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Industrial
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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
,
Mariusz
J.
Stolarski
,
Bogusława
Waliszewska
,
Stefan
Szczukowski
,
Józef
Tworkowski
,
Dariusz
Załuski
,
Malwina ´Snieg
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
For
example,
the
average
price
of
oil
supplied
by
OPEC
countries
increased
from
23
to
almost
110
USD
per
barrel
between
2001
and
2012
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
(
These
changes
will
have
serious
environ-
mental
effects:
they
will
increase
droughts,
coral
bleaching
and
∗ Corresponding
author.
Tel.:
+48
895246146.
address:
(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
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
(
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
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
(
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)
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
(
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
(
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
(
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
(
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
(
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
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)
(
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%
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
(
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.
(
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
(
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
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
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
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
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%
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
The
content
of
substances
soluble
in
cold
and
hot
water,
ethanol
and
pH
of
biomass
are
shown
in
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)
(
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.
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.
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.
(
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
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.
234
M.
Krzy ˙zaniak
et
al.
/
Industrial
Crops
and
Products
58
(2014)
230–237
The
average
lignin
content
in
willow
biomass
was
25.52%
d.m.
Its
highest
content
was
found
in
the
Start
variety
(26.33%
d.m.).
The
same
homogeneous
group
with
the
statistically
highest
lignin
con-
tent
included
the
Tur,
Turbo
varieties
and
the
UWM
155
clone.
The
other
clones
made
up
a
homogeneous
group
with
lignin
contents
ranging
from
24.62%
to
24.98%
d.m.
Willow
wood
is
commonly
used
as
feedstock
in
the
production
of
heat
and
power,
chipboards,
hardboards,
paper,
cardboard,
etc.
Because
of
strong
competi-
tion
in
the
market,
these
products
are
widely
available
and
cheap.
Traditional
processes
for
paper
production
use
cellulose,
whose
content
in
wood
biomass
is
50%
d.m.
or
less.
Hemicelluloses
and
lignin,
in
the
paper
industry,
are
often
undesirable
waste,
which
is
nowadays
also
used
in
the
production
of
low-value
products
such
as
heat
or
process
steam.
The
aim
of
an
integrated
multi-
product
biorefinery
is
to
produce
the
highest
possible
volume
of
high-value
products
from
cellulose,
hemicelluloses
and
lignin.
The
production
of
low
value-products
is
a
secondary
priority.
Impor-
tantly,
practically
all
of
the
biomass
components
should
be
used
and
a
modern
refinery
should
produce
as
little
waste
as
possible.
High-value
products
made
from
lignocelluloses
include
speciality
cellulose,
used
in
the
manufacturing
of
cosmetics,
textiles,
pharma-
ceutical,
tyres
and
more.
Another
derivative,
not
less
important,
is
levulinic
acid,
which
is
a
precursor
of
many
pharmaceuticals,
plas-
ticizers
and
a
platform
for
biofuels.
Hemicelluloses
are
also
used
in
the
production
of
ethanol
and
furfural.
The
latter
can
be
used
as
a
feedstock
for
the
production
of
several
non-petroleum
derived
chemicals,
e.g.
furfuryl
alcohol,
methyltetrahydrofuran
and
furan
Lignin,
whose
con-
tent
in
biomass
ranges
from
15%
to
30%,
is
very
difficult
to
process
due
to
its
properties.
It
is
often
burned
to
produce
heat
and
process
steam.
Currently,
it
is
increasingly
often
used
to
produce
syngas.
On
the
other
hand,
it
can
be
potentially
used
as
a
raw
material
for
manufacturing
high-value
products,
e.g.
vanillin,
biopoly-
mers
in
petro-chemistry,
pesticides
and
others
A
Bartlett
test
(U
=
912;
df
=
153;
p
=
0.000)
confirmed
that
the
use
of
PCA
method
to
analyse
the
thermophysical
and
chemi-
cal
properties
of
the
biomass
was
justified.
The
eigenvalues
and
Kaiser’s
criterion
were
used
to
select
5
factors,
which
explain
90.6%
of
the
total
variability
(
The
Varimax
rotation
was
used
to
improve
the
(raw)
structure.
The
rotated
loadings
show
that
components
F1
and
F2
combined
explain
more
than
48%
of
the
vari-
ability
(24.5%
and
23.9%),
which
is
the
largest
part
of
explaining
the
variance
among
the
five
analysed
components.
