Summary
High energy prices cause the use of agglomerates to increase sharply. The utilisation of wood pellets offers a useful form of heating competing with gas heating systems. In order to make their use general not only should we summarise the qualitative parameters of primary and final products, but also make up rules and guides to determine standards. Most countries have their own qualification systems, but a quality system standard is not established either in the foreign countries or in Hungary. The process of standardisation of solid fuels is administered by Technical Committee 335 within the European Committee for Standardization (CEN). Its aim is to promote the development of solid biofuel market.
In this research we shall examine the combustion related fuel properties of pellets through samples distributed in Hungary. On the basis of the results we will make suggestions regarding the validation of the proposed European standards and the application of a unified qualification method.

1. Introduction
A distinction must be drawn between pellets and briquettes. Briquettes are agglomerates made of several by-products with a diameter of ≥50 mm of oval, square or polygon shape. Pellets are compressed in a flat-die or ring-die pellet press with a diameter of 3-25 mm. They became widely known with the foundation of companies selling seeds mixture (Barótfi, 1998.;
Kovács, 1997).
Pellets and briquettes can be manufactured in two ways, but the techniques differ in their investment and maintenance costs. A simple technique utilises the dried by-products of wood processing plants, such as sawdust and sawdust powder. The more complex method uses primary products from forestry (shavings, bark waste) and agricultural by-products; these materials should be dried, re-split, sorted and transported to the mill before pelletising.
(Kovács, 1988).
Although briquettes have several positive features, they can hardly be used in small-scale combustion devices because of the relatively big size of the particles. In contrast, small-sized pellets can be loaded automatically into the burner with force feeders (auger, cell), thus lowefficiency equipments can operate with high effectiveness. The production of pellets is increasing rapidly due to their convenient features and the high level of automation of combustion equipments.
In order to facilitate the widespread use of solid biofuel the qualitative parameters of primary and final products, as well as the rules and guides to specification must be determined. The standardisation of products, methods and services is the process of developing technical standards.
Standards enhance the proper application of products, procedures and services, remove trade barriers, contribute to technical collaboration and help the creation of a single market. During the process of standardisation norms are established, issued and adopted. Standards must be based on scientific and technical experiences and serve the interests of the community at their best. Maladjusted national standards may be detrimental to economy and trade. (Bíró-Rátzné
Ludányi, 2004; Szigeti et al., 2003).
In the last few years, the European Union has highly promoted alternative power generation and the standardisation of renewable energy sources, and there has been a growing interest regarding the standardisation of biomass fuels. In the near future Hungary also will be forced to adopt and apply the new technical directives and standards (Vityi, 2006).
The technical recommendation (CEN/TS 14961:2005) defines the fuel specifications and classes of solid biofuels. According to this specification solid biofuels include the following biomasses:
 Products from agriculture and forestry

Vegetable waste from agriculture and forestry

Vegetable waste from the food processing industry

Wood waste, with the exception of wood waste which may contain halogenated organic compounds or heavy metals, and wood waste originated from construction

Fibrous vegetable waste from the pulp and paper industry

Cork waste
The standards determining the groups and their products are summarised in Table 1.

