Energy wood from early thinnings

Transcription

1 Case study North Karelia 3 Energy wood from early thinnings 5 EURES EIE//86/S Kari Väätäinen, Timo Tahvanainen, Esko Sirparanta, Sami Lamminen

2 Väätäinen, K., Tahvanainen, T., Sirparanta, E. & Lamminen, S. 7. Energy wood from early thinnings. Joensuu. Finnish Forest Research Institute, 5 EURES (EIE//86/S7.3858) Project Report 1. 3 p. Keywords energy wood, early thinning, wood ash, recycling, energy wood harvesting, farm-tractor Abstract In North Karelia the target in bioenergy production of forest chips equals to 75 GWh in. Early thinnings from young stands will represent an important role in fullfilling the needs of bioenergy use; 3% of the total bio energy production is estimated to be obtained form young stands. Increasing and more intensive energy wood harvesting from forests calls for the recycling of nutrients back to the forest, especially in poor soils and peatlands. Recycling of wood ash, the product of the combustion of energy wood, back to the forest, is a natural and profitable way to correct the nutrient inbalance of forest and, moreover, to solve the waste problem of the wood combustion. Furthermore, existing and new harvesting machinery needs to be activated for energy wood harvesting. Lighter and cheaper machines such as forestry equipped farm-tractors could be one solution for the cost-effective energy wood harvesting from young stands. In this case study, the recycling costs of granulated wood ash were calculated. Furthermore, the profitability of recycling wood ash back to the peatland forest as a fertilizing purpose was analyzed at the forest owner s point of view. Commercial artificial fertilizer was used as a comparable forest fertilizer in the profitability analyze. The recycling options to be studied were: A. forest fertilizing with ground based method by using the forwarder system and B. forest fertilizing with aerial method by using the helicopter-loader system. In addition, forestry equipped farm-tractors cost-competitive productivity levels in energy wood harvesting generating the same operational costs than conventional forest machines were investigated. The cost-competitive productivities of two different forestry equipped farm-tractor concepts were analyzed, when tractors were used either solely in wood energy harvesting or both in agriculture and in wood energy harvesting operations.

3 Preface This report is a national case study (WP3) report of the 5EURES Five European RES- Heat Pilots project (EIE//86/S7.3858). In WP3 of 5EURES local feasibility studies, case studies and demonstrations are performed. The main objective of the 5EURES project is to increase of the actual energy produced from bioenergy in the EU. In WP3, the target is to create regional bioenergy producing and/or using pilots. The target is achieved through feasibility studies, case studies and demonstrations. This report brings up the challenges in energy wood harvesting in early thinnings in Finland, and especially in the North Karelia. Paper consists of two important study cases regarding to energy wood extraction from early thinnings: balancing the nutrient loss from the energy wood extracted forests via wood ash recycling, focused especially on the ash recycling on peatland forest, which has a very important role in maintaining and even increasing the production potential of forest ecosystems after intensified biomass harvesting. It also affects the supply of energy wood by increasing the forest owners confidence on sustainable forest management. The second study case, assesment of the potential of the forestry equipped farm-tractor in energy wood thinnings, has a great importance for entrepreneurs and contractors in rural areas, and who are entering to bioenergy markets and making their first investments on forest machinery. The terms of cost-competitive productivity rates defined in this case study are basic parameters, when defining the economics of energy wood harvesting from thinnings. In regions, where services of forest machine contractors are currently lacking, these results have a major importance, and can smooth the way for expanding the use of local bioenergy resources. Joensuu..7 Kari Väätäinen & Timo Tahvanainen The sole responsibility for the contact of this report lies with authors. It does not necessarily reflect the opinion of the European Communities. The European Commission is not responsible for any use that may be made of the information contained therein. 3

4 Contents Abstract... Preface Introduction...6. Wood ash recycling Wood ash as a fertilizer...9. Wood ash refining processes and products....3 Ash spreading technologies Spreading cost calculations for granulated wood ash Profitability calculations for forest-owners Cost-competitiveness of the farm-tractor based energy wood harvesting Energy wood harvesting from young stands Cost calculation for both the forestry use and the dual use of farm-tractors Cost-competitive productivity level in energy wood harvesting.... Conclusions...7 References...9

