utilization of biomass in slovakia

Ecological Engineering 16 (2000) S83–S89

Utilization of biomass in Slovakia

Jan Ilavsky *, Milan OravecForest Research Institute Masory ko6a, Str.22, 960 92 Z6olen, Slo6ak Republic

Accepted 14 December 1999

Abstract

At present, approximately 400 000 ton of biomass annually are utilized for energy. It is a question of fuel woodutilized mainly by inhabitants. Utilization of the rest of forest biomass is small even though an annual utilizablepotential is almost 7000 TJ. Increase and higher effectiveness of biomass utilization for energy in Slovakia requiresdevelopment of preparation technology for fuel biomass, including transportation and chipping. At present, adevelopment of chippers is in progress, and production of chippers is as follows: Chipper S-800, Disk chipper inmobile version (tree-point attachment of tractor) and in stationary version (electric motor). Maximal diameter ofwood processed is 150 mm and size of chips to 25 mm. The chipper of waste wood is D-1000. Chipper is placed oncontainer frame; driving unit is electric motor or combustion engine. Maximal diameter of wood is 600 mm and sizeof chips is to 40 mm. Research and development of energy production technologies based on biomass are aimed atcombustion equipment with capacity of 100–3000 kW, and gasification equipment with subsequent production ofelectric power with capacity of 50 kW and biomass briquetting. Direct production costs for 1 ton of fuel biomass areexpected to be between 100 to 620 SKK, which makes biomass competitive after expected increase of prices of fueland energy in Slovakia. © 2000 Elsevier Science B.V. All rights reserved.

Keywords: Biomass; Chipper; Bioenergy

www.elsevier.com/locate/ecoleng

1. Introduction

The economic transformation in Slovakia, ac-companied by the considerable decrease in pro-duction within all parts of the national economy,has caused a decrease in energy and fuel con-sumption. Compared to the year of 1989, the totalannual energy consumption during the year 1994has decreased by 20%. Since the year 1995, asresult of gradual increase in economic production,

the consumption of energy and fuel has beenincreasing and the level of their consumptionreached in the year 1989 will be reached againround the year 2000, when the total annual con-sumption of energy and fuel will be at 950 up to1000 PJ.

During this decade, there has been a gradualchange in the structure of fuel consumption, espe-cially a considerable increase in natural gasconsumption.

The electric energy produced from nuclear fuelwill exceed more than 50% of the total produc-tion. More than 25% of the electricity has been* Corresponding author.

0925-8574/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.

PII: S 0925 -8574 (00 )00056 -2

J. Ila6sky, M. Ora6ec / Ecological Engineering 16 (2000) S83–S89S84

produced by means of coal combustion in thethermal power stations equipped with the desul-phurisation systems. It is assumed that the con-struction of the steam-gaseous equipment andplants based on natural gas, will be used, andthat, there will be an increase of renewablesources of energy.

Slovakia has to import approximately 90% ofits primary sources of energy; the reserves ofdomestic, non-restorable sources of energy arevery limited, indeed. Therefore, the increased de-mands on energy have been forcing us towardsthe more rationalized use of non-renewablesources of energy, together with the expansion ofthe renewable sources of energy, as well as thecreation of ecologically and economicly accept-able combinations.

Until the year of 1991, very little attention waspaid within Slovakia to the use of renewableenergy sources. The main reasons had been thecentralization of the sources of energy and theconsiderable financial support and subsidies to-wards the classical fuels and produced energy.These reasons are responsible for the long-termcharacterization whereas now the existing pricedeformations have been eliminated and graduallyremoved. Nevertheless, the slow development inthe use of the restorable sources, even in presenttimes, has been caused by the lack of financialmeans.

The exception among the restorable sources ofenergy is water energy. At the present, the hy-droenergy potentials in Slovakia have only beenused in little more than 60%. Even the smallhydroelectric power stations have produced aninsignificant proportion of the Slovak energy.

Except for energy, within Slovakia there is po-tentially the most important renewable source ofenergy, ready almost for immediate use; this is theforest and agricultural biomass.