Subsequent
factors,
i.e.
F4,
F3
and
F5,
contribute
decreasing
parts
of
the
variability
being
explained
–
they
equalled
18.6,
14.8
and
8.9,
respectively.
The
structure
of
factorial
loadings
(which
may
be
construed
in
a
similar
way
to
correlation
coefficients)
revealed
that
the
ther-
mophysical
properties
which
affect
the
energy
value,
such
as
LHV,
moisture
content,
HHV,
sulphur
and
carbon,
are
associated
with
F1
most
strongly.
The
following
interpretation
can
be
developed
from
these
loadings:
24.5%
of
variability
of
the
phenomena
arises
from
the
effect
of
moisture
content
on
the
other
parameters,
because
an
increase
in
moisture
content
(0.94)
is
accompanied
by
decreasing
LHV
(
−0.95),
HHV
(
−0.86)
and
(
−0.59),
and
increasing
sulphur
con-
tent
(0.76).
Subsequent
groups
F2
and
F3
in
separate
components
determine
the
features
of
chemical
composition
of
biomass.
F2
contributes
relatively
a
lot
to
explaining
variability
(23.9%)
and
it
is
most
strongly
associated
with
hot
water-soluble
substances
(0.94),
ethanol-soluble
substances
(0.87),
cold
water-soluble
sub-
stances
(0.85)
and
cellulose
(
−0.68).
On
the
other
hand,
F3
informs
about
the
association
of
chlorine
(
−0.93)
nitrogen
(0.84)
and
lignin
(
−0.66).
It
has
been
shown
that
18.6%
of
variance
results
from
the
effect
of
ash
content
(0.83)
on
the
content
of
hydrogen
(
−0.87)
and
holocellulose
(
−0.70).
The
last
of
the
factors
with
the
greatest
effect
Fig.
1.
Biplot
for
analysed
data
without
Varimax
rotation.
on
the
biomass
variability
is
the
presence
of
pentosans
(
−0.85),
which
explains
nearly
9%
of
variance.
Biplot
(
the
similarity
between
genotypes
in
regard
to
the
examined
features
(variables)
which,
owing
to
PCA,
were
assigned
to
five
coordinates
(F1,
F2,
F3,
F4,
F5).
In
order
to
make
interpretation
easy,
only
a
two-dimensional
presentation
of
coor-
dinates
–
F1
(PCA1)
and
F2
(PCA2)
–
was
made,
which
explains
the
highest
percentage
of
variance
(variability).
The
diagram
shows
that
the
genotypes
differed
in
terms
of
their
physical
and
chemical
properties.
The
UWM
043
clone
contained
the
highest
percent
of
cellulose.
The
UWM
035
clone
was
on
the
other
end
of
the
spectrum,
containing
a
small
percent
of
cellulose,
but
many
substances
soluble
in
1%
NaOH,
in
ethanol
as
well
as
in
cold
and
hot
water.
The
properties
of
clone
UWM
155
biomass
were
similar,
the
only
difference
being
its
higher
moisture
content.
On
the
other
hand,
the
Tur
variety
contained
a
high
percent
of
carbon,
it
had
a
high
LHV
and
low
moisture
content.
Among
all
tested
willow
cultivars,
the
highest
yield
was
given
by
the
clone
UWM
006.
The
UWM
043
clone
was
in
the
second
homogeneous
group.
Start
and
Turbo
varieties
were
allocated
to
the
third
homogeneous
group.
After
recalculation
of
obtained
results
to
one
year
of
plant
cultivation,
the
yield
of
dry
matter
ranged
from
2.79
to
14.23
Mg
ha
−1
year
−1
d.m.
for
clones
UWM
155
and
UWM
006,
respectively
The
average
content
of
holocellulose
in
the
biomass
of
the
crops
under
study
was
5.50
Mg
ha
−1
year
−1
d.m.
A
high
standard
devia-
tion
(3.09)
indicates
that
great
variability
exists
between
the
yield
of
the
varieties
and
clones
under
study.
The
significantly
highest
yield
of
holocellulose
was
harvested
with
the
biomass
of
the
UWM
006
clone
(10.84
Mg
ha
−1
year
−1
d.m.).
It
was
higher
by
over
22%
than
that
of
the
UWM
043
clone.
