**2.1 Heating value and ultimate analysis of biomass**

Heating value of biomass is usually measured using a bomb calorimeter. Table 1 shows the ultimate analyses and heating value of some fossil fuels and common biomass. In the absence of equipment for measuring heating values of biomass, two most common equations are used. These are the Dulong equation (Gupta and Manhas, 2008) and the Boie equation (Annamalai, et al., 1987) shown in equations (1) and (2).


Table 1. Ultimate analysis data and heating values for selected solid and biomass fuels (from LePori and Soltes, 1985, with permission).

The Dulong equation is given by the following equation (1),

$$\rm{HV (k)/kg} = 33.823^{\circ}\rm{C} + 144.250^{\circ} (H\cdot O/8) + 9.419^{\circ}\rm{S} \tag{1}$$

where C, H, O, N and S are the elemental mass fractions in the material.

Example. From the ultimate analysis data shown in Table 1, estimate the heating value in MJ/kg of douglas fir.

Solution.

210 Sustainable Growth and Applications in Renewable Energy Sources

The important biomass properties include the following: (a) heating value, (b) proximate analysis and (c) ultimate analysis. Any biomass conversion process begins with knowing its energy content in units of MJ/kg and compared with traditional resources like coal. Further, biomass resources may be describe based on its proximate analysis whereby its moisture content (MC) is reported, followed by the volatile combustible matter (VCM) contents, fixed carbon (FC) and ash. Finally, the ultimate analysis is important to illustrate the biomass composition in relation to the top five elements it contains as follows: (a) carbon (C), (b) hydrogen (H) (c) oxygen (O), (d) nitrogen (N) and (e) sulphur (S) content. Other characterization would include describing its compositional contents such as lignin,

When biomass is converted thermally in the presence of excess amounts of air, (i.e. combustion) the total energy released in the form of heat is termed its heating value or calorific value. The heating value of biomass is reported in units of kJ/kg. Gasoline used as fuel for running internal combustion engines has a reported heating value of about 47 MJ/kg and diesel has heating value of about 45 MJ/kg. Biomass on the other hand may

Heating value of biomass is usually measured using a bomb calorimeter. Table 1 shows the ultimate analyses and heating value of some fossil fuels and common biomass. In the absence of equipment for measuring heating values of biomass, two most common equations are used. These are the Dulong equation (Gupta and Manhas, 2008) and the Boie

Material Elements (% dry weight) Heating

Pittsburgh seam coal 75.5 5.0 1.2 3.1 4.9 10.3 31.7 Utah coal 77.9 6.0 1.5 0.6 9.9 4.1 32.9 Wyoming Elkol coal 71.5 5.3 1.2 0.9 16.9 4.2 29.5 Lignite 64.0 4.2 0.9 1.3 19.2 10.4 24.9 Charcoal 80.3 3.1 0.2 0.0 13.0 3.4 57.4 Douglas fir 52.3 6.3 0.1 0.0 40.5 0.8 21.3 Pine bark 52.3 5.8 0.2 0.0 38.8 2.9 20.4 Redwood 53.5 5.9 0.1 0.0 40.3 0.2 21.0 Rice hulls 38.5 5.7 0.5 0.0 39.8 15.5 15.4 Rice straw 39.2 5.1 0.6 0.1 35.8 19.2 15.2 Sawdust 49.7 6.2 0.7 0.2 42.5 0.7 20.0 Paper 43.4 5.8 0.3 0.2 44.3 6.0 17.6 Feedlot manure (fresh) 45.4 5.4 1.0 0.3 32.0 15.9 17.4 Municipal solid waste 47.6 6.0 1.2 0.3 32.9 12.0 19.9 Corn cobs 46.2 7.6 1.2 0.3 42.3 2.4 26.3 Sorghum stalks 40.0 5.2 1.4 0.2 40.7 12.5 15.4 Cotton gin trash (CGT) 42.0 5.4 1.4 0.0 36.7 14.5 15.5 Table 1. Ultimate analysis data and heating values for selected solid and biomass fuels (from

C H N S O Ash MJ/kg

Values

**2. Biomass properties and characterization** 

cellulose and hemi-celluloses , carbohydrates and fat contents.

have heating values ranging from 15 – 25 MJ/kg.

LePori and Soltes, 1985, with permission).

**2.1 Heating value and ultimate analysis of biomass** 

equation (Annamalai, et al., 1987) shown in equations (1) and (2).


HV (kJ/kg) = 17,689 + 1,785 + 0 = 19,474 kJ/kg (19.5 MJ/kg).

Note that the heating value from the table is given as 21.3 MJ/kg, an 8.45% difference. The Dulong equation is valid when the oxygen content of the biomass is less than 10%. In this example, the oxygen content of douglas fir is 40.5% and way above 10% , hence a large difference.

The Boie equation is given by the following equation (2),

$$\text{HV (k)}/\text{kg} = 35.160 \text{°C} + 116.225 \text{°H} - 11.090 \text{°O} + 6.280 \text{°N} + 10.465 \text{°S} \tag{2}$$

where C, H, O, N and S are the elemental mass fractions in the material.

### **2.2 Proximate analysis of biomass**

The proximate analysis is a good indicator of biomass quality for further conversion and processing. Proximate analysis is important for thermal conversion processes since the process require relatively dry biomass (normally less than 10% moisture). If gaseous combustible fuel from biomass is to be produced, the feedstock with the highest volatile matter content is ideal to use. For slagging and fouling issues, the feedstock with the lowest ash content is an excellent choice. The fixed carbon is used to relate the heating value of the product and coproducts. Table 2 shows some proximate analysis data for some biomass resources.


Table 2. Proximate analysis data for selected biomass.