Table 1 : Main properties and technical specifications of biofuels
Properties Standards/technical recommendations to define properties
Standard reference Title
Traded forms, origin, source
CEN/TS 14961:2005 Fuel specifications and classes
Moisture content
Ash content, ash melting behaviour
Net calorific value
Volatile matter content
Particle size distribution
Particle density
Bulk density
CEN/TS 14774-1-3:2004
CEN/TS 14775:2004
CEN/TS 15370-1:2006
CEN/TS 14918:2005
CEN/TS 15148:2005
CEN/TS 15149-1-3:2006
CEN/TS 15150:2005
CEN/TS 15103:2005
Mechanical durability CEN/TS 15210-1-2:2005
Methods for the determination of moisture content
Method for the determination of ash content and ash melting behaviour
Method for the determination of calorific value
Method for the determination of the content of volatile matter
Methods for the determination of particle size distribution
Methods for the determination of particle density
Methods for the determination of bulk density
Methods for the determination of mechanical durability of pellets and briquettes
Calculation of analyses to different bases
Determination of total content of carbon, hydrogen and nitrogen
Analysis of elements CEN/TS 15296:2006
Carbon, hydrogen and nitrogen content
Water soluble content
CEN/TS 15104:2005
CEN/TS 15105:2005 of chloride, sodium and potassium
Sulphur and chlorine content
CEN/TS 15289:2006
Methods for determination of the water soluble content of chloride, sodium and potassium
Determination of total content of sulphur and chlorine
Major and minor elements
CEN/TS 15290:2006
CEN/TS 15297:2006
Determination of major elements (e.g.: Al, Si, K, Na,
Ca, Mg, Fe, P, Ti, Ba, Mn) and minor elements (e.g.:
As, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn,
V, Zn)
Source: own work based on “Solid biofuels - Fuel specifications and classes CEN/TS
14961:2005”
Major fuel characteristics (moisture content, ash content, net calorific value, volatile matter content) and physical/mechanical properties (mechanical durability, particle size distribution, bulk density) must be determined to specification.
Solid biofuels can be classified by origin, source and traded form. Specification based on traded form: briquettes, pellets, fuel powder, sawdust, wood chips, shavings, logs, whole wood, straw bales, bundle, bark, chopped straw, grain or seed, shell and fruit stones, fibre cake.
Several countries have developed their own biomass fuel standards, but these national specifications have little in common. In the past years, there have been many attempts to develop unified qualification methods and procedures, concerning pellets in particular.
Nowadays most European countries have standards for pellets at national level, the three major are the Swedish (SS187120), the German (DIN 51731) and the Austrian (ÖNORM
M7135) ones.
The three national standards and the international proposed standard (CEN/TS 14961:2005) can be seen in Table 2.

Table 2 : Comparison between the Austrian/Swedish/German and the European standards for pellets
Properties
Origin
Size
Bulk density
Amount of fines a
Austria
Önorm
M7135
-
ø 4-20 mm max. length
100 mm
-
-
Group
1
-
Sweden
SS 18 71 20
Grou p 2
-
Group
3
-
ø max.
4 mm**
ø max.
5 mm
ø max.
6 mm
≥ 600 kg/ m 3
≤ 0,8
%
≥ 500 kg/m 3
≤ 1,5
%
≥ 500 kg/m 3
≤ 1,5
%
Germany
DIN 51731/DIN plus
Mark
HP1
HP2
HP3
HP4
HP5
-
Length mm
> 30
15-30
10-15
<10
<5
-
-
ø mm
>10
6-10
3-7
1-4
0,4-1
EU
CEN/TS 14961:2005
ø mm
D06 ≤ 6
± 0,5
D08 ≤ 8
± 0,5
D10 ≤ 10
± 0,5
D12 ≤ 12
± 0,5
D25≤ 100
± 0,5
-
Length mm
D06≤ 5x
ø
D08 and above ≤
4x ø
To be stated kg/ m 3
F 1,0 ≤ 1 %
F 2,0 ≤ 2 %
F 2,0+> 2 %
Particle density
Moisture content
Ash content
≥ 1,0 kg/ dm 3
≤ 12 %
≤ 0,5 % b
-
≤ 10 %
≤ 0,7
%
-
≤ 10
%
≤ 1,5
%
-
≤ 12
%
≤ 1,5
%
1,0 -1,4 g/cm 3
≤ 12 %
≤ 1,5 %
-
M10 ≤10
M15 ≤15
M20 ≤20
A0.7 ≤ 0,7 b
A1.5 ≤ 1,5
A3.0 ≤ 3,0
A6.0 ≤ 6,0
A6.0+ ≥ 6,0
Net calorific value
≥ 18,0 MJ/kg b
≥ 16,9
MJ/kg
≥ 4,7 kWh/ kg
≥ 16,9
MJ/kg
≥ 4,7 kWh/ kg
≥ 16,9
MJ/kg
≥ 4,7 kWh/ kg
17,5 - 19,5 MJ/kg c d
Sulphuric content
Nitrogen content b
Chlorine content
≤ 0,04 %*
≤ 0,3 %
≤ 0,02 % b
≤ 0,08
%
-
≤ 0,03
%
≤ 0,08
%
-
≤ 0,03
%
-
-
-
< 0,08 %
< 0,3 %
< 0,03 %
S 0,05 ≤ 0,05%
S 0,08 ≤ 0,08%
S 0,10 ≤ 0,10%
S 0,20+ >0,20%
N 0,3 ≤ 0,3%
N 0,5 ≤ 0,5%
N 1,0 ≤ 1,0%
N 3,0 ≤ 3,0%
N3,0+ > 3,0%
Cl 0,03 ≤ 0,03% b
Cl 0,07 ≤ 0,07%
Cl 0,10 ≤ 0,1%
Cl 0,10+ > 0,1% a) percentage of particles with size
<
3 mm (SS 18 71 20) and
<
3,15 mm (CEN/TS 14961:2005) b) dry base c) dry ash-free d) no limit, value must be indicated
Source: Own work based on the data by Hahn 2004; Fenyvesi et al., 2008, CEN/ TS 14961:2005
These national standards and technical recommendations define moisture content, net calorific value, size categories and the percentage of major elements.

