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  • Mechanized Harvesting of EucalyptCoppice for Biomass Production Using

    High Mechanization Level

    Rodolfo Picchio, Alessandro Sirna, Giulio Sperandio, Raffaello Spina, Stefano Verani

    Abstract Nacrtak

    The main aims of this study were to determine the productivity, profitability and energy ba-lance (output/input) of mechanized harvesting applied to a eucalyptus plantation in centralItaly. The study area was located in Rome, at an altitude of 35 m a.s.l., on a flat, even site(average slope gradient 3%). The stand was a eucalypt coppice (Eucalyptus camaldulensisDehnh.) harvested for the first time in 2000. The planting pattern was square with 3 mamong stumps (1111 trees ha1). By 2009, insect (Phorachantha semipunctata) attackshad reduced stump density to 592 stumps ha1. The work system applied was the Whole TreeSystem (WTS) and the final assortement chips for energy. Machine rates were calculated us-ing coefficients and mathematical formulas extracted from the main methodologies proposedby different authors. Energy balance was estimated with the Gross Energy Requirements(GER) method. In these plantations, mechanized harvesting seems most appropriate: this isdemonstrated by the high productivity recorded (PSH15 6.5 td.w. h

    1 worker1) and by the fa-vorable energy balance (output/input 23.8, 95.8% system efficiency). However harvestingcost is still high (44.30 tf.w.

    1) and can only be reduced through careful operationalplanning.

    Keywords: harvester; work productivity; operating costs; energetic balance; chipper; forwarder;forest plantation

    1. Introduction Uvod

    In Italy, eucalypt was used mainly for windbreaksand reforestation, especially in the South and in theIslands. Large reforestation programs were launch-ed in 1950s mainly for soil protection purposes inSouthern Italy (Calabria and Sicily). Later on, in1980s new projects were launched for the productionof pulpwood (Mughini 2000). Most popular Euca-lypt species were E. globulus ssp. bicostata, E. globulusssp. globulus, E. occidentalis, E x trabutii, E. camaldu-lensis and E. viminalis. The surface of eucalypt planta-tions is now estimated at 72,000 hectares (54,000 hapure, 18,000 ha mixed with other species). Yieldsvary a lot, depending on species and site. For instan-ce, E. globulus ssp. globules may produce from 10 to35 m3 ha1 year1, whereas E. occidentalis will producebetween 3 and 8 m3 ha1 year1 (Gemignani 1988).The outlook for eucalypt plantations in Italy can besummarized in three points:

    naturalization of less productive plantations, es-pecially in Southern Italy;

    intensification of crop modules for industrialplantations, in order to increase both the qualityand quantity of production (medium rotation cop-pice and short rotation coppice for wood chips).This will be done using selected clones;

    rationalized use in agroforestry, where row plan-tations can offer timber, firewood and wood chips.

    Energy crops appear as a promising option forensuring bioenergy feedstock. The profitability ofenergy crops is highly dependent on appropriate lo-gistics, harvest planning and crop yield (Vega-Nievaet al. 2008). The greatest potential for cost reductionlies in mechanization, which may increase producti-vity with the introduction of innovative harvestingequipment. Although stand management researchregarding the definition of proper practices is nowcompleted, there is always some potential for further

    Croat. j. for. eng. 33(2012)1 15

    Original scientific paper Izvorni znanstveni rad

  • cost reduction (e.g. refinement of yield-response in re-lationships for various management practices). Manyexperimental plots are now entering the coppice stage.In many cases, the primary maintenance practiceconsists of frequent harvesting that rejuvenates thestand and stimulates fast growth. Traditional practi-ces for harvesting fuel wood are labor intensive,which may discourage maintenance causing the de-plorable state of abandonment of many coppice standsin industrialized countries (Spinelli et al. 2006). Themain aims of this study were to determine the pro-ductivity, profitability and energy balance (output/in-put) of mechanized harvesting applied to eucalyp-tus plantation in central Italy. In order to estimate theenergy balance, we determined: indirect inputs, i.e.the energy used for equipment production; directinputs, i.e. fuel and oil consumption; and humanenergy consumption during work; output, i.e. ener-getic value of total wood fuel produced.

