truck transportation and chipping productivity of … transportation and chipping productivity of...

Originalscietificpaper–Izvorni znanstveni rad

Croat. j. for. eng. 33(2012)2 199

Truck Transportation and Chipping

Productivity of Whole Trees and Delimbed Energy Wood in Finland

Juha Laitila, Kari Väätäinen

Abstract – Nacrtak

The present study aims to evaluate the competitiveness of various supply systems of small-diameter wood harvested from young stands for fuel. Trees were harvested for the cost comparison either as (i) multi-stem delimbed shortwood or (ii) as whole trees or (iii) the harvesting was based on bundle-harvesting using the Fixteri II bundle harvester. The cutting of whole trees and multi-stem delimbed shortwood was carried out using a conventional harvester head equipped with multi-tree-handling accessories. Forwarding was carried out using a standard medium-sized forwarder. The comparison of procurement costs was done at stand level as a function of breast height diameter (5–13 cm) and on-road transportation distance (5–160 km). The harvested wood was chipped either at a roadside landing or at a terminal using a trailer-mounted drum chipper. The comparison of the supply systems was done using recently published productivity parameters and data obtained from complementary field studies reported herein.According to the cost assessment, whole-tree harvesting and chipping at the roadside landing was almost invariably the most cost-efficient supply system. The cost of whole-tree and multi-stem delimbed shortwood chips was at the same level when the breast height diameter of the harvested trees was 11 cm (pine) or more. The cutting of whole trees is cheaper, but the cost difference diminished as a function of tree size. The productivity of forwarding, transportation and chipping of multi-stem delimbed shortwood was significantly higher compared to that of whole trees. When applying roadside chipping in Finnish conditions with small and sparsely located forest holdings, acquiring large enough concentrations of wood for profitable production is a great challenge. Machine relocations can be reduced by transporting raw material to terminals or the end-use facility to be chipped. However, the low bulk density of the initial material restricts the operation radius unless the wood biomass is pre-processed. According to the results of our study, harvesting of multi-stem delimbed shortwood is a promising way to simplify operations and to reduce transportation and chipping costs. In the case of whole-tree bundling, savings in transportation and chipping costs did not offset the high felling and compaction costs, and the bundling system was the least competitive alternative.

Keywords: whole trees, multi-stem delimbed shortwood, chipping, transportation, small tree harvesting, young stands, terminals

1. Introduction – Uvod

Thenumberofheatingandpowerplantsusingfor-estchipshasincreasedfrom250unitscloseto1000unitsduringthelastten-yearperiodinFinland(Asi-kainenandAnttila2009).Furthermoreseveralnew

biomass plants are planned or under construction(Laitilaetal.2010a).In2007theCouncilofEuropeac-ceptedtheproposaloftheEuropeanCommissionthattheEUmembercountriesshouldproduce20%oftheirenergyusingrenewablesourcesbytheyear2020.Eachmembercountryhasitsowntarget.TheEUobligates

J. Laitila and K. Väätäinen Truck Transportation and Chipping Productivity of Whole Trees ... (199–210)

200 Croat. j. for. eng. 33(2012)2

Finland to increase the share of renewable energysourcesinenergyconsumptionfrom28.5%to38%bytheyear2020.TheFinnishlong-termclimateandenergystrategy

assigns wood-based energy an important role inachieving thisgoal.Currently,processing residuesfromtheforestindustryarethemostimportantsourceofwood-basedfuels,buttheseby-productscanbecon-sideredtobecurrentlyfullyutilised(Ylitalo2011).Inaddition,theavailabilityofprocessingresidueshasdecreasedduringthelastfewyearsasaconsequenceofseveralclosuresofpulpandpapermillsandthedecreasedproductioncapacityofsawmillsandply-woodmills(Kallioetal.2011;Ylitalo2011).Thus,themostimportantmeansofincreasingtheconsumptionofwoodforenergyinthefutureistheutilisationofforestchipresources.Accordingly,theMinisterialWorkingGroupofthe

FinnishGovernmentforclimateandenergypolicyhastargetedtheuseofforestchipsforenergy,i.e.loggingresiduesandstumpsfromfinalfellingsandsmalltreesfromearlythinnings,to13.5millionsolidcubicmetresin2020.Intheyear2010,Finnishheatingandpowerplantsconsumed16.0millionm³ofsolidwoodfuels,ofwhich6.2millionm³comprisedforestchips(Ylitalo2011).Thisamountincluded2.5millionm3ofwholetreesanddelimbedtreesoriginatingfromearlythin-nings,whileloggingresiduesandstumpsfromclear-cuttingareasweretherawmaterialformorethanhalfoftheforestchipsconsumedbyheatingandpowerplantsin2010(Ylitalo2011).Thetechnicalharvestingpotentialofforestchipsin