5 1. Introduction In North Karelia Bioenergy Programme 6-15 the goal is to.5 fold the use and harvesting of forest chips in energy production from the figures in the year (Table 1). In the target for production of forest chips equals to 75 GWh, of which 3% (5 GWh) is estimated to to be harvested from thinning of young stands. The importance of young stands as a wood fuel potential is more important in North Karelia than in Southern Finland on average. This is because of lack of mature spruce stands, which are the most feasible sources for collecting harvesting residues and stump wood. Meanwhile, there are large areas of young stands coming to the phase of first thinning, especially pine-dominating stands in relatively poor sites, and large amount of them growing in peatlands. And due to the growing demand of biofuels during the next decade, the importance of thinnings as fuel source is even growing. Table 1. The use of forest chips in North Karelia in and the goals for and 15. The BTL-15 option refers to scenario in which also liquid biofuels are produced. Source: Tahvanainen et al BTL-15 PRODUCTION GWh GWh GWh GWh Logging residues 3 5 Stumps Thinnings Together The situation is challenging for the procurement of energy wood, as well as of industrial timber, because the harvesting costs in first commercial and pre-commercial thinnings are much higher than in final fellings or in later thinnings. Typically, the costs for one MWh of wood chips is about 5% higher if chips are produced from first thinnings compared to residues from final cuttings. A basic means to compensate the high harvesting costs due to small stem size and low harvesting harvesting removal per hectare is to use full tree and part tree logging methods. The challenge in reducing the harvesting costs is extra demanding in peatlands, where the low bearing capacity of the soil sets extra restrictions for mechanical harvesting and forwarding. Also, in peatlands the maintenance of nutrient balance needs more attention than in mineral soils, especially when needles and branches are collected. The relevant existing logging technologies for unthinned young stands are: a) manual felling bunching using felling handles (Figure 1), harvester heads with accumulating energy wood grips (Figure ), multi-tree-processing harvester heads (Figure 3) and conventional harvester heads (Figure ). The latter suits best the forest stands, where both industrial timber and energy wood are produced, because conventional harvester head provides the best 5

6 debranching and bucking abilities. The option is usually used only for full tree harvesting of energy wood in early thinnings. Figure 1. Manual felling bunching using felling handles in the chain saw Figure. Energy wood harvesting head with accumulating grips 6

7 Figure 3. Multi-tree-processing harvesting head Figure. Conventional harvesting head 7

8 Recycling of ash into forest instead of dumping the residues of wood combustion to landfills - is a natural, environmentally sound and economically profitable way for balancing the nutrient removal caused by intensive harvesting. The use of wood ash as a fertilizer has proved to be an efficient and long-lasting way to increase the forest growth particularly in nitrogen-rich peatlands. The technology for producing high-quality and easy-to-handle fertilizer through granulating or pelletizing process has already been successfully commercialized, and there are currently three companies in Finland in this growing business. Two of those companies are located in North Karelia. The methods and technology for ash logistics and spreading of ash into forest are under fast development. One of the purposes of this case study is to clarify the recycling costs of wood ash as a forest fertilizer in Finnish conditions. Moreover, the profitability of recycling wood ash back to the peatland forest as a fertilizing purpose at the forest owner s point of view will be investigated. In the chapter 3, forestry equipped farm-tractors cost-competitive productivity levels in energy wood harvesting generating the same operational costs than conventional forest machines will be defined. 8

9 . Wood ash recycling.1 Wood ash as a fertilizer The unburnable inorganic solid waste, which remains of a combustible material after burning, is called ash. Correspondingly, wood ash remains after burning wood material. Combusting wood waste creates ash, which contains nutrients useful for trees. Instead of dumping ash in dump pits, it can be used as a long term fertilizer in forests. In the future the production of wood based ash would be expected to increase due to the goals of the European Union to increase remarkably the utilization of wood based fuels for energy production. In order to solve growing waste problem, recycling of wood ash will raise its importance. In Finland energy industries utilisation of both wood based and peat fuels produce ash about 381, tonnes per year, and from that amount the pulp and paper industry alone produces wood based ash over /3 (Energiateollisuus ry 3, Finnish Forest Industries 5). Majority of the ash (about 133, tonnes) is transported and dumped to power plants and industries own dump pits or public ones. About 1% of the ash produced by the forest industries heat production is utilized for earth and road constructions and forest fertilizing (Finnish Forest Industries 5). Ash has a long-lasting fertilizing effect and its elements diminish acidity in soil. Excluding nitrogen, ash contains all the nutrients that trees need for growth. The increasing effect to the tree growth in peatlands is based on the phosphorus and potassium contents of the ash. Ash as a strong alkali matter decreases the acidity of the peat. This improves the bacteria activity on the peat and as a consequence of that the nitrogen of peat is mobilised for the use of trees (Kaunisto 1997). In order to obtain growth increase in mineral soils, nitrogen should be added to the ash. Various studies have pointed out that ash is a good fertilizer in forests, especially in peatland forests, where the growth of trees has considerably increased (Malmström 195, Paavilainen 198, Silfverberg & Huikari 1985, Eriksson & Börjesson 1991, Lauhanen et al. 1997). For example, according to Silfverberg s and Huikari s (1985) study - in which the experimental plot material was fairly extensive from the national wide point of view - the wood-ash fertilization (dosage 5-6 tonnes/ha) has increased mean productivity in drained peatland pine stands with 3 m 3 /ha/a after years. 9