    These data were used to determine the economicand energetic sustainability of mechanized harvest-ing chains. Over these last years, mechanization hasbeen rapidly introduced to forest operations. TheItalian harvester and processor fleet now counts over84 units, and its number doubled in the last five years(Spinelli et al. 2010). Although mechanized harvest-ing was originally designed and first applied to highforest logging (poplar plantation, coniferous planta-tion), in recent years it has been employed for har-vesting coppice stands. However, the smaller vo-lume of coppice trees implies a lower productivity(Martins et al. 2009). An adequate training of workersand planners is necessary, especially when intro-ducing mechanized harvesting to the sustainableuse of forest biomass, as a renewable source of cleanenergy with reduced greenhouse gases (GHG) emis-sion balance (Picchio et al. 2009).

    The term energy analysis refers to the study ofthe energy used for the production of a service or astock. Total energy use includes both the energy direct-ly used during the production process (direct), andthe energy stocked in the materials used for the pro-duction process (indirect). The Gross Energy Require-ments (GER) method is commonly used in energyanalyses (IFIAS 1975, Picchio et al. 2009). Althoughthe GER method and the ISO 14040 standard (UNIEN ISO 14040 2006) do not include the assessment ofhuman energy input, man work is of relevant contri-bution in many production activities, such as fo-restry activities with low mechanization level. So fora proper comparison between yards with high andlow mechanization levels, it will be appropriate toput the human energy input in the energy balance ofall forestry yards, even if it represents a low percent-age contribution to the total energy inputs. A basic

    requirement for any bioenergy generation system isthat the energy produced (output) must be greaterthan the inputs of non-renewable energy required toestablish and operate the system (Matthews 2001,Picchio et al. 2009).

    2. Materials and methods Materijali metode

    The study was carried out in Rome (4154'32,55'' N,1221'32,34'' E). The study area was characterized bymild climate and volcanic substrata (sand 60%; silt20%; clay 20%). It had an elevation of 35 m a.s.l. andits terrain was even and flat (average slope gradient3%, maximum 10%).

    The stand was a eucalypt coppice (Eucalyptuscamaldulensis Dehnh.) (Table 1) harvested for the firsttime in 2000. The plantation was established in 1989;trees were planted according to 3 m square pattern(1111 trees ha1). By 2009, insect (Phorachantha se-mipunctata) attacks had reduced stump density to592 stumps ha1.

    Logging was conducted in summer 2009 on atotal area of about 2 ha. All area was surveyed with aTrimble Juno ST GPS device. All operations werecarried out by the same private Forest Company. Themachines used were: one harvester John Deere (ex Timberjack) 1270 C

    with a felling-processing head JD (ex TBJ) 762 C,for felling and bunching the trees;

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    R. Picchio et al. Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (1524)

    Table 1 Site characteristicsTablica 1. Zna~ajke radili{ta

    Place Mjesto Rome (Italy)

    Surface, ha Povr{ina, ha 1.72

    Slope gradient, % Nagib terena, % 3

    Elevation, m a.s.l. Nadmorska visina, m n. v. 35

    Species Vrsta drve}a E. camaldulensis

    Age in years Dob u godinama 10

    Density, stumps/ha Gusto}a, panjeva/ha 592

    Average DBH, cm Prosje~ni srednji promjer, cm 12.9

    Average height, m Prosje~na visina, m 14.3

    Average mass, tf.m. Prosje~na masa, tf.m. 0.329

    Average number of shoot per stump

    Prosje~an broj izbojaka po panju3.6

    Average mass harvested, tf.m.ha1

    Prosje~na masa sje~e, tf.m.ha1 194.768

    Wood characteristics, chips Zna~ajke drva, ivera

    Bulk density, kg m3 Gusto}a, kg m3 320

    Moisture content, % Udio vlage, % 37.59

  • one forest loader OP T80, to assist the harvester intree bunching;

    one forwarder JD (ex TBJ) 1100 with chipper Erjofor chipping whole trees from bunches;

    one truck DAF CF 85.430 with trailer VIBERTI 7LOMASS 22 R for chips transport.

    There were two forestry operators. The work sys-tem applied was the Whole Tree System (WTS). Wholetrees were chipped at the stump site, and chips weredischarged directly into the transportation vehicles,which could easily access the cutover.

