Industrial

 

Crops

 

and

 

Products

 

58

 

(2014)

 

230–237

Contents

 

lists

 

available

 

at

 

ScienceDirect

Industrial

 

Crops

 

and

 

Products

j o

 

u

 

r

 

n

 

a l

 

h o m e p

 

a g e :

 

w w w . e l s e v i e r . c o m / l o c a t e / i n d c r o p

Willow

 

biomass

 

as

 

feedstock

 

for

 

an

 

integrated

 

multi-product

biorefinery

Michał

 

Krzy ˙zaniak

a

,

∗

,

 

Mariusz

 

J.

 

Stolarski

a

,

 

Bogusława

 

Waliszewska

b

,

Stefan

 

Szczukowski

a

,

 

Józef

 

Tworkowski

a

,

 

Dariusz

 

Załuski

a

,

 

Malwina ´Snieg

a

a

University

 

of

 

Warmia

 

and

 

Mazury

 

in

 

Olsztyn,

 

Faculty

 

of

 

Environmental

 

Management

 

and

 

Agriculture,

 

Department

 

of

 

Plant

 

Breeding

 

and

 

Seed

 

Production,

Plac

 

Łódzki

 

3/420,

 

10-724

 

Olsztyn,

 

Poland

b

Pozna´

n

 

University

 

of

 

Life

 

Sciences,

 

Institute

 

of

 

Chemical

 

Wood

 

Technology,

 

ul.

 

Wojska

 

Polskiego

 

38/42,

 

60-637

 

Poznan,

 

Poland

a

 

r

 

t

 

i

 

c

 

l

 

e

 

i

 

n

 

f

 

o

Article

 

history:

Received

 

31

 

October

 

2013

Received

 

in

 

revised

 

form

 

4

 

April

 

2014

Accepted

 

17

 

April

 

2014

Keywords:
Willow

 

biomass

Thermophysical

 

properties

Chemical

 

and

 

elemental

 

composition

Biorefinery

a

 

b

 

s

 

t

 

r

 

a

 

c

 

t

Biomass

 

has

 

enormous

 

potential

 

for

 

use

 

in

 

the

 

chemical

 

industry.

 

It

 

is

 

a

 

source

 

of

 

a

 

large

 

number

 

of

chemical

 

components

 

and

 

manufactured

 

products.

 

Lignocellulosic

 

biomass

 

can

 

be

 

a

 

source

 

of

 

high-value

products

 

produced

 

on

 

an

 

industrial

 

scale

 

in

 

a

 

profitable

 

way.

The

 

aim

 

of

 

this

 

study

 

was

 

to

 

determine

 

the

 

chemical

 

composition

 

of

 

seven

 

varieties

 

and

 

clones

 

of

 

willow

grown

 

in

 

the

 

moderate

 

climate

 

of

 

Europe

 

and

 

to

 

choose

 

cultivars

 

which

 

can

 

provide

 

a

 

sufficient

 

quantity

 

of

feedstock

 

to

 

operate

 

an

 

integrated

 

multiproduct

 

biorefinery.

 

The

 

biomass

 

of

 

the

 

willow

 

cultivars

 

under

study

 

had

 

good

 

thermophysical

 

compositions

 

and

 

they

 

contained

 

only

 

small

 

amounts

 

of

 

undesirable

components

 

(ash,

 

sulphur,

 

chlorine).

 

The

 

average

 

higher

 

heating

 

value

 

and

 

lower

 

heating

 

value

 

of

 

willow

biomass

 

was

 

19.50

 

MJ

 

kg

−1

d.m.

 

and

 

8.38

 

MJ

 

kg

−1

,

 

respectively.

 

The

 

content

 

and

 

yield

 

of

 

cellulose

 

and

hemicelluloses

 

in

 

biomass

 

of

 

the

 

UWM

 

006

 

and

 

UWM

 

043

 

clones

 

of

 

Salix

 

viminalis

 

L.

 

makes

 

them

 

highly

useful

 

for

 

an

 

integrated

 

multi-product

 

biorefinery,

 

based

 

on

 

lignocellulosic

 

raw

 

material.

©

 

2014

 

Elsevier

 

B.V.

 

All

 

rights

 

reserved.

1.

 

Introduction

The

 

global

 

consumption

 

of

 

energy,

 

which

 

is

 

generated

 

mainly

from

 

fossil

 

fuels,

 

is

 

increasing.

 

Fossil

 

fuels

 

are

 

also

 

the

 

main

 

feed-

stock

 

in

 

use

 

by

 

the

 

chemical

 

industry.

 

The

 

constant

 

increase

 

in

their

 

consumption

 

and

 

their

 

shrinking

 

resources

 

are

 

making

 

them

increasingly

 

expensive

 

(

IEA,

 

2012

).

 

For

 

example,

 

the

 

average

 

price

of

 

oil

 

supplied

 

by

 

OPEC

 

countries

 

increased

 

from

 

23

 

to

 

almost

 

110

USD

 

per

 

barrel

 

between

 

2001

 

and

 

2012

 

(

OPEC,

 

2013

).

 

Moreover,

their

 

production

 

and

 

use

 

causes

 

greenhouse

 

gas

 

emission,

 

with

a

 

consequent

 

increase

 

in

 

the

 

greenhouse

 

effect.

 

The

 

atmospheric

concentrations

 

of

 

greenhouse

 

gases

 

such

 

as

 

carbon

 

dioxide

 

(CO

2

),

methane

 

(CH

4

)

 

and

 

nitrous

 

oxide

 

(N

2

O)

 

have

 

all

 

increased

 

since

1750

 

due

 

to

 

human

 

activity.

 

In

 

2011,

 

the

 

concentrations

 

of

 

these

gases

 

exceeded

 

the

 

pre-industrial

 

levels

 

by

 

about

 

40%,

 

150%

 

and

20%,

 

respectively.

 

At

 

the

 

same

 

time,

 

global

 

average

 

temperatures

have

 

increased,

 

each

 

of

 

the

 

past

 

three

 

decades

 

being

 

warmer

 

than

previously

 

(

IPCC,

 

2013

).

 

These

 

changes

 

will

 

have

 

serious

 

environ-

mental

 

effects:

 

they

 

will

 

increase

 

droughts,

 

coral

 

bleaching

 

and

∗ Corresponding

 

author.

 

Tel.:

 

+48

 

895246146.

E-mail

 

address:

 

michal.krzyzaniak@uwm.edu.pl

 

(M.

 

Krzy ˙zaniak).

influence

 

crop

 

productivity.

 

Moreover,

 

they

 

have

 

a

 

dramatic

 

effect

on

 

ice

 

melting

 

in

 

polar

 

zones

 

and,

 

consequently,

 

rising

 

sea

 

levels

and

 

frequent

 

occurrences

 

of

 

abnormal

 

weather

 

conditions

 

(

Watson

and

 

Albritton,

 

2001

).