Main producers of biomass, which is suitablefor the use in energetics are mostly the variousbranches within forestry, the woodworking indus-try, and agriculture. All these branches were inexistence during the period of the considerablechanges in proprietary relationships.

Within the forestry sector, there are :25% ofthe forests, which are under the management of

non-state organizations. In any event, we expectthe portion of the non-state organizations to in-crease in the future. Due to existing efforts for thepartial finalization in production, forestry organi-zations have been trying to expand, or even toconstruct small woodworking facilities, opera-tions, and plants.

After the year 1990, within the woodworkingindustry there have been established very manysmall private plants, mostly saw mills, with theannual capacity of woodworking up to 10 000 m3

of wood. By means of privatization of the stateowned woodworking industrial plants, atomiza-tion in ownership has occurred and as the resultof such activities the independent, separate privateindustrial plants have been established with an-nual woodworking production capacity up to50 000 m3 of wood. In Slovakia there are eightlarge integrated woodworking plants with theirannual production capacity from 150 000 up to900 000 m3 of wood. In a majority of these inte-grated woodworking plants, there have been grad-ual changes in production plans as well as intechnologies.

Within the agricultural branches, a relativelysmall number of new plants or facilities have beenestablished. The process of economic changes hasbeen forcing the plants to take rationalizationalmeasures, based on the changes in technologiesand also, partially, even towards the changes inproduction plans.

The above-mentioned changes within the indi-vidual sectors of the industrial and agriculturalbranches that have been producing biomass arecreating the need for changes or modernization inthe energy systems of plants. Thus the conditionsfor development in the use of biomass energyproduction have been created.

At present, within Slovakia, biomass is used forthe purposes of energy only in the production ofheat. The forestry sector produces annually, onaverage, 400 000 ton of fuel wood, with an energyvalue of 3 800 TJ, while more than 90% of it hasbeen sold to inhabitants. Only a very small quan-tity, in the form of chips :10 000 ton, has beenused for the purposes of energy production withthe energy value of 180 TJ annually. The organi-zations within the forestry sector have their own

J. Ila6sky, M. Ora6ec / Ecological Engineering 16 (2000) S83–S89 S85

consumption, which is represented by the quantityof 2000 ton annually.

Within the woodworking industry, the quantityof 250 000 ton of waste wood has been usedannually for the purposes of energy production.

Within agriculture, biomass for energy produc-tion, has practically not been used. The exceptionis represented by means of one piece of the strawincinerator with the output of 230 kW. Superflu-ous straw from the area of the southwest Slovakiais occasionally exported to the Austria.

Total quantity of biomass, used annually forenergy production within Slovakia is representedby the amount of 660 000, tonnes with the energyequivalent of 6270 TJ, which means 0.6% of thetotal fuels and energy consumption for the entireSlovak Republic.

Majority of the boilers, that have burnedbiomass do not meet requirements from the pointof view of environmental and energy parameters.The main obstacle to the development and mod-ernization in technologies for energy productionmade of biomass is the lack of financial means.

2. Technologies and machinery for production offuel-biomass

Technologies and machinery have been de-signed for the utilization of dendromass in clear-ings, thinnings, as well as in regeneration fellingsdepending on the place of performance of theindividual working operations and composition ofmachinery sets according to users’ subjects (largestate enterprises, private firms, etc.). The calcula-tions were executed on the basis of the annualefficiency of the machinery sets for which themachines were chosen so that their efficiency iscomparable. The calculations were made on thebasis of direct production costs, which provide abetter possibility for comparison without influ-ence from the other costs, especially overheadcosts, which deform the resulting values.

Homogenization of the wood waste is a decisivetechnological operation during its processing. Thechoice of kind and type of equipment for the sizeadjustment depends on the locality of occurrence,kind and concentration of raw material and the

method of utilization — technological, energeti-cally direct combustion, gasification, briquetting,etc.

