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5 EURES CASE STUDY. BIOMASS DISTRICT
HEATING IN LLES DE CERDANYA
March 2006
CTFC. AFiB 15/03/2006
INDEX
5 EURES CASE STUDY. BIOMASS DISTRICT HEATING IN LLES DE
CERDANYA ........................................................................................1
1. Assessment of biofuel potential.........................................................1
1.1. Forest industry residues..............................................................1
1.2. Logging residues........................................................................2
1.2.1. Annual allowable cut in La Cerdanya ........................................2
1.2.2. Annual allowable cut in Lles de Cerdanya..................................5
2. Planning of the wood fuel supply chain...............................................6
2.1. Evaluation of existing supply chain for timber production .................6
2.2. Evaluation of the applicability of the Finnish wood fuel supply
technology ......................................................................................7
2.2.1. Timber harvesting operations..................................................7
2.2.2. Chipping at roadside landing...................................................9
2.2.3. Chipping at the terminal: harvesting chain..............................16
2.2.4. Chipping at stand: harvesting chain .......................................20
2.2.5. Chipping at power plant .......................................................22
2.2.6. Bundling technology ............................................................24
2.2.7. Evaluation of the methods ....................................................25
2.3. Evaluation of the possible wood fuel supply structures...................28
2.3.1. Specialized biomass enterprise..............................................29
2.3.2. Loggers .............................................................................30
2.3.3. Municipal brigade ................................................................32
2.4. Calculation of wood fuel harvesting costs for different methods ......33
2.4.1. Cost for chipping at roadside landing......................................34
CTFC. AFiB 15/03/2006
2.4.2. Cost for chipping at power plant ............................................37
2.5. Evaluation of the environmental and forest regulations..................39
2.5.1. Protected areas in La Cerdanya .............................................39
2.5.2. Protected areas in Lles de Cerdanya.......................................41
2.5.3. Other regulations and restrictions ..........................................42
2.6. Suggested harvesting technology ...............................................44
3. Planning of the plant .....................................................................45
3.1. Biomass plant type...................................................................45
3.2. Calculation of the boiler capacity ................................................47
3.3. Evaluation of the fuel consumption .............................................47
3.3.1. Fuel consumption ................................................................47
3.3.2. Timber yard dimensions .......................................................50
3.3.3. Wood hog dimensioning .......................................................52
3.4. Calculation of the plant efficiency ...............................................53
3.5. Emissions: NOx-, SO2-, CO2- and dust emissions ............................56
3.6. Energy cost calculation .............................................................61
3.6.1. Investment costs ................................................................61
3.6.2. Maintenance furnace cost .....................................................62
3.6.3. Fuel cost ............................................................................63
4. Conclusions .................................................................................64
4.1. Conclusions about biofuel potential.............................................64
4.2. Conclusions about fuel supply chain............................................65
4.3. Conclusions about the plant.......................................................66
ANNEXES ........................................................................................67
Annex 1 ........................................................................................68
CTFC. AFiB 15/03/2006
Annex 2 ........................................................................................74
CTFC. AFiB 15/03/2006
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1. Assessment of biofuel potential
1.1. Forest industry residues
Nowadays in La Cerdanya we can only find one sawmill in the small village
of Bellver de Cerdanya (18 km). Its annual wood consumption is about
37,000 t. This means that the industry produces every year 35,573 loose
cubic meters of chips, 1,200 t of bark and 6,800 loose cubic meters of
sawdust.
Besides the sawmill industry, there are sources of residual wood: the
residual managers. In this case, due to the reduced population of the shire,
the residuals barely reach 70 t/year (Waste Agency of Catalonia).
Table 1. Average residual wood in La Cerdanya
Residual amount (t) Municipality
2001 2002 2003 2004 Average Bolvir 1.28 1.28 1.28 Ger 1.06 1.06 Guils de Cerdanya 0.13 0.13 0.13 0.13 Llívia 0.97 0.77 0.89 0.89 0.88 Puigcerdà 75.32 58.26 65.82 64.72 66.03 Total general 77.35 60.43 68.12 65.74 67.91
Source: Waste Agency of Catalonia
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1.2. Logging residues
1.2.1. Annual allowable cut in La Cerdanya
According to the data provided by the Departament de Medi Ambient i
Habitatge of the Generalitat de Catalunya, there are thirty public forests
and many communal forests distributed all over La Cerdanya. This means
that the wood harvesting doesn’t depend of the will or independent plans of
the private owners of the forests to extract the timber. This situation makes
it possible to plan long term and sustained harvestings in the shire, and to
create a fuel supply chain of biomass to feed local boilers.
The annual allowable cut in the public and communal forests are the
following:
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Table 2. Annual allowable cut in public forests in La Cerdanya
Ownership Forest name (Public Use Catalogue) Annual
allowable cut (m3/any)4
1,275 Aransa Muntanya d'Aransa (32-L); Comunals d'Aransa
1801
1,541 3501Lles
Muntanya de Lles (71-L); Avellanosa (70-L); Caules i Costa de les Gralles (31-L); Santa Llocaia (33-L): Comunals de Lles 4001
Solana de Bellver (47-L) 150 Solà i Comes (47-L) 3801
Vila i Batllia (48-L) 3,080 Bellver de Cerdanya
Santa Eugènia (46-L) 600 El Bosc (17-L) 3751Generalitat de
Catalunya Pinatella (9-L) 1801
Prullans Erms (L-3035) 6001
Meranges Muntanya de Meranges (21-G) 3,100 Ger Muntanya de Ger (16-G) 3002
Guils Muntanya de Guils (20-G) 3402
Llívia Neguila, Castell i altres (G-3026) 2351
Puicerdà Saltegat (8-G); Vilallobent (54-G) 1,970
Fontanals Muntanya de Quixans (9-G); Muntanya d'Urtx (46-G); Comunals
1,559
Alp Muntaya d'Alp (7-Gi) 1,850 Das Muntanya de Das (14-G) 1,158 Urús Muntanya d'Urús (45-L) 1,451
8452
Riu Muntanya de Riu (79-L); Comunals de Riu 3503
Pi Muntanya de Pi (45-L) 9001
Montellà Clot, Mata i Prat d'Aguiló (74-L) 1,200 Estana i La Seu d'Urgell
Llobaters i Estemaló (313-L) 180
Estana Muntanya de Béixec (92-L); Baixos de Villec-Estana (92-b-L) Obaga i Brancals (320-L)
1,161
TOTAL 25,710 1 Management plan pending 2 Not updated
3 Still not ratified by the Centre Tecnològic Forestal de Catalunya
4 m3 of wood with bark
Source: F. Cano, Forest Engineer of the Department of the Environment and
Housing. Government of Catalonia
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According to the IEFC (Ecological and forest Inventory of Catalonia) by the
CREAF (Centre for Ecological Research and Forestry Applications) the
amounts of biomass described on the tables 3 and 4 is what can be found in
La Cerdanya. As it can be seen there is a significative gap between the
production of the annual allowable cut in public forests (25,710 t/year) and
the estimations made for the whole shire (54,500 t).
Table 3. Biomass total stock in La Cerdanya
Biomass type Biomass stocks
Wood (t) 1,563,100
Bark (t) 256,100
Branches (t) 325,500
Leafs (t) 82,000
Total (t) 2,226,700
Source: IEFC (CREAF)
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Table 4. Biomass total production in la Cerdanya
Biomass type Biomass production
Wood (t/ha) 74.7
Bark (t/ha) 12.2
Branches (t/ha) 15.6
Leafs (t/ha) 3.9
Total (t/ha) 106.3
Aerial woody production (t/ha/year) 2.6
Aerial woody production (t/year) 54,500
Source: IEFC (CREAF)
1.2.2. Annual allowable cut in Lles de Cerdanya
In the public forests of Lles de Cerdanya there is an estimated annual
allowable cut of, at least, 4,000 solid m3 with bark per year of timber. This
means that in a whole year 536 tones of branches may be expected.