 

Global

 

efforts

 

have

 

been

 

made

 

to

 

slow

 

climate

change

 

and

 

growing

 

interest

 

has

 

been

 

focused

 

on

 

using

 

renewable

resources

 

to

 

replace

 

non-renewable

 

products

 

of

 

the

 

chemical

 

and

energy

 

industry,

 

which

 

have

 

an

 

adverse

 

impact

 

on

 

the

 

environ-

ment.

Biomass

 

has

 

enormous

 

potential

 

for

 

use

 

in

 

the

 

chemical

 

indus-

try.

 

It

 

is

 

a

 

source

 

of

 

a

 

large

 

number

 

of

 

chemical

 

components

 

and

products

 

manufactured

 

around

 

the

 

world.

 

Lignocellulosic

 

biomass

can

 

be

 

a

 

source

 

of

 

high-value

 

products,

 

such

 

as:

 

speciality

 

cellulose

and

 

vanillin.

 

Importantly,

 

they

 

can

 

be

 

produced

 

on

 

an

 

industrial

scale

 

in

 

a

 

profitable

 

way

 

(

Sjöde,

 

2013

).

Lignocellulosic

 

biomass

 

is

 

frequently

 

obtained

 

from

 

forest

 

wood

and

 

from

 

wood

 

industry

 

waste.

 

Directive

 

2009/28/EC

 

introduced

the

 

minimum

 

requirements

 

for

 

the

 

sustainability

 

of

 

solid

 

biomass,

such

 

as

 

a

 

ban

 

on

 

the

 

production

 

or

 

acquisition

 

of

 

biomass

 

in

 

pro-

tected

 

areas

 

of

 

unique

 

natural

 

value,

 

primeval

 

forests

 

or

 

areas

of

 

high

 

biodiversity

 

(

European

 

Commission,

 

2009

).

 

The

 

European

Union

 

also

 

intends

 

to

 

implement

 

sustainability

 

standards

 

for

 

solid

biomass

 

and

 

to

 

devote

 

more

 

attention

 

to

 

wood

 

products

 

originat-

ing

 

outside

 

its

 

borders

 

(

Simmet,

 

2013

).

 

Since

 

the

 

forest

 

resources

in

 

the

 

EU

 

are

 

limited

 

and

 

its

 

use

 

is

 

frequently

 

unsustainable

 

(e.g.

http://dx.doi.org/10.1016/j.indcrop.2014.04.033

0926-6690/©

 

2014

 

Elsevier

 

B.V.

 

All

 

rights

 

reserved.

M.

 

Krzy ˙zaniak

 

et

 

al.

 

/

 

Industrial

 

Crops

 

and

 

Products

 

58

 

(2014)

 

230–237

 

231

long-distance

 

transport),

 

lignocellulosic

 

biomass

 

produced

 

in

 

agri-

culture

 

is

 

of

 

increasing

 

interest.

 

Apart

 

from

 

agricultural

 

residues,

energy

 

crops

 

can

 

also

 

be

 

used

 

as

 

feedstock

 

in

 

energy

 

generation.

Such

 

crops

 

with

 

a

 

stable

 

yield

 

and

 

well-developed

 

cultivation

 

tech-

nology

 

include:

 

herbaceous

 

plants

 

(e.g.

 

Miscanthus

 

giganteus,

 

giant

reed,

 

Virginia

 

mallow)

 

as

 

well

 

as

 

short

 

rotation

 

trees

 

and

 

coppice

(e.g.

 

willow,

 

poplar,

 

black

 

locust)

 

(

Angelini

 

et

 

al.,

 

2009;

 

Borkowska

and

 

Molas,

 

2012;

 

Dini-Papanastasi,

 

2008;

 

Wang

 

and

 

MacFarlane,

2012

).

Trees

 

and

 

coppice

 

of

 

genus

 

willow

 

(Salix

 

L.)

 

can

 

be

 

grown

 

in

a

 

short-rotation

 

system.

 

Such

 

cultivation

 

produces

 

a

 

high

 

yield

 

of

dry

 

biomass,

 

which

 

ranges

 

from

 

10

 

to

 

20

 

Mg

 

ha

−1

year

−1

.

 

Among

the

 

characteristic

 

features

 

of

 

willow

 

crops

 

are:

 

uniform

 

chemical

composition

 

and

 

small

 

amounts

 

of

 

contaminants

 

and

 

undesirable

components

 

(

Stolarski

 

et

 

al.,

 

2013b

).

 

Therefore,

 

willow

 

is

 

a

 

high

quality

 

uniform

 

material,

 

which

 

can

 

be

 

harvested

 

and

 

subsequently

stored

 

before

 

delivery

 

to

 

a

 

biorefinery

 

as

 

needed.

 

Therefore,

 

wood

can

 

be

 

successfully

 

used

 

as

 

feedstock

 

in

 

an

 

integrated

 

multiproduct

biorefinery

 

(

García

 

et

 

al.,

 

2014;

 

Krzy ˙zaniak

 

et

 

al.,

 

2013;

 

Liu

 

et

 

al.,

2012;

 

Röser

 

et

 

al.,

 

2011

).

Many

 

studies

 

have

 

been

 

conducted

 

worldwide

 

on

 

inte-

grated

 

multiproduct

 

biorefineries.

 

Among

 

them

 

there

 

are

 

research

projects,

 

advanced

 

pilot

 

installations

 

and

 

operating

 

biorefineries.

Eurobioref

 

is

 

a

 

research

 

project

 

within

 

which

 

pilot

 

installations

 

are

developed

 

(

FitzPatrick

 

et

 

al.,

 

2010;

 

Menon

 

and

 

Rao,

 

2012;

 

Rødsrud

et

 

al.,

 

2012;

 

Star-COLIBRI,

 

2013;

 

Thomsen

 

et

 

al.,

 

2013

).

 

The

 

project

will

 

develop

 

a

 

new

 

highly-integrated

 

and

 

diversified

 

concept,

including

 

multiple

 

feedstocks

 

(including

 

lignocellulosic

 

biomass),

multiple

 

processes

 

(chemical,

 

biochemical,

 

thermochemical)

 

and

multiple

 

products

 

(aviation

 

fuels

 

and

 

chemicals).

 

This

 

flexible

approach

 

will

 

widen

 

biorefinery

 

implementation

 

to

 

the

 

full

 

geo-

graphical

 

range

 

of

 

Europe

 

and

 

will

 

offer

 

opportunities

 

to

 

export

biorefinery

 

technology

 

packages

 

to

 

more

 

local

 

markets

 

and

 

feed-

stock

 

hotspots

 

(

EuroBioRef,

 

2013

).