    The main dendrometric parameters (DBH and treeheight) were measured in 2 circular plots randomlyselected inside the stand (total surface 5652 m2). A ttest for independent samples was applied to eachdendrometric parameter and showed no significantdifference between the two plots (DBH n 309,p-value 0.079; height n 97, p-value 0.647). A treecaliper (Silvanus type 1208, accuracy 0.5 cm) wasused for measuring the diameter at breast height(DBH) and a tape logger for determining tree height,after felling. After the harvesting, the height of thefelled stump was measured in 2 rectangular plotsrandomly selected (total surface 1200 m2). A t testshowed significant differences between two plots(n 134, p-value 0.0233).

    Moisture content and wood density were deter-mined on 30 wood discs (3 cm thick) collected ran-domly in each plot. The 60 wood discs were imme-diately weighed with a precision scale (Orma modelBC16D) and then taken to the laboratory for determin-ing moisture and wood density, according to thethermo-gravimetric method (UNI EN 13183-1 2003,UNI ISO 3130 1985, UNI ISO 3131 1985, Lo Monacoet al. 2011). Statistical analysis (Kruskal Wallis) show-ed no significant differences (wood density freshweight: KW 0.259, p-value 0.611; wood density dryweight KW 0.188, p-value 0.665) between the twoplots.

    For the conversion of volume into fresh mass, weused the measured average density of 1.13 kg dm3.The top and branches were considered to be the 25%of the stump mass. This figure was determined byweighing the stem, the top and the branches of asample of 60 shoots, randomly selected on 60 diffe-rent stumps.

    The experimental data (felling/bunching andchipping) were recorded for one hectare of planta-tion. To relate the felling time to tree mass, 110 stumps(396 shoots) were numbered, randomly selected.

    Slope gradient was measured with a clinometer(Meridian MI 4007). Work time was recorded forevery single phase, using a chronometric table Mi-nerva equipped with three centesimal chronometers

    (Anon. 1988, Harstela 1991, Berti et al. 1989, Savelliet al. 2010). In order to calculate outputs in differentplots, effective time and delays in the work routineup to 15 min (UT, unavoidable time and AT, avoid-able time) (Anon. 1988, Harstela 1991, Picchio et al.2009) were recorded.

    Based on work times, volume and mass, the pro-ductivity per worker for the different operations wascalculated as: average gross productivity (PHS15),measured on the basis of time consumption, inclu-sive of all delays up to the maximum event durationof 15 minutes; average net productivity (PHS0), com-puted with the exclusion of delays.

    The cycle times of the machines were dividedinto time elements (process steps) that were consi-dered typical of the work.

    Harvester time consisted of: positioning, beginn-ing when the machine approached the stump andending when the machine head rested on a tree; fel-ling, beginning when the felling cut started and end-ing when the tree touched the ground; bunching,beginning when the tree touched the ground andending when the tree was dropped onto a bunch.Loader time consisted of bunching the tree that theharvester was not able to pile; beginning when thetree was taken from the loader and ending when thetree was put on the pile.

    Chipping time consisted of: positioning, i.e. thetime necessary for the truck to approach the chipperand park by its side; chipping, i.e. the time duringwhich the chipper produced the chips; moving thetime necessary for the truck and the chipper to ap-proach a bunch of trees. For all operations, delay wasalso recorded, i.e. the time during which the ma-chine was not engaged in any productive work pro-cess (e.g. repair and/or maintenance, rest, etc.).

    The influence of tree weight on the felling timewas estimated by linear regression, calculated with aregression analysis.

    Total labor cost (including taxes and all socialcosts) was 23 h1 for the harvester operator and thechipper operator, whereas the loader operator costwas 15 h1. Stumpage was 15 t1. Fuel cost wasassumed at July, 2009. Machine rates (Table 2) wereestimated using the coefficients and the mathemati-cal formulas already applied by many authors (Mi-yata 1980, Picchio et al. 2011a, Spinelli et al. 2011).Further details on cost calculation are reported inTable 2.

