POSSIBILITIES OF USING OLIVE KERNEL WOOD FOR PELLETS PRODUCTION IN CRETE –
GREECE
John Vourdoubas
TEI of CRETE
Department of Natural resources and environment
Romanou 3, Chalepa
73133, Chania – Crete – Creece
Tel +30-28210-46197, Fax +30-28210-20620
e-mail: gboyrd@tee.gr
ABSTRACT: Wood pellets consist a renewable energy source and are used to day in many EU countries for
heating buildings. Since they find increasing use, various quality standards related with their physical and chemical
characteristics have been introduced. The olive kernel wood is a byproduct of the olive oil producing industry and
its production in Crete – Greece to day is approximately 110.000 tn/year. It is used without any standardization for
heat production in buildings, industries and greenhouses. Currently in Crete its price in relation to its heating value
is low and it can be easily used for pellets production with proper processing. It is necessary though, that its quality
characteristics must comply with the existing EU specifications, particularly in relation with its high ash content.
Keywords: solid biofuels, olive residues, pellets
1.
INTRODUCTION
Renewable
energy
high ash content will create probably problems a)
sources
including
With high aerosol formation in the exit gases and b)
biomass, find increasing use to day in EU countries
with creation of ash slagging in the burner. Probably
for heat production, power generation, and as
its mixing with other wood residues, will reduce the
vehicle fuels.
ash content and the final pellets will have a
Current EU policies for reducing the fossil
permissible ash concentration. Studies of the ash
fuel dependence, and mitigating CO2 emissions,
content of the olive tree wood [ 13 ] , have shown
significantly contribute to that.
that its ash content is 5,5% wt on dry basis.However
Wood pellets consist a renewable and
according to the same researchers other types of
environmentally friendly solid fuel, which is
wood like Eucalyptus , Willow Salix and branches
increasingly used for heat generation in E.U.
and tops from a Scandinavean forest have lower ash
Recently in Greece wood pellets are produced from
content , 0,7% wt ,1,2% wt and 1,9% wt
agricultural residues and the existing agricultural
representively.
byproducts and residues in the country could be
used for the production of large quantities of pellets.
2.
THE USE OF PELLETS AS FUELS
Olive trees grow in many areas in Greece and give
many wood byproducts and residues.
Wood pellets consist a simple and
Olive kernel wood is a byproduct in olive
standardized solid biomass source which is mainly
kernel oil producing factories, and is used for heat
used for heating buildings. Since their chemical
generation. It is an attractive solid fuel since its
energy, is stored solar energy, wood pellets present
price 0.05 €/kg, is relatively low in comparison with
many advantages which are .
its heating value, 3.500-4.000 kcal/kg (16 MJ/kg).
a)
Its transformation in the form of pellets could
improve its use for heating buildings. However the
As a biomass source they have a neutral
impact to the greenhouse effect.
b)
Wood pellets are produced from wood
ash content of the olive kernel wood is higher than
residues which otherwise were going to be
the existing specifications for wood pellets. The
disposed to the environment. The wood
1
c)
pellets industry was initially developed to
energy
countries with many forests like the north
electricity, LPG)
in
Crete,
like
oil,
European countries.
b)
Its availability, all over the year.
Wood pellets are usually consumed near
c)
The use of simple and standardized
the place of their production. Therefore
burning systems.
the environmental impacts from their
The main disadvantages of its use are:
transport are rather low.
d)
sources
a)
Wood pellets consist a clean solid fuel.
makes necessary that the consumer must
Their size is small and they are easily
stored. Their use in simple and their
The lack of its standardization which
buy it directly from the plant.
b)
The absence of fully automated burners,
energy density in high. They are burnt in
makes necessary their regular systematic
modern
cleaning and the removal of the ash. Also
systems
which
are
highly
automated.
Pellets
are
the absence of exit gas filters in small
feeded
in
the
burners
commercial
mechanically and the burning system does not need
frequent cleaning.