 

Biorefineries

 

set

 

up

 

as

 

part

 

of

the

 

project

 

will

 

use

 

material

 

obtained

 

from

 

oil

 

crops,

 

biowaste

 

and

lignocellulosic

 

crops.

 

The

 

choice

 

of

 

feedstock

 

will

 

be

 

suited

 

to

 

the

local

 

conditions.

The

 

aim

 

of

 

this

 

study

 

was

 

to

 

determine

 

the

 

chemical

 

composi-

tion

 

of

 

seven

 

varieties

 

and

 

clones

 

of

 

willow

 

grown

 

in

 

the

 

moderate

climate

 

of

 

Europe

 

and

 

to

 

choose

 

cultivars

 

which

 

could

 

provide

 

a

 

suf-

ficient

 

quantity

 

of

 

feedstock

 

to

 

operate

 

an

 

integrated

 

multiproduct

biorefinery.

2.

 

Material

 

and

 

methods

2.1.

 

Field

 

research

A

 

willow

 

plantation

 

was

 

established

 

between

 

the

 

11th

 

and

 

20th

of

 

April

 

2010

 

at

 

the

 

Educational

 

and

 

Research

 

Station

 

in

 

Ł ˛e ˙zany,

owned

 

by

 

the

 

University

 

of

 

Warmia

 

and

 

Mazury

 

in

 

Olsztyn.

 

It

 

is

located

 

in

 

north-eastern

 

Poland

 

near

 

Samławki

 

village

 

(53

◦

59

N,

21

◦

05

E).

 

The

 

main

 

factor

 

in

 

the

 

field

 

experiment

 

are

 

three

 

varieties

and

 

four

 

clones

 

of

 

willow,

 

all

 

of

 

them

 

created

 

by

 

the

 

Department

of

 

Plant

 

Breeding

 

and

 

Seed

 

Production

 

of

 

the

 

University

 

of

 

Warmia

and

 

Mazury

 

in

 

Olsztyn:

 

Salix

 

viminalis

 

varieties

 

Start,

 

Tur,

 

Turbo;

Salix

 

viminalis

 

clones

 

UWM

 

006,

 

UWM

 

043;

 

clone

 

UWM

 

035

 

Salix

pentandra;

 

clone

 

UWM

 

155

 

Salix

 

dasyclados.

The

 

plant

 

density

 

was

 

18,000

 

per

 

ha.

 

A

 

strip

 

planting

 

system

 

was

applied,

 

in

 

which

 

2

 

rows

 

in

 

a

 

strip

 

were

 

arranged

 

at

 

an

 

inter-row

distance

 

of

 

0.75

 

m,

 

with

 

an

 

inter-row

 

of

 

1.50

 

m

 

for

 

separation

 

from

the

 

next

 

2

 

rows

 

in

 

a

 

strip

 

(with

 

an

 

inter-row

 

distance

 

of

 

0.75

 

m,

etc.)

 

and

 

the

 

distance

 

between

 

the

 

plants

 

in

 

a

 

row

 

was

 

0.50

 

m.

After

 

the

 

third

 

year

 

of

 

growth,

 

in

 

December

 

2012,

 

willow

 

plants

were

 

harvested

 

with

 

a

 

Jaguar-Claas

 

harvester.

 

The

 

harvester

 

trans-

ported

 

the

 

chips

 

on

 

a

 

tractor

 

trailer.

 

The

 

trailer

 

with

 

chips

 

from

different

 

cultivars

 

was

 

subsequently

 

weighed

 

and

 

the

 

yield

 

of

 

fresh

biomass

 

was

 

calculated

 

(Mg

 

ha

−1

).

 

Next,

 

the

 

yield

 

of

 

dry

 

biomass,

(Mg

 

ha

−1

)

 

was

 

calculated

 

from

 

the

 

moisture

 

content

 

and

 

the

 

fresh

biomass

 

yield.

 

Biomass

 

samples

 

of

 

seven

 

willow

 

varieties

 

were

 

col-

lected

 

for

 

laboratory

 

analyses.

 

Fresh

 

chips

 

were

 

collected

 

from

 

a

tractor

 

trailer.

 

Subsequently,

 

chips

 

were

 

transported

 

on

 

a

 

tractor

trailer,

 

from

 

which

 

10

 

one-litre

 

primary

 

samples

 

of

 

chips

 

were

taken

 

from

 

random

 

places.

 

Then,

 

10

 

primary

 

samples

 

were

 

poured

into

 

one

 

container,

 

yielding

 

an

 

average

 

sample.

 

After

 

this

 

was

mixed,

 

a

 

3-litre

 

laboratory

 

sample

 

was

 

taken

 

and

 

transported

 

to

the

 

laboratory

 

of

 

the

 

Department

 

of

 

Plant

 

Breeding

 

and

 

Seed

 

Pro-

duction

 

of

 

the

 

UWM

 

in

 

Olsztyn.

 

Subsequently,

 

in

 

the

 

laboratory,

analytical

 

samples

 

were

 

made

 

and

 

each

 

attribute

 

was

 

determined

in

 

triplicate.

2.2.

 

Laboratory

 

analyses

The

 

biomass

 

moisture

 

content

 

was

 

determined

 

in

 

fresh

 

wil-

low

 

chips

 

in

 

a

 

laboratory,

 

with

 

the

 

drying

 

and

 

weighing

 

method

according

 

to

 

PN

 

80/G-04511.

 

The

 

biomass

 

was

 

dried

 

at

 

105

◦

C

 

until

a

 

constant

 

mass

 

was

 

achieved.

 

After

 

drying,

 

the

 

biomass

 

samples

were

 

ground

 

in

 

an

 

IKA

 

KMF

 

10

 

basic

 

analytic

 

mill

 

using

 

a

 

0.25

 

mm

sieve.

 

The

 

ash

 

content

 

was

 

determined

 

in

 

the

 

prepared

 

analyti-

cal

 

samples

 

at

 

550

◦

C

 

in

 

an

 

ELTRA

 

TGA-THERMOSTEP

 

automatic

thermogravimetric

 

analyser

 

with

 

the

 

standard

 

methods

 

as

 

follows:

ASTM

 

D-5142,

 

D-3173,

 

D-3174,

 

D-3175,

 

PN-G-04560:1998

 

and

PN-ISO

 

562.

 

Moreover,

 

the

 

higher

 

heating

 

value

 

of

 

dry

 

biomass

was

 

determined

 

in

 

an

 

IKA

 

C

 

2000

 

calorimeter

 

using

 

the

 

dynamic

method,

 

in

 

accordance

 

with

 

the

 

PN-81/G-04513

 

standard.

 

The

lower

 

heating

 

value

 

of

 

the

 

fresh

 

biomass

 

was

 

calculated

 

on

 

the

 

basis

of

 

the

 

higher

 

heating

 

value

 

and

 

moisture

 

content

 

of

 

the

 

biomass

(

Kopetz

 

et

 

al.,

 

2007

).