Finlandhasbeenestimatedtobe14–20millionm3peryear(Laitilaetal.2008;Kärhäetal.2008).About45%ofthisamountcouldbeobtainedfromsmall-dimen-sionwoodfromearlythinnings(Laitilaetal.2008).Accordingtothemostrecentestimates(Salminenetal.2012),some75%ofthesustainablecuttingpotentialofindustrialwoodisbeingmadeuseof,andthisisassumedtomeananincreasingproportionoftheen-ergywoodaccruedwillbecomposedofstemwoodofindustrialwooddimensionsordimensionsveryclosetoindustrialwood.Theharvestingofindustrialround-woodandenergywoodfromearlythinningsiscostly,owingtothesmallstemsizeandlowremovals.Fur-thermore,denseundergrowthoftenweakenstheprof-itabilityofearlythinnings(Oikarietal.2010).InFinlandtheprocurementofthinningwoodchips

ismainlybasedonchippingattheroadsidestorage(73%)orattheterminal(24%)(Kärhä2011).Chippingattheend-usefacilityisnotsocommoninthinningwood harvesting compared to logging residue orstumpwoodchipproduction.Chippingatthelanding

isasuitableandquitecost-competitiveprocurementsystemforpowerandheatingplantsofallsizecatego-ries.Aterminaloperatesasabufferstorage,whichenablesamoresecuresupplyoffuelchips,andalsoservesasaprocessmanagementtoolforthewholesupplychain.Theterminalisalsoacompromisebe-tweenchippingatthelandingandattheplant.Therawmaterialistransportedinanunprocessedformtotheterminalanddeliveredtotheplantaschips.How-ever,thelowbulkdensityoftheinitialmaterialre-strictstheoperationradiusunlessthewoodbiomassispre-processed.Thewhole-treebundler(Fixteri)wasdevelopedin

ordertorationalisetheintegratedharvestingofsmall-diameterenergywoodandpulpwoodandtoreducetransportationcoststhroughloadcompaction(JylhäandLaitila2007;Nuutinenetal.2011;Jylhä2011).Thetransportationcanbearrangedusingstandardfor-wardingequipmentandlong-distancetransportationequipment(Laitilaetal.2009).Thebundlesare,onaverage,2.7minlength,0.65mindiameter,and0.5m³(solid)involume.Conventionalsingle-gripharvesterheadsequipped

withmulti-treehandlingequipmentarealsosuitablefor cutting whole trees and multi-stem delimbedshortwood(Laitilaetal.2010b;Belbo2011).Thework-ingtechniqueofwhole-treecuttingandmulti-stemdelimbed shortwood cutting is basically the sameapartfromthedelimbingofthetopsoftreebunches(e.g.Laitilaetal.2010b).Inenergywoodcuttingwithsingle-gripharvesters,thetreesarecutandaccumu-latedtothechamberofthemulti-treehandlinghar-vesterhead.Subsequentlythetreebunchismovedtoanuprightpositionalongsidethestriproadfortheprocessingofthetreestoforwardinglengthandpil-ing. Inwhole-treeharvesting the treebunch is fedthroughthefeedrollersanddelimbingknivesoftheharvesterheaduptothecrosscuttingpointofforward-inglength(5–7metres).Aftercross-cutting,thehar-vestercranemovestheundelimbedtopbunchontothebasebunchalongsidethestriproad.Inmulti-stemdelimbedshortwoodharvesting,boththebaseandtopbunchofthetreesarefedthroughthefeedrollersanddelimbingknivesoftheharvesterheadandpiledatthesideofthestriproad.Thetopbunchistoppedatthetopdiameterof3–5cmandthetargetlengthoftheboltsisusuallyabout5metres.Aftermulti-treede-limbingonlyshortbitsofbranchesareleftinthetreebunches.

1.1 Aim of the study – Cilj radaThisstudyaimstoevaluatethecompetitivenessof

varioussupplysystemsofsmall-diameterwoodhar-

Truck Transportation and Chipping Productivity of Whole Trees ... (199–210) J. Laitila and K. Väätäinen

Croat. j. for. eng. 33(2012)2 201

vestedfromyoungstandsforfuel.Treeswerehar-vestedforthecostcomparisoneitheras(i)multi-stemdelimbedshortwoodor(ii)aswholetreesor(iii)theharvestingwasbasedonbundle-harvestingusingthenewly-developedFixteriIIbundleharvester(Fig.1).Thecuttingofwholetreesandmulti-stemdelimbedshortwoodwascarriedoutusingaconventionalhar-vesterheadequippedwithmulti-tree-handling(MTH)accessories.Forwardingwascarriedoutusingastan-dardmedium-sized forwarder. The comparisonofprocurementcostswasdoneatstandlevelasafunc-tionofbreastheightdiameter(5–13cm)andon-roadtransportationdistance(5–160km).Theharvestedwoodwaschippedeitherataroad-

sidelandingorataterminalusingatrailer-mounteddrumchipper (Fig. 1).Multi-stemdelimbedshort-

woodandwhole-treebundlesweretransportedtotheterminalusingaconventionaltimbertruckandwholetreesweretransportedusingabiomasstruckequippedwithsolidsidepanelsandbottom(Fig.2).Thechipsfromtheroadsidelandingandfromtheterminalweretransportedusingastandardchiptruck(Fig.2).Thecomparisonofthesupplysystemswasdoneusingre-centlypublishedproductivityparametersanddataobtainedfromcomplementarychippingandtranspor-tationstudiesreportedherein.Thestrategicgoalofthestudywastoimprovethecost-efficiencyofproductionof forest chips fromwood harvested from youngstands,especiallybytestingtechnologiesforchippingandon-roadtransportingofsmall-diameterthinningwood.Updateddataoncostsandproductivityareusefulwhenselectingtheappropriatesupplysystemsforwoodharvestedfromvariousyoungstands.