They are produced in cylindrical form,
systems,
which
creates
pollution problems.
c)
The lack of social acceptance for its use in
dense populated areas. In many cases the
when wood residues are pressurized in high
neighbours
pressures and their size varies in length 10-30mm
unaccepted odours and pollution.
and width 6-10mm. During their compression their
result, the olive kernel wood does not find
water content is decreased. The E.U. specifications
many applications to day in Crete as a fuel
for the max water content of pellets, when they are
for heat generation and there are not either
used for heating is 10% p.w. The capacity of the
applications for power generation. It
plants producing pellets varies from 100 tn/year to
should be noted that some quantities of
10.000 tn/year. Usually the production of pellets in
raw olive kernel wood are exported to
low capacity plants is not profitable. Various E.U.
other
countries have introduced quality specifications for
analysis of olive kernel wood is presented
the wood pellets and soon will be available common
in table 1.
E.U.
are
protested
countries.
The
against
As a
chemical
E.U. specifications. The prices of wood pellets in
TABLE 1
various E.U. countries are competitive with the oil
CHEMICAL ANALYSIS OF OLIVE KERNEL
prices and this contributes to their success as an
WOOD [ 3 ]
alternative fuels.
3.
OLIVE KERNEL WOOD
Olive kernel wood is a byproduct of the
Water content
6.30%
Ash
8.80%
Organic matter
65.50%
Sulphur
0.11%
Chlorine
0.69%
olive processing industry and it is produced in the
Total Carbon
45.30%
olive kernel oil producing plants. Its production in
Hydrogen
5.17%
Crete to day varies to 110.000 tn/year. The main
Nitrogen
1.33%
Oxygen
34.30%
Heating value
4051 Kcal/kg
uses of olive kernel wood are for heat generation in
the factories, in buildings and in greenhouses.
The main advantages of its use are:
a)
The low price in comparison with the
heating value (compared with other
16.96 MJ/Kg
Residual Oil
2.44%
Residual hexane
<10 mg/kg
2
4.
POSSIBILITIES
PELLETS
OF
FROM
PRODUCING
OLIVE
KERNEL
WOOD
Comparing tables 1,2 and 3 it is
concluded that the concentration of olive kernel
wood in various elements, exceeds the E.U.
proposals for maximum permissible concentrations.
The production of wood pellets from olive kernel
Therefore
wood is easily feasible and the product can be used
a)
The ash content is significantly higher
for heating buildings. Pellets can be produced
than the maximum accepted. This could
without the use of additives. For its utilization as a
lead to ash slagging during combustion
fuel, it should comply with the existing
and probably the final product is not
specifications for wood pellets, which apply in
suitable for burning in existing residential
varions E.U. countries (table 2). Proposals also exist
pellets burners [ 9 ]. Also its high ash
for future quality specifications of wood pellets in
content could lead to formation of high
all E.U. countries (table 3).
temperature aerosols [ 12].
TABLE 2
b)
The sulphur concentration is slightly
higher than the max accepted
WOOD PELLETS SPECIFICATIONS IN VARIOUS
c)
E.U. COUNTRIES [ 4 ]
the max accepted for good quality pellets
AUSTRIA
SWEDEN
GERMANY
<12
<10
<12
Water
The Nitrogen concentration is higher than
d)
The Clorine concentration is also higher
than the max accepted.
content
e)
(%)
Some times the produced olive kernel
ash (%)
<0.5*
<1.5
<1.5
wood has water content higher than 10%,
heating
≤18*
≥16.9
17.5-19.5
but this can be reduced with proper
drying.
value
(MJ/kg)
Therefore for the production of wood
Sulphur
≤0.04*
≤0.08
≤0.08
≤0.3*
-
≤0.3
≤0.02*
≤0.03
≤0.03
(%)
Nitrogen
(%)
Chlorine
pellets form olive kernel wood, it should be mixed
with other agricultural of forest by products or
residues, having very low ash content, resulting in a
final
product
complying
with
the
E.U.
specifications. The most important parameter of
(%)
olive kernel wood which must be reduced
*in dry basis
significantly is its ash content.