 

The

 

carbon,

 

hydrogen

 

and

 

sulphur

 

content

were

 

also

 

identified

 

by

 

means

 

of

 

an

 

ELTRA

 

CHS

 

500

 

automatic

analyser,

 

according

 

to

 

PN/G-04521

 

and

 

PN/G-ISO

 

35

 

standards.

 

The

nitrogen

 

content

 

was

 

determined

 

with

 

the

 

Kjeldahl

 

method,

 

using

a

 

K-435

 

unit

 

and

 

a

 

B-324

 

BUCHI

 

distiller

 

and

 

the

 

chlorine

 

content

using

 

the

 

Eschka

 

mixture.

 

All

 

of

 

the

 

analyses

 

were

 

performed

 

in

three

 

replications.

The

 

biomass

 

for

 

chemical

 

analyses

 

was

 

prepared

 

in

 

accor-

dance

 

with

 

PN-92/P-50092.

 

Samples

 

were

 

ground

 

in

 

a

 

laboratory

mill

 

(Fritsch

 

type

 

15)

 

using

 

a

 

sieve

 

with

 

1.0

 

mm

 

square

 

screens.

The

 

material

 

was

 

passed

 

through

 

brass

 

sieves

 

to

 

separate

 

the

0.5–1.0

 

mm

 

fraction.

 

The

 

chemical

 

composition

 

was

 

determined

with

 

standard

 

methods

 

applied

 

for

 

wood

 

chemical

 

analysis.

 

Before

determination

 

of

 

the

 

cellulose,

 

lignin

 

and

 

holocellulose

 

contents,

extraction

 

in

 

96%

 

ethyl

 

alcohol

 

was

 

performed

 

in

 

a

 

Soxhlet

 

appara-

tus

 

according

 

to

 

TAPPI

 

T

 

204

 

cm-07

 

(

Baeza

 

and

 

Freer,

 

2000;

 

Fengel

and

 

Wegener,

 

1989

).

 

Subsequently,

 

the

 

material

 

was

 

dried

 

under

laboratory

 

conditions

 

and

 

the

 

extracted

 

substances

 

(lipids,

 

waxes,

resins

 

and

 

others)

 

were

 

dried

 

at

 

103

 

±

 

2

◦

C

 

and

 

the

 

contents

 

of

 

the

following

 

substances

 

was

 

determined:

 

cellulose

 

(with

 

the

 

Seifert

method)

 

(according

 

to

 

PN-92/P-50092),

 

lignin

 

with

 

the

 

Tappi

 

T

 

222

om-06

 

method,

 

using

 

72%

 

H

2

SO

4

,

 

pentosans

 

(with

 

Tollen’s

 

method)

(TAPPI

 

223

 

cm-01),

 

holocellulose

 

(using

 

sodium

 

chlorite,

 

accord-

ing

 

to

 

PN-75/50092)

 

(

Rowell,

 

2005

),

 

base-soluble

 

substances

 

(1%

aqueous

 

solution

 

of

 

NaOH)

 

according

 

to

 

TAPPI

 

T

 

212

 

om-07,

 

and

the

 

content

 

of

 

substances

 

soluble

 

in

 

cold

 

and

 

hot

 

water

 

(TAPPI

 

T

204

 

cm-07).

 

Hemicellulose

 

content

 

was

 

calculated

 

as

 

the

 

differ-

ence

 

between

 

the

 

content

 

of

 

holocellulose

 

and

 

cellulose.

 

However,

it

 

must

 

be

 

stressed

 

that

 

this

 

is

 

a

 

calculated,

 

theoretical

 

value.

 

Addi-

tionally,

 

pH

 

was

 

assessed

 

according

 

to

 

PN-Z-15011-1.

 

First,

 

50

 

g

 

of

the

 

resource

 

material

 

was

 

mixed

 

in

 

a

 

conical

 

flask

 

with

 

200

 

cm

3

of

 

distilled

 

water.

 

The

 

flask,

 

tightly

 

closed,

 

was

 

put

 

into

 

a

 

shaker

and

 

shaken

 

for

 

0.5

 

h.

 

It

 

was

 

then

 

left

 

for

 

1

 

h

 

and

 

the

 

contents

 

were

stirred

 

prior

 

to

 

the

 

pH

 

measurement.

 

All

 

of

 

the

 

tests

 

were

 

repeated

232

 

M.

 

Krzy ˙zaniak

 

et

 

al.

 

/

 

Industrial

 

Crops

 

and

 

Products

 

58

 

(2014)

 

230–237

simultaneously

 

in

 

three

 

replications.

 

The

 

results

 

were

 

calculated

 

in

relation

 

to

 

wood

 

dry

 

matter.

2.3.

 

Statistical

 

analysis

The

 

results

 

of

 

the

 

tests

 

were

 

analysed

 

statistically

 

using

 

STA-

TISTICA

 

PL

 

software.

 

The

 

mean

 

arithmetic

 

values

 

and

 

standard

deviation

 

of

 

the

 

examined

 

features

 

were

 

calculated.

 

Homogeneous

groups

 

for

 

the

 

examined

 

characteristics

 

were

 

determined

 

by

 

means

of

 

an

 

Tukey

 

(HSD)

 

multiple

 

test

 

with

 

the

 

significance

 

level

 

set

 

at

p

 

<

 

0.05.
The

 

PCA

 

(Principal

 

Component

 

Analysis)

 

was

 

applied

 

to

 

evalu-

ate

 

the

 

thermophysical

 

and

 

chemical

 

features

 

of

 

the

 

biomass.

 

The

justifiability

 

of

 

the

 

analysis

 

was

 

confirmed

 

by

 

the

 

Bartlett’s

 

Test

of

 

Sphericity.

 

The

 

number

 

of

 

components

 

was

 

selected

 

based

 

on

Kaiser’s

 

criterion,

 

in

 

which

 

the

 

method

 

of

 

eigenvalues

 

(

i

)

 

larger

than

 

one

 

(>1).

 

Diagram

 

of

 

the

 

Component

 

Scores

 

for

 

the

 

first

 

two

PCs

 

were

 

presented

 

in

 

the

 

form

 

of

 

biplot.

 

The

 

PCA

 

analysis

 

did

 

not

include

 

hemicelluloses

 

because,

 

unlike

 

other

 

attributes

 

which

 

are

determined

 

by

 

laboratory

 

analyses,

 

it

 

is

 

a

 

subtraction

 

between

 

the

content

 

of

 

holocellulose

 

and

 

cellulose.

 

Its

 

analysis

 

in

 

PCA

 

results

 

in

a

 

singular

 

matrix

 

which

 

distorts

 

its

 

results.

3.

 

Results

 

and

 

discussion

The

 

average

 

moisture

 

content

 

in

 

willow

 

stems

 

was

 

50.66%

(

Table

 

1

).