Besides, there are 17,000 m3 of death wood scattered all over the forests of
Lles de Cerdanya. The problem of this material is that, as is not gathered, it
might be not profitable to pick it up.
Furthermore, it’s pendant an auction of nearly 13,000 trees. The idea is to
seize the opportunity to collect the non commercial wood and the branches
produced by the harvesting.
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2. Planning of the wood fuel supply chain
2.1. Evaluation of existing supply chain for timber
production
The forests in Lles de Cerdanya are harvested following the traditional
method established in Catalonia. Wood is sold at auction to the loggers that
bid for the material offered in the forests. At the present time branches are
left over the terrain and only the timber is extracted.
Apart from the wood harvesting, and some small firewood marketing
enterprises, now there is no biomass supply chain because there is few
demand of woody fuel at the present moment. Even though this situation,
the town council has decided to start spending biomass instead of gas-oil.
Right now the town council is evaluating three options:
• Hiring a French specialized enterprise in biomass supply chains
• Buying a chipper and work in combination with some Catalan loggers
• Creating a forest brigade, maybe in combination with other
municipalities, and acquiring the necessary equipments to supply all
the needed fuel.
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2.2. Evaluation of the applicability of the Finnish
wood fuel supply technology
2.2.1. Timber harvesting operations
Different systems are used in Finland for production of forest chips. The
methods can be classified on the basis of the phase in which the chipping is
carried out. The main methods used in Finland for forest chip production are
chipping at the terrain, at roadside, at the terminal and at the mill. There is
another harvesting technology which is based on bundling of forest
residues. Each method can be divided into different working phases like
terrain haulage, storage and drying, chipping or crushing and road transport
to power plant (Figure 2).
The most common tree harvesting method in Finland is the cut-to-length
system. It is used both in final felling and thinning sites. In this method
trees are felled, delimbed and sawn into logs of 3-6 m with a harvester.
Logs are then hauled to the roadside, and transported to the sawmills and
paper mills.
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In order to make the collecting of forest residues easier and more efficient,
the working techniques of the harvester need to be changed a little.
Normally the harvester cuts the trees on either one or both sides of the
strip road. Processing of the stems takes place in front of the harvesting
machine. In the traditional way of logging, the logging residues remain on
the strip road and get trampled under the tires of the moving harvester.
Forwarders use the same tracks for timber haulage. This means that logging
residues are difficult to collect and often contain harmful stones, soil and
humus material. Therefore the working methods have to be modified so
that the logging residues are piled up on one or both sides of the harvester.
This helps the loading of the forest residues from the ground and reduces
stones coming with forest residues, being harmful for chippers and also for
chip users (Savolainen & Bergren 2000).
Figure 1. Two main forest residues harvesting chains: chipping at roadside
and bundling technology chain (picture from VTT Energy).
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2.2.2. Chipping at roadside landing
The production phases of the forest residues harvesting chain based on the
chipping at roadside landing are terrain haulage, storage and drying,
chipping or crushing and road transport of forest residue chips to power
plant (Figure 2).
Logging residues are hauled to roadside landing all year round from the
surroundings of the terminal. Residues are stored at the terminal and dried
there over next summer, so it is possible to improve the quality of the fuel.
Chipping of residues is carried out all-year round, and chips are delivered by
common solid fuel transportation vehicles equipped with closed containers.
The objective is that logging residues are chipped directly to long distance
transport trailers without any storage of forest residue chips at the landing.
Figure 2. Forest residues harvesting chain based on chipping at roadside
landing - terrain haulage (left above), storage (right above), chipping into
truck trailer (left below) and truck trailer road transport (right below)
(photographs by VTT Energy).
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2.2.2.1 Terrain haulage
Terrain haulage of forest residues is usually carried out with a conventional
forwarder (Figure 3). The productivity of a forwarder with regular
equipment remains low for hauling logging residues because of a small load
space. The load space needs to be enlarged to achieve better hauling
productivity. The load space can be extended backwards, sideways and
upwards. A medium-size forwarder with a regular load space can carry 4-5
m3 load of fresh logging residue. By extending the load space backwards
and by installing extra bolsters, a load size from 8 to 14 m3 can be attained
(Savolainen & Bergren 2000). Since bulk green density of logging residues
is low, 80-150 kg/loose m3, the mass of the load will remains below the
limits of the machine capacity.
The regular timber grapple of the forwarder is not suitable for forest
residues loading. The best grapple model for forest residue harvesting is a
fingered grapple. This one is like the timber grapple but the frontblade has
been taken away (Alakangas et al. 1999).
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The productivity of a normal forwarder is 10-20 m3 per hour depending on
the haulage distance and load size (Figure 3). For instance, if the load size
is 7 m3, productivity of the forwarder is about 7.64 dry tons (18 m3) per
hour with a haulage distance of 100 m. If the distance is 500 m the
productivity is about 3.36 dry tons (8 m3) per hour. When the load size is
11.6 m3 the productivity using the same haulage distances is between 5.27
dry tons (12.4 m3) and 9.54 dry tons (22.5 m3) per hour (Alakangas et al.
1999).
Figure 3. Haulage of forest residues with forwarder (left) and with Havu-
Hukkatrailer (right).
Vapo Oy Energy has introduced a Havu-Hukka logging residues trailer
(Figure 4). Logging residues are collected with the tractor's loader into the
trailer. The trailer is equipped with compressing sides, with which it is
possible to compress the load into smaller volume. With the sides
compressed, the trailer of approximately 45 m3 carries about 10 tons of
fresh logging residues, twice the amount carried by a regularly equipped
forwarder (Leinonen et al. 2000).
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When the trailer is filled the compression sides are closed to road transport
width and to keep the logging residues inside the trailer. When both sides
are closed the trailer is suitable for road transport so the logging residues
can be transported directly from the forest to the terminal. The maximum
transportation distance is about 10 km. Collection of logging residues can
be done all-year round (Leinonen et al. 2000).
2.2.2.2. Storing and drying
Storing is an essential part of the forest residues harvesting chain. When
planning the storage of forest residues and timing of the storage, compared
to the other working phases of the harvesting chain, must be taken into
account. Forest residues are stored in heaps on the stand, in big stockpiles
beside the road, or in central stockpiles at a special fuel terminal.
When building a residue pile, a few bundles of whole trees or treetops
should be placed transversely on the bottom of the pile, in order to prevent
the undermost logging residues from becoming contaminated with sand and
from freezing to the ground in wintertime. Logging residues should be
placed so that butts of trees face to the road (Savolainen & Bergren 2000).
According the research results, stockpiles dry effectively during summer
season (Figure 4), from a initial moisture content of 50-60%, at the last
even to less than 30%. The best possible place for drying a logging residue
stockpile is a site as open and windy as possible located in south-north
direction. However stockpiles shall not be placed too close to each other
because this slows down the drying process. Stockpiles can be made as
high as possible because it has been noticed that making the stockpile 5 m
high did not slow down the drying compared to the drying of 3 m stockpiles.
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The tops of the stockpiles should be covered already during the storage or
latest in August before the autumn rain season (Leinonen et al. 2000).
Forest residues on the stand dry up as fast as in the stockpiles. So the
forest residues produced during spring and summer should be left for drying
before forwarding them to the stockpile (Leinonen et al. 2000).
Figure 4. A forest residue stockpile (left) beside the road) (photo by Arvo
Leinonen) and a graph of forest residues drying in a stockpile (right).
2.2.2.3 Chipping or crushing
Tractor-driven, lorry-based and mobile crushers are used for chipping forest
residues at the terminal (Figure 5).
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Fundamental feature of the tractor-driven equipment is the agility and
mobility even in hard conditions and on a ground with poor loadbearing
capacity. The present tractor operated chippers are equipped with turntable
outlet pipe that makes possible to place the chip stockpile on a clean
surface by the side of the machine combination. Jenz HEM 25Z and TT -
97RMT drum chippers have been tested. The average output of these
tractor chippers is 50 loose m3 of chips per productive hour, and the power
demand of the tractor is 100 kW (Tiihonen et al. 2000).