10 Minor amounts of heavy metals are also concentrated in burning waste. There has been no proof, that the recommended wood-ash amounts (3 5 kg/ha) would have any harmful environmental effects (Perkiömäki ). Compared to artificial fertilizers, the effect of ash fertilization on N-rich drained peat lands is more permanent (Silfverberg 1996). In harvesting, nutrients are removed from forests and it is necessary to return these nutrients back to soil so that growing potential could be stabilised in the long run. The importance of recycling nutrients increases, if the use of logging residues and small wood as fuel is going to increase.. Wood ash refining processes and products Some studies as well as practical operations have been made on spreading different forms of ash. Spreading ash, which has been mixed with bio suspension, has been practised in Northern Savo in Finland starting from 1996 (Korpilahti 1998). Spreading is carried out with a forwarder which has a disc spreading device. With this method, dust formation is avoided and therefore no health problems are caused in handling ash. Ash moisturised with bio suspension is, however, easily dissolved in ground water, and the overall view of the spread area looks dirty. Another method of modifying powdered ash is self hardening of ash moistened with water. Before transporting into the forest storage, the self hardened ash will be crushed, so that the size of the granules varies from dust to clumps of a few centimetres in diameter (Koponen 1998). Self hardened ash has been spread at least in Finland and in Sweden (Palmberger et al. 199, Korpilahti 1998). Some improvements have been made in the process of transforming powdery wood-ash into a form, which facilitates the recycling of ash back to the forest. Perhaps the best way is to modify powdery ash into a form similar to artificial fertilizers. According to the latest studies, granulation of ash is proved to be the most feasible method (Hakkila and Kalaja 1983, Palmberger et al. 199, Hakkila 1996, Väätäinen et al. ). The principle of ash granulation is to blend ash and water in its right contents with a special mixer. The mix of ash and water is then granulated either with a disc granulator or with a drum granulator. Immediately after granulating the small sized granules and the larger clumps are returned back to the granulation process and crushed again. The average size of ash granules is 3-8 millimetres, and the density of granulated ash is about 1 kg/m 3 (Pekkarinen 1998). During the last decade the refining wood ash for special kind of fertilizing purposes has been developed to industrial level. Different types of wood ash fertilizing products are already available in Finnish forest fertilizer markets (FA Forest Oy). In addition to basic wood ash fertilizer for peat-lands, ash fertilizers fortified with some minerals like boron

11 are ready in markets and usable for the mineral soils lacking minerals, for example boron (FA Forest Oy). FA Forest Ltd. is manufacturing and marketing different types of wood ash fertilizers. In year 7 the company will launch a production of the fertilizer for mineral soils mixed with ash and communal bio sludge. Thus, with nitrogen addition to the fertilizer reveals better possibilities to spread the product also to mineral soils, where nitrogen is the nutrient of which shortage is mostly reducing tree growth..3 Ash spreading technologies After the granulating process of wood ash, warm granules are conveyed straight to the intermediate storage right next to the production plant. Most feasible and economic way of storing ash granules is cement floored, cement semi-walled and light tin plate coated storage, where the rain and moisture do not cause any quality losses on stored ash granules. The size of intermediate storages of ash granules has to be adjusted to the production volume of the plant and the smoothness of following steps of the ash recycling chain (Väätäinen et al. ). Most economical method for transporting granulated ash to the spreading area storages is to use a gravel transporting truck with a trailer. Because of heavy specific density of granulated wood ash, the payload of transporting unit can be reached up to the maximum loading capacity. There is no need for specific and own transporting fleet for long distance transporting of ash, which could create higher costs mostly due to lower annual machine utilization, compared to existing transporting fleet for earth mowing. Both aerial spreading (a helicopter) and ground spreading (a forwarder mounted with a centrifugal spreader) can be used in spreading granulated ash. A helicopter spreading is not dependent on cuttings and other forestry works, whereas a forwarder spreading requires skid roads. Additionally, ground based spreading should be carried out in peatland sites before reditching operations. A helicopter spreading can also be carried out during summer, whereas a forwarder needs solid ground, therefore peatlands can be operated only in winter when the ground is properly frozen. The most common and profitable method for ground based ash recycling is spreading ash with a forwarder. The ash container and centrifugal disc spreader is mounted to the forwarder. This spreading unit is possible to install into the log bunk so, that there is no need to remove the stanchions. In addition, the timber grip has to be replaced with a bucket in order to load the ash granules to the container with forwarder itself. Moreover, cost efficiency of ground spreading improves due to the use of forwarder in its main purpose, loggings. Thus, the utilization of the base machine will increase. 11