 

The

 

significantly

 

lowest

 

moisture

 

content

 

was

 

found

 

in

biomass

 

of

 

Tur

 

Salix

 

viminalis

 

(47.34%).

 

The

 

moisture

 

content

 

in

the

 

other

 

cultivars

 

ranged

 

from

 

49.53

 

to

 

53.18%,

 

for

 

UWM

 

035

 

Salix

pentandra

 

and

 

UWM

 

155

 

Salix

 

dasyclados,

 

respectively.

 

The

 

average

ash

 

content

 

was

 

1.30%

 

for

 

all

 

of

 

the

 

cultivars

 

under

 

study

 

(

Table

 

1

).

The

 

significantly

 

lowest

 

ash

 

content

 

was

 

found

 

in

 

biomass

 

of

 

the

UWM

 

006

 

Salix

 

viminalis

 

clone

 

(1.04%

 

d.m.).

 

A

 

slightly

 

significantly

higher

 

ash

 

content

 

was

 

found

 

in

 

the

 

Turbo

 

and

 

Tur

 

varieties.

 

The

significantly

 

highest

 

ash

 

content

 

was

 

found

 

in

 

the

 

UWM

 

035

 

Salix

pentandra

 

clone

 

(1.60%

 

d.m.).

 

The

 

average

 

higher

 

heating

 

value

(HHV)

 

of

 

willow

 

biomass

 

was

 

19.50

 

MJ

 

kg

−1

d.m.

 

(

Table

 

1

).

 

The

homogenous

 

group

 

with

 

the

 

highest

 

HHV

 

included

 

the

 

Tur

 

vari-

ety,

 

the

 

UWM

 

035

 

Salix

 

pentandra

 

and

 

UWM

 

006

 

Salix

 

viminalis

clones.

 

The

 

HHV

 

for

 

them

 

was

 

19.54–19.58

 

MJ

 

kg

−1

d.m.

 

The

 

vari-

ability

 

of

 

the

 

feature

 

in

 

the

 

other

 

clones

 

may

 

be

 

regarded

 

as

 

small,

though

 

statistically

 

significant.

 

The

 

difference

 

between

 

the

 

Tur

 

vari-

ety

 

and

 

the

 

UWM

 

155

 

Salix

 

dasyclados

 

clone

 

with

 

the

 

lowest

 

HHV

was

 

0.22

 

MJ

 

kg

−1

d.m.

 

A

 

higher

 

diversity

 

between

 

the

 

clones

 

and

varieties

 

under

 

study

 

was

 

shown

 

to

 

exist

 

in

 

the

 

lower

 

heating

 

value

(LHV).

 

Its

 

average

 

value

 

was

 

8.38

 

MJ

 

kg

−1

(

Table

 

1

).

 

The

 

highest

 

LHV

was

 

determined

 

for

 

the

 

Tur

 

Salix

 

viminalis

 

variety

 

(9.16

 

MJ

 

kg

−1

).

The

 

second

 

homogeneous

 

group

 

included

 

the

 

UWM

 

035

 

Salix

 

pen-

tandra

 

clone

 

with

 

the

 

LHV

 

lower

 

by

 

0.50

 

MJ

 

kg

−1

.

 

The

 

other

 

clones

and

 

varieties

 

made

 

up

 

three

 

homogeneous

 

groups

 

with

 

LHV

 

values

ranging

 

from

 

8.42

 

to

 

7.77

 

MJ

 

kg

−1

.

The

 

elemental

 

composition

 

of

 

the

 

clones

 

under

 

study

 

and

 

the

willow

 

grown

 

in

 

the

 

three-year

 

harvest

 

system

 

is

 

shown

 

in

 

Table

 

2

.

The

 

average

 

carbon

 

content

 

in

 

the

 

biomass

 

was

 

50.76%

 

d.m.

 

The

significantly

 

highest

 

content

 

of

 

the

 

element

 

was

 

found

 

in

 

the

 

Tur

variety

 

(51.48%

 

d.m.).

 

The

 

carbon

 

content

 

in

 

the

 

other

 

varieties

and

 

clones

 

was

 

lower

 

by

 

1.15–3.48

 

percentage

 

points,

 

for

 

the

 

Start

variety

 

and

 

the

 

UWM

 

035

 

clone,

 

respectively.

The

 

average

 

hydrogen

 

content

 

was

 

6.11%

 

d.m.

 

It

 

was

 

signifi-

cantly

 

the

 

highest

 

in

 

the

 

Tur

 

variety

 

and

 

the

 

UWM

 

006

 

and

 

UWM

043

 

clones

 

(6.18–6.15%

 

d.m.).

 

The

 

average

 

nitrogen

 

content

 

was

0.47%

 

d.m.,

 

ranging

 

from

 

0.51%

 

d.m.

 

in

 

the

 

UWM

 

035

 

clone

 

to

0.43%

 

d.m.

 

in

 

the

 

Start

 

variety

 

and

 

the

 

UWM

 

006

 

clone.

 

The

 

willow

biomass

 

contained

 

a

 

small

 

percentage

 

of

 

sulphur,

 

whose

 

average

content

 

was

 

0.025%

 

d.m.

 

The

 

willow

 

varieties

 

and

 

clones

 

under

study

 

made

 

up

 

two

 

homogeneous

 

groups

 

in

 

which

 

the

 

sulphur

 

con-

tent

 

ranged

 

from

 

0.020

 

to

 

0.030%

 

d.m.

 

The

 

average

 

chlorine

 

content

was

 

also

 

low-0.019%

 

d.m.

 

It

 

was

 

the

 

significantly

 

highest

 

in

 

biomass

of

 

the

 

Start

 

variety

 

(0.028%

 

d.m.)

 

and

 

was

 

the

 

lowest

 

in

 

the

 

UWM

043

 

clone

 

(0.011%

 

d.m.).

The

 

thermophysical

 

properties

 

and

 

the

 

elemental

 

composition

of

 

the

 

willow

 

varieties

 

and

 

clones

 

under

 

study

 

are

 

typical

 

of

 

fresh

biomass

 

of

 

short

 

rotation

 

coppices

 

such

 

as

 

willow,

 

poplar

 

and

 

black

locust.

 

The

 

higher

 

heating

 

value

 

of

 

the

 

cultivars

 

under

 

study

 

was

within

 

the

 

limits

 

typical

 

of

 

SRC

 

and

 

hardwood

 

(

Klasnja

 

et

 

al.,

 

2002;

Van

 

Loo

 

and

 

Koppejan,

 

2008

).

 

This

 

parameter

 

largely

 

depends

 

on

the

 

carbon

 

and

 

hydrogen

 

content

 

in

 

biomass

 

and

 

it

 

is

 

much

 

lower

than

 

for

 

fossil

 

fuels.