The Austrian standard (ÖNORM M 7135-Pellets produced from untreated wood or untreated bark – requirements and conditions) sets up exact requirements regarding the quality of pellets. Apart from the values indicated in the table the standard specifies the quantity of auxiliary pressing materials and adhesives, the inspection method of pellet manufacturers and the transportation and storage conditions (M 7136; M 7137).
DIN Certco (a certification institute of the German Institute for Standardisation (Deutsches
Institut für Normung, DIN)) has forced a new regulation „DIN Plus” since 2002 to guarantee good quality of pellets. Specifications of DIN Plus and Önorm are in accordance. The adaptation of DIN Plus requires close control over the process of production assuring that the production and quality standards are strictly interpreted (Boros, 2004). The German national standard (DIN 51731/DIN Plus-Pellets produced from untreated wood – requirements and conditions) classifies pellets into five groups on the basis of their length and diameter. DIN
Plus applies similar parameters as the Austrian ÖNORM M7135, though there may be minor differences in fuel specifications.
Associations in Germany and Austria include the German Energy Pellet Association
(Deutscher Energie Pellet Verbandes), German Pellet Association (Pelletverbrand
Deutschland), and Austrian Pellet Association (Pelletverbrand Austria). These associations mark standard quality with a “stamp of approval” on the products.
The Swedish standard (SS 18 71 20-Quality of pellets produced) arranges three product groups and specifies their qualitative parameters. The groups differ mainly in size, sizerelated properties, moisture content and ash content.
The proposed European standard (CEN/TS 14961:2005 - Standard for solid biofuels - fuel specifications and) classifies pellets according to their size, moisture content and ash content.
There are no limits concerning net calorific value, but the exact value must be indicated by the retailer.
National standards, technical recommendations and qualification systems create a top-quality product chain by establishing a set of requirements for the manufacturers and serving as a guideline for the consumers.
Hungary has not established national standards for pellet production, we use norms set up by other countries. Since the country lacks both legal regulation and an organisation capable of controlling and supervising pellet production and trade, Hungarian pellet market is short of permanent and reliable quality of pellets. For the time being, only consumer preferences require the observation of national and international directives ( Fenyvesi et al.,2008; Burján,
2009).
There are, however, efforts to build up trust between manufacturers and consumers. The
Hungarian Pellets Association and the Regional Pellet Cluster founded in 2009 aim to intensify the production of quality pellets in Hungary and develop a controlled trademark system, which is a significant step towards the realisation of the necessity for quality specifications.
2. Material and method
We carried out research on the combustion related fuel properties of pellet samples distributed in Hungary. First we collected and studied the technical recommendations regarding fuel properties (e.g.: calorific value, moisture content, ash content etc.), sampling methods and