A lorry-based chipper can also be used in terminal chipping. The advantage
of this is the large momentary productivity. The limitations in operation are
caused by the high total weight of the lorry-based chipping equipment as
well as the high axle loads, which make the operation on the areas with low
load-bearing capacity difficult or even impossible. The lorry-based JENZ
chipper, equipped with 380 kW chipper, was tested at a terminal. The outlet
pipe of the chipper can be turned sideward so it is possible to chip the
logging residues either to the ground or directly into the long distance
transportation vehicle. The output of the chipper has been low, being only
same as with a tractor chipper (Tiihonen et al. 2000).
Mobile crushers, equipped with own power sources; have also been tested
in terminal chipping. Morbark 1100 bucket-crusher and Jenz 55 hammer-
crusher, equipped with moving hammers, have been tested. Both crusher
units are relatively large and the axle loads are high so they only can be
used on areas with high load-bearing capacity. The maximum output of this
equipment has been 100 bulk-m3 per productive hour. The power demand
of the crusher is 225-275 kW (Tiihonen et al. 2000).
When chipping in winter, special attention has to be paid to snow removal
from the top of the logging residue stockpile. Additionally, operators have to
be protected against the moulds in the chips.
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Figure 5. A mobile chipper on a truck chassis (left), a mobile tractor chipper
(in the middle) and a crusher (right) (photos by VTT Processes).
2.2.2.4 Loading and long-distance transport
Normally logging residues are chipped directly into a chip trailer lorry. Chip
lorry can be a full trailer lorry or a lorry without a trailer. Chip lorries used
for long-distance transport are equipped either with bottom discharging
devices or by a tipping gear. The load volume of a full trailer lorry is usually
90-120 m3. Dead load of a chip-trailer is 23 tons and the maximum
allowable total load is 60 tons, so the maximum payload is 37 tons. Devices
which enable the load to be discharged from the back of the trailer make
possible to deliver chips to more plants at the same time, unlike with
trailers capable for dipping by the side or to the back of the trailer.
Depending on the chipper or crusher type the container of the chip truck
must be loaded either from the back of the trailer or from above it
(Leinonen et al. 2000).
The capacity of long-distance transport vehicles depends directly on the
transport distance and on the number of the chip lorries used for the
transport. Attaining a satisfactory annual output of 65,000 to 70,000 loose-
m3 for a logging residues chipper on a lorry chassis, two full trailer lorries or
three lorries without trailers are required for a long distance transportation
range of 80 km. Two lorries without trailers are sufficient for distances
below 40 km (Alakangas et al. 1999).
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2.2.3. Chipping at the terminal: harvesting chain
2.2.3.1 Harvesting chain
The production phases of the forest residues harvesting chain of forest
residues for fuel based on the chipping at the terminal are: terrain haulage,
storage and drying, chipping or crushing of forest residues and road
transport of forest residue chips to power plant. The working phases are the
same as in the harvesting chain when chipping at roadside.
In this method the forest residues are hauled from the surroundings to the
power plant. The haulage distance is about 100-500 m to roadside landing
while it is less than 10 km to fuel terminal. For the terrain haulage of forest
residues e.g. the Havu-Hukka forest residue trailer is used. It is more
effective than the normal forwarder and also is allowed to be used for road
transport (Figure 6).
When chipping at the fuel terminal, it is possible to chip forest residues
either onto the ground or directly with the truck trailer. By chipping onto the
ground it is possible to get rid of the so called hot chain, provided the
amount of forest residues is big enough and the chip storages become large
enough.
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Figure 6. Forest residue harvesting chain based on chipping at the fuel
terminal -terrain haulage with Havu-Hukka trailer (left above), storage and
chipping (right above), truck loading (left below) and truck trailer road
transport (right below) (photos by V1T Processes) (Leinonen et al. 2000).
2.2.3.2 Fuel terminal
The main factors affecting the selection of the location for a mixed fuel
terminal are: enough fuel reserves, enough storage space for piles of both
raw material and chips, roads with sufficient load bearing capacity and
proper condition, open and windy location of the terminal area, and flat and
load bearing ground with no extra impurities. Stockpile areas of peat
production sites, gravel pits, storage field, etc. are proper locations for the
terminals (Figure 7) (Leinonen et al. 2000).
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The terminals size varies on the basis of the working site conditions and raw
material stocks, being 5,000-20,000 loose m3 of logging residues. If the
height of the storage is 5.0 m, the corresponding amount of chips is 2,000-
8,000 loose m3. A circular terminal, dimensioned for logging residues, is
presented in the Figure 7. The volume of the terminal is about 5,000 loose
m3 of logging residues. The height and the width of the logging residue
stockpile in this model is 5 m, so the volume of terminal chip s produced
from this amount is about 2,000 loose m3.
The ground of the biomass terminal area, especially the raw material and
chips stockpile area, has to be load bearing and flat, and it must not contain
stones or sand. If operated on unpaved areas, the stockpile areas have to
be backed in order to prevent the impurities such as stones from getting
into the logging residues and chips. Additionally, the backing of the areas
makes the terminals flat, which ease the loading of the chips. Peat, bark,
sawdust or ash can be used as backing material for the stockpile areas.
Figure 7. A schematic picture of a circular terminal (left), chipping at
circular terminal (in the middle) and storage of forest residue chips at
terminal (right) (Leinonen et al. 2000).
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2.2.3.3 Storing of forest residue chips
Chips have to be stored for several months before the use in order to
ensure constant delivery of chips to the plant throughout the year. Storage
problems include dry substance (ds) losses, wetting and freezing of the
chips. Biological and chemical reactions, as well as the activity of wood
decaying fungi cause ds-losses. Wetting of the chips in stockpiles is caused
by rainfall and chemical reactions in the wood (Leinonen et al., 2000)
The main factor affecting the stockpiling of logging residue chips is the
initial moisture content of the chips. The higher the initial moisture content
is the greater are also the ds-losses. In long-term storage it is possible to
prevent ds-losses by covering the stockpiles (Leinonen et al., 2000
Long-term storage of the chips is not recommended due to high moisture
and ds-losses. If long-term storing is necessary the initial moisture content
of the chips has to be less than 30% and the stockpile has to be covered, so
that the ds-losses remain under 5%. Long-term storing of chips is
reasonable if the deliveries have to be ensured under all circumstances
(Leinonen et al., 2000).
It is usually profitable to store the chips only for short-term to keep the
moisture and ds-losses as low as possible. In short-term storing the ds-
losses are low ( < 1.0 %) if the storage time is less than two weeks. Short-
term chip-stockpile does not need to be covered, but the stockpile has to be
made as large as possible. The initial moisture content should also be as low
as possible ( < 30%) (Leinonen et al., 2000).
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2.2.3.4. Advantages of fuel terminal - harvesting chain
Forest residues dry very well at open terminals. Also the harmful impurities
like stones are easily avoided in this harvesting chain. By using terminal
chipping of logging residues it is possible to produce high quality chips, the
properties of which include homogenous chip size and low moisture content.
These high quality chips are excellent fuels for communal scale heating
plants.
2.2.4. Chipping at stand: harvesting chain
Terrain chipping is based on a single machine so called terrain chipper,
which chips forest residues into a container at the stand, and haul the chips
in the container to the landing or to the roadside (Figure 8). The container
is emptied by tipping the chips into exchangeable containers at roadside.
The truck picks up the exchangeable container and transports it to the
power plant and returns the emptied container to the landing.
For terrain chipping, forest residues need to be piled along the logging track
or strip road, from where they can easily be loaded to the chipper feeding
table of the chip harvester. Chip harvesters are typically built on a
forwarder chassis. There are several machine sizes available on the market.
The terrain chipper made by the Finnish S. Pinomaki is equipped with 26
cubic yard (20 m3) container (Savolainen & Bergren 2000).