Fig. 1 A conventional harvester head equipped with multi-tree-handling accessories (up) and Fixteri II bundle harvester. Chipping of energy wood at a roadside landing or at a terminal using a trailer-mounted drum chipper (down)Slika 1. Harvesterska glava (gore lijevo) i bandler harvester Fixeri II – stroj za izradu svežnjeva (gore desno). Iveranje energijskoga drva na pomoćnom stovarištu ili u energani pomoću priključenoga bubnjastoga iverača (dolje)


202 Croat. j. for. eng. 33(2012)2

2. Material and Methods – Materijal i metode

2.1 The time studies of truck transportation Studije vremena kamionskoga prijevozaInthetrucktransportationstudy,thepayloadand

theloadingandunloadingtimesofwholetreeswerecomparedtothoseofmulti-stemdelimbedshortwoodwhenwoodmaterialwastransportedfromaroadsidelandingtobechippedattheterminal.Bothloadingandunloadingweredoneusingthecraneofthetimbertruck.Thestudieswerecarriedoutduringdaylighthours inMay 2010. The empirical data comprisedfourteentruckloads,ofwhichfiveweremulti-stemdelimbedshortwood (146 tonnes/184m³)andninewhole trees (165 tonnes/269m³).Thevolumesandpayloadsofthetimberlotswerebasedonmeasure-

ments at the terminal. The dry green densities ofmulti-stemdelimbedshortwoodandwholetreesweredefinedaccordingtotheSCAN-CM43:95standardand theirmoisture contents according to CEN/TS1477-2.Samplingofwoodwasintegratedintotheter-minalchippingexperiment,whichwascarriedoutimmediatelyafterthetransportingexperiment.Theaveragedrygreendensityofthemulti-stemdelimbedshortwoodwas398kg/m³andmoisture49.6%.Thecorrespondingvaluesforthewholetreeswere357kg/m³and41.8%.Wholetreesconsistedofbirch(Betula pendulaandBetula pubescens),pine(Pinus sylvestris),spruce(Picea abies)andaspen(Populus tremula).Multi-stemdelimbedshortwoodconsistedofpineandbirch.Theaveragelengthofthewholetreeswas8.7mandthelengthofthemulti-stemdelimbedshortwoodwaseither3mor5m.Thebreastheightdiameters(d1.3)of

Fig. 2 A biomass truck equipped with solid side panels and bottom (left up), a standard chip truck (right up), and a standard timber truck (down)Slika 2. Kamion za prijevoz biomase s obloženim tovarnim prostorom (gore lijevo), uobičajeni kamion za prijevoz iverja (gore desno) te kamion za prijevoz drva (dolje)


Croat. j. for. eng. 33(2012)2 203

thewholetreesandmulti-stemdelimbedshortwoodwere7–9cmand10–12cm,respectively.ThetimberwastransportedbyaVolvoFH460tim-

bertruckcomprisedofathree-axletractorandafour-axletrailerequippedwithsolidsidepanelsandbot-tomandinsidemovingcarriage(Fig.2).ThetruckwasequippedwithaKesla2011ZThydraulictimbercrane.Theideawastoloadthebackendofthecarriagefirstandmove itbackwards to load the frontpart last.Thankstotheinsidemovingcarriage,eventherear-mostpartoftheloadspacecouldbeloadedbyusingthecraneofthetimbertruckwithoutdisconnectingthetrailer.Onebunchofthewholetreesandmulti-stemdelimbedshortwoodwasloadedonthetractorand two or three bunches on the trailer. The totallengthofthetruck-trailercombinationwas25.25mandthebulkvolumewas150m³(45m³+105m³).Thetareweightofthetruck-trailercombinationwas29760kg,whichisabout8000–10000kgheaviercomparedtoaconventionaltimbertruck(Peltola2004).Thetimestudywascarriedoutmanuallyusingthe

Rufco-900fieldcomputer(Nuutinenetal.2008).Theworkingtimewasrecordedbyapplyingacontinuoustimingmethod,whereaclockrunscontinuouslyandthetimesfordifferentelementsareseparatedfromeachotherbynumericcodes(e.g.Harstela1991).TheaccuracyoftheRufco-900fieldcomputerwas0.6s(Nuutinenetal.2008).Theharvester’sworkingtimewasdividedintoeffectiveworkingtime(E0h)andde-laytime(Harstela1991),whichisacommonmethodemployed inNordicworkstudies.Auxiliary times(e.g.planningofworkandpreparations)wereinclud-edintheworkphasesinwhichtheywereobserved.Theskilfultruckdriverhadextensiveworkingexperi-ence.Hehadfifteenyearsofworkingexperienceintransportingroundwoodandtwoyearsofworkingexperienceintransportingbiomass.