The
statistically
lowest
content
of
this
substance
was
found
in
the
plants
of
the
Tur
variety
and
the
UWM
155
clone.
Their
yields
of
holocellulose
were
lower
by
74%
and
81%,
respectively.
The
cellulose
yield
in
dry
willow
biomass
ranged
widely,
depending
on
the
cultivar’s
dry
matter
yield.
The
aver-
age
cellulose
content
for
all
the
cultivars
under
study
was
M.
Krzy ˙zaniak
et
al.
/
Industrial
Crops
and
Products
58
(2014)
230–237
235
Table
5
Raw
(no
rotation)
and
rotated
(Varimax
rotation)
factorial
loadings.
Feature
No
rotation
Varimax
rotation
F1
F2
F3
F4
F5
F1
F2
F3
F4
F5
Moisture
content
−0.89
0.14
−0.06
0.38
0.03
0.94
−0.02
−0.02
0.16
−0.26
Ash
−0.47
−0.46
−0.28
−0.63
−0.10
0.05
0.21
0.40
0.83
0.15
HHV
0.78
0.03
0.01
−0.31
0.30
−0.86
−0.09
0.06
−0.18
−0.11
LHV
0.90
−0.13
0.05
−0.38
0.00
−0.95
0.01
0.02
−0.16
0.23
C
0.71
−0.57
−0.13
0.01
−0.25
−0.59
0.55
0.11
−0.25
0.42
H
0.78
0.24
−0.17
0.44
−0.04
−0.35
−0.02
0.09
−0.87
0.07
S
−0.63
0.34
−0.34
0.11
−0.45
0.76
−0.29
0.33
0.07
0.26
N
−0.42
−0.08
−0.83
−0.17
−0.26
0.39
0.07
0.84
0.24
0.19
Cl
−0.17
0.06
0.90
0.26
−0.12
0.22
−0.07
−0.93
0.01
0.07
Substance
solube
in
cold
water
0.03
−0.68
−0.52
0.45
0.02
0.14
0.85
0.39
−0.21
−0.01
Substance
solube
in
hot
water
0.08
−0.92
−0.16
0.19
−0.07
−0.08
0.94
0.08
0.08
0.16
Substance
solube
in
ethanol
0.24
−0.89
−0.06
0.04
0.21
−0.36
0.87
0.02
0.13
−0.06
Substance
solube
in
1%
NaOH
−0.42
−0.76
0.23
0.37
0.06
0.37
0.80
−0.33
0.24
−0.08
Cellullose
0.16
0.88
−0.33
0.26
−0.08
0.19
−0.68
0.30
−0.63
−0.06
Holocellulose
0.69
0.58
−0.07
0.15
−0.15
−0.35
−0.47
0.06
−0.70
0.17
Lignin
−0.14
−0.30
0.68
−0.05
−0.56
0.11
0.15
−0.66
0.28
0.59
Pentosans
−0.48
0.12
−0.02
0.19
0.75
0.32
−0.01
−0.03
0.13
−0.85
pH
−0.66
0.18
0.13
−0.57
0.13
0.24
−0.40
0.00
0.76
−0.17
Eigenvalue
i
5.58
4.70
2.69
1.92
1.42
4.40
4.30
2.66
3.35
1.60
Share
(%)
31.0
26.1
14.9
10.7
7.9
24.5
23.9
14.8
18.6
8.9
3.27
Mg
ha
−1
year
−1
d.m.
(
Its
significantly
highest
content
was
found
for
the
UWM
006
clone
(6.45
Mg
ha
−1
year
−1
).
A
high
cellulose
yield
(although
lower
by
18%)
was
determined
in
the
UWM
043
clone.
The
significantly
lowest
yield
of
the
substance
was
obtained
from
the
UWM
155.
The
amount
was
five
times
smaller
than
in
the
UWM
006
clone.
The
average
theoretical
yield
of
hemicellulose
in
the
biomass
of
all
the
varieties
and
clones
was
2.23
Mg
ha
−1
year
−1
d.m.
The
standard
deviation
was
high
–
1.20.
As
for
holocellulose
and
cel-
lulose,
the
significantly
highest
content
of
hemicellulose
was
found
in
biomass
of
the
UWM
006
clone
(4.40
Mg
ha
−1
year
−1
d.m.)
and
the
lowest
was
in
that
of
UWM
155
(0.85
Mg
ha
−1
year
−1
d.m.).
