CONVERSION TABLES
MOISTURE CONTENT
The forestry sector has traditionally used the value of moisture content on dry basis
(DB), while in the sector of bioenergy the moisture content is usually assessed on wet
basis (WB):
Dry basis
Dry
basis (humitat – humedadfeuchtigkeit – moisture content dry basis –
humidité sur base sèche)
X·100
Wet basis
Wet basis
(contingut d’aigua-contenido
de agua - wassergehalt – moisture content
wet basis – humidité sur masse brute)
Figure 1. Difference of the calculation of moisture content based on dry and wet basis
Source: AFIB-CTFC
Table 1. Equivalences between the two concepts of moisture
Equivalences between values of moisture content in dry basis and wet basis
%WB
0
5
10
15
20
25
30
35
40
45
50
55
60
65
%DB
0
5
10
15
20
25
30
40
50
60
70
80
90
100
%DB
0,0
5,3
11,1
17,6
25,0
33,3
42,9
53,8
66,7
81,8
100,0
122,2
150,0
185,7
%WB
0,0
4,8
9,1
13,0
16,7
20,0
23,1
28,6
33,3
37,5
41,2
44,4
47,4
50,0
Source: AFIB-CTFC
The moisture from the freshly cut wood is round 45% wet basis for the conifers, little less for the
oaks and holm oaks (Q. ilex). Regarding the season, trees in winter has moisture contents
lower than in the seasons of vegetative activity.
Àrea d'Aprofitaments Fusters i Biomassa - http://afib.ctfc.cat/
Centre Tecnològic Forestal de Catalunya - http://www.ctfc.cat/
Ctra de Sant Llorenç de Morunys, km 2 (Direcció Port del Compte) , ES-25280 SOLSONA (Lleida) - Telf: +34 973 48 17 52 · Fax: +34 973 48 04 31
e-correu: [email protected] i [email protected]
Butlletí Infobiomassa - http://infobio.ctfc.cat/ · Rok-FOR - http://www.rokfor.eu/ · Wood E3 - http://www.woode3.eu
WOOD DENSITY
The density of wood is the mass per unit volume and is measured in kg/dm3 or
tonnes/m3.
When talking about basic density of wood, it refers to the absolute dry (0% of moisture
content) mass of wood referred to the green volume..
Table 2. Equivalences between different wood densities of wood moisture content
Specie
Abies alba
Pinus uncinata
Pinus sylvestris
Pinus nigra
Pinus halepensis
Pinus pinea
Pinus pinaster
Pinus insignis
Fagus sylvatica
Betula pendula
Quercus ilex
Quercus sp. (oaks)
Castanea sativa
Fraxinus angustifolia
Populus sp.
Platanus x hispanica
Conifers
Deciduous
Basic
(t0/m3)
0,51
0,50
0,48
0,51
0,55
0,51
0,44
0,46
0,69
0,60
0,87
0,73
0,59
0,67
0,43
0,65
0,51
0,67
Wood density
50%WB
30%WB
(t50/m3)
(t30/m3)
0,87
0,62
0,86
0,61
0,81
0,58
0,88
0,63
0,93
0,66
0,87
0,62
0,74
0,53
0,78
0,56
1,16
0,83
1,03
0,73
1,47
1,05
1,24
0,88
1,00
0,71
1,13
0,81
0,74
0,53
1,11
0,79
0,87
0,62
1,14
0,82
The basic density was considered as a weighted average between the density of bark and wood bulk density; the fiber
saturation point is considered at 30%DB.
Source: AFIB-CTFC from SIBosC (CREAF-DMAH, 2011) and CPF (2004)
Àrea d'Aprofitaments Fusters i Biomassa - http://afib.ctfc.cat/
Centre Tecnològic Forestal de Catalunya - http://www.ctfc.cat/
Ctra de Sant Llorenç de Morunys, km 2 (Direcció Port del Compte) , ES-25280 SOLSONA (Lleida) - Telf: +34 973 48 17 52 · Fax: +34 973 48 04 31
e-correu: [email protected] i [email protected]
Butlletí Infobiomassa - http://infobio.ctfc.cat/ · Rok-FOR - http://www.rokfor.eu/ · Wood E3 - http://www.woode3.eu
CALORIFIC VALUES
The potential energy value of biomass materials is determined by its chemical
composition and is measured in units of energy per mass of fuel (e.g. J/g). For
convenience this measure is usually expressed as MJ/kg or GJ/t, but in the commercial
field, frequently used units are kWh/tonne and kcal/kg.
We must differentiate between the gross calorific value (qGR) and net calorific value
(qNET). The qGR is the amount of energy released when a unit mass is burned with
oxygen, where water being produced in the burning process is in liquid form. In
condensing to liquid, energy is released. The concept is similar to qNET, where the
water released in the combustion process is in gaseous state. The qGR will always be
greater than the qNET. qNETis commonly used because the water is almost always in
gaseous state in the flue gases of the boiler.
Table 3: Energy equivalences
Joule
(J)
Joule (J)
Calorie (cal)
Kilowatt hour (kWh)
Ton of oil equivalent (toe)
Calorie
(cal)
Ton of oil
equivalent
(toe)
0,239·10-10
1·10-10
8,60·10-5
1
Kilowatt hour
(kWh)
1
0,239
4,184
1
6
0,860·106
3,600·10
41,840·109
1010
Source: Rodríguez, 2006
-6
0,278·10
1,162·10-6
1
11,622·103
The net calorific value of a ton anhydrous (0% moisture) of wood is about 5.000-5.600
kWh/t (4.300-4.815 kcal/kg).
Table 4 Calorific values (en kWh/t) at different moistures
Moisture wet basis
Specie
0
20
30
35
40
45
Quercus ilex
Quercus sp (oaks)
Pinus sylvestris
Pinus nigra
Pinus halepensis
Pinus pinea
Populus sp.
Castanea sativa
Fagus sylvatica
Conifers
Deciduous
5.307
4.975
5.338
5.296
5.082
5.374
4.815
5.184
4.951
5.272
5.078
4.110
3.844
4.135
4.101
3.930
4.164
3.716
4.012
3.825
4.082
3.927
3.512
3.279
3.533
3.504
3.354
3.558
3.167
3.425
3.262
3.487
3.351
3.212
2.996
3.232
3.205
3.066
3.256
2.892
3.132
2.981
3.190
3.063
2.913
2.714
2.931
2.906
2.778
2.953
2.618
2.839
2.699
2.892
2.775
2.614
2.431
2.631
2.607
2.490
2.651
2.343
2.546
2.418
2.595
2.488
50
2.314
2.148
2.330
2.309
2.202
2.348
2.068
2.253
2.136
2.297
2.200
Source: AFIB-CTFC from: Biocalor-Hargassner, ETA Heiztechnik GmbH, Energuía, Pla de biomassa, Projecte Biosouth
and Technologie-und Förderzentrum
The higher moisture content, the lower the calorific values, both derived from the
relative decrease in the amount of wood per unit mass of fuel, and also because of the
need to use some energy from the wood to evaporate the water.
Àrea d'Aprofitaments Fusters i Biomassa - http://afib.ctfc.cat/
Centre Tecnològic Forestal de Catalunya - http://www.ctfc.cat/
Ctra de Sant Llorenç de Morunys, km 2 (Direcció Port del Compte) , ES-25280 SOLSONA (Lleida) - Telf: +34 973 48 17 52 · Fax: +34 973 48 04 31
e-correu: [email protected] i [email protected]
Butlletí Infobiomassa - http://infobio.ctfc.cat/ · Rok-FOR - http://www.rokfor.eu/ · Wood E3 - http://www.woode3.eu