The chipper S-800 has been developed andmade at the Forest Research Institute and wascreated for processing less-valuable wood thatoccurs in lower concentrations, with the annualefficiency of 2000–3000 ton of chips. The wastewood chipper D-1000 has been developed forprocessing wood in higher concentration.

2.1. Chipper S-800

S-800 is a disk chipper intended for processingwood with diameter to 15 cm. It operates asmobile equipment mounted on the three-pointtractor suspension or it can be stationary drivenby electric motor. It has either two or three knifeson the chipping disk. The chipper with two knifesproduces chips of 12–25 mm in length, suitablefor direct combustion, or in the case of rawmaterials of better quality for technological pur-poses, the chipper with three knives per diskproduces chips 4–8 mm long, suitable for theproduction of fuel briquettes.

Basic technical specifications

830 mmdiameter of chipping disknumber of chipping 2 (3)/1 psknives/counter knives

265×285admission aperturemm

150 mmmax. diameter of chipped wood5–25 mmchips length adjustable40 kWdrive — electric motor50 kW—three-point tractor suspension750 rpmchipping disk speed stationary

—mobile 950 rpm900 kgweight of chipper

2.2. Wastewood chipper D-1000

The wastewood chipper is intended for the di-mensional homogenization of raw wood material


that is not workable at all or only with largeproblems. In forestry it is the question of shorttail cuts-off (wastewood) that results from round-wood handling, branches of coniferous trees frombranch-trimming machines, stems, roots, brushes,etc. In agriculture it involves mainly branchesfrom cut fruit trees, shrubs from pasture landsclearings and from recultivation, switches fromvineyards cutting, etc. The wastewood chipperwill have also a more extensive use in liquidationof various kinds of wood waste in the buildingtrade and industry, for instance sheeting units,pallets, rafters, etc. In the long run this equipmentwill be needed in biomass utilization from forestswith a very short rotation period (so-called en-ergetic forests).

Basic technical specifications

600 mmdiameter of chipping drum1000 rpmnumber of drum turns (speed)20 piecesnumber of knives1000 mmadmission aperture — width

— height 350 mm20–40 mmaverage size of chipped material300 mmmax. diameter of wood

capacity 18 m3/h8000 kgweight

3. Production of energy from forest biomass

Forest biomass is classified with considerabledimensional diversity. For better transport han-dling and increasing of energy production effi-ciency, it is necessary to adjust dimensionally theraw material by chipping (branches, trees) andcrushing (manipulation and processing of waste,stems).

For the conditions in Slovakia there are thefollowing prospective forms of energy production:1. Direct combustion of moist dimensionally ad-

justed raw material;� hot-water heating of buildings;� production of technological steam;

� production of electric energy (steam tur-bine, gas turbine) and heating of buildings;

� hot-air drying in agriculture.2. Energetic gasification of dried raw material

adjusted dimensionally;� production of electric power (gas engine

and generator);� production of electric power and building

heating (waste heat);3. Briquetting of dried fine-grained waste� heating of houses, recreational buildings,

etc.At present, the direct combustion of forest

biomass is the most energetically and economi-cally efficient method of its energy utilization inwoody regions for heating of buildings by theform of a central source of heat (CSH), or indi-vidually and in the larger concentrations of fuelthere is also production of electrical energy andheat.

Energetic gasification with production of elec-tric power is usable in wood-working plants oroutside of public electricity-distributionalnetworks.

Briquets are an environmentally friendly substi-tute to coal in classical furnaces without the ne-cessity for their adjustment where the continuoussupply of wood fuel is not available.

Achieving the goals of expansion of energyproduction from biomass depends on the avail-able technologies with acceptable prices and thetechnical level at a European standard.

The price policy in fuel and energy applied bythe year 1990 in former socialist countries did notstimulate a development of the utilization of re-newable energy sources. Renewal of interest inutilization of renewable energy sources due toliberalization of prices has elicited the need fortechnological development.

