**3. Process of energy conversion of biomass**

High moisture content biomass, such as the herbaceous plant sugarcane, lends itself to a "wet/aqueous" conversion process, involving biologically mediated reactions, such as fermentation, while a "dry" biomass such as cassava and corn stalks, is more economically suited to gasification, pyrolustion. Aqueous processing is used when the moisture content of the material is such that the energy required for drying would be inordinately large compared to the energy content of the product formed. It is the inherent properties of the biomass source that determines both the choice of conversion process and any subsequent processing difficulties that may arise. Equally, the choice of biomass source is influenced by the form in which the energy is required, and it is the interplay between these two aspects that enables flexibility to be introduced into the use of biomass as an energy source.

The World Energy Council defines bioenergy to include traditional biomass (example forestry and agricultural residues), modern biomass and biofuels [38].

#### *Biotechnological Applications of Biomass*

The typical biomass materials used for power generation are bagasse, cotton stalk, straw, rice husk, soya husk, saw dust, de-oiled cakes, coconut shells, coffee waste, groundnut shells, Neem, *Jatropha curcas*, Mahua, and Jute wastes, [39]. These biomass materials are being converted into energy via two major energy conversion routes, that is, thermochemical and biochemical. The possible ways in thermochemical route are illustrated in **Figure 1** [40].

The main material properties of interest, during subsequent processing as an energy source, relate to:


For dry biomass conversion processes, the first five properties are of interest, while for wet biomass conversion processes, the first and last properties are of prime concern.

In biomass the moisture content is presented as intrinsic (without the influence of climate effects) and extrinsic (the influence of climate in the moisture content).

**85**

**Table 2.**

**Table 1.**

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

laboratory setting.

for some biomass materials.

In practical terms, it is only concerned with the extrinsic moisture content because the intrinsic moisture content is usually only achieved, or applicable, in a

• the volatiles content, or volatile matter (VM) of a solid fuel, is that portion driven-off as a gas (including moisture) by heating (to 950 C for 7 min).

• the fixed carbon content (FC), is the mass remaining after the releases of

The chemical breakdown of a biomass fuel, by either thermo-chemical or bio-chemical processes, produces a solid residue. When produced by combustion in air, this solid residue is called "ash" and forms a standard measurement parameter for solid and liquid fuels. The ash content of biomass affects both the handling and processing costs of the overall, biomass energy conversion cost. During biochemical conversion, the percentage of solid residue will be greater than the ash content

Dependent on the magnitude of the ash content, the available energy of the fuel is reduced proportionately. In a thermo-chemical conversion process, the

**Biomass VM (%) FC (%) Ash (%) HHV (MJ/Kg)** Sugar cane [41, 42] 85.49 12.39 2.12 18.73 Cassava [43, 44] 79.89 13.40 5.43 15.39 Corn stalk [45] 75.38 17.95 6.67 16.59

**Material C H O N S** Sugar cane [41] 49.8 6.00 43.90 0.20 0.06 Cassava [42] 49.4 6.10 44.60 0.17 0.10 Corn stalk [43] 42.53 6.17 43.59 0.93 0.11

Elemental analysis of a fuel, presented as C, N, H, O and S together with the ash content, is termed the ultimate analysis of a fuel. **Table 2** gives the ultimate analyses

The significance of the VM and FC contents is that they provide a measure of the ease with which the biomass can be ignited and subsequently gasified, or oxidized,

volatiles, excluding the ash and moisture contents.

depending on how the biomass is to be utilized as an energy source.

formed during combustion of the same material.

*Immediate analysis of some biomass feedstocks (wt%).*

*Ultimate analyses for typical biomass materials (wt%).*

The calorific value (CV) of a material is an expression of the energy content, or heat value, released when burnt in air. The CV is usually measured in terms of the energy content per unit mass, or volume; hence MJ/kg for solids, MJ/l for liquids, or MJ/Nm3 for gases. The CV of a fuel can be expressed in two forms, the gross CV (GCV), or higher heating value (HHV) and the net CV (NCV), or lower heating value (LHV). In practical terms, the latent heat contained in the water vapor cannot be used effectively and therefore, the LHV is the appropriate value to use for the energy available for subsequent use. In **Table 1** is shown the immediate analysis of some biomass feedstocks. Fuel analysis has been developed based on solid fuels, such as coal, which consists of chemical energy stored in two forms, fixed carbon and volatiles:

*Thermochemical and biochemical routes for conversion of biomass to energy [40].*

*Biotechnological Applications of Biomass*

energy source, relate to:

• calorific value,

• ash/residue content,

• alkali metal content,

• cellulose/lignin ratio.

prime concern.

chemical route are illustrated in **Figure 1** [40].

• moisture content (intrinsic and extrinsic),

• proportions of fixed carbon and volatiles,

The typical biomass materials used for power generation are bagasse, cotton stalk, straw, rice husk, soya husk, saw dust, de-oiled cakes, coconut shells, coffee waste, groundnut shells, Neem, *Jatropha curcas*, Mahua, and Jute wastes, [39]. These biomass materials are being converted into energy via two major energy conversion routes, that is, thermochemical and biochemical. The possible ways in thermo-

The main material properties of interest, during subsequent processing as an

For dry biomass conversion processes, the first five properties are of interest, while for wet biomass conversion processes, the first and last properties are of

In biomass the moisture content is presented as intrinsic (without the influence of climate effects) and extrinsic (the influence of climate in the moisture content).

**84**

**Figure 1.**

*Thermochemical and biochemical routes for conversion of biomass to energy [40].*

In practical terms, it is only concerned with the extrinsic moisture content because the intrinsic moisture content is usually only achieved, or applicable, in a laboratory setting.

The calorific value (CV) of a material is an expression of the energy content, or heat value, released when burnt in air. The CV is usually measured in terms of the energy content per unit mass, or volume; hence MJ/kg for solids, MJ/l for liquids, or MJ/Nm3 for gases. The CV of a fuel can be expressed in two forms, the gross CV (GCV), or higher heating value (HHV) and the net CV (NCV), or lower heating value (LHV). In practical terms, the latent heat contained in the water vapor cannot be used effectively and therefore, the LHV is the appropriate value to use for the energy available for subsequent use. In **Table 1** is shown the immediate analysis of some biomass feedstocks.

Fuel analysis has been developed based on solid fuels, such as coal, which consists of chemical energy stored in two forms, fixed carbon and volatiles:


Elemental analysis of a fuel, presented as C, N, H, O and S together with the ash content, is termed the ultimate analysis of a fuel. **Table 2** gives the ultimate analyses for some biomass materials.

The significance of the VM and FC contents is that they provide a measure of the ease with which the biomass can be ignited and subsequently gasified, or oxidized, depending on how the biomass is to be utilized as an energy source.

The chemical breakdown of a biomass fuel, by either thermo-chemical or bio-chemical processes, produces a solid residue. When produced by combustion in air, this solid residue is called "ash" and forms a standard measurement parameter for solid and liquid fuels. The ash content of biomass affects both the handling and processing costs of the overall, biomass energy conversion cost. During biochemical conversion, the percentage of solid residue will be greater than the ash content formed during combustion of the same material.

Dependent on the magnitude of the ash content, the available energy of the fuel is reduced proportionately. In a thermo-chemical conversion process, the


**Table 1.**

*Immediate analysis of some biomass feedstocks (wt%).*


#### **Table 2.**

*Ultimate analyses for typical biomass materials (wt%).*

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 and result in increased operating costs.