    The energy balance was estimated with the GERmethod (IFIAS 1975, Picchio et al. 2009). It was usedto estimate the direct and indirect input require-ments for the machinery used as showed by Picchioet al. 2009. Furthermore, by an indirect method toassess the energy expenditure in forestry operations

    Croat. j. for. eng. 33(2012)1 17

    Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (1524) R. Picchio et al.

  • in situ (Scott and Christie 2004, Christie 2008) humanenergy consumption was estimated, on the basis of ahuman heart-rate response during field work. Thetwo workers were assessed for five work day. Mi-nute-to-minute heart rate was recorded using a Polarheart rate monitor during the test in order to calcu-late the predicted energy expenditure from workingheart rate responses on the basis of individual re-gression equations. This technique has been validat-ed by several authors (Haskell et al. 1992, Scott andChristie 2004, Strath et al. 2001).

    To calculate the energy output, the Higher Heat-ing Value (HHV) was determined on 30 chip samples,collected randomly from 10 truck loads (Volpi 1992).Calorimetric tests were conducted with an adiabathiccalorimeter (Parr, model 6200) (Canagaratna andWitt 1988). A Kruskal Wallis test suggested limitedvariability (KW 0.679, p-value 0.712). The averageHHV of E. camaldulensis wood was 20.14 MJ kgd.w.

    1.

    3. Results and discussion Rezultatii rasprava

    Harvester delays represented 18.1% of the totalwork time, and in line with the values reported bySpinelli and Visser (2008) for short-rotation planta-tions (Fig. 1). Harvester delays were mostly due tothe need for sharpening the cutting chain; this isexplicable considering the type of wood harvested.

    Chipping delays had a very small incidence (9%),much lower than reported in previous bibliography(Spinelli and Visser 2009) (Fig. 2). Moving and po-

    18 Croat. j. for. eng. 33(2012)1

    R. Picchio et al. Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (1524)

    Table 2 Principal calculation elements and machine costsTablica 2. Glavne sastavnice izra~una i tro{kovi strojeva

    Description

    Stavka

    Unit of measure

    Mjerna jedinicaJD 1270 c Advance

    Chipper Eryo onForwarder (JD 1100)

    Loader OP T80

    Purchase price Nabavna cijena 380,000 520,000 127,000

    Salvage value* Preostala vrijednost* 84,094 115,076 20,786

    Service life Vrijeme trajanja y 10 10 12

    Annual usage Godi{nja uporaba H 1,200 800 600

    Power Snaga kW 173 440(+118) 132

    Interest rate Kamatna stopa % 5 5 5

    Fuel consumption Potro{nja goriva l h1 15 35 13

    Lubricant consumption Potro{nja maziva l h1 0.6 1.4 0.52

    Garage space Gara`ni prostor m2 35 45 23

    Labor cost Tro{ak radnika h1 23 23 15

    Fuel cost Tro{ak goriva l1 1.04 1.04 1.04

    Lubricant cost Tro{ak maziva l1 9 9 9

    Fixed Costs Fiksni tro{kovi h1 41.56 88.12 24.20

    Variable Costs Varijabilni tro{kovi h1 66.31 114.93 47.57

    Total machine Costs (included labour cost)

    Ukupni tro{kovi stroja s tro{kom radnika h1 107.87 203.05 71.77

    (*) The salvage value was calculated by multiplying the purchase price for 0.86N, where N = service life of the machine

    (*) Vrijednost na kraju vremena kori{tenja izra~unata je uve}avanjem nabavne cijene za 0,86N, gdje je N = vrijeme kori{tenja stroja

    Fig. 1 Harvesting and bunching time analysis, percent incidence of timeelements

    Slika 1. Analiza utro{aka vremena sje~e i uhrpavanja, postotni udjelitrajanja sastavnica rada

  • sitioning also had a very low incidence, due to thegood trafficability of the test area (Fig. 1 and 2).

    Productivity (PSH15 and PSH0) of each workingphase was good (Table 3). As compared to literaturedata of felling and bunching operations, it had ahigher productivity than a harvester used for fellingand processing (Spinelli et al. 2002a), but it had alower productivity and a higher cost than a properfeller-buncher (Spinelli et al. 2002b). The averagegross time only for felling and bunching (averagestump fresh mass 0.33 tons) was 1.25 minutes, cor-responding to a PSH15 per worker of 15.8 fresh t h

    1.