In 1991 the Forest Research Institute designedthe scientific and technical project ‘The Utilizationof Forest Biomass for Energy’, included in theprogramme ‘The Utilization of the Secondary andRenewable Energy Sources’ by the former FederalMinistry of Economy in Prague. In 1991–1992the Forest Research Institute in Zvolen completedthe above-mentioned project within the frame-work of the whole Czechoslovak Federal Repub-


lic. Since, 1993 the Forest Research Institute hasbeen co-ordinating and investigating a workingplace for the project ‘The Utilization of ForestBiomass for Energy, on the basic of requirementsof the Ministry of Economy of the Slovak Repub-lic’ (Oravec and Ilavsky, 1997).

The above mentioned projects have been de-signed to solve the following problems:� design and development of technologies and

machines for harvest, collection, transportationand dimensional homogenization of biomasssuitable for energy utilization;

� development of combustion equipment formoist biomass adjusted dimensionally withinthe range of capacity from 100 to 3000 kW;

� development of an internal combustion enginefor wood gas with an electrical generator witha capacity from 23 to 50 kW;

� development of gasification generator for woodgas production for gas engines with a capacityto 88 kW

� development of briquetting press, at a capacity500 kg per h.The solutions are in the phases of realization

and pre-realization phase, for the time being.In 1993 the Forest Research Institute Zvolen

proposed the concept of energy utilization offorest biomass in Slovakia. The Ministries ofAgriculture and Economy of the Slovak Republichave accepted the submitted concept and it wasconsequently included in the state energy conceptof the Slovak Republic by the year 2005, ap-proved by the Government of the Slovak Repub-lic in July 1993.

4. Energetically benefits

Through the use of 400 000 ton of forestbiomass 6250 TJ energy can be produced up tothe present time and by more effective utilizationof fuel wood. 115.2 TJ of energy, i.e. 1.84% of anamount produced, is consumed for preparationand energy production.

Through management of energy forests andutilization of their production, it is possible toproduce 4200 TJ in the year of 2005. For manag-ing, felling, and producing energy it is necessary

to increase the given amount to 3.8%. The aver-age annual energetic profit is 4040 TJ.

5. Ecological benefits

Brown coal (600 960 ton) with the heatingvalue 13 MJ/kg and energy production efficiencyof 80% will be converted into production of 6250TJ of energy from forest dendromass. Thus, thepollution load to the environment will be reducedby 3.08 million t of CO2, 93 300 ton of SO2, 7810ton of NOx, 30 400 ton of fly ash, and 120 000ton of slag and ash. The production of CO2

during the combustion of biomass is part of thenatural cycle of substances and it does not in-crease its share in the air.

In the case of implementation of energy forestprojects, 401 000 ton of brown coal can be substi-tuted in 2005, which will prevent the productionof 2.06 million ton of CO2, 62 300 ton of SO2,5210 t of NOx, 20 300 ton of fly ash, and 80 000ton of slag and ash.

6. Economical benefits

The costs of obtaining raw material in suitableconditions based on grain size and moisture areone of the decisive economic criteria forprofitability valuation of energy production fromwood.

According to grain size, the assortment isclassified as follows: fuel wood assortment, pieceand fine-grained waste from processing and woodhandling, respectively, and chips and chipped ma-terial. Dimensional homogenization of wood bysplitting or chipping often increases the cost offuel; however a direct combustion enables utiliza-tion of simpler and cheaper furnaces and bettercontrol of combustion process and by this way ahigher efficiency of energy production. Energygasification and briquetting require utilization ofraw material that is homogenized dimensionally.

Production costs of the preparation of wood asa fuel depend on the number and quality of workinvested in performances to be executed. The leastcosts are with waste originating during processing


or wood handling when a considerable part of thecost is included in the price of the main product.Direct costs of preparation of fuel consist only ofpotential dimensional homogenization and neces-sary transport.

Preparation of fuel from harvesting residuesfrom stands includes all working operations fromskidding to transportation to the place of con-sumption. Counting the economic profitability, itis necessary to consider the savings from theremoval of the raw material from the felling area.The savings resulting from hygiene improvementof the stand are hard to be calculated in advance.

