure turbines have few stages with simple structure and small exhaust parts, which results in low cost of the equipment [49], currently this route is the most used and is already well developed commercially, having in Brazil several producers for most equipment [48].

### **4.4 Steam cycle with extraction condensing turbines**

This process is similar to the previous one, however, the steam is totally or partially condensed, after its use in the production process, therefore, its main difference is found in the presence of a condenser in the exhaust of the turbine and specific levels for heating the feedwater boiler supply [48].

In addition, extraction condensing turbines can independently change the production of electricity and process steam, through the control of valves [49], thus, this type of cycle has greater operational flexibility for power generation, concerning with the back pressure turbines [48, 49], also having higher global energy efficiency, allowing obtaining a larger volume of power produced [48].

However, the disadvantage of this type of process is the higher investments for its implementation in relation to the use of back pressure turbines [49] and simple condensing systems [48].

#### **4.5 Biomass integrated gasification combined cycle**

By biomass gasification, the fuel gas is obtained and can be used in thermoelectric plants operating on gas for power generation, and applied on a large scale, transforms biomass into an important feedstock for the large thermoelectric plants and through the use of combined cycles of gas and steam, increases the system efficiency [48].

However, it is still a technological route that is not yet commercially competitive, since its greatest difficulty for its application is the production of quality fuel gas, with reliability and safety, adapted to the parameters of biomass and operation [48].

#### **4.6 Biomass thermoelectric plants in Brazil**

The participation of thermoelectric plants operating on biomass plays an increasingly important role for the national panorama concerning the supply of electricity. The immense Brazilian land surface located mainly in tropical and rainy regions favors the production and energy use of biomass on a large scale [50].

Sugarcane bagasse is the most widely used biomass as fuel in Brazil for the production of electricity, corresponding to 82% of the electricity exported to the National Interconnected System (in Portuguese, Sistema Interligado Nacional or SIN), this is only possible, because its plants can be energetically self-sufficient [51]. As a result, the power generation costs are competitive with the conventional supply system, which makes the plants through cogeneration being energetic self-sufficient [50].

Sugarcane stands out among biomasses because its high productivity crops together with the gains from the transformation processes of sugar-alcohol biomass, make available an enormous amount of organic matter, mainly in the form of bagasse in the plants and distilleries, also, there is still an interesting complementary relationship between the electricity generated through sugarcane bagasse biomass and hydroelectric power plants, since the sugarcane harvest season coincides exactly in the dry months, thus, the generation of electricity through biomass acts to complement the electrical demand, **Figure 2** [50, 51].

The share of electricity generated through sugarcane in Brazil's energy matrix in 2019 was 3.8%, of which, out of 366 sugar-energy plants in operation in 2019, 220 exported to the network about in mean 2.6 GW [51].

Recently, there has been a significant increase in the export of power to the electrical system generated through other biomasses, especially black liquor, biogas, forest residues, rice husk and others, being important for energy security and reliability, given the seasonality of sugarcane biomass [51]. **Figure 3** shows the biomass thermoelectric plants in operation in Brazil and the potential installed by states in September 2003.

**Figure 2.**

*Participation of sugarcane biomass in electricity generation from January 2018 to December 2019 [51].*

**89**

*Agroenergy from Residual Biomass: Energy Perspective DOI: http://dx.doi.org/10.5772/intechopen.93644*

ally in mitigating greenhouse gas emissions.

electrical system generated by other biomasses.

The global energy market's dependence on fossil fuel energy sources such as coal, oil, and natural gas needs to give way to alternative and sustainable ways to meet this demand. One of the most promising alternatives is the use of biomass, the only natural and renewable resource based on carbon that is vast enough to be used

The biomass conversion process can generate solid, liquid, or gaseous fuels, the biomass energy being one of the renewable energies, the only one that can be converted into liquid fuel. In addition, biomass energy is renewable energy, an abundant and easily produced source. The use of biomass energy is an important

Brazil occupies a prominent position in the world production of cassava, alongside countries in subtropical regions. Cassava starch produces a significant amount of waste, which must be used rationally to minimize the environmental impact of agricultural activities. Brazil is also the largest producer of sugarcane. In addition, the cultivation of sugarcane has the potential to increase environmental benefits, increasing carbon sequestration and optimizing the agricultural production chain. Corn stands out among agricultural species with the potential to provide biomass for energy production, as it has a large acreage worldwide and is a biomass with

The inherent properties of the biomass source are that determine the choice of the conversion process and the possible processing difficulties. In this way, the choice of the biomass source is influenced by the way in which energy is needed, and it is the interaction between these two aspects that allows flexibility to be introduced in the use of biomass as an energy source. Biomass is converted into energy through two main energy conversion routes, namely, thermochemistry and

Due to its vast territory, Brazil has high potential or effective rates of waste from agro-industrial products, making the use of biomass a great possibility for increasing energy production in the Brazilian energy matrix. The results achieved in the year 2019, by 220 sugar-energy plants in operation, exported about 2.6 average GW to the network, showing that the participation of biomass thermoelectric plants assumes an increasingly important role for the national panorama about electricity supply. Sugarcane bagasse is the biomass most used as fuel in Brazil to produce electric energy, due to the high productivity of sugarcane in its crops to serve the sugar and alcohol sector. The energy generated by this biomass stands out, and due to the sugarcane harvest exactly coincides with the dry months, the generation of electricity from biomass acts as a complement to the electric demand produced by hydroelectric plants; there was also a significant increase in energy exports for the

**5. Conclusions**

as a substitute for fossil fuels

high calorific value.

biochemistry.

**Figure 3.** *Biomass thermoelectric plants in operation in Brazil by states in September 2003 [51].*