    For the regression analysis between dependent vari-able gross time (T [min]) for felling and bunchingand independent variable stump fresh mass (x [t])110 stumps were sampled randomly among all thedata observed. The regression was expressed by theequation: T = 0.774 + 1.458 x; R2 = 0.678 (Fig. 3).According the regression analysis (Table 4) the mo-del is significant at p

  • transfer of machines; 15 t1 for the stumpage (com-pensation to the forest owner). In this case, the re-location unitary cost was calculated dividing thetotal cost sustained (2,000 ) for the total surfaceworked by the yard (5 ha), and the result obtainedwas divided for the tons of fresh biomass harvestedper hectare (195 t). The resulting profit for the en-terprise is 5.70 t1.

    The human energy consumption was estimatedon the basis of a human heart-rate response duringfield work. The heart rate was recorded on five workdays and the ANOVA test showed no significant dif-ferences between the two workers (p

  • intermediate mechanization. This obviously affectsthe energy balance (output/input ratio), which is23.8 for mechanized harvesting and 12.9 for interme-diate mechanization. The calculated detail data ofenergy indirect input requirements for machinerywere: harvester 2.37 GJ ha1 (19%); loader 1.28 GJ ha1

    (10%); forwarder with chipper 2.11 GJ ha1 (17%);truck with trail 6.94 GJ ha1 (54%).

    Fig. 5 shows the incidence of single work phaseson total energy input. Truck transport had the high-est incidence (45% or 379 MJ td.w.

    1), as also found inother studies (Baldini et al. 2007, Picchio et al. 2009),than chipping (33% or 283 MJ td.w.

    1) and finallyfelling and bunching (22% or 185 MJ td.w.

    1).

    Also due to the large amount of biomass harvest-ed, the average output/input ratio was twice as highas the literature data (8.611.7, Baldini et al. 2007)available for the harvesting of eucalypt plantations,with intermediate mechanization. Higher values(3648, Picchio et al. 2009) were also reported, butthey were obtained in other forest types (Quercuscerris L. coppice).

    The percentage energy efficiency (i.e 100*(output input)/output) was high and on average 95.8% 0.3. This value was similar to those reported in otherstudies (about 91% Baldini et al. 2007, about 97%Picchio et al. 2009).

    4. Conclusions Zaklju~ci

    Mechanized harvesting allowed a substantial in-crease of the operational productivity recorded forany single work step: felling/bunching, extractionand chipping. Comparison with other two fellingstudies (Baldini et al. 2007, Martins et al. 2009) re-flecting different mechanization levels with escalat-ing investment requirements, confirmed the excel-lent performance of the harvester John Deere 1270,with a JD 762 C harvester head. However, it had alower productivity and a higher cost than a properfeller-buncher (Spinelli et al. 2002b) but the harvesterwas a machine more multipurpose and versatile,and therefore preferred by Italian forestry compa-nies that work in different agroforestry systems.

    Mechanization resulted in a dramatic reductionof felling costs: moreover, it strongly enhanced ope-rator comfort and safety (Bell 2002).

    In this kind of plantations, mechanization is mostappropriate, as demonstrated by high productivityrecorded in our study (PSH15 6.5 td.w. h

    1worker1)and by the very favorable energy balance (output/input 23.8 and 95.8% system efficiency). These per-formances far exceed those reported for intermediatemechanization, still very popular in Italy. However,harvesting cost is still high (44.30 tf.w.

    1, Fig. 4) andcould be reduced only through careful work planning.The cost of harvesting (6.76 t1) would certainlyhave been lower if it was a proper feller-buncher; themachine has a lower hourly rate and can ensure high-er productivity. The unusual use of harvester was

    Croat. j. for. eng. 33(2012)1 21

    Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (1524) R. Picchio et al.