12 . Spreading cost calculations for granulated wood-ash For calculating the ash spreading costs for different spreading options, the system analysis model of ash spreading costs was used. This system analysis model was produced in 5EURES project. Constant and ranging parameters for cost calculations of ash spreading with different methods are presented in table. The average values represent average ash spreading conditions in North Carelia in Finland. Currently, the shares of the use of ground based and aerial based methods are about 5% for forwarder spreading and 75% for helicopter spreading. The ash spreading cost calculations are based on the annual ash granule production of, tonnes at the ash refinery plant of the FA Forest in North Karelia. Table. The characteristics of spreading conditions for ash spreading both with forwarder and helicopter. Forwarder spreading Helicopter spreading Annual spreading amount,, 8, tonnes Area of the spreading site, ha 5 (avg. 3) 5 (avg. 8) Spreading dosage, tonnes/ha 5 (avg. ) 5 (avg. ) Spreading distance, km. 3 (avg..5). (avg..8) Purchase prices, pay loads and annual use of base machines for both spreading options are presented in table 3. A light wheeled loader (Bobcat) was used in the helicopter spreading for loading the ash spreading containers ( units). This type of loader is commonly used for example construction sites. Annual use of machines illustrates the maximum annual machine utilization for all purposes, including ash spreading. Table 3. Basic values of machines used in ash spreading. Ground based spreading Aerial spreading Forwarder Disc spreader Helicopter Bobcat Purchase price (VAT %), 3,, 1,3, 57, Pay load, kg 6, 6, 9 9 Annual use in ash spreading, h/a Total annual use, h/a, ,6 Hourly operating costs of different spreading options is compared in the spreading situation, where spreading distance was 5 metres and the average spreading area was 3 ha. The total hourly cost of ground based system was 7.9 euros, wherein the hourly cost of forwarder was 6. euros and disc spreader.9 euros, respectively. With the annual use of 6 operating hours of the helicopter, the total hourly cost of aerial based system was 85.3 euros, wherein the hourly costs of helicopter was euros and 1

13 Bobcat 33.7 euros. With the use of 1, operating hours of the helicopter the total cost was 78.7 euros. Ash spreading productivities both for forwarder and helicopter based spreading methods are presented in figure 5 as a function of spreading distance. Depending on spreading distance, helicopter spreading is approximately times more productive than forwarder based spreading. For example, in a spreading distance of 5 metres the productivity of helicopter method was 6. tonnes/h-e 15, whereas the productivity of forwarder spreading was 6. tonnes/h-e Productivity, tonnes/hour (E 15 ) Forw arder Helicopter Spreading distance, metres Figure 5. Productivities of spreading of granulated ash with forwarder based and helicopter based systems. Pay loads were 6 tonnes for the forwarder system and.9 tonne for the helicopter system. Spreading cost, /tonne 8 6 Helicopter Forw arder Spreading distance, metres Figure 6. Spreading costs of granulated ash with both the forwarder and the helicopter based systems. Pay loads were 6 tonnes for the forwarder system and.9 tonne for the helicopter system. 13