 

The

 

moisture

 

content

 

in

 

the

 

three-year

 

stems

ranged

 

from

 

49.53%

 

to

 

53.18%.

 

In

 

other

 

studies,

 

it

 

was

 

shown

 

to

range

 

between

 

45%

 

and

 

60%,

 

depending

 

on

 

the

 

species,

 

harvest

time,

 

harvest

 

conditions

 

and

 

rotation

 

length

 

(

Kauter

 

et

 

al.,

 

2003;

Stolarski

 

et

 

al.,

 

2013a

).

 

Lignocellulosic

 

biomass

 

obtained

 

in

 

long

rotations,

 

i.e.

 

from

 

older

 

trees

 

and

 

coppices,

 

contains

 

less

 

moisture,

which

 

results

 

in

 

its

 

higher

 

LHV.

 

The

 

willow

 

biomass

 

moisture

 

con-

tent

 

may

 

be

 

twice

 

as

 

high

 

compared

 

to

 

herbaceous

 

energy

 

crops

 

and

straw,

 

which

 

is

 

important

 

for

 

selecting

 

the

 

method

 

of

 

its

 

conver-

sion

 

in

 

an

 

integrated

 

biorefinery

 

(

Clifton-Brown

 

and

 

Lewandowski,

2002

).

 

If

 

fresh

 

biomass

 

is

 

to

 

be

 

used

 

as

 

feedstock

 

for

 

manufacturing

chemical

 

products

 

from

 

hemicelluloses,

 

a

 

high

 

moisture

 

content

 

is

not

 

usually

 

an

 

obstacle

 

in

 

its

 

pre-processing.

 

However,

 

the

 

ther-

mal

 

and

 

thermochemical

 

conversion

 

may

 

be

 

hindered.

 

If

 

that

 

is

 

the

case,

 

logistical

 

solutions

 

should

 

be

 

sought

 

in

 

which

 

biomass

 

could

be

 

delivered

 

with

 

lower

 

moisture

 

content.

 

To

 

reduce

 

it,

 

one

 

can

 

har-

vest

 

whole

 

willow

 

stems

 

(two-stage

 

harvest),

 

which

 

can

 

later

 

be

seasoned,

 

which

 

results

 

in

 

a

 

moisture

 

content

 

decrease

 

by

 

20–30%

(

Gigler

 

et

 

al.,

 

2000;

 

Stolarski

 

et

 

al.,

 

2012

).

 

Thus

 

stored,

 

biomass

 

can

be

 

delivered

 

to

 

a

 

biorefinery

 

as

 

needed.

 

However,

 

a

 

two-stage

 

har-

vest

 

is

 

more

 

expensive

 

than

 

when

 

willow

 

is

 

harvested

 

in

 

one

 

stage.

In

 

one

 

stage

 

technology,

 

biomass

 

is

 

obtained

 

as

 

chips

 

which

 

are

 

not

too

 

good

 

for

 

storage.

 

Piles

 

of

 

such

 

wood

 

biomass

 

undergo

 

intensive

processes

 

of

 

microbiological

 

decomposition,

 

as

 

a

 

consequence

 

of

which

 

as

 

much

 

as

 

20–30%

 

of

 

wood

 

can

 

be

 

lost.

 

However,

 

moisture

content

 

in

 

the

 

biomass

 

will

 

still

 

be

 

high

 

compared

 

to

 

fossil

 

fuels,

such

 

as

 

coal,

 

which

 

is

 

a

 

hydrophobic

 

product.

 

Obviously,

 

biomass

can

 

be

 

processed

 

to

 

make

 

briquette

 

and

 

pellet

 

or

 

carbonised,

 

but

this

 

requires

 

additional

 

energy

 

outlays

 

and

 

increases

 

the

 

cost

 

of

biorefinery

 

feedstock.

A

 

short

 

rotation

 

willow

 

coppice

 

usually

 

contains

 

small

 

amounts

of

 

ash,

 

sulphur

 

and

 

chlorine,

 

much

 

less

 

than

 

the

 

biomass

 

of

 

herba-

ceous

 

energy

 

crops

 

and

 

agricultural

 

residues.

 

These

 

components

have

 

an

 

adverse

 

effect

 

on

 

the

 

thermal,

 

thermochemical

 

and

 

bio-

chemical

 

conversion

 

of

 

biomass.

 

Compared

 

to

 

willow,

 

herbaceous

crops

 

and

 

residues,

 

depending

 

on

 

the

 

species,

 

may

 

contain

 

as

much

 

as

 

6

 

times

 

more

 

ash

 

and

 

4

 

times

 

more

 

chlorine

 

and

 

sulphur

(

Greenhalf

 

et

 

al.,

 

2012;

 

Osowski

 

and

 

Fahlenkamp,

 

2006;

 

Stolarski

et

 

al.,

 

2013b

).

The

 

content

 

of

 

substances

 

soluble

 

in

 

cold

 

and

 

hot

 

water,

 

ethanol

and

 

pH

 

of

 

biomass

 

are

 

shown

 

in

 

Table

 

3

.

 

The

 

average

 

pH

 

of

 

biomass

of

 

the

 

varieties

 

and

 

clones

 

under

 

study

 

was

 

6.03

 

and

 

its

 

values

 

lay

within

 

the

 

range

 

from

 

5.79

 

to

 

6.25.

 

The

 

average

 

content

 

of

 

sub-

stances

 

soluble

 

in

 

cold

 

and

 

hot

 

water

 

was

 

5.75%

 

and

 

7.38%

 

d.m.

 

The

significantly

 

highest

 

content

 

of

 

cold

 

water-soluble

 

substances

 

was

found

 

in

 

the

 

UWM

 

155

 

clone

 

(6.54%

 

d.m.),

 

while

 

their

 

content

 

in

the

 

Start

 

variety

 

(the

 

last

 

homogeneous

 

group)

 

was

 

lower

 

by

 

2.17

percentage

 

points.

 

The

 

significantly

 

highest

 

content

 

of

 

hot

 

water-

soluble

 

substances

 

was

 

found

 

in

 

the

 

UWM

 

035,

 

UWM

 

155

 

clones

and

 

in

 

the

 

Tur

 

variety

 

(7.91–7.97%

 

d.m.).

 

The

 

homogeneous

 

group

with

 

significantly

 

the

 

lowest

 

value

 

of

 

hot

 

water-soluble

 

substances

was

 

made

 

up

 

by

 

the

 

UWM

 

043

 

clone

 

and

 

the

 

Start

 

variety.

The

 

average

 

holocellulose

 

content

 

was

 

75.41%

 

and

 

it

 

ranged

from

 

73.51%

 

d.m.

 

(UWM

 

155)

 

to

 

76.78%

 

d.m.

 

(UWM

 

043)

 

(

Table

 

4

).

M.