    Table 5 Total energy value of outputs and inputs (GJ ha1) for all worksteps, transport included

    Tablica 5. Ukupna vrijednost izlazne i ulazne energije (GJ ha1) za svesastavnice rada s uklju~enim transportom

    Output

    Izlaz

    Machines & Tool Input

    Ulaz strojeva i alata

    Human Input

    Ulaz radnika

    Total Input

    Ukupni ulaz

    Direct

    Neposredni

    Indirect

    Posredni

    2,565.8 95.2 12.7 0.2 108.1

    Table 6 Energy efficiency, labor use and operational productivity (PSH15 e PSH0)

    Tablica 6. Energetska u~inkovitost, korisnost rada i operativna proizvodnost (PSH15 e PSH0)

    Output/Input

    Izlaz/ulaz

    System efficiency

    U~inkovitost sustava

    Man work time

    Vrijeme rada radnikaPSH15 PSH15 PSH0 PSH0

    % min td.w.1 td.w. h

    1 worker1 m3 h1 worker1 td.w. h1 worker1 m3 h1 worker1

    23.8 95.8 23.12 6.5 10.3 7.6 12.3

    Fig. 5 Percent incidence of work steps on total energy useSlika 5. Postotni udjeli radnih zahvata u ukupnoj energetskoj potro{nji

  • determined by the fact that the dedicated CTL ma-chine was nearby for the poplar plantation logging.

    Furthermore, Italian forestry is still confronted witha lack of trained forest workers, which may slowdown the transition towards mechanized harvesting.

    As confirmed by many previous studies (e.g. Bal-dini et al. 2007, Picchio et al. 2009), this study alsoshows the urgent need to minimize the costs andenergy inputs related to transportation, which canbe obtained by developing local markets for energybiomass, thus reducing transportation distance. Thecost of chipping was particularly low, due to thepower of the machine used and the efficient worksystem adopted. Field chipping excludes the extrac-tion operation, which often results in long waitingdelays for the chipper.

    The damages to soil and topsoil have not beendiscussed in this study. The surveys and studiesabout this yard are still running and they will be thesubject of a forthcoming work. In fact, as mentionedby other authors (Picchio et al. 2011), the research ondamage caused by forest operations to the remain-ing trees and/or to the regeneration in forest standsstarted at the beginning of the twentieth century andits importance has been rising with the increasinguse of mechanized wood harvesting.

    5. References Literatura

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    Baldini, S., Picchio, R., Savelli, S., 2007: Energy analysis oflight mechanization yards for the Eucalyptus coppice har-vest, Journal of Agricultural Engineering 38(3): 4956.

    Bell, J., 2002: Changes in logging injury rates associatedwith the use of feller-bunchers in West Virginia; J. SafetyRes. 33(4): 463471.

    Berti, S., Piegai, F., Verani, S., 1989: Manuale di istruzioneper il rilievo dei tempi di lavoro e delle produttivit neilavori forestali; Quaderni dellIstituto di Assestamento eTecnologia Forestale dellUniversit di Firenze, IV, p. 65.

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    Sa`etak

    Visoko mehanizirano pridobivanje {umske biomase iz eukaliptusovih panja~a

    Glavni su ciljevi ove studije bili utvr|ivanje proizvodnosti, isplativosti i energetske bilance (izlaz/ulaz) strojnesje~e primijenjene na eukaliptusovim planta`ama u sredi{njoj Italiji. Da bi se procijenila energetska bilanca,odre|eni su: posredni ulazi, tj. energija kori{tena za proizvodnju; neposredni ulazi, tj. potro{nja goriva, maziva ipotro{nja energije radnika tijekom posla; izlaz, tj. energetska vrijednost ukupno proizvedenoga drva. Povr{ine podeukaliptusovim planta`ama danas po procjenama zauzimaju oko 72 000 hektara (54 000 ha ~iste, a 18 000 hamje{ovite sastojine). Istra`ivano je u okolici Rima, na nadmorskoj visini od 35 m, u ravni~nom predjelu (prosje~anje nagib terena 3 %). Sastojina je bila panja~a eukaliptusa (Eukaliptus camaldulensis Dehnh.) posje~ena prviput 2000. godine. Prostorni je raspored panjeva bio kvadrati~an s 3 m izme|u panjeva (1111 panjeva po hektaru).Od 2009. napadi kukaca (Phorachantha semipunctata) smanjili su gusto}u panjeva na 592 panja po hektaru.