fuel specifications, then we examined the samples. The following devices were used: Radwag
MAC 250 moisture analyser to determine moisture content; IKA C-400 calorimeter to measure net calorific value; NABERTHERM LV ashing furnace to determine ash content
(samples were combusted at 500°C); Defender industrial scale with a maximum capacity of
150 kg to calculate bulk density.
Measurements were in accordance with CEN/TS 15103:2005 - Methods for the determination of bulk density. Having received the test results the samples were categorised according to
CEN/TS 14961:2005 - Fuel specifications and classes.
3. Results
At present, Hungary imports major share of pellets from the neighbouring countries, only a small portion is produced in the country. Properties of test samples are summarised in Table
3, arranged by origin, raw material and packaging.
Sample number
No. 1
No. 2
No. 3
No. 4
Raw material
Table 3.: Pellet samples examined
Packaging
Country of origin
Mixed, soft- and hardwood
Mixed, soft- and hardwood
Hardwood
Hardwood (high bark content) bagged, palletised bagged bagged, loose bagged, loose
Austria
Ukraine
Hungary
Hungary
No. 5 Softwood bagged, 15 kg or 1200 kg
(„big bag”)
Romania
No. 6
Mixed, soft- and hardwood bagged Hungary
Quality specification used
ÖNORM M7135
-
-
-
DIN 51731
FVM-MI examination certificate
Source: own work
Raw materials are mixed, soft- and hardwood mainly. Pellets are available either in 15 kg bags/1200 kg „big bags” or in bulk. The countries of origin are Hungary and the neighbouring states. Since there is no unified European standard, it is common to adopt the specifications of a certain country.
Table 4. sums up the combustion related fuel properties of the samples. Categories regarding pellets as defined in CEN/TS 14961:2005 - Fuel specifications and classes are also listed.
Some properties greatly influence their applicability for combustion devices and their economy.

Fuel properties
Moisture content
(%)
6,1
Table 4.
Fuel properties of pellets
Sample
No. 1
Sample
No. 2
7,0
Sample
No. 3
6,3
Sample
No. 4
6,3
Sample
No. 5
7,6
Sample
No. 6
7,2
Categories according to
CEN/TS
14961
M10 ≤ 10
M15 ≤ 15
M20 ≤ 20
Dry matter content
(%)
Net calorific value
(MJ/kg)
93,9 93,0 93,7 93,7 92,4 92,8
16,97 16,95 16,81 16,78 17,24 16,87
-
-*
Ash content
(%)
Diameter
(mm)
Length
(mm)
Min.
Max.
0,80
6
7
43
0,76
8
7
36
2,04
8
6
25
3,55
6
5
30
0,98
6
9
35
1,66
6
8
37
A0.7 ≤ 0,7
A1.5 ≤ 1,5
A3.0 ≤ 3,0
A6.0 ≤ 6,0
A6.0 + ≥ 6,0
D06 ≤ 6 ± 0,5
D08 ≤ 8 ± 0,5
D10 ≤ 10 ± 0,5
D12 ≤ 12 ±
0,5
D25≤ 100 ±
0,5
D06 ≤ 5x diameter
D08 and above
≤ 5x diameter
Bulk density
(kg/ m 3 )
Price
(Ft/kg)**
632
50
647
53
709
49
692
56
Price
(Ft/MJ)
2,94 3,12 2,91 3,33
* No limit value determined, value must be indicated when distributed.
** Market prices fixed in 2009.
580
48
2,78
656
48
2,84
*
-
-
Source: Own research
Moisture contents affecting heating value are low, between 6,1 % and 7,6 %. The respecting calorific values are about 17 MJ/kg, ranging from 16,78 MJ/kg to 17,24 MJ/kg.
Ash contents depending on raw materials and bark content are between 0,80 % and 3,55 %.
Diameters and lengths alternate owing to the different types of pellet mills. Diameters are 6 mm (in four cases) and 8 mm (in two cases), lengths range from 5 mm to 43 mm. Bulk densities are between 580 kg/ m3 and 709 kg/ m3 depending on raw materials and pressing properties (e.g.: pressure applied).
Prices range from 48 Ft/kg to 56 Ft/kg, although in most cases price does not reflect quality.
Samples have been categorised on the basis of CEN/TS 14961:2005. Table 5. shows the following categories:
- Moisture content
- Net calorific value
- Ash content
- Diameter
- Bulk density