 

Krzy ˙zaniak

 

et

 

al.

 

/

 

Industrial

 

Crops

 

and

 

Products

 

58

 

(2014)

 

230–237

 

233

Table

 

1

Thermophysical

 

properties

 

of

 

willow

 

biomass.

Variety

 

or

 

clone

 

Moisture

 

content

 

(%)

 

Ash

 

content

 

(%

 

d.m.)

 

Higher

 

heating

 

value

 

(MJ

 

kg

−1

d.m.)

 

Lower

 

heating

 

value

 

(MJ

 

kg

−1

)

Start

 

50.81

 

±

 

0.99

 

c

 

1.35

 

±

 

0.02

 

c

 

19.48

 

±

 

0.01

 

b

 

8.35

 

±

 

0.21

 

c

Tur

 

47.34

 

±

 

0.30

 

e

1.19

 

±

 

0.02

 

d

19.58

 

±

 

0.03

 

a

 

9.16

 

±

 

0.05

 

a

Turbo

 

52.34

 

±

 

0.47

 

b

 

1.13

 

±

 

0.07

 

d

 

19.47

 

±

 

0.04

 

b

 

8.00

 

±

 

0.12

 

d

UWM

 

006

 

50.59

 

±

 

0.17

 

c

 

1.04

 

±

 

0.01

 

e

 

19.54

 

±

 

0.07

 

a

 

8.42

 

±

 

0.07

 

c

UWM

 

035

 

49.53

 

±

 

0.21

 

d

 

1.60

 

±

 

0.01

 

a

 

19.56

 

±

 

0.03

 

a

 

8.66

 

±

 

0.03

 

b

UWM

 

043

 

50.86

 

±

 

0.06

 

c

 

1.30

 

±

 

0.04

 

c

 

19.49

 

±

 

0.05

 

b

 

8.34

 

±

 

0.01

 

c

UWM

 

155

 

53.18

 

±

 

0.46

 

a

 

1.50

 

±

 

0.11

 

b

 

19.36

 

±

 

0.04

 

c

 

7.77

 

±

 

0.12

 

e

Mean

 

50.66

 

±

 

1.84

 

1.30

 

±

 

0.19

 

19.50

 

±

 

0.08

 

8.38

 

±

 

0.43

±,

 

standard

 

deviation.

 

a.

 

b.

 

c,

 

.

 

.

 

.,

 

homogenous

 

groups.

Table

 

2

Elemental

 

analysis

 

of

 

the

 

willow

 

biomass.

Variety

 

or

 

clone

 

C

 

(%

 

d.m.)

 

H

 

(%

 

d.m.)

 

N

 

(%

 

d.m.)

 

S

 

(%

 

d.m.)

 

Cl

 

(%

 

d.m.)

Start

 

50.33

 

±

 

0.23

 

c

6.04

 

±

 

0.01

 

c

 

0.43

 

±

 

0.01

 

c

 

0.024

 

±

 

0.002

 

b

 

0.028

 

±

 

0.005

 

a

Tur

 

51.48

 

±

 

0.16

 

a

 

6.18

 

±

 

0.01

 

a

 

0.44

 

±

 

0.00

 

c

 

0.021

 

±

 

0.001

 

b

 

0.020

 

±

 

0.004

 

b

Turbo

 

50.69

 

±

 

0.18

 

c

 

6.12

 

±

 

0.04

 

b

 

0.46

 

±

 

0.00

 

b

 

0.028

 

±

 

0.002

 

a

 

0.025

 

±

 

0.006

 

b

UWM

 

006

 

50.62

 

±

 

0.21

 

c

 

6.17

 

±

 

0.04

 

a

 

0.43

 

±

 

0.01

 

c

 

0.020

 

±

 

0.001

 

c

 

0.020

 

±

 

0.001

 

b

UWM

 

035

 

51.00

 

±

 

0.14

 

b

 

6.07

 

±

 

0.01

 

c

 

0.51

 

±

 

0.02

 

a

 

0.022

 

±

 

0.001

 

b

 

0.012

 

±

 

0.004

 

c

UWM

 

043

50.58

 

±

 

0.05

 

c

6.15

 

±

 

0.01

 

a

0.53

 

±

 

0.02

 

a

 

0.030

 

±

 

0.000

 

a

 

0.011

 

±

 

0.001

 

c

UWM

 

155

 

50.62

 

±

 

0.23

 

c

 

6.04

 

±

 

0.00

 

c

 

0.52

 

±

 

0.01

 

a

 

0.027

 

±

 

0.000

 

a

 

0.019

 

±

 

0.001

 

b

Mean

 

50.76

 

±

 

0.39

 

6.11

 

±

 

0.06

 

0.47

 

±

 

0.04

 

0.025

 

±

 

0.004

 

0.019

 

±

 

0.007

±,

 

standard

 

deviation.

 

a.

 

b.

 

c,

 

.

 

.

 

.,

 

homogenous

 

groups.

Table

 

3

The

 

content

 

of

 

substances

 

soluble

 

in

 

ethanol

 

and

 

cold

 

and

 

hot

 

water

 

in

 

willow

 

biomass.

Variety

 

or

 

clone

 

Substances

 

soluble

 

in

 

cold

 

water

 

(%

 

d.m.)

 

Substances

 

soluble

 

in

 

hot

 

water

 

(%

 

d.m.)

 

Substances

 

soluble

 

in

 

ethanol

 

(%

 

d.m.)

 

pH

Start

 

4.37

 

±

 

0.12

 

d

6.58

 

±

 

0.06

 

d

5.15

 

±

 

0.11

 

d

 

6.25

 

±

 

0.08

 

a

Tur

 

6.00

 

±

 

0.22

 

b

 

7.91

 

±

 

0.13

 

a

 

7.49

 

±

 

0.23

 

b

 

5.79

 

±

 

0.04

 

d

Turbo

 

5.87

 

±

 

0.19

 

b

 

7.55

 

±

 

0.33

 

b

 

6.96

 

±

 

0.18

 

c

 

6.07

 

±

 

0.05

 

b

UWM

 

006

 

5.83

 

±

 

0.18

 

b

 

7.08

 

±

 

0.00

 

c

 

6.58

 

±

 

0.34

 

c

 

5.91

 

±

 

0.03

 

c

UWM

 

035

 

6.21

 

±

 

0.06

 

b

 

7.97

 

±

 

0.12

 

a

 

8.49

 

±

 

0.10

 

a

 

6.14

 

±

 

0.10

 

b

UWM

 

043

 

5.40

 

±

 

0.23

 

c

 

6.61

 

±

 

0.29

 

d

 

4.52

 

±

 

0.23

 

e

 

6.03

 

±

 

0.01

 

b

UWM

 

155

 

6.54

 

±

 

0.38

 

a

 

7.95

 

±

 

0.10

 

a

 

6.80

 

±

 

0.24

 

c

 

6.03

 

±

 

0.09

 

b

Mean

 

5.75

 

±

 

0.69

 

7.38

 

±

 

0.61

 

6.57

 

±

 

1.29

 

6.03

 

±

 

0.15

±,

 

standard

 

deviation.