14 Even thought the productivity of helicopter spreading is much higher than forwarder spreading, it does not fully compensate higher fixed costs when comparing to the costs against forwarder spreading (figure 6). Depending on the spreading distance, the spreading costs of forwarder system is about 35% to 5% of the spreading costs of the helicopter system. Economically feasible size of spreading area was analyzed for both spreading concepts (figure 7). When the size of the spreading area is ranging, the absolute cost difference is greater in spreading costs of the helicopter system than in spreading costs of the forwarder system. Economically feasible spreading area of the cost-effective spreading of forwarder system should be to hectares or more, whereas respective operational minimum size of helicopter spreading is between 3 and hectares. 3 Spreading cost, /hectare Helicopter, 1 km distance Helicopter,.5 km distance Forw arder, 1 km distance Forw arder,.5 km distance Spreading area, hectares Figure 7. The influence of the average size of the spreading area on ash spreading costs of the forwarder and the helicopter systems..5 Profitability calculations for forest-owners An Excel based analyze tool for the profitable use of forest fertilizers was developed for analyzing different fertilizing options for peatlands. Ash fertilizing was compared to an artificial forest fertilizer product (Suometsän PK-lannos produced by Kemira GrowHow Ltd.). Spreading dosage differs greatly among the granulated ash and the artificial fertilizer. Used dosages of these fertilizers were, kilos per hectare for the granulated ash, and 6 kilos per hectare for the artificial fertilizer. With those dosages, both fertilizers yields approximately the same amount of main growth increasing nutrients such as phosphorus and potassium. In addition, the growth increasing influence of ash fertilizer is approximately times longer than of an artificial fertilizer. For example, the influencing time of the growth 1

15 increase is estimated to be 15 to 5 years for the artificial fertilizer (Silfverberg & Hartman 1999). Therefore, the profitability calculation includes two fertilizing times for the artificial fertilizer, and one time for the ash fertilizer during stand rotation. Main purpose of this analyse was to study the profitability of the forest fertilizing investments in pine dominated N-rich type peatland sites, from the forest owners point of view. The profitability of different fertilizing options was assessed using internal rate of return (IRR) as an indicator. In the other words, the calculation tool searches for the discount rate, that makes the net present value of all cash flows from a particular investment equal to zero. Generally speaking, the higher investment s internal rate of return, the more desirable it is to undertake the investment. Table. Used initial values in the calculation of the profitability of forest fertilizing. Granulated ash Artificial fertilizer Fertilizing info: Helicopter Forwarder Helicopter Dosage, tonnes/ha.6 The duration of fertilizing effect, years The moment of the first fertilizing, years from the first thinning The moment of the second - 5 fertilizing, years from the first thinning Division of growth increase among timber assortments: Pulpwood, % Timber, % 6 6 Costs of fertilizing: Price of the fertilizer, /tonne 18 6 Transportation cost, /tonne 7 1 Spreading cost, /tonne Supervision cost, /tonne 5 Costs total, /tonne Costs total, /hectare Subsidies: KEMERA subsidy*, % of the total cost Tax allowance, % of the total cost 8 8 Prices of timber: Pulp wood, /m³ Saw logs, /m³ 5 5 Removal-% from the thinning (removal from the growth increase) 3 3 The moment of nd thinning, years from the 1 st fertilizing The moment of final felling, years from the 1 st fertilizing 5 5 * KEMERA is a state subsidy for silvicultural operations in order to improve the growth conditions of trees in young forest stands 15

16 All the costs and subsidies related to forest fertilizing in Finland are included in the calculation. In addition, the fertilizing revenues in forms of additional timber selling incomes are included. The additional incomes of selling the timber derive from the extra growth increment of trees, due to the fertilizing effect of used fertilizer options. In the table some initial values of the fertilizing analyse are presented. The figure 8 illustrates the IRR percent for the fertilizing investment as a function of expected growth increase (m³/ha/year). The forest fertilizing seems to be very profitable investment in particularly in the N-rich type peatlands, where the growth increase could be expected to be about 3 m³/ha/year for ash fertilizing. Even one cubic-metre growth increase in hectare per every years results more than 6% internal rate of return. Ash fertilizing with forwarder system results even percent unit higher IRR value, compared to other fertilizing options. As a result of the subsidy aid for the investment, the profitability of the forest fertilizing improves remarkably. 16 Internal rate of return (IRR), % Ash fertilizer, helicopter spreading Ash fertilizer, forwarder spreading Artificial fertilizer, helicopter spreading 1 3 Growth increase, m3/ha/year Figure 8. Internal rate of return of different fertilizing investments as a function of expected growth increase. 16