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For terrain chipping the productivity of forest haulage and chipping of 200
m is 2.73 to 3.64 dry tons (15 to 20 loose m3) per schedule hour
(Alakangas et al. 1999). In terrain chipping the logging residues are mostly
processed when they are still fresh. Consequently, the resulting logging
residue chips can have lower moisture content than fresh logging residue
only in the summer season (Alakangas et al. 1999).
The main advantage of terrain chipping compared to roadside chipping, is
that less machinery is required for harvesting, which makes the
organization of the work remarkably easier. Additionally, less landing space
is required for terrain chipping than for roadside chipping, and the chipping
and lorry transportation do not function as a hot chain, as in the case of
road side chipping (Alakangas et al. 1999).
The disadvantages of terrain chipping include a fairly poor off-road
capability and difficulties in achieving a satisfactory chip quality because of
snow moistening the chips during the winter time (Alakangas et al. 1999).
Figure 8. Harvesting chain of forest residues based on the terrain chipper –
harvester (left), loading of chips into the exchangeable container (in the
middle) and loading of the container for truck transport to power plant
(right) (photos by Arvo Leinonen and Biowatti ay).
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2.2.5. Chipping at power plant
The fourth major chain of processing logging residues for fuel is chipping or
crushing them at the end use facility, which normally can be implemented
more economically than in terrain or at roadside (Figure 9). Also processing
at plant avoids the problems of the hot chain, and chipping/crushing can be
implemented more economically than at the stand, landing or roadside
(Savolainen & Bergren 2000, Alakangas et al. 1999).
With chipping at the power plant, the terrain haulage is made by the same
equipment as in roadside chipping. Also the chipping or crushing can be
made by similar mobile machines as when chipping at roadside. In some
power plants the chipping or crushing machine is stationary.
The main challenges of this chain are related to long distance transportation
of logging residues. At the moment normal peat and wood chip lorries are
used for transportation of forest residues to power plant. Bulk density of
forest residues varies between 130-180 kg/loose m3, depending on the
moisture content (30-50%). Forest residues must be compacted while
loading them into the trailer. By this way it is possible to increase the bulk
density of the forest residues in trailer by 20 % (Korpilahti 2000).
The productivity of the chipper at power plant is improved if there is no idle
time of waiting for chips lorries. Chipping at the plant is 20 % more
productive than chipping carried out at a roadside landing (Alakangas et al.
1999).
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Figure 9. Harvesting chain of forest residues based on chipping at power
plant. Terrain haulage with forwarder (left above), loading of forest residues
into truck trailer (right above), truck trailer transport (left below) and
chipping at power plant (right below). Photos by VTT Processes.
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2.2.6. Bundling technology
John Deere's subsidiary Timberjack has developed since 1997 bundling
technology for forest residues in Finland. The whole harvesting chain
consists of the bundling machine, forwarder, truck and crusher which is
situated at the power plant. The bundling machine is constructed on a
normal forwarder chassis (Figure 10). The bundling machine (Timberjack
370) will produce “slash logs” which are about 3 m long and about 0.6-0.8
m in diameter. The bundles are wrapped with strings in every 0.4 m. The
bundling machine produces about 20 bundles in one hour in the best of
cases. Each bundle contains about 1 MWh of energy. Forest residues like
tops, branches and small trees from clear cuttings are suitable raw material
for a bundling machine. Also small trees from thinnings are suitable for
bundling. The bundler is developed to be used together with the cut-to-
length felling method. In this method trees are delimbed on cutting site and
the forest residues are left there (Timperi 2000).
The bundles are hauled with a standard forwarder to the road side. The
bundles are handled like other assortments and the bundles form their own
stacks at roadside landing. The bundles are transported to the power plant
with standard on-road trucks. Crushing or chipping is done at the power
plant. The power demand of the crushers is 500-1000 kW. The capacity of
the crushers is between 23.64-35.45 dry tons per hour (130-200 bulk-
m3/h) (Timperi 2000).
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In Finland there were in 2004 nine bundling units that produce bundles for
fuel. The biggest consumer of forest residue bundles is Pietarsaari power
plant which consumes about 300,000 bundles per year. The use of bundles
for fuel in Finland is increasing (Timperi 2000). There are several chippers
and crushers which are suitable for end use chipping. The power demand of
these chippers and crushers are 265-400 hp (200-300 kW). The capacity of
these machines is 37.27-79 dry short tons (150-445 bulk-m3) of chips per
effective hour.
Figure 10. The bundling technology chain - bundling (left above), terrain
hauling (right above), storage (left below) and road transport (right below).
2.2.7. Evaluation of the methods
Systems above described are different examples of different wood fuel
supply technology and each of them have their own particularities to apply
it in Lles de Cerdanya.
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2.2.7.1. Chipping at roadside landing
On first term in La Cerdanya there will probably be no need of landing the
logging residues all year round up to the summer because weather is much
warmer than in Finland.
On second term, if this method adopted, it will be necessary to acquire
forwarders instead of tractors or buying a trailer with compressing sides.
Both solutions are rare to find in the shire and too expensive for a first step.
The main problem with the crushers and the chippers described above is its
size because of the lack of big enough forests roads, the high terrain slope
and the low load-bearing capacity. This obliges to work with small and not
too big and productive machinery.
The main problem in transport, it’s again, the size of the trucks for many
reasons. In Finland, the legislation allows to load more material in the
trucks than in Catalonia and the terrain its not as plain than in Finland but,
otherwise, the distances in La Cerdanya are really short, about 30 km
maximum.
2.2.7.2. Chipping at the terminal
As chipping at roadside is a method very similar to the one described
above, the problems and the advantages are the same. The unique
difference lays in how the material is stocked.
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In this method a big and flat surface where to stock the material near of
every harvested forest is needed. In la Cerdanya the weather is warmer
than in north Europe and the time of stocking could be reduced. As a
consequence, the need of space is smaller, so the problems produced by
long term storage get reduced.
2.2.7.3. Chipping at stand
There would be several problems for using this method in Catalonia. The
main one is the way the forests are harvested in Catalonia:
• The most common forest operation are selective cuttings (thinnings)
• Machinery is not used to go inside forests
• The most common are steep slopes of the terrain
Even tough those two problems, the terrain chipper is an interesting
machine when cleaning both sides of the forest trucks from inside the trails.
2.2.7.4. Chipping at power plant
Applying this method in La Cerdanya could be quite interesting due to the
particular conditions of the harvesting chain. When applying this method,
the main restriction lies in the long distance transportation, but as the
municipality is not big enough, distances are reduced and the increase of
the cost may not be important. Moreover, the system for harvesting can be
easily adapted at the current resources.
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When talking about La Cerdanya things may change a bit as is a bigger
territory with larger distances.
2.2.7.5. Bundling technology
Maybe the main handicap of this method is the highly specialized and
expensive machinery needed to obtain the biomass. Acquiring such
equipment implies to make a large chip production to obtain low cost
energy. As the case that we are studying, by it’s self doesn’t ensures this
matter, bundling technology may result a non competitive method.
Moreover, the bundler is a machine that needs to work with the cut-to-
length felling method and this implies to use a harvester previously.
Furthermore, that kind of machinery need to work in clear cuttings in
forests with reduced slopes to reach high performance and, as a
consequence, low costs. Unfortunately, the first matter is not usual in
Catalonia, and the second one is rare.
2.3. Evaluation of the possible wood fuel supply
structures
Lles de Cerdanya council is considering three different options to establish
the wood supply chain. The final decision will depend on the necessary
investments and the availability of subsidies. However, whatever the initial
chosen alternative will be, the project will probably grow get consolidated.
Thus, the initial solution will evolve in time.
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The best choice at this early stage is to receive the help of a specialized
enterprise in the beginning, and evolve bit by bit until having a municipal
crew without ever forgetting the punctual contributions of the local loggers.
2.3.1. Specialized biomass enterprise
The first choice is to hire services of a specialized biomass enterprise. The
method used consists on a tractor of 150 CV equipped with a container, a
chipper and a crane. The harvested wood is put into the chipper, and the
chips are stocked into the container. When the container is full, the chips
are changed into a bigger one that is brought to the wood yard by a lorry.