2.2 The time studies of chipping – Studije vremena iveračaTheaimofthetimestudywastocomparethechip-

pingproductivityofwholetreesandmulti-stemde-limbedshortwoodinterminalconditions.ThestudieswerecarriedoutduringdaylighthoursinMay2010.Themobileindustrialchipperusedfortheexperimentwasatrailer-mountedRudnick&EnnersMTH900X1000/13drumchipper.Theweightofthetandemaxletrailerchipperwas19000kganditwas9650mmlong,2550mmwideand4000mmhigh.Theheightofthefeedingtubewas900mmanditswidthwas1000mm.Thechainfeedranlongitudinallyandthedischargeofthechippedmaterialwasrealisedbyapivotableblow-erwiththrowcontrol(Rudnick&EnnersMaschinen

undAnlagenbauGmbH2003).Thedrumcarriedfourbladesandthebladesweresharpenedatthebegin-ningoftheshift.Thechipperyearmodelwas2004andithadbeenrenovatedduetoafirein2007.Thechipperwasdrivenindependentlyanditwaspoweredbya368kWScaniaV8dieselengine.Thetowingvehiclewasathree-axleScania144G530andthetractorwasequippedwithaheavy-dutyKesla2010Ttimberload-erusedforbringingthewoodtothehydraulicin-feedsystem.Theskilfulchipperoperatorhadthreeyearsofworkingexperienceinchipping.Thetimestudywascarriedoutmanuallyusingthe

continuous timing method and field computer(Nuutinenetal.2008).ThedrygreendensityofthechippedmaterialwasdefinedaccordingtotheSCAN-CM43:95 standard,moisture content according toCEN/TS1477-2andparticlesizedistributionaccord-ingtotheCEN/TS15149-1standard.Thechippedtim-berwasfreeofimpurities(stones,mineralsoil,etc.),whichenableduninterruptedchippingworkattheasphaltfieldoftheterminal.Inthechippingexperi-mentthechipswereblowntotheground.

2.3 The cost comparison of the supply systems Usporedba troškova s obzirom na duljinu daljinskoga transportaThe loggingcostcalculationsweremadeforan

artificialstand,wherethecuttingremovalwas1500pine(Pinus sylvestris)stemsperhectareandthebreastheight diameter (d1.3) of the removed trees variedbetween5–13cm(Laitilaetal.2010b).Thevolumeofthemulti-stemdelimbedshortwoodasafunctionof5–13cmbreastheightdiameterwas4–73dm3andthevolumeofwholetreeswas8–99dm3,respectively.Theharvestingintensityamountedto12–149m3/hawhentreeswereharvestedwithbranchesand7–110m3/hawhentreesweredelimbed.Thetotallengthofthestriproadnetworkatthestandwasassumedtobe600m/ha,basedonanaveragestriproadspacingof20m(Ni-emistö1992).Theforwardingdistancewas300mandtheon-roadtransportationdistancevariedbetween5–160km.Thedistancebetweentheterminalandend-use-facilitywasconstant,15km,exceptwhentheter-minalwaslocatedattheend-use-facility.Theproductivityofcuttingwholetreesandde-

limbed stemwood using themulti-tree processingtechniquewasbasedonthestudyofHeikkiläetal.(2005)andtheproductivitymodelwaspublishedintheExcel-based»Costcalculatorfordelimbedenergywood”«costcalculationprogram(Laitila2006).Inthecaseofbundleharvesting,theproductivitymodelofNuutinenetal.(2011)wasused.Theforwardingpro-ductivityofmulti-stemdelimbedshortwoodwascal-


204 Croat. j. for. eng. 33(2012)2

culatedusingthemodelofKuittoetal.(1994).Whenforwardinglooseandbundledwholetrees,thefunc-tionsofLaitilaetal.(2007and2009)wereapplied.Thepayloadofthemedium-sizedforwarderwassetat9m³formulti-stemdelimbedshortwood,6m³forwholetrees,and24piecesforbundles(Laitila2008;Laitilaetal.2009;Laitilaetal.2010).Theeffectivetime(E0)pro-ductivitiesofcutting,bundlingandforwardingwereconvertedintogrosseffectivetime(E15)productivitieswiththecoefficientsappliedinthestudyofJylhäetal.(2010).Thehourlycostswereas follows:medium-sizedthinningharvesterequippedwithmulti-tree-handling accessories, 81 €/h (VAT 0%), forwarder,61€/h(VAT0%),andFixteriIIbundle-harvester,107€/h(VAT0%)(LaitilaandVäätäinen2011).Multi-stemdelimbedshortwoodandwhole-tree

