08.08.2015   Cellulosic Energy Cropping Systems

Moisture Content

Biomass moisture content is defined as the amount of water in the biomass expressed as a percentage of the material’s weight; reporting on a wet basis is most common. Moisture content at harvest for woody feedstocks is usually 40-60% (wet basis); for herbaceous crops, it typically ranges from 10 to 70% (wet basis) depending upon the species, climate, geographic location, and stage of maturation. Biomass net energy density per unit mass decreases with increasing moisture content. Transport efficiency of biomass feedstock, therefore, decreases as moisture content increases. Storage of high-moisture biomass is also less efficient, both because of reduced energy density and increased probability of biological degradation, fire risk, and mold formation. Moisture content also affects down­stream processing, especially for thermochemical conversion. High-moisture feedstocks must be dried to levels of less than 50% for conventional combustion and less than 20% for gasification and pyrolysis. In biological processing for which some form of thermal pretreatment is used, moisture content can also significantly affect the energy efficiency of the process.

Herbaceous Crops Crop Residues Woody Crops

Composition/

Property

Units

Miscanthus

Switchgrass

Energy

Cane

Sorghum

Corn Stover

Wheat

Straw

Eucalyptus

Poplar

Willow

Pine

Productivity

Mg/ha/yr

1-44

7-10

26.7

7.8

1.2-3.6

0.1-1.75

33

7-48

14-16

11

Moisture

% WM

4-5

13-65

73

87

15-35

5-8

59-63

53-63

44-60

49-62

Components

Cellulose

% DM

40-60

31-35

43

45

31-38

32.6

47-50

39-43

44.1

42

Hemicellulose

% DM

20-40

24-28

24

27

19-25

22.6

13-14

17-19

21.8

21

Lignin

% DM

10-30

17-22

22

21

17-21

16.9

27-28

24-28

20.4

26

Extractives

% DM

0.3-2.2

5-17

nr

nr

3-12

13.0

0.6-4.2

1.3-2.4

5.4

3

Ash

% DM

2.2-3.5

5-6

0.8

0.4

10-14

10.2

0.6-1.2

2-7

2.1

0.3

Juice

% WM

na

na

54

72

na

na

na

na

na

na

Juice Sugars

% juice

na

na

10

12

na

na

na

na

na

na

Proximate Analysis

Volatile Matter

% DM

72.6-78.2

72.6-77.9

78.6-81.1

78.3

70.2-74.8

69.4

79.5-82.5

78.2-80.1

87.6

80.5

Fixed Carbon

% DM

15.1-20.4

17.0-22.1

17.0-18.8

18.0

20.0-22.6

21.5

17.2-19.0

18.3-19.9

10.7

19.4

Ultimate Analysis

C

% DM

47.1-49.7

46.6-48.5

48.2-49.0

47.5

44.8-48.0

43.9

49.5-49.9

49.4-51.7

49.9

50.3

H

% DM

5.4-5.9

5.3-5.7

5.5-6.0

6.7

5.4-6.1

5.3

5.7-6.3

4.5-6.4

6.5

6.0

О

% DM

41.4-44.6

38.2-42.1

39.2-41.6

41.1

37.0-41.4

38.8

42.0-43.5

35.1-42.4

39.9

42.1

N

% DM

0.1-1.0

0.4-0.7

0.2

0.9

0.6-0.7

0.6

0.1-0.5

0.2-0.5

0.2

0.0

s

% DM

0.07-0.1 9

0.07-0.11

0.02-0.03

0.09

0.06-0.1

0.2

0.01-0.04

0.02-0.03

nr

0.0

Energy Density

LHV

MJ/kg

17-20

18-19

19.0

19.1

18-19

17.4

20

20

19.3

20.0

Sources:

[10]

[11,12]

[11,13]

[13,14]

[11,15,16]

[11,17,18]

[11,19-21]

[11,22]

[19,23,24]

[11,19,

21,25]

WM = wet mass; DM = dry mass; na = not applicable; nr = not reported.

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