Figure 11. Tractor with crane, chipper and container
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Those are the main advantages and disadvantages of choosing this option:
Table 5. Advantages and disadvantages: specialized biomass enterprise
Advantages Disadvantages
• Experienced enterprise that
ensures the supply
• Fixed cost: no risk
• No worries for the council
personnel
• Zero investment
• No need to buy machinery
• No need to contract staff
• No direct job creation
• More expensive fuel
(supposedly)
• No direct control over the fire
prevention tasks
A part of the convenience whether working with this kind of supply chain or
not in the future, it may be a good option now due to the experience the
enterprise brings and the serious planning mistakes that will prevent to
occur.
2.3.2. Loggers
Loggers represent the traditional way of harvesting forests in Catalonia.
Until the present time, only the commercial stems bigger than 15 cm of
diameter have been harvested due to the low wood price and the
inexistence of biomass demand. This is the reason why this kind of
enterprises don’t have machinery specialized on working with biomass.
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Loggers, after harvesting, will bring the residual wood and the branches to
the yard, and the city council will have to chip all the material.
The loggers equipment lack obliges the city council to acquire a chipper, buy
a perspiring and water proof cloth to cover the chips and contract personnel
to chip de rests.
May be it’s not an expensive investment and it’s a start to reach the
objectives of having the whole supply chain but it depends on the subsidies
to make it possible in the short term. Specially if considering that Lles the
Cerdanya is a low populated municipality.
Table 6. Advantages and disadvantages: loggers
Advantages Disadvantages
• Availability: most common
forestry enterprises in
Catalonia
• No worries for the council
personnel
• Reduced investment in
machinery: chipper
• Reduced direct job creation
• More expensive fuel
(supposedly)
• No direct control over the fire
prevention tasks
• Need of a timber yard
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2.3.3. Municipal brigade
Having a municipal brigade represents the most complex option for the
town council but the one that is potentially more profitable: it implies
having the whole supply chain under the council command from the forest
up to the boiler.
Table 7. Advantages and disadvantages: municipal brigade
Advantages Disadvantages
• Direct control over the forest
fire prevention works
• Accomplishment of the forest
management plans
• Creation of many local jobs
• Maximum saving on fuel
• Important investment in
machinery
• Need of a timber yard
• Variable fuel cost: risk
One way of mitigating disadvantages of having a municipal brigade is to
share the invested resources between many town councils by:
• Sharing the investment costs between many town councils.
• Reducing fuel cost by increasing the potential market: the more
clients, the more biomass volume served and the cheaper fuel cost.
(Economies of scale).
• A bigger biomass demand creates more local jobs.
• Ensure the created jobs and giving them continuity during the year.
• Reducing the risk for each council if the initiative fails.
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2.4. Calculation of wood fuel harvesting costs for
different methods
The costs of two different wood fuel harvesting methods are going to be
evaluated. The Pyrenees conditions, the resources availability and the
particular conditions of the municipality restrict the harvesting methods that
can be applied in the region. Roadside landing chipping and chipping at the
terminal are considered to be the most suitable methods.
To determine the exact cost of a forest work, the specific conditions of the
environment must be known. It’s obvious that there are as many particular
conditions as forests can be found in the municipality. But, even we have no
specific data, it can be said that the global costs of biomass obtaining is
about 24-30 €/t when harvesting trees bigger than 15 cm of diameter and
up to 60 €/t when the diameter is under 15 cm (branches, thinnings …).
For calculating the costs the following variables have been considered:
• Terrain slope
• Wood diameter (DBH)
• Forest trees density
• Machinery power
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2.4.1. Cost for chipping at roadside landing
Table 8. Biomass obtaining cost for chipping at roadside landing (part 1)
Operation Performance and cost
Slope Ø (cm) trees/ha €/stere
ø<12 --- 22.62
<1,000 9.83
1,000 to
1,800 10.86
12<
ø<
20
>1,800 14.16
<750 7.94
%<25 20<
ø<
30
>750 9.77
ø<12 --- 27.75
<1,000 11.89
1,000 to
1,800 13.71
12<
ø<
20
>1,800 16.97
<750 9.54
Harv
est
ing
Harvesting of a Loose cubic
meter of wood. Felling,
hewing, delimbing, cutting off
and piling up included
%>25
20<
ø<
30
>750 11.56
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Table 9. Biomass obtaining cost for chipping at roadside landing (part 2)
LCM/h €/h
Min 10.7
Chipping of small branches
at roadside done it by a
chipper with crane and
container powered by a
tractor of 150 HP Max 11.5
120
LCM/h €/h
Chipping of big branches at
roadside done it by a chipper
with crane and container
powered by a tractor of 150
HP
Average 12.8 120
LCM/h €/h
Min 13.8 120
Ch
ipp
ing
Chipping of whole trees at
roadside done it by a chipper
with crane and container
powered by a tractor of 150
HP Max 17.5 120
LCM/trip €/h
Min 30.3 38.36
Tra
nsp
ort
Transport with a container
carrier. Truck between 350
and 380 HP
Max 73.8 45.29
LCM: Loose Cubic Meter
Sources: Prontuario Forestal. Bois Énergie 66. ACOTRAM. SAEM
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Considering the following conditions:
• Slope < 25%
• DBH < 12 cm
• Forest density: non-significant
• Average speed: 30 km/h (includes loading and unloading)
• Round trip distance: 30 km
• Truck chips carrying capacity: 30,3 LCM/trip
• Branch stacking factor: 0.634 solid m3/ stacked m3
• Chip stacking factor: 0.33 solid m3/ LCM
• Chipped biomass: Big branches
• Wood density: 1 t/solid m3
Table 10. Total Biomass obtaining cost for chipping at roadside landing
Operation Cost (€/t)
Harvesting 35.78
Chipping 28.4
Transport 3.8
Total 67.9
As a conclusion it must be said that 67.9 €/t it is a high cost because of the
expensive of small wood harvesting. In most cases, branch harvesting cost
is supported by commercial wood and branches are left as a residual. In
that case costs are cheaper as branches only are collected and piled.
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2.4.2. Cost for chipping at power plant
In this method, the harvesting procedure is the same as in “chipping at
roadside”. So the part 1 of table 11 (part 1) is valid for the “chipping at the
power plant method” also.
Table 11. Cost for chipping at power plant (part 2)
Ø (cm) Distance (m) €/m3
<200 5.36
200-400 7.66 Ø<20
400-600 11.7
<100 2.5
100-200 7.59
200-400 10.93
Hau
lag
e
Wood extraction up to timber
yard with slope between 25
and 50% using wheel tractor
Ø>20
400-600 18.26
Ø (cm) t/trip €/h
Tra
nsp
ort
Transport with wood forest
truck of 380 HP
Average 20 40.26
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Table 12. Cost for chipping at power plant (part 3)
HP LCM/h €/h
Min 20
90
Max 30
18.08
Min 40
120
Max 50
22.78
Min 60
150
Max 70
27.47
Min 100
Ch
ipp
ing
Chipping at timber yard with
static chipper
430
Max 120
71.32
LCM: Loose Cubic Meter
Considering the following conditions:
• Slope < 25%
• 12 cm < DBH < 20 cm
• Forest density: 1,000-1,800 trees/ha
• Average speed: 30 km/h (includes loading and unloading)
• Round trip distance: 30 km
• Truck chips carrying capacity: 20 t/trip
• Branch stacking factor: 0.652 solid m3/ stacked m3
• Chip stacking factor: 0.33 solid m3/ LCM
• Chipped biomass: Big branches
• Wood density: 1 t/solid m3
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Table 13. Total Biomass obtaining cost for chipping at power plant
Operation Cost (€/t)
Harvesting 16.66
Haulage 2.5
Transport 2.013
Chipping 1.39
Total 22.56
As a conclusion it must be said that 22.56 €/t it is very low cost, mainly,
because of the use of big stems. A part from this particularity, as far we
know, chipping at the power plant results cheaper if the piling factor is not
too low.