    Zna~ajke gospodarenja eukaliptusovim planta`ama u Italiji su: povratak autohtonoj {umskoj vegetaciji na podru~jima pod nisko proizvodnim planta`ama, posebno u

    ju`noj Italiji pobolj{anje sastojina industrijskih planta`a radi pove}anja kakvo}e i koli~ine proizvodnje (sastojine sred-

    njih i kratkih ophodnji namijenjenih proizvodnji drvnoga iverja); navedeno se namjerava posti}i selekcijomklonova

    racionalizirana uporaba proizvoda u tzv. poljskom {umarstvu (eng. agroforestry), gdje planta`e mogu pro-izvoditi i tehni~ke drvne sortimente, ogrjevno drvo i drvni iver.

    Primijenjena je stablovna metoda izradbe i krajnji je proizvod bio drvni iver za energiju. Nasadi za proizvodnjuenergije dobar su izbor pri osiguravanju sirovine za bioenergane. Isplativost energetskih nasada uvelike je ovisna oodgovaraju}oj logistici, planiranju proizvodnje i prinosa. Tro{kovi strojnoga rada bili su izra~unati pomo}u koefi-cijenata i matemati~kih formula preuzetih iz vode}ih metodologija koje su predlo`ili razni autori. Ti su podaci biliupotrijebljeni za odre|ivanje ekonomske i energetske odr`ivosti strojne sje~e. Pro{lih godina mehanizacija se brzouvodila u {umske operacije. Pravilna je izobrazba radnika i planskoga osoblja nu`na, posebno kada se uvodi strojnasje~a za odr`ivo kori{tenje {umske biomase kao obnovljivoga izvora energije uz smanjivanje emisije stakleni~kihplinova. Energetska je bilanca bila procijenjena metodom GER (eng. Gross Energy Requirements). Metoda GERtako|er je primijenjena za procjenu neposrednih i posrednih inputa za uoptrijebljene strojeve. Nadalje, kod posrednemetode procjene utro{aka energije u {umarskim operacijama u sastojini bila je procijenjena potro{nja energije radnika

    Croat. j. for. eng. 33(2012)1 23

    Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (1524) R. Picchio et al.

  • prema otkucajima srca tijekom rada. Dva su radnika bila pra}ena svakoga radnoga dana. Pri dolasku na posaoodabrani su radnici bili opremljeni s Polarovim mjera~em otkucaja srca. Za izra~un izlazne energije ve}a ogrjevnavrijednost (HHV) bila je odre|ena na 30 uzoraka drvnoga iverja, koje se skupljalo nasumi~no s 10 kamionskih tovara.Kalorimetri~ni su testovi bili izvedeni s adijabatskim kalorimetrom (Parr, model 6200). Prosje~na vi{a ogrjevnavrijednost eukaliptusa bila je 20,14 MJ kgd.w.

    1. Tijekom radnoga vremena prekidi rada harvestera bili su 18,1 %ukupnoga radnoga vremena, prekidi rada pri iveranju zauzimali su manje vrijednosti (9 %), kao i premje{tanje izauzimanje polo`aja zbog dobre kretnosti na istra`ivanom podru~ju. U tim je planta`ama strojna sje~a omogu}ilabitno pove}anje operativne proizvodnosti zabilje`ene za svaku sastavnicu radnoga procesa: ru{enje/uhrpavanje,izvo`enje i iveranje, {to je pokazano visokom zabilje`enom proizvodno{}u (PSH15 = 6,5 td.w.h

    1radnik1) i povoljnomenergetskom bilancom (izlaz/ulaz = 23,8; 95,8 % u~inkovitosti sustava). Takva djelotvornost prema{uje onuzabilje`enu kod sustava ni`e razine mehaniziranosti koji su i dalje vrlo popularni u Italiji. Cijena sje~e (6,76 t1)svakako bi bila ni`a u slu~aju da je kori{ten feler ban~er (eng. feller buncher) koji ima ni`e tro{kove po satu rada i kojimo`e osigurati vi{u proizvodnost. Neobi~na uporaba harvestera u tom slu~aju bila je odre|ena ~injenicom da je strojbio u blizini i da je radio na pridobivanju drva iz topolovih planta`a. U svakom je slu~aju cijena sje~e visoka (44,30 TF.w.1) i mo`e se smanjiti samo pa`ljivim operativnim planiranjem. Prosje~na je visina panjeva bila 11,4 3 cm (p

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