bundlesweretransportedusingaconventionaltimbertruckwithatrailer,assumingapayloadof48m³formulti-stemdelimbedshortwood(LaitilaandVäätäin-en2011).Inthecaseofbundletrucking,amaximumpayloadof100pieceswasused(LaitilaandVäätäinen2011).Thepayloadofloosewholetreeswassetat30m³onthebasisofthestudyreportedherein.Thepay-loadofthechiptruckwas44m³(Laitila2012).Theroadtransportationtimeswerecomposedofdrivingwith an empty load, driving loaded and terminaltimes(incl.loading,unloading,waitingandauxiliarytime).Timeconsumptionofdriving,withfullloadandemptyload,wascalculatedasafunctionoftransporta-tiondistanceaccordingtothespeedfunctionsofNur-minenandHeinonen(2007).Onebunchof thedelimbed5mlongwoodwas

loadedonthetractorandtwobunchesonthetrailer.Thebundleloadconsistedoftwobunchesonthetrac-torandthreebunchesonthetrailer.Accordingtothetimestudy,theloadingtimeofatruckwith5mmulti-treedelimbedshortwoodwas19.0minutesandtheunloadingtimewas14.2minutes.Forwhole-treebun-dles,theloadingtimewas25.1minutesandunloadingtime17.1minutes(Laitilaetal.2009).Inthecaseofloosewholetrees,aloadingtimeof30.0minutesandanun-loadingtimeof11.6minuteswererecorded.Theprep-arationtimeofthecranewas2.6minutesattheroadsidelandingand2.3minutesatthedeliverypointforalltimberassortments.Cleaningofresiduesfromtheroad-sidelandinganddeliverypointtook4.2minutesperloosewhole-treeorbundletruckload(Laitilaetal.2009).Handlingoftheinsidemovingcarriagetook1.2min-utesperloadwhentransportingloosewholetrees.Withmulti-stemdelimbedshortwoodandbundles,thehandlingtimesofthebunksandtrailerwere1.4and2.2minutes,respectively(Laitilaetal.2009).Bind-ing and opening the load ofmulti-stemdelimbed

shortwoodtook9.9minutes,whileittook12.5minuteswithbundles (Laitila et al. 2009). 25minuteswereaddedtotheterminaltimes,correspondingtothetimethetrucksspentonitemsotherthanactualloadingorunloading,e.g.drivingatstoragepoint,turning,wait-ing,weighing,arrangementsatthedeliverypointandsampling.Theloadingtimeofthechiptruck-trailerunitatthe

roadsidelandingwasequaltothedirectandindirectchippingtimes.Thechipperproductivityattheroad-sidestoragewasestimatedtobe34m³/E15hforwholetreesandattheterminalthechippingproductivitywas44m³/E15h(Laitila2008).Accordingtothecom-parativetimestudyreportedherein,thechippingpro-ductivityofmulti-stemdelimbedshortwoodwas1.22highercomparedtowholetrees.Thisdenotesthatthechipperproductivityattheroadsidestoragewasesti-matedtobe41m³/E15hformulti-stemdelimbedshort-woodand54m³/E15hattheterminal.Thechippingproductivityofwhole-treebundleswasestimatedtobeequaltothatofmulti-stemdelimbedshortwood.35minuteswereaddedtothedirectandindirectchip-pingtimes,correspondingtothetimethechiptrucksspentonitemsotherthanactualloading,e.g.drivingatstoragepoint,turning,detachingthetrailer,waiting,weighing,unloadingandsampling(Laitila2012).Attheterminal,theloadingtimeofchipswases-

timatedtobe15minutesandtheworkwasdoneus-ingawheelloader.Theunitcostofchiploadingwas1€/m3(Laitila2008).Chipsweretransportedfromtheterminal to the end use facilitywith truck-trailerunitsthataresimilartotheonesusedwhentrans-portingchips fromtheroadsidestorages.Theun-loadingtimeofthechipsattheendusefacilitywasestimatedtobe25minutes.Thehourlycostofthemobiledrumchipperwas154.2€/E15hintheroadsidechippingoperationsand145.1€/E15hwhenoperatingattheterminal(LaitilaandVäätäinen2011).Thetim-bertruckhourlycostwas86.4€/E15hfordrivingand60.7€/E15hforterminaltime(LaitilaandVäätäinen2011).Thecorrespondingvaluesforthechiptruck-trailerunit andbiomass truckwere 88.2 €/E15h&63.3€/E15hand89.0€/E15h&63.2€/E15h,respectively(LaitilaandVäätäinen2011).

3. Results – Rezultati

3.1 The time studies – Studije vremenaTheaveragepayloadofloosewholetreeswas30m3

inthetransportationstudy.Theloadingproductivityofwholetreeswas1.0m3perminute,andunloadingpro-ductivitywas2.58m3perminute.Theloadingand