2.5. Evaluation of the environmental and forest
regulations
2.5.1. Protected areas in La Cerdanya
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Table 14. Protected areas in La Cerdanya
Protected area Total Surface
(ha)
Surface in La
Cerdanya
(ha)
Parc Natural del Cadí-Moixeró (ENPE also
included in PEIN and Natura 2000
Network)
39,3301 9,795
Serres del Cadí-El Moixeró (PEIN) 41,060 9,795
Tossals d’Isòvol i Olopte (PEIN) 330 330
Tossa Plana de Lles-Puigpedrós (PEIN) 10,111 10,111
Reserva Natural Parcial de la Llosa
(ENPE). Tossa Plana de Lles Puigpedros
(PEIN)
84 84
Reserva Natural Parcial Segre-Prullans
(ENPE). Riberes de l’Alt Segre (PEIN) 44 44
Riberes de l’Alt Segre (Natura 2000
Network) 2162 216
Total protected surface 51,717 20,452
La Cerdanya 53,299
Source: Department of the Environment and Housing. Government of
Catalonia
1Included in Serres del Cadí-El Moixeró;
2Includes RNP Tossa Plana and Segre Prullans
ENPE: Specially Protected Natural Area
PEIN: Natural Interest Areas Plan
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EIN’s are protected areas created to preserve the environment from
degradation: urbanization, infrastructure building, change of soil use,
landscape abandon. Depending on the sensibility of the environment
biomass extraction could be restricted or not. These include all kind of
protected areas: form minimum protection (simple EIN) to maximum
protection (National Parks).
ENPE’s only include Parcs Nacionals (National Parks), Paratges naturals
(National Interest Nature Place) and Reserves Naturals (Nature reserves).
Although ENPE’s are also included in the PEIN, those areas have a more
restrictive protection and in many cases active protection. In this case,
biomass extraction can suffer restrictions, especially if heavy machinery is
used.
This handicap must be taken into consideration when planning future
biomass exploitations because the protection restrictions may affect the
38.37% of the shire surface. Moreover this is especially important due to
the inclusion of the main Cerdanya’s forests in these areas. In fact, the
amounts described in this document have been calculated according to
these restrictions.
2.5.2. Protected areas in Lles de Cerdanya
The municipality of Lles de Cerdanya (10,238 ha) has 58.6% of its surface
included in protected areas. In this case, almost 6,000 ha belong to the EIN
“Tossa Plana de Lles-Puigpedrós” and supposes having restrictions in a very
important part of the municipality surface.
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Table 15. Protected areas in Lles de Cerdanya
Protected area Total surface
(ha)
Surface in
Lles (ha)
Tossa Plana de Lles-Puigpedrós (PEIN) 39,330 5,999
2.5.3. Other regulations and restrictions
In Catalonia, private forests management can be planned according two
different technical documents: The “Plans Tècnics de Gestió i Millora
Forestal” (Forest management and improvement Technical Plans), for the
estates with a surface bigger than 25 ha, and the “Plans Simples de Gestió
Forestal” (Forest Management Simple Plans), for the estates smaller than
25 ha.
Those documents were created with the aim of improving profitability by
structuring and planning the harvestings, reaching sustainability, making
compatible the social and productive forest use and involving the forest
owners in forest management.
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Table 16. Private managed area on 31st of December of 2004
Surface in la Cerdanya ha %*
Forest management and improvement Technical
Plans (4 in the shire) 1,186 2.82
Forest Management Simple Plans (0 in the shire) 0 0
Total managed private areas 1,186 2.82
Private
area
Private forest area 21,885 51.98
Clearing woodland 1,084 2.57
Dense woodland 19,900 43.26
Shrubs, grassland, and non-productive 21,121 50.17
Forest
area
Total 42,105 100
*Considering 100% as total forest area
Table 17. La Cerdanya’s surface
Surface in la Cerdanya ha %
Forest area 42,105 77,1
La Cerdanya 54,637 100
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2.6. Suggested harvesting technology
The suggested harvesting technologies for Lles de Cerdanya are:
• Chipping at roadside landing as described on 2.2.2.
• Chipping at power plant as described on 2.2.5.
It must be taken always into account the differences between La Cerdanya
and Finland as it has been considered on “Evaluation of the methods”
(2.3.7.).
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3. Planning of the plant
3.1. Biomass plant type
The plant that it’s going to be build in Lles de Cerdanya is determined by
the will of heating and giving hot water, in a first stage, to the city council,
the school, the rectory, a hotel and between six or seven buildings with
some housings.
In a second stage the heating system it’s going to reach the church, the
Creueta’s social premises, thirteen subsidised flats and twenty homes all
around in the village.
According to this objective the city council has chosen to implant a district
heating in the city centre. The chosen boiler is a KWB TDS Powerfire of 150
kW design with a turbo rotary-grate self-cleaning that improves it’s
performance. The furnace is equipped with:
• Rotary-Grate Firing System
• Cyclone Combustion Chamber
• Lambda Probe
• Heat Exchanger
• Ash removal
• Backfire protection
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Figure 12. TDS Powerfire 150 kW
The furnace can be equipped optionally with a handling system.
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3.2. Calculation of the boiler capacity
Taking into consideration the heating needs in Lles de Cerdanya, two boilers
of 150 kWh are the selected proposal for being installed in the district
heating and cover its needs. In a near future, depending on the evolution of
heating demand, another 150 kWh power furnace may be installed.
Nowadays in Lles de Cerdanya gas-oil is the most used kind of fuel. The
total amount of spend energy that it’s going to be substituted by biomass is
estimated in 600,000 kW/h/year. This means 913,535 €/year.
3.3. Evaluation of the fuel consumption
3.3.1. Fuel consumption
The fuel consumption table has been constructed from the following data:
• Furnace rated power: 150 kwh (x2)
• Furnace performance: 90%
• Chips heating power: 4 kWh/kg
• Chips density: 230 kg/m3
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Table 18. Daily energy consumption if 300 kWh installed
Month Daily worked
hours (h/day)
Daily average
consumption (kWh/day)
Daily average
consumption (kg/day)
Daily average
consumption (m3/day)
January 10.00 3,333.33 833.33 3.62
February 8.00 2,666.67 666.67 2.90
March 5.50 1,833.33 458.33 1.99
April 3.00 1000.00 250.00 1.09
May 1.00 333.33 83.33 0.36
June 0.50 166.67 41.67 0.18
July 0.50 166.67 41.67 0.18
August 0.50 166.67 41.67 0.18
September 1.00 333.33 83.33 0.36
October 3.00 1,000.00 250.00 1.09
November 6.50 2,166.67 541.67 2.36
December 10.00 3,333.33 833.33 3.62
Average 4.13 1,375.00 343.75 1.49
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Table 19. Monthly and yearly energy consumption with 300 kWh installed
Month Days Month use (h)
Month consumption
(kWh)
Month consumption
(kg)
Month consumption
(m3)
January 31 310.00 103,333.33 25,833.33 112.32
February 28 224.00 74,666.67 18,666.67 81.16
March 31 170.50 56,833.33 14,208.33 61.78
April 30 90.00 30,000.00 7,500.00 32.61
May 31 31.00 10,333.33 2,583.33 11.23
June 30 15.00 5,000.00 1,250.00 5.43
July 31 15.50 5,166.67 1,291.67 5.62
August 31 15.50 5,166.67 1,291.67 5.62
September 30 30.00 10,000.00 2,500.00 10.87
October 31 93.00 31,000.00 7,750.00 33.70
November 30 195.00 65,000.00 16,250.00 70.65
December 31 310.00 103,333.33 25,833.33 112.32
Year use
(h)
Year consumption
(kWh)
Year consumption
(kg)
Year consumption
(m3)
TOTAL 365 1,499.50 499,833.33 124,958.33 543.30
As humidity is a critical parameter that affects the performance of the
boiler, the wood chips must accomplish with the following specifications.
