1

Institut technologique FCBA : Forêt, Cellulose, Bois - construction, Ameublement

Conversion factorsA necessity for an accurate estimation

of wood consumption by industries

Alain THIVOLLE-CAZATTechnological Institute FCBA

10, avenue de St Mandé75012 Paris (France)

alain.thivolle-cazat@fcba.fr

Workshop on National Wood Resource

Balances30th Marsh –1 st April 2008

Page : 2

Existing conversion factors

Conversion factors are necessary for estimation of wood inputted in industrial processes used for wood final products (sawn timber, pulp and panels, processed wood fuel).

Conversion factors yet exists but:• There is important variations from a country to

another• Variations inside countries and processes• Use of existing conversion factors leads to under

estimate industrial wood consumption Need of improvement of existing conversion factors by country and process, defined with verified data

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Page : 3

Compilation of existing conversion factors

FAO 1979

EFSOS 2000

M.Fonseca (p.c.) 2005

EPF 2008

Finland (p.c.)

France (p.c.)

Sawnwood Softwood 1.32 -2.39 1.42 - 2.1 1.99 1.83 1.5 - 1.9 Hardwood 1.44 - 2.55 1.4 - 3.52 1.95 2.32 1.7 - 2.30 Veneer 1.2 - 3.1 1.59

Veneer/Ply

Plywood 1.63 - 2.94 1.5 - 3.1 2.02 1.8 – 1.9 Panels Particle board 1.1 - 2.2 1.2 - 1.8 1.32 1.53 1.2

OSB 1.7 2.07 1.5 Hardboard 1.98 - 3.01 2.16 MDF 1.73 1.86 1.9 Insulation board 0.63 - 0.91

1.5 - 3.3

0.66

Mechanical 2.4 - 3.27 2.16 - 2.9 2.68 2.72 – 3.18 2.4 Semi mechanical 2.04 -3.30 2.2 - 3.2 2.78

2.5 – 3.26 2.6

Sulfate 3.68 - 5.64 4.9 4.26 – 4.73 4.6 Sulfite 4.65 - 6.24

4.48 - 6.4 4.6

Page : 4

Conversion factor =

Round wood input (M3 u.b.)

Final product output

Round wood input u.b. = cubic meter under bark equivalent to round woodFinal product output = unit depends on product and process

outputproductFinalu.b.input woodRound

Typical flow of an industrial wood process

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Page : 5

Round wood inputs Product outputs

Definitions

• At mill• In forest

• At road side

• On mill yard• At the entrance of the process

Where ?

• Volume

• Surface

• Air dry weight

• Absolute dry weight

• Volume over bark

• Volume under bark

• Fresh weight

• Air dry weight

How ?

• Final product

• By-products

• Round wood

• Chips

• Recovered wood

What ?

Page : 6

Final product : cubic metersquare metertonnes

Input wood : cubic meter over bark/under bark (saw log) green tonnes, air dry tonnes (pulp wood, chips, recovered wood)

Units

Construction of a conversion matrix for transformat ion of different wood measurements into others :

• Bark factor• Humidity• Dryness• Specific gravity

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Page : 7

Conversions factors between units of measurements

Construction of a conversion matrix for transformation of different wood measurements into others :

• Bark factor• Humidity• Dryness• Specific gravity

Page : 8

Saw mill industry

5

Page : 9

Location of logs volume measurement

• Forest

• Road-side

• Mill yard

Forwarding

Road transport Losses risks

Losses risks due to :• logs forgotten in forest or at road side• slashing for cull elimination

Page : 10

Logs volume measurement

Log is assumed as a cylinder

Sm

all D

iam

.

Total Length

Mid. Diam.

Big

Dia

m.

Sm

all D

iam

.

Total Length

Mid. Diam.

Big

Dia

m.

Cylinder volume ≤ log volume

12diam)smalldiam(bigxlenght

Difference2−= length

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Page : 11

Metric decrease on diameter = 2 cm/m

D=15 cmD=20 cm

D=25 cm

D=50 cm

D=35 cm

0%

2%

4%

6%

8%

10%

3 4 5 6 7 8 9 10

Log length (m)

Vol

ume

diffe

renc

e (%

)Metric decrease on diameter = 1 cm/m

D=50 cm

D=25 cm

D=20 cm

D=15 cm

0%

2%

4%

6%

8%

10%

3 4 5 6 7 8 9 10Log length (m)

Vol

ume

diffe

renc

e (%

)

Logs volume measurement

Difference increases with :• Log length• Difference between big and small diameter

Page : 12

Log volume measurement

Due to different specifications of the saw mill, the log volume measurement can lead to an under evaluation of volume.

Example of some French and German sawmills :

• Length is rounded to the 1m or 50cm inferior• Diameter is rounded to the 1cm or 2cm inferior

These rounding leads to an under estimation of 3 to 5 %of the real volume.

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Page : 13

Recovery rate : Species variations

• Large variation of recovery rate due to quality degree asked to final product

• Bark factor varies between species

-40%

-20%

0%

20%

40%

60%

80%

100%

Oak Beech Spruce Maritime pine

Pro

duct

s an

d by

-pro

duct

s (%

)

Bark Final product Final Offcut Edgings

Slabs Log Offcut Saw dust

Page : 14

Log volume measurementBark volume

Log volume can be measured over or under bark.