The direct production costs for preparation offorest dendromass, including transportation, areas follows:

Raw material Direct produc- Price per 1 GJ(Sk)/US$ (1tion costsUS$=32 Sk)(DPC) (Sk/

ton)Dendromass 415–600 43.70–63.20/1.0

from–2.0

clearingsDendromass 156–619 16.40–65.29/0,5

from–2.0

thinnings28.20–51.50/0.9Dendomass 268–489

regeneration–1.6

felling410–610Underground 43.20–64.20/1.4

dendromass–2.0

100–200Sawdust from 10.50–21.10/0.3forest de-

–0.7pots andsmall wood-workingplants

15.80–36.80/0.5150–300Cuts-off fromforest de-

–1.2pots andsmall wood-workingplants

The present price of forest chips in Slovakia is600–750 Sk/t (18.8–23.4 US$/ton), representing

63.20–78.90 Sk (2.0–2.5 US$)/1 GJ.The price of fuel wood is approximately 350

SK/m3 (10.9 US$/ton) and it represents 38.90 Sk(1.2 US$)/1 GJ.

In the evaluation of competitiveness of fueldendromass it is necessary to consider two basicsituations:� fuel consumed by producer (forestry, forest

owners);� fuel sold to other consumers.

In the first case a producer can add only thenecessary overhead to the direct production costs.The price of the fuel sold to other consumersincludes overhead and profit.

The price of heat produced in a boiler housewith installed capacity of 0.5 to 1.6 MW usingvarious kinds of fuel (as presented in data fromthe Forest Research Institute in Zvolen based onthe study of reconstruction possibilities of coalmunicipal boiler houses):

Fuel Price for 1 GJUS$/GJSk/GJ

Brown coal 216–268 6.8–8.45.9–6.9188–222Natural gas

150–181Forest chips 4.7–5.7

The production costs for 1 kWh of electricpower by a power plant with a capacity of 40 kWwith natural gas engine range from 1.96 to 2.55Sk/kWh according to the capacity utilization levelof equipment.

Realization of energy utilization of forestbiomass prepared in Slovakia will yield the aver-age annual savings in the costs of energy produc-tion 61 million Sk by 2000.

7. Conclusion

Approximately 1% of the total consumption offuels and energy in Slovakia will be covered bythe production of energy from utilizable amountsof less-valued dendromass. The potential of do-mestic fuel-energy sources used for the time beingwill increase by 6.7%.


Through utilization of fuel dendromass,the import of brown coal will be reduced by500 000 ton/year and of natural gas by 200 mil-lion m3.

In Slovakia a direct combustion, energetic ga-sification and adjustment of fine-grained waste bybriquetting are the most prospective methods ofenergetically utilization of dendromass.

A wider and more efficient utilization of thatfuel will affect ecology as well as the economy.Dendromass as an ecologically less-damaging fuelenables a considerable reduction of local pollutionof the environment. Occurrence of that raw mate-rial will enable a supply of fuel from local sourcesyielding savings in coal transportation, especiallyto remote regions.

Further advantages of biomass energeticallyutilization:� more flexibility of reaction to local changes in

amount and structure of energy consumption;� reduction of negative impacts caused by fluctu-

ation of prices of basic fuels;

� possibility of integration of investments at localand regional levels, respectively, and by reduc-tion of state budget load;

� creation of new working places;� improvement of self-sufficiency of the state in

the sphere of fuels.Measures for utilization extension:

� reduction of state subsidies for heat and energyor their provision for renewable sources aswell;

� preference for ecologically convenient domesticenergy sources;

� support of regional projects including local re-newable energy sources;

� credit and tax policy supporting utilization ofrenewable sources;

� charges for an increase in air pollution by fossilfuel combustion.

References

Oravec, Milan, Ilavsky, Jan. Present state of energetic biomassutilization in Slovak agriculture study. Zvolen 1997, pp. 27

.

utilization of biomass in slovakia

Documents