Croat. j. for. eng. 33(2012)2 205

unloadingproductivityof5mand3mlongmulti-stemdelimbedshortwoodamountedto2.53&3.39m3 perminuteand1.7&2.56m3perminute,respectively.Whenloadingorunloading5mlongmulti-stemde-limbedshortwood,thesizeofhandlingunit(grappleloadvolume)issignificantlybiggercomparedto3mlong multi-stem delimbed shortwood, which im-provesproductivity.Theaveragerepositiontimeofthechipperatthe

terminal–thatis,whenthechipperismovedwithintheworksiteasworkproceeds–was4.5minutes.Pre-paringtimeforchipping,includingallpreparatorymeasuresfromstartingthemachinetoraisingtherota-tionspeedofthemachineinreadinessforchipping,wasonaverage2.4minutesattheterminal.Thechip-pingproductivitywas55m3/E0hforwholetreesand67m3/E0hformulti-stemdelimbedshortwood(Fig.3).Theaveragegrappleloadvolumeinchipperfeedingwas 0.33m3 (211 kg) forwhole trees and 0.49m3 (317kg)formulti-stemdelimbedshortwood.Feedingofthechipperwaseffective.Thechipperwasonlyrun-ningidleduring1.5%oftheeffectivechippingtimewhenchippingwholetreesand0.9%whenchippingmulti-stemdelimbedshortwood.Theparticlesizedis-

tribution of whole-tree and multi-stem delimbedshortwoodchipswascomparable,excludingthepro-portionofsmallparticles(<8mm).Thisisduetothehighpercentageofbranchesandneedlesinthewhole-treematerial.

3.2 The cost comparison – Usporedba troškovaThesupplysystembasedonwhole-treeharvesting

resultedinthelowestloggingcostinthecostcom-parison(Fig.4).Theloggingcostsofwhole-treeandmulti-stemdelimbed shortwoodwere at the samelevelwhenthebreastheightdiameteroftheharvestedtreeswas11cm(pine)ormore.Thecuttingofwholetreesischeaper,butthecostdifferencediminishedasafunctionoftreesize.Theforwardingcostsofmulti-stemdelimbedshortwoodandwhole-treebundleswerelowerduetohigherbulkdensityandthereforebiggerpayloads.Alsotheloadingandunloadingweremoreefficientcomparedtowholetrees.Inthecaseofwhole-treebundling.theloggingcostsexceededtheharvestingofmulti-stemdelimbedshortwoodwhenthebreastheightdiameteroftheremovedtreeswas8cmormore(Fig.4).Thetransportingcostsofloosewholetreeswere

thehighest(Fig.5)andthesecostswerealsothemostsensitivetochangesintransportingdistance.Trans-

Fig. 3 Chipping productivity of whole trees & multi-stem delimbed shortwood at the terminal (m3/E0h) and average grapple load in chipper feedingSlika 3. Proizvodnost iveranja cijelih stabala i debala kratkoga drva na glavnom stovarištu (m3/E0h) te prosječan zahvat hvatala prilikom iveranja

Fig. 4 Logging costs of whole trees, multi-stem delimbed short-wood and whole-tree bundles at the roadside landing. Logging cost, €/m3 = Cutting + ForwardingSlika 4. Troškovi pridobivanja biomase (sječa i privlačenje) iz cijelih stabala, okresanoga kratkoga drva i cijelih stabala u svežnjevima do pomoćnoga stovarišta uz šumsku cestu


206 Croat. j. for. eng. 33(2012)2

portingcostsofwhole-treebundlesandmulti-stemdelimbedshortwoodwereabout2€/m3lowercom-paredtowhole-treeandmulti-stemdelimbedshort-woodchipsmainlyduetoshorterloadingandunload-ingtimesandsomewhatbiggerpayloads.Alsothe

standard timber truckhourlycostwas lowercom-paredtothechiptruck-trailerunit.Theharvestingcostofwhole-treeandmulti-stem

delimbedshortwoodchipsat theplant rangedbe-tween42.0and51.0€/m3whenthebreastheightdiam-

Fig. 5 Transporting costs of chips, loose whole trees, whole-tree bundles and multi-stem delimbed shortwood as a function of transporting distanceSlika 5. Usporedba troškova prijevoza iverja, cijelih stabala, svežnjeva cijelih stabala i okresanoga kratkoga drva kao funkcija udaljenosti prijevoza

Fig. 6 Cost structure of whole-tree and multi-stem delimbed shortwood chips at the plant, €/m3. Forwarding distance is 300 m and transport-ing distance to the plant or the terminal is 50 kmSlika 6. Sustav troškova pri iveranju na glavnom stovarišru (energani), €/m3. Udaljenost je privlačenja 300 m, a udaljenost je prijevoza do energane ili glavnoga stovarišta 50 km


Croat. j. for. eng. 33(2012)2 207

eteroftheharvestedtreeswas8cm(Fig.6).Whole-treeharvestingandchippingattheroadsidelandingwasthemostcost-efficientsupplysysteminthecostas-sessment,becausethecuttingofwholetreeswassig-nificantlycheapercomparedtowhole-treebundlingorharvestingtreesthathavebeendelimbed.Thelow-ercomminutioncostattheterminalwasnotenoughtocovertheextrahandlingcostofchipsattheterminalorthedeliverycosttotheplant.Fig.7showsthehar-vestingcostofchipsattheplantcalculatedasafunc-tionofbreastheightdiameterwhentheterminalwaslocatedindirectconnectiontotheend-usefacility.Ac-cordingtotheresults,theharvestingsystembasedonterminal chippingandmulti-stemdelimbedshort-woodundercuttheharvestingcostoftheharvestingsystembasedonwhole-treeharvestingandroadsidechippingwhenthebreastheightdiameterofthehar-vestedtreeswas11cm(pine)ormore.Inthecaseofwhole-treebundling,savingsintransportationandchippingcostsdidnotoffsetthehighfellingandcom-pactioncosts,andthebundlingsystemwastheleastcompetitivealternative(Fig.7).