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Table 20. Fuel humidity content
Fuel Units Pellets
Wood
chips
w30/w50
Water-content homologation Kg/kg WM 9.8 32.3
Maximum water content “w” (design) Kg/kg WM1 50
Maximum fuel humidity “u” Kg/kg DM2 100
Maximum fuel size acc. to ÖNORM G30**
**G50 upon request
1WM: wet matter
2DM: dry matter
3.3.2. Timber yard dimensions
As wood chips must be stored to ensure the fuel supply, a timber yard
where stock the chips is needed. The size of the yard depends on four main
factors:
• Time of storage: determined by the buffer of fuel demanded
according to the special needs and conditions of the supply chain. In
this case, on wintersnow covers the forest tracks.
• Time required by the chips to reach the required humidity. To ensure
that humidity reaches 30%, two months are needed at least in the
worst of cases.
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• Fire prevention measures according to the RD 2267/2004 Reglament
de Seguretat contra Incendis
• Material qualities: Coefficient of stacking, chip size, Angle of Internal
Friction, etc.
Considering storage calculations, the size of the biomass yard is
determined, basically, by the total number of chip piles that must be piled
up as is established by the laws.
Table 21. Storage needs
Period of storage (month)
Cases 1 2
(drying)
4
(snow)
6 12
(year)
Stocked chips (t) 45.275 90.55 181.1 271.65 543.3
Pile number 1 1 1 2 3
Minimum timber
yard surface (m2) 628.31 628.31 628.31 1,223.21 1,812.62
Table 22 shows that taking into consideration the fire prevention
restrictions, the surface needs, considering an average consume, are:
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Table 22. Storage piles and surface needs
From Up to Piles Timber yard
surface (m2)
0 days 5 months and one
week 1 628.31
5 months and one
week
10 months and two
weeks 2 1,223.21
10 months and two
weeks
15 months and three
weeks 3 1,812.62
3.3.3. Wood hog dimensioning
For avoiding over cost when buying machinery is necessary not to acquire
equipment with excess of productive capacity.
Table 23. Average diary consumption and chipping capacity
Min Average Max
LCM/day 0.09 0.75 1.81 Consumption
LCM/week 0.63 5.25 12.68
Minimum needed chipper
performance (LCM/h1) 0.016 0.13 0.32
1Working 40 hours per week
LCM: Loose Cubic Meter
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Those figures mean that there’s no need to have a huge chipper to feed the
boilers if continuous chipping is done and small diameter wood is used.
Table 24. Disc chipper
Chipper model: Pezzolato H 780/200
Tractor minimum power (HP) 60
Diesel engine power (HP) 60
Max chippable Ø (mm) 200
Feeding hopper dimension (mm) 1,360x940
Disc Ø (mm) 780
Disc thickness (mm) 35
Number of knives 3
Production per hour (LCM) 14/18
PTO version weight (Kg) 885
Source: www.pezzolato.it
3.4. Calculation of the plant efficiency
According to the technical specifications of the boilers the plant efficiency is
the one that follows.
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Table 25. Plant efficiency
Designation Pellets Wood
Chips*
Rated power (kW) 150 150
Partial load (kW) 45 45
Boiler-efficiency at rated power (%) 91.5 90.4
Boiler-efficiency al partial load (%) 93.6 92.9
Fuel thermal output at rated power (kW) 164 166
Fuel thermal output at partial load (kW) 48 49
A part from the boiler the pipes are the second most important part of the
district heating that affects the efficiency of the system. The technical
characteristics of Ecoflex Thermo Twin pipes, the chosen water ducts for
distribute the heat, are:
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Table 26. Pipes thermal characteristics
Thermal properties Value Units DIN
Thermal conductivity 0.35 W/m°C 4725
20 ºC 1.4x10-4 m/m°C --- Linear
dilatation 100 ºC 2.05x10-4 m/m°C ---
Soften temperature +133 °C ---
Temperature work range -100 a +100 °C 16892
Specific heat 2.3 kJ/kg°C ---
Figure 13. Thermo twin pipe
This means that the loss heat per linear kilometre of pipe only reaches
0.7ºC.
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3.5. Emissions: NOx-, SO2-, CO2- and dust emissions
As wood chips are burned, pollution it’s emitted due the chemical
composition of such material. The average composition of the most
important compounds in Catalan wood is the one that follows.
Table 27. Average chemical wood density and chemical concentration
Average
wood density
(g/cm³)
Average
wood carbon
concentration
(g/100g)
Average
wood
nitrogen
concentration
(g/100g)
Average
wood
phosphorus
concentration
(g/100g)
Average
wood sulphur
concentration
(g/100g)
0.64 48.62 0.13 0.01 0.02
So taking into consideration that wood, as other fuels, contains many
chemical compounds that are involved in the green house effect and in the
acid rain, it’s a good thing to take a look into a comparison between various
fuels.
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Table 28. Quantitative inventories of environmental releases for the
production of 1 MJ heat from various fuels*
Emission type Unit Coal Heavy
fuel
Natural
gas Wood Straw
Carbon dioxide, CO2 g/MJ 96 80 56 98a 99a
Carbon monoxide, CO mg/MJ 50 10 150 6000 4500
Sulphur dioxide, SO2 mg/MJ 650 500 1 33 110
Nitrogen Oxides, NOx mg/MJ 500 240 350 50 130
Volatile Organic
compounds, VOC mg/MJ 15 7 15 1200 -
Polycyclic Aromatic
Hydrocarbons, PAH mg/MJ 2.0 0.25 0.13 5000 25
Dioxins, PCDD, PCDF mg/MJ 0.04 - 0 - 0.3
Arsenic, As mg/MJ 8 2 0.0 5 -
Cadmium, Cd mg/MJ 0.9 0.7 0.0 10 -
Chromium, Cr mg/MJ 4 1.2 0.0 50 -
Mercury, Hg mg/MJ 1.7 0.1 0.0 1 0.0
Nickel, Ni mg/MJ 6 400 0.0 - -
Lead, Pb mg/MJ 7.6 25 0.0 200 1.0
Particles mg/MJ 25 1.3 0 45 20
a: Does not contributes to increasing CO2 level of atmosphere
* http://www.col.org/
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A part from the biomass composition the boiler role is very important on
determining the amount of emissions produced in combustion. The following
two tables gather the information referred to the emissions produced by one
of the two furnaces that are going to be installed. So if we want to know the
total amount of the emissions produced by the district heating we must
double the amount collected in the table below.
The following data have been obtained thanks an inspection report done by
TÜV in Austria on the twentieth of January of 2003. The inspection report
number is the 03-UWC/Wels-Ex-0225/1. All the measures were done with
reference 13% O2 dry.
Table 29. Emissions of the TDS Powerfire 150 kW boiler at rated power
Pellets Wood chips*
O2 (vol%) 7 7,2
Emissions mg/Nm3 mg/MJ mg/Nm3 mg/MJ
CO at rated power 20 14 16 11
NOx 116 78 115 78
OGC <2 (<2) <2 (<2)
Dust 18 12 28 19
*Wood chips B1 according to EN 303-5
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Table 30. Emissions of the TDS Powerfire 150 kW boiler at partial load
Pellets Wood chips*
O2 (vol%) 8.9 10
Emissions mg/Nm3 mg/MJ mg/Nm3 mg/MJ
CO at rated power 64 44 34 23
NOx 80 54 95 64
OGC <2 (<2) <2 (<2)
Dust 16 11 8 5
*Wood chips B1 according to EN 303-5
The technical specifications for the chimney are:
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Table 31. Chimney design
Fuel-gas side (data for chimney
design) Units Pellets
Wood
chips
w30/w50
Firebox temperature ºC 900-1,200 900-1,000
Firebox pressure mbar 0.2-0.3
Required draft at rate power mbar 0.16
Required draft at partial load mbar 0.08
Required induced draft fan Yes
Exhaust gas temperature at rated power ºC 160
Exhaust gas temperature at partial load ºC 80
Exhaust gas mass flow at rated power Kg/h 388 493/565
Exhaust gas mass flow at partial load Kg/h 110 137/157
Exhaust gas volume at rated power Nm3/h 300 388/455
Exhaust gas volume at partial load Nm3/h 87 180/130
Smoke pipe diameter mm 250
Recommended chimney diameter mm 300
Min. chimney connection height mm 1,615
Chimney design Moisture resistant
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3.6. Energy cost calculation
3.6.1. Investment costs
The total investment required to construct the whole district heating is the
one that follows.