A bark factor must be applied on log volume over bark.

Bark factor depends mainly on :• species• log size

DBH Diameter

13 %

5,5 %

9 %13 %

23 %

14,5 %

6 %

12 %14 %

23 %

19 %

10 %

15 %16 %

27 %

Oak

Beech

Norway spruceDouglas fir

Maritime pine

∅ > 40 cm∅ 25-35 cm∅ ≤ 20 cm

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Page : 15

Volume measurement of sawn timber

• Rough sawn timber

• Dried sawn timber : shrinkage can induce 15 to 25 % of volume reduction

• Planning and surfacing : can induce 5 to 10 % of volume reduction

Page : 16

Pulp industry

Main problem : conversion of green tonnes in volume u.b.

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Page : 17

Fibre/Particle Panel industry

Roundwood

By

products

Internal use

for energy

Green

Weight

Green

Weight

Chips

Air dry

Weight

Humidity

Specific

gravity

HumiditySpecific

gravity

Round

wood

equivallent

volume

u.b.

Bark factor

Fibre / particle

Pannel

Chips /

recovered

wood

Main problem : conversion of green tonnes in volume u.b.

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Measurement realised• fresh weight of round wood over bark• fresh weight of chips• air dry weight of pulp

Needed values of inputted wood• Volume under bark

density woodfactorbarkxdrynessxweightfresh

Necessity of conversion factors for conversion of fresh weight measurement in volume u.b. ⇒

Pulp wood measurement

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Page : 19

2.078

Volume over bark(m3 o.b.)

Volume under bark

(m3 u.b.)

Fresh Weightover bark

(ft o.b.)

Fresh Weightunder bark

(ft u.b.)

Dry Weightover bark (dt o.b.)

Dry Weightunder bark

(dt u.b.)

0.8801.136

0.750

2.17

1.333

0.460

0.890

2.470

1.124

0.405

0.361

2.774

0.481

0.8521.173

2.078

Volume over bark(m3 o.b.)

Volume under bark

(m3 u.b.)

Fresh Weightover bark

(ft o.b.)

Fresh Weightunder bark

(ft u.b.)

Dry Weightover bark (dt o.b.)

Dry Weightunder bark

(dt u.b.)

0.8801.136

0.750

2.17

1.333

0.460

0.890

2.470

1.124

0.405

0.361

2.774

0.481

0.8521.173

Matrix conversion factorMaritime pine example

Page : 20

Pulp wood measurement

• Dryness =

• Humidity =

• Bark factor =

• Seasonal variations

• Great variability inside a short log

• Species variations

weightGreenweightDry

weightDrycontent Water

o.b. Volumeu.b. Volume- o.b. Volume

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Pulp wood measurementHumidity variation

50%

55%

60%

65%

70%

75%

80%

Jan

uary

Feb

ruary

Mar

sh

Apr

il

May

Jun

e

Jul

y

Augu

st

Sept

em

ber

Octo

ber

Nov

embe

r

Dece

mber

Measurment Month

Moi

stur

e co

nte

nt (

%)

Oak Beech

Seasonal variations of green tonne ⇒ necessity of association of humidity measure to weight measure

Page : 22

Pulp wood measurement

Difference of dryness between the point of sampling and the mean dryness of the short log.

Mean dryness is best estimated when sampling is made at about 50cm from the end of the log.

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Page : 23

Pulp wood measurement

Number of samples by truck load for a given precision rate

12821481894 m

12514321282 m

15 %10 %5 %3 %2 %1 %Log length

Aberrant values probably due to insufficient number of samples

40

45

50

55

60

65

70

75

80

10/12/02 20/03/03 28/06/03 06/10/03 14/01/04 23/04/04 01/08/04 09/11/04 17/02/05

Sampling date

Dry

ness

Douglas Fir Norway Spruce

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Proposition for conversion factor improvement

Accurate conversion factors must be calculated with accurate data :

We need :

• Data knowledge / Process knowledge

• Accurate volume measurement and conversion in volume u.b.

• Weight measure and accurate conversion in volume u.b.

• Work level : country and process

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Page : 25

Data knowledge

• Inputted wood volume� Measurement procedure� Unit� Object � Procedure of calculation of equivalent round wood

under bark (measures used, bark factor, volume calculation formula)

• Output quantities of final product� Object� Characteristics� Unit

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Volume measurementSawing / veneer industry

• Quantify the difference between volume measured u.b. and real volume u.b.

• Real bark factor at mill yard

• Verify that final product measurement is raw sawn timber

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Page : 27

Weight measurementPulp / fibre and particle panel industry

• Matrix of conversion between green/rough tonne to round wood equivalent volume u.b. by species, country and type of wood

• Real bark factor at mill yard

• Specific gravity

• Mean annual humidity or monthly mean humidity

Page : 28

Panel industry(and processed wood fuel)

• Bark content in final products

All industries

• Loss analysis and estimation

• By products generation

• By products utilisation (energy, pulp and panel industry)