An
analysis
of
the
data
shows
that
the
largest
amounts
of
cellu-
lose
and
hemicelluloses
can
be
obtained
from
the
UWM
006
clone,
whose
yield
per
1
ha
is
the
highest.
Willow
cultivars
should
be
cho-
sen
to
obtain
the
highest
biomass
yield,
and
not
only
the
content
of
the
substances
mentioned
above,
as
fluctuations
in
the
content
of
cellulose
can
exceed
10%.
The
differences
in
cellulose
yield
per
1
ha,
recorded
in
this
study,
exceeded
500%.
Therefore,
if
differ-
ences
in
yield
are
great,
one
can
choose
a
species
whose
yield
is
Fig.
2.
The
yield
of
dry
biomass,
holocellulose,
cellulose
and
hemicelluloses
(theoretical
value)
harvested
with
the
biomass
of
willow
cultivars;
the
error
bars
show
the
standard
deviation;
a,
b,
c,
.
.
.
homogenous
groups.
236
M.
Krzy ˙zaniak
et
al.
/
Industrial
Crops
and
Products
58
(2014)
230–237
high,
which
will
reduce
the
cost
of
production,
harvest
and
trans-
port
of
biomass
and,
in
consequence,
the
cost
of
feedstock
for
a
biorefinery.
These
willow
cultivars
were
tested
for
integrated
biorefineries
in
the
regions
of
Europe
in
which
sufficient
amounts
of
biomass
can
be
produced.
The
area
of
cultivation
of
energy
crops
in
Poland
is
10,202
ha,
with
willow
and
poplar
SRC
being
cultivated
on
6,810
ha.
Along
with
the
average
yield
of
cellulose
and
hemicelluloses
(the-
oretical
value),
it
will
total
over
22,300
tonnes
of
cellulose
and
nearly
15,200
tonnes
of
hemicelluloses
a
year.
The
yield
of
those
substances
would
be
twice
higher
if
biomass
was
obtained
by
grow-
ing
the
UWM
006
Salix
viminalis
clone.
A
still
higher
yield
could
be
obtained
on
better
soils
than
in
this
experiment.
Other
studies
which
involved
the
cultivation
of
SRC
on
good
quality
soils
in
Poland
leads
one
to
the
conclusion
that
the
amount
of
biomass
from
a
com-
mercial
willow
plantation
in
Poland
could
be
still
higher
It
is
noteworthy
that
the
soils
suitable
for
growing
energy
crops
in
Poland
cover
an
area
of
569,000
ha.
These
are
soils
of
lower
usability
for
growing
food
crops.
If
willow
were
grown
on
soils
with
lower
usability
for
cultivation
of
perennial
energy
crops,
the
total
potential
area
of
soils
usable
for
willow
cultivation
would
be
as
high
as
954,000
ha
This
would
provide
a
yield
of
over
3.1
million
tonnes
of
cellulose
and
over
2.1
million
tonnes
of
hemicelluloses.
Some
large
wood
processing
companies
have
already
appreciated
the
possibility
of
obtaining
high
cellu-
lose
yield
from
biomass
of
short
rotation
coppices.
For
example,
International
Paper
Kwidzyn
(Poland)
is
interested
in
increasing
the
area
of
willow
and
poplar
commercial
plantations
for
indus-
trial
purposes.
So
far,
the
company
has
set
up
about
2000
ha
of
SRC
plantations.
4.
Conclusion
The
biomasses
of
the
willow
cultivars
under
study
had
good
thermophysical
compositions
and
they
contained
only
small
amounts
of
undesirable
components,
such
as
ash,
sulphur
or
chlo-
rine.
However,
the
high
moisture
content
in
the
fresh
biomass
may
be
a
problem.
The
content
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
biorefin-
ery,
based
on
lignocellulosic
raw
material.
The
quantity
of
cellulose
and
hemicelluloses
which
can
be
currently
provided
from
the
exist-
ing
SRC
plantations
in
Poland
for
biorefineries
should
not
be
less
than
37,000
tonnes;
in
the
future
it
could
potentially
be
up
to
5.2
million
tonnes
a
year.
Acknowledgements
The
research
leading
to
these
results
has
received
funding
from
the
European
Union
Seventh
Framework
Programme
(FP7/2007-
2013)
under
grant
agreement
no.
241718
EuroBioRef.
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