 

a.

 

b.

 

c,

 

.

 

.

 

.,

 

homogenous

 

groups.

The

 

average

 

content

 

of

 

cellulose

 

was

 

44.37%

 

d.m.

 

Its

 

significantly

highest

 

content

 

(47.64%

 

d.m.)

 

was

 

found

 

in

 

the

 

UWM

 

043

 

clone.

The

 

biomass

 

of

 

the

 

UWM

 

006

 

clone

 

contained

 

less

 

cellulose

 

by

 

2.33

percentage

 

points.

 

The

 

significantly

 

lowest

 

content

 

of

 

cellulose

 

was

found

 

in

 

biomass

 

of

 

the

 

UWM

 

035

 

clone

 

which

 

was

 

lower

 

by

 

5.28

percentage

 

points

 

than

 

in

 

biomass

 

of

 

the

 

UWM

 

043

 

clone.

The

 

average

 

content

 

of

 

substances

 

soluble

 

in

 

1%

 

NaOH

 

was

26.86%

 

d.m.

 

(

Table

 

4

).

 

The

 

significantly

 

highest

 

content

 

of

 

those

substances

 

was

 

found

 

in

 

biomass

 

of

 

the

 

UWM

 

155

 

clone

 

(28.24%

d.m.).

 

Significantly

 

(though

 

only

 

slightly)

 

less

 

substances

 

soluble

 

in

1%

 

NaOH

 

was

 

found

 

in

 

the

 

Turbo

 

variety

 

(less

 

by

 

0.94

 

percentage

point)

 

and

 

the

 

least

 

(significantly)

 

was

 

in

 

the

 

UWM

 

043

 

clone

 

(less

by

 

2.87

 

percentage

 

points).

 

The

 

average

 

content

 

of

 

hemicellulose,

obtained

 

after

 

subtracting

 

the

 

content

 

of

 

cellulose

 

from

 

that

 

of

holocellulose,

 

was

 

31.04%

 

d.m.

 

(

Table

 

4

).

 

The

 

significantly

 

highest

content

 

of

 

these

 

substances

 

was

 

found

 

in

 

biomass

 

of

 

the

 

Tur

variety

 

(33.03%

 

d.m.).

 

The

 

second

 

homogeneous

 

group

 

comprised

the

 

UWM

 

035

 

clone,

 

which

 

contained

 

less

 

hemicellulose

 

by

 

1.23

percentage

 

points.

 

The

 

other

 

cultivars

 

contained

 

from

 

31.16

 

(Start)

to

 

29.14%

 

d.m.

 

(UWM

 

043)

 

of

 

hemicelluloses.

 

The

 

average

 

content

of

 

pentosans

 

in

 

the

 

biomass

 

of

 

the

 

varieties

 

and

 

clones

 

under

 

study

was

 

20.93%

 

d.m.

 

(

Table

 

4

).

 

However,

 

it

 

should

 

be

 

pointed

 

out

 

that

it

 

did

 

not

 

vary

 

statistically.

 

Six

 

clones

 

made

 

up

 

a

 

homogeneous

group,

 

with

 

the

 

highest

 

content

 

of

 

those

 

substances

 

(from

 

20.85

to

 

21.15%

 

d.m.).

 

A

 

second

 

homogeneous

 

group

 

with

 

the

 

lowest

pentosan

 

content

 

included

 

only

 

the

 

Tur

 

variety

 

(20.38%

 

d.m.).

Table

 

4

Chemical

 

composition

 

of

 

willow

 

biomass.

Variety

 

or

 

clone

 

Holocellulose

 

(%

 

d.m.)

 

Cellulose

 

(%

 

d.m.)

 

Hemicelluloses

a

(%

 

d.m.)

 

Substances

 

soluble

 

in

 

1%

 

NaOH

 

(%

 

d.m.)

 

Pentosans

 

(%

 

d.m.)

 

Lignin

 

(%

 

d.m.)

Start

 

74.94

 

±

 

0.40

 

b

 

43.78

 

±

 

0.26

 

c

 

31.16

 

±

 

0.41

 

c

 

26.53

 

±

 

0.28

 

c

 

20.98

 

±

 

0.50

 

a

 

26.33

 

±

 

0.18

 

a

Tur

 

76.74

 

±

 

0.45

 

a

 

43.70

 

±

 

0.39

 

c

 

33.03

 

±

 

0.65

 

a

 

26.75

 

±

 

0.25

 

c

 

20.38

 

±

 

0.17

 

b

 

26.22

 

±

 

0.11

 

a

Turbo

 

75.56

 

±

 

0.51

 

b

 

44.89

 

±

 

0.32

 

b

 

30.66

 

±

 

0.46

 

d

 

27.30

 

±

 

0.21

 

b

 

20.85

 

±

 

0.22

 

a

 

25.81

 

±

 

0.49

 

a

UWM

 

006

 

76.19

 

±

 

1.17

 

a

 

45.31

 

±

 

0.44

 

b

 

30.88

 

±

 

0.73

 

c

 

26.82

 

±

 

0.06

 

c

 

21.32

 

±

 

0.05

 

a

 

24.62

 

±

 

0.26

 

b

UWM

 

035

 

74.16

 

±

 

0.64

 

c

 

42.36

 

±

 

0.04

 

e

 

31.80

 

±

 

0.61

 

b

 

27.01

 

±

 

0.10

 

c

 

20.94

 

±

 

0.27

 

a

 

24.98

 

±

 

0.08

 

b

UWM

 

043

76.78

 

±

 

0.37

 

a

47.64

 

±

 

0.38

 

a

 

29.14

 

±

 

0.75

 

e

 

25.37

 

±

 

0.06

 

d

 

20.87

 

±

 

0.29

 

a

 

24.65

 

±

 

0.19

 

b

UWM

 

155

 

73.51

 

±

 

0.14

 

c

 

42.88

 

±

 

0.25

 

d

 

30.63

 

±

 

0.40

 

d

 

28.24

 

±

 

0.18

 

a

 

21.15

 

±

 

0.26

 

a

 

25.99

 

±

 

0.37

 

a

Mean

 

75.41

 

±

 

1.31

 

44.37

 

±

 

1.70

 

31.04

 

±

 

1.24

 

26.86

 

±

 

0.83

 

20.93

 

±

 

0.37

 

25.52

 

±

 

0.74

±,

 

standard

 

deviation.

 

a.

 

b.

 

c,

 

.

 

.

 

.,

 

homogenous

 

groups.

a

Calculated

 

theoretical

 

value.