4. Discussion – RaspravaWhole-treeharvestingandchippingattheroad-

sidelandingwasthemostcost-efficientsupplysysteminthecostcomparison.Thecostofwhole-treeandmulti-stemdelimbedshortwoodchipswasatthesamelevelwhenthebreastheightdiameteroftheharvested

treeswas11cm(pine)ormore.Thecuttingofwholetrees ischeaper,butthecostdifferencediminishedasafunctionoftreesize.Theproductivityofforwarding,transportationandchippingofmulti-stemdelimbedshortwoodwassignificantlyhighercomparedtothatofwholetrees.WhenapplyingroadsidechippinginFinnishconditionswithsmallandsparselylocatedforestholdings,acquiringlargeenoughconcentrationsofwoodforprofitableproductionisagreatchallenge.Machinerelocationscanbereducedbytransportingrawmaterialtoterminalsortheend-usefacilitytobechipped.However,thelowbulkdensityoftheinitialmaterialrestrictstheoperationradiusunlessthewoodbiomassispre-processed.Accordingtotheresultsofourstudy,harvestingofdelimbedenergywoodisapromisingwaytosimplifyoperationsandtoreducetransportation and chipping costs. In the case ofwhole-treebundling,savingsintransportationandchippingcostsdidnotoffsetthehighfellingandcom-pactioncosts,andthebundlingsystemwastheleastcompetitivealternative.Eriksson andBjörheden (1989)figuredout that

supplyviaterminalsdoesnotpayoff,andourresultsdonotrefutethisingeneral.TheGISstudyofKanzianetal.(2009)indicatethatsupplycostswillincreasebyjust10%ifhalfthefueland26%ifallthefuelgoesthroughterminalsinAustria.Ontheotherhand,theadditionalcostscanbedesignatedasexpensesneces-sarytoensureconstantsupplythroughouttheyear(e.g.Gronalt andRauch 2007;Kanzian et al. 2009;Laitilaetal.2010a).

Fig. 7 Harvesting cost of chips at the plant as a function of breast height diameter, €/m3

Slika 7. Troškovi pridobivanja drvnoga iverja kao funkcija prsnoga promjera stabla, €/m3


208 Croat. j. for. eng. 33(2012)2

Delimbedmaterialproducesuniformfuelstockdevoidofneedlesandbranches,whichmaybeaben-efitespeciallyatsomepowerplantswitharestrictedcapabilitytohandlehighlevelsofchlorineandalkalimetals contained in thebranchmaterial. Sufficientquantitiesofalkalimetalsandchlorinecauseagglom-erationofbedsandaswellascorrosioninfluidisedandcirculatingfluidisedbedboilersandheatexchang-ers (NurmiandHillebrand2007).Sinceharvestingundelimbed assortments increases nutrient exportfromthesite,whichcanaffectsoilproductivity,thewhole-tree harvesting alternatives included in thepresentstudycannotberecommendedoninfertilesoilstands(Äijäläetal.2010).However,inScandinavianstudies,nosignificantgrowthreductionshavebeenobservedduetowhole-treeharvestingfromScotspinefirst-thinningstandswithinthefollow-upperiodsofatmost20years (Jylhä2011). In thesimulationbyHeikkiläetal.(2007)basedonnitrogenremovalfromthesites,leaving40%ofloggingresiduesonFinnishfirst-thinning sites, increased thte stemvolumeby2.6%overa10-yearpost-harvestingperiodcomparedtocompletewhole-treeharvesting.

5. References – LiteraturaÄijälä,O.,Kuusinen,M.,Koistinen,A.,2010:Hyvänmetsän-hoidonsuositukset.Energiapuunkorjuujakasvatus(Forestmanagementrecommendations.Energywoodharvestingandsilviculture).MetsätaloudenkehittämiskeskusTapio.56p.(InFinnish)

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Belbo,H.,2011:Efficiencyofaccumulatingfellingheadsandharvestingheadsinmechanizedthinningofsmalldiametertrees.LinnaeusUniversityDissertationsNo66/2011.42p.

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Kuitto,P.-J.,Keskinen,S.,Lindroos,J.,Oijala,T.,Rajamäki,J.,Räsänen,T.,Terävä,J.,1994:Puutavarankoneellinenhak-kuujametsäkuljetus.(Mechanizedcuttingandforesthaul-age).MetsätehoReport410.38p.(InFinnish.)