Table 32. Investment costs
Description Total cost (€)
TDS Powerfire 150 kW (2 units) 78,964.00
TDS Powerfire accessories 9,610.81
District heating: pipes and accessories 10,748.19
Transport, installation, stainless steel pipes, accessories and start-up tests
39,800.00
Project (2% of installations) 2,860.46
Project design and construction supervision (2% of
installations) 2,860.46
Civil engineering works 80,000.00
TOTAL 228,743.92
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3.6.2. Maintenance furnace cost
Table 33. Maintenance furnace cost
BIOMASS Amount Units Calorific power 4.50 kWh/kg Price 0.08 €/kg Annual price increasing 0.00 % Biomass consumption 133,333 kg Energy consumption 600,000 kWh FINANCING Total investment 85,664 € Term 10 Year Financed percentage 50 % Interest rate 0.00 % Financed capital 42,832 € Initial payment 42,832 € ENERGY PRICE 0.018 €/kWh INVESTMENT Boiler and fuel feeding 82,864 € Installation 2,800 € Civil engineering 0 € TOTAL INVESTMENT 85,664 € Subvention percentage 30 % Subsidy 25,699 € TOTAL SUBVENTIONS 25,699 € EXPENSES Electric power 60 €/year Management and maintenance 700 €/year Insurances and others 250 €/year Fuel cost 10,667 €/year
REDUCTIONS Tax reduction 0 % f/inv Corporation tax 35 % Tax reduction for investing in RREE 0 €
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3.6.3. Fuel cost
The comparison between different kinds of energy shows that biomass
reaches, in the term of ten years, the lowest cost.
Figure 14. Energy cost
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4. Conclusions
4.1. Conclusions about biofuel potential
• Biomass in La Cerdanya shire:
o Public Use Catalogue forests biomass: The annual available cut
reaches 25,710 t/year. Far more than needed.
o Industrial by-products: 16,650 t/year of biomass are produced,
but only about 8,700 t/year might be available at a competitive
price. Barks, used in gardening, and sawdust, used in
cleanings, have alternative markets.
o Other residual biomass: The residual biomass picked up in the
rubbish dumps in the whole shire (67.91 t/year), which is an
excellent and cheap material to be used as biofuel, can barely
only cover 12.83 % of biomass demand (543.3 t/any).
o The total biomass potential in the shire is about 34,500 t/year
or 120,750 Gcal/year.
• Lles de Cerdanya’s forests own an annual allowable cut of 4,000 m3
(with bark) and 536 t/year of branches. Moreover, 17,000 t of death
wood are scattered all over the municipality forests.
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4.2. Conclusions about fuel supply chain
• At this time Lles de Cerdanya council has three options for obtaining
biomass:
o Hiring a specialized enterprise
o Buying a chipper and obtain the biomass from loggers
o Create a forest brigade
• Advantages and disadvantages of the methods:
Supply options
Th
eo
reti
cal
bio
fuel
cost
Fin
an
cial
risk
Nece
ssary
in
vest
men
t
So
cial
ben
efi
ts
Fir
e f
ore
st p
reven
tio
n
Hiring a specialized enterprise
Buying a chipper and obtain
the biomass from loggers
Create a forest crew
• The most suitable supply methods are “chipping at roadside landing”
and “chipping at power plant”.
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• Even though the needed average productivity (0.32 LCM/h) of the
chipper is not as high to need a high performance wood hog, if the
size of the timber to be chipped is big enough, a high capacity
chipper will be required. The bigger maximum chippable diameter is
needed, the higher performance the chipper will have.
• In winter, when most fuel is consumed, forest tracks are covered with
snow and drying conditions are worst. Besides, working conditions
are more difficult and labour force is more reduced. This makes that
most part of biomass must be extracted from May to November.
4.3. Conclusions about the plant
• The chosen burner model for the district heating is a TDS Powerfire
150 kW. Two burners will be installed
• The average daily biomass consumption reaches 1.49 m3, and the
maximum is 3.62 m3. The annual consumption is 543.30 m3.
• The minimum timber yard size for storing the wood needed for a
whole year is 1,812.62 m2.
• District heating investment cost: 228,743.92 €
• Burner costs:
o Financing. Initial investment (after subsidies): 42,832 €
o Total expenses cost: 11,667 €/year
• Energy price: 0.018 €/kWh
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ANNEXES
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Annex 1
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Boiler full technical specifications
Designation Pellets Wood
Chips*
Rated power kW 150 150
Partial load kW 45 45
Boiler-efficiency at rated power % 91.5 90.4
Boiler-efficiency al partial load % 93.6 92.9
Fuel thermal output at rated power kW 164 166
Fuel thermal output at partial load kW 48 49
Water side
Water content l 295
Water connection diameter in 2 (inner thread)
Diameter of termal safety valve in 3/4
Water-side resistance at 20 K (6.5
m3/h) Pa 2800
Water-side resistance at 15 K (10
m3/h) Pa 5000
Boiler temperature ºC 65-90
Minimal boiler-entry temperature* ºC 55
Max. operational pressure bar 3.5
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Fuel-gas side (data for chimney
design) Pellets
Wood
chips
w30/w50
Firebox temperature ºC 900-1,200 900-1,000
Firebox pressure mbar 0.2-0.3
Required draft at rate power mbar 0.16
Required draft at partial load mbar 0.08
Required induced draft fan Yes
Exhaust gas temperature at rated
power ºC 160
Exhaust gas temperature at partial
load ºC 80
Exhaust gas mass flow at rated
power Kg/h 388 493/565
Exhaust gas mass flow at partial
load Kg/h 110 137/157
Exhaust gas volume at rated power Nm3/h 300 388/455
Exhaust gas volume at partial load Nm3/h 87 180/130
Smoke pipe diameter mm 250
Recommended chimney diameter mm 300
Min. chimney connection height mm 1615
Chimney design Moisture resistant
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Fuel
Water-content homologation Kg/kg
WM 9.8 32.3
Maximum water content “w”
(design)
Kg/kg
WM150
Maximum fuel humidity “u” Kg/kg
DM2100
Maximum fuel size acc. to ÖNORM G30**
Ash
Ash-container volume – fly ash Liter 35
Ash-container volume – grate ash Liter 66
Ash-removal system Yes
Electrical system
Connection
400 V, 3-phase with fed-
through zero conductor
Total max. rated capacity 3,337
Total weight (empty) 1,550
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Emissions according to
inspection report TÜV Austria
Inspection report No. 03-UWC/Wels-Ex-0225/1
Inspection report date 20-01-2003
Fuel
Pellets Wood
chips*
Reference 13% O2 dry
O2 at rated power Vol% 7 7,2
O2 at partial load Vol% 8,9 10
CO at rated power
mg/Nm3
20
mg/MJ
14
mg/Nm3
16
mg/MJ
11
CO at partial load 64 44 34 23
NOx at rated power 116 78 115 78
NOx at partial load 80 54 95 64
OGC at rated power <2 (<2) <2 (<2)
OGC at partial load <2 (<2) <2 (<2)
Dust at rated power 18 12 28 19
Dust at partial load 16 11 8 5
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*Wood chips B1 according to EN 303-5
**G50 upon request
***Data for Austria
mg/Nm3: milligram per standard cubic meter (Nm3 under 1,013 hPa at 0ºC)
1WM: wet matter
2DM: dry matter
Referred to the KWB Biomasseheizungen TDS Powerfire 150 kW Technology
Planning cathalog
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Annex 2
1. Lles de Cerdanya municipality map
2. Protected areas map
3. Soil use map
