03.08.2015   Technologies for Converting Biomass to Useful Energy

Biomass composition and analysis

To evaluate which conversion process is more suitable for different biomasses, a preliminary characterization is necessary to analyze their chemical, physical and energetic properties.

Biomass is composed of water, ashes and dry matter without ashes and only the latter component is interesting for energy conversion yielding a calorific value. Ashes and water decrease the commercial value of biomass because:

• they decrease the bulk energy content of biomass;

• moisture absorbs energy for evaporation;

• ashes have to be disposed of;

• light ashes are transported by flue gases and contribute to PM (particulate matter) emissions;

• low melting point ashes foul heat exchangers.

Given the presence of these three different main components, the measurable quantities contained in a biomass can be expressed (Fig. 5.2): [6]

Table 5.1. Selected biomass characteristics. VM: volatile matter, HHV: higher heating value, LHV: lower heating value (Mancosu, 2011)

Bulk

Biomass

Moisture [%] wb

VM

[%]

Ashes

[%]

C

[%]

H

[%]

N

[%]

HHV

[MJ/kgdb]

LHV

[MJ/kgdb]

density

[kg/m3]

Oak wood

6.2

86.0

0.9

49.7

6.5

0.2

20.4

18.9

750

Pine wood

9.5

89.3

0.7

51.3

6.1

0.2

19.2

—

440-560

Pine bark

—

—

1.8

46.9

5.3

—

—

—

—

Pellet

10.0

85.6

0.8

49.8

6.4

0.3

18.5

17.4

650

Sorghum

—

—

2.1

43.9

6.2

0.2

16.8

—

220-260

Salix wood

7.9

85.7

1.9

49.1

6.2

0.3

18.8

—

300-400

Poplar wood

8.6

80.3

1.3

49.7

6.5

0.2

19.6

19.3

420

Fire wood

7.7

77.0

5.8

48.6

6.5

0.2

18.9

—

700-800

Birch wood

7.4

80.9

2.6

48.3

8.3

0.1

19.3

—

600

Vine pruning

45.0

86.0

2.3

46.5

6.4

0.4

18.6

17.1

790-900

Olive tree pruning

40.0

86.0

3.9

49.3

5.5

0.6

18.5

17.4

800-900

Sawdust

11.6

81.5

0.8

49.5

6.8

0.4

19.7

—

100

Bamboo

8.5

76.5

0.8

50.6

5.3

0.2

19.3

—

200-250

Wood chips

9.3

88.0

1.0

50.0

5.8

0.3

19.3

—

150

Giant reed

40.0

—

8.5

45.5

5.7

0.2

18.0

17.5

180-200

Black locust

30.0

85.7

3.6

50.7

5.7

0.5

19.7

18.5

625

Straw

8.7

72.3

14.9

43.0

6.3

0.8

16.0

14.9

100-180

Wheat

6.4

75.0

8.0

43.0

10.85

0.3

16.0

—

—

Rice husk

—

69.3

19.0

36.7

5.0

0.9

14.5

13.9

75

Sugarcane

—

85.2

2.2

52.5

6.8

0.5

18.9

—

130-150

Rapeseed

6.1

77.6

3.8

42.4

7.1

0.2

16.6

—

—

Stone fruit resid.

6.9

85.6

0.5

51.6

6.0

0.5

21.6

—

—

Almond shell

8.7

81.7

2.8

52.4

6.7

0.5

19.0

17.7

—

Hazelnut shell

9.3

71.0

7.9

42.8

5.15

0.6

15.7

—

—

Walnut shell

6.7

76.1

3.6

51.5

7.3

0.7

—

—

—

Tomato

7.0

86.1

3.8

52.3

7.6

3.4

—

—

—

Olive husk

8.3

78.4

6.4

49.6

5.5

1.4

20.9

19.1

—

Bagasse

—

77.7

2.1

51.5

6.0

1.0

18.2

—

—

Ultimate analysis is defined as “the determination of the elemental composition of the organic portion of carbonaceous materials, as well as the total ash and moisture” (Miller and Tillman, 2008; ASTM D 5373-02; Milne et al., 1990).

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