Table 5.
Classification of pellets according to the categories set up by CEN/TS 14961:2005
Properties
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Moisture content (%)
M10
M10
M10
M10
M10
M10
Net calorific value
(MJ/kg)
16,97
16,95
16,81
16,78
17,24
16,87
Ash content
(%)
A 1.5
A 1.5
A 3.0
A 6.0
A 1.5
A 3.0
Diameter
(mm)
D06
D08
D08
D06
D06
D06
Bulk density
(kg/ m 3 )
632
647
709
692
580
686
Source: own research
After all, samples can be ranked applying CEN/TS 14961:2005, if the main combustion related fuel properties are given. The application would be beneficial for the participants of the biofuel market. Short description of Sample No. 1 can be executed according to technical specifications, as seen in Table 6.
Table 6.: Quality classification of pellets based on test results of Sample No. 1
Property
Moisture content
(%)
Calorific value (MJ/kg)
Ash content (%)
Size (mm)
Categories defined by
CEN/TS 14961
M10 ≤ 10
M15 ≤ 15
M20 ≤ 20
-*
A0.7 ≤ 0,7
A1.5 ≤ 1,5
A3.0 ≤ 3,0
A6.0 ≤ 6,0
A6.0 + ≥ 6,0
D06 ≤ 6 ± 0,5
D08 ≤ 8 ± 0,5
D10 ≤ 10 ± 0,5
D12 ≤ 12 ± 0,5
D25≤ 100 ± 0,5
Pellet quality
M10
16,97
A 1.5
D06
Bulk density
(kg/ m 3 )
-* 632
Price (Ft/kg) - 50
Price (Ft/MJ) - 2,94
Country of origin - Austria
*No limiting value, value must be indicated by retailer.
Source: Own research
National standards (e.g.: Önorm) should be replaced with international quality standards. This may help improve pellet trade, make consumers’ decisions easier and employ the advantages of a single market. Categorisation in Table 6 does not involve quality rankings but gives a clear description of main combustion related fuel properties. Pellet prices indicated in Ft/kg and Ft/MJ may become easy to compare and support the development of trade competition.
4. Conclusions and proposals
Pellet production and consumption has been increasing rapidly due to the convenient features of pellets and the high degree of automation of combustion devices. Pellets distributed in

Hungary are produced abroad mainly, however, several pellet manufacturing and selling companies have been founded in the country.
Quality and price of pellets influence their economical application. Most countries have created their own qualification systems, but there is no standard regulation either in the EU or in Hungary. National standards, technical recommendations and quality specifications set up requirements for the producers, guide the consumers and develop quality product chains.
General use of agglomerates needs a wide range of quality pellets. Failing this, consumers distrust new products.
Hungary does not have a unified standard system, so we often adopt the specifications made up by a certain country. Standard classification applied in our research may advance the creation of a single biofuel market in Hungary. We attach importance to develop a unified classification system in the biomass supply chain at all levels (producer/manufacturer, retailer, consumer) administering the available proposed standards of the European Union.
Consequently prices and quality features of products will become easy to compare intensifying market competition.
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