CONCLUSIONS
TABLE 3
1.
Wood pellets are a rather new solid
biomass fuel which is used increasingly in
PROPOSED WOOD PELLETS SPECIFICATIONS
E.U., for heating buildings.
FOR E.U. COUNTRIES [ 4 ]
2.
Various E.U. countries which use broadly
Water content (%)
≤10
Ash (%)
≤0.7
wood
heating value (MJ/kg)
≥16.9
specifications for it, and soon new quality
Sulphur (%)
≤0.05
Nitrogen (%)
0.3-3
Chlorine (%)
0.03-1
Additives (%)
<2 in dry basis
pellets as fuel, have quality
specifications for
EU countries are
expected.
3.
For wood pellets productions, agricultural
and forest residues are used to day.
4.
Olive kernel wood is a byproduct of olives
processing plants, and it is used to day as
3
a solid fuel without any standardization.
5.
The chemical concentration of olive
, “ Using biomass for climate change
Kernel wood does not allow its use for
mitigation and oil use reduction” , Energy
wood
policy , 35 , (2007) ,p. 5671-5691.
the
pellets
production,
since
its
existing
quality
specifications.
D.
Bostrom
,
”
Slagging
combustion in residential pellet burners.” ,
concentration of various substances and to
Biomass and Bioenergy , 27 ,(2004), p.
produce good quality pellets. The high ash
585-596.
10. P. Lehtikangas , “ Quality properties of
pellets production.
pelletised sawdust logging residues and
The high ash content of olive kernel wood
bark” Biomass and Bioenergy , 20 ,(
could probably lead to ash slagging for
2001) ,p. 351-360.
burning temperatures 900-1000 oC .
11. Yadong.li. , Henry Liu , “ High pressure
Further experiments are needed to find the
densification of wood residues to form an
degree of sintering of the ash deposits.
upgraded fuel”, Biomass and Bioenergy ,
Also the formation of high temperature
19,( 2000) , p. 177-186.
12. H. Wiinikka , R. Gebart , C. Boman , D.
Bostrom , M. Ohman.
„Influence of fuel ash composition on high
REFERENCES
M. Griffiths “Pellets appeal”, Renewable
temperature aerosol formation in fixed bed
energy world, March – April 2005, vol. 8,
combustion of woody biomass pellets.“, Fuel ,
number 2, p. 52-59.
86 ,(2007) , p. 181-193.
B. Hahn Umbera “Establishing a wood
13. B.J. Skrifvars , R. Backman , M. Hupa ”
pellet market – Incorporating total quality
Chartacterization of the sintering tendency of
management”, Competence center wood
ten biomass ashes in FBC conditions by a
technologie – Holzforschung, Austria.
laboratory test and by phase equilibrium
ABEA, Chemical
calculations” , Fuel processing technology , 56,
Analysis
of olive
Kernel wood, Chania, Crete, Greece.
4.
Nordin,
other solid biomass sources, to reduce the
concentration.
3.
M.Ohman, C. Boman, H. Hedman , A.
tendencies of wood pellet ash during
aerosols are expected due to high ash
2.
9.
Therefore it is necessary to mix it with
content makes possible its use for bark
1.
L.Gustavsson,J.holmberg,V.Dornburg,R.S
thre,T.Eggers, K. Mahapatra , G. Marland
concentration in various elements exceeds
6.
8.
Its price is attractive .
( 1998) , p. 55-67.
Quality standards for pellets in E.U.
countries, www.pelletcentre.info
5.
Heating buildings with wood – An
investors guide (in Greek), Greek centre
of
Renewable
energy
sources.
www.cres.gr
6.
Energy plantations for the production of
solid biofuels in Greece (in Greek), Greek
centre of Renewable energy sources.
www.cres.gr
7.
Heating buildings with biomass, technical
guide (in Greek), Greek centre of RES,
www.bioheat.info
4