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Sažetak

Kamionski prijevoz i proizvodnost iveranja cijelih stabala i okresanoga kratkoga drva u Finskoj

Ovo je istraživanje usmjereno na ocjenu konkurentnosti nekoliko sustava pridobivanja energijskoga drva iz mladih sastojina. Za usporedbu troškova sustava rada korištena je biomasa iz triju izvora: (i) energijsko drvo iz okresanoga kratkoga drva, (ii) cijelih stabala i (iii) svežnjeva načinjenih pomoću novorazvijenoga stroja bandlera harvestera (stroja za izradu svežnjeva) Fixteri II (slika 1). Sječa stabala provedena je pomoću harvestera, a privlačenje je obavljeno forvarderom. Usporedba troškova pridobivanja biomase učinjena je na razini sastojine kao funkcija prsnoga promjera stabala (5–13 cm) i udaljenosti prijevoza (5–160 km).

Iveranje je biomase obavljeno na pomoćnom stovarištu uz šumsku cestu ili u energani (glavnom stovarištu) pomoću priključenoga bubnjastoga iverača. Okresano kratko drvo i svežnjevi cijelih stabala prevezeni su do energane pomoću kamionskoga skupa, dok su cijela stabla prevezena kamionima s obloženim tovarnim prostorom.

Sustav je rada ocijenjen pomoću nedavno objavljenih podataka o proizvodnosti te usporedbom sličnih istraživanja. Cilj je istraživanja bio poboljšati troškovnu učinkovitost proizvodnje drvnoga iverja dobivenoga iz mladih sastojina, a posebno ispitati tehnologije iveranja tankoga drva iz proreda na pomoćnom stovarištu.

Prema procjeni troškova iveranje cijelih stabala na pomoćnom stovarištu uz šumsku cestu bilo je gotovo uvijek najučinkovitiji sustav pridobivanja biomase. U slučaju izrade svežnjeva uštede u prijevozu i iveranju ipak nisu dostigle troškove nastale pri sječi i izradi svežnjeva, pa je taj sustav najmanje konkurentan. Trošak pridobivanja iverja iz cijelih stabala i iz okresanoga kratkoga drva bio je jednak pri prsnom promjeru stabala od 11 cm (bor) ili više. Privlačenje debala i svežnjeva biomase isplativije je zbog veće iskoristivosti tovarnoga prostora (veća gustoća tovara). Također, utovar i istovar bili su učinkovitiji u odnosu na utovar i istovar cijelih stabala.


210 Croat. j. for. eng. 33(2012)2

Prosječan tovar cijelih stabala pri prijevozu bio je 30 m3, utovar je bio 1,0 m3 po minuti, a istovar 2,58 m3 po minuti. Utovar i istovar debala (duljine od 3 i 5 m) iznosio je 2,53 i 3,39 m3 po minuti te 1,7 i 2,56 m3 po minuti. Pri utovaru debala duljine 5 m mnogo je bolja iskoristivost hvatala, pa tako i proizvodnost raste.

Priprema za iveranje, uključujući sve pripremne radove od pokretanja stroja do povećanja brzine iverača, trajala je u prosjeku 2,4 minute. Proizvodnost iveranja bila je 55 m3/E0h za cijela stabla i 67 m3/E0h za iverje od okresanoga kratkoga drva. Prosječan zahvat hvatalom iznosio je 0,33 m3 (211 kg) za cijela stabla i 0,49 m3 (317 kg) za okresana kratka drva. Raspodjela veličina čestica sječke dobivenih od cijelih stabala i okresanoga kratkoga drva usporediva je, isključujući udio malih čestica (< 8 mm) koje nastaju zbog visokoga postotka grana i iglica u sustavu iveranja cijelih stabala.

Pri primjeni iveranja na pomoćnom stovarištu uz šumsku cestu u finskim uvjetima s malim i prostorno udaljenim šumskim poduzećima velik je izazov jer je potrebna velika količina biomase da bi sustav njezina pridobivanja bio isplativ. Premještanje strojeva može se izbjeći prijevozom sirovine (biomase) do energana i glavnih stovarišta gdje se potom obavlja iveranje. Prema rezultatima ovoga istraživanja pridobivanje iverja iz okresanoga kratkoga drva može smanjiti troškove prijevoza i iveranja biomase.

Deblovna metoda stvara jedinstvenu i homogenu zalihu goriva oslobođenu iglica i grana koje mogu biti prednost pogotovo u onim energanama s ograničenim mogućnostima za obradu visoke razine klora i alkalijskih metala sadržanih u granama stabala. Uporaba cijelih stabala prilikom pridobivanja biomase smanjuje proizvodnost tla jer se nutrijenti iznose iz šume, stoga se takvi sustavi pridobivanja ni ne preporučuju.

Ključne riječi: iveranje cijelih stabala, iveranje okresanoga kratkoga drva, prijevoz, glavno stovarište

Received(Primljeno):March22,2012Accepted(Prihvaćeno):July17,2012

Authors’address–Adresa autorâ:

JuhaLaitila,PhD.e-mail:[email protected]äätäinen,MSc.e-mail:kari.vaatainen@metla.fiFinnishForestResearchInstituteJoensuuResearchUnitP.O.Box68,FI-80101JoensuuFINLAND

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