17 3. Cost-competitiveness of the farm-tractor based energy wood harvesting 3.1 Energy wood harvesting from young stands In Finland, repeated thinnings are a standard and essential silvicultural practice for the efficient production of good quality and well priced industrial wood. Nearly all stands are thinned one to three times during a rotation time. Most of the commercial thinnings are preceded by pre-commercial thinnings, from which felled trees are not collected because of the small tree size. Young thinnings are a potential source of biofuel. Currently, the highest biofuel yields are found in stands, were silvicultural activities have been neglected. These stands are over-dense, and the trees that have to be removed are too thin or of undesireable tree species for industrial purposes. As such, they are attractive for biofuel harvest (Hakkila ). It has been discussed, that management guidelines adapted to biofuel production in young forests could include a so called energy wood thinning. The energy wood thinning is carried out before commercial thinning, and it can delay the first commercial thinning compared to traditional silvicultural regime (Hakkila ). In pine stands, an extra benefit can be gained by better quality of the remaining stems, if young trees are growing in more dense position. Most of the machines used in mechanized CTL-loggings are designed aiming to high productivity in final fellings. The operating costs of these expensive and heavy-duty logging machines can grow relatively high in first thinnings with small sized trees and low removal. Annual harvesting removal carried out from first thinnings is only about % of total harvesting in Finland. Not only first thinnings, but also energy wood harvesting in young stands promotes the use of lighter and cheaper machines, such as thinning harvesters and farm tractors especially equipped for forestry use. A farmtractor with relatively high productivity and moderate purchase price, can be a competitive option, if terrain conditions are favourable and the annual operational hours are adequate (Ryynänen et al. ). In general, costly investments of machines enforce a pressure to increase the machine utilization as high as possible. Correspondingly, the hourly costs will be reduced, if the lay-days of machines could be lowered (Pentti et al. 5). The average annual use of farm-tractors in agriculture operations in Finland is comparatively low, and the use is concentrated practically on the growth season. The supplementary use of farm-tractors in biofuel harvesting operations could lower machine hourly costs, and give 17

18 complementary business activity to farmers. Moreover, forestry use equipped farmtractors could be even feasible option for year round business in forestry operations in young forests. Principally, farm tractors used for forestry works needs to be equipped for forest work purposes. In the tractor assembly line a special forest cabin, revising techniques and cut prevented tyres are already installed in the forest farm-tractor. Additionally, the bottom shield and hydraulic pump are also vital to install to the tractor. Depending of the prospective forestry use of the tractor, there are several accessories possible to attach to the tractor, such as crane, forestry trailer, accumulating harvester head for energy wood and chipper. The cost calculator for forestry equipped farm-tractors was created within 5EURES project. More closely, a competitive productivity level for biofuel harvesting of smallsized trees was analyzed. In other words, farm-tractors productivity level in biofuel harvesting - generating the same operational costs than conventional forest machines - was explored. The comparable productivity and harvesting cost values of conventional forest machines were collected from the recent Kärhä s et al. (6) publication. The used method for biofuel harvesting was full tree method with accumulating harvesting head. 3. Cost calculation for both the forestry use and the dual use of farm-tractors The cost calculator for the dual use of farm-tractors was used for analyzing machine hour costs separated with main work purposes. Machine cost calculating was based on the general cost calculating method. Two different forestry equipped farm-tractor concepts were used: The first one (Concept 1) was a new forestry equipped tractor (Valtra 685), which purchase price was 73, euros (VAT %). The second tractor concept (Concept ) was lighter and cheaper second-hand forestry equipped tractor (Valtra 6, year model 1996), which purchase price was 8, euros (VAT %). Base information for the cost calculation of these tractor concepts is presented in table 5. In addition to tractor investment, accessories for energy wood harvesting have to be included. For the bigger and more expensive base machine (Concept 1) accessories for energy wood harvesting were fitted to the size of the base tractor. In the Concept, accessories were somewhat lighter (table 6). The accessories included in both cases were a crane, an energy wood harvesting head and a trailer. 18

19 Table 5. Base information for the cost calculations of the forestry equipped tractors. Concept 1 Concept Model Valtra 685 (6) Valmet 6 (1996) Engine power, hp Purchase price (VAT %), 77,9 1 / 73, 3, 1 / 8, Service life, machine hours,, Salvage-% of purchase price 3 3 Interest rate, % 5 5 Hourly wage.5.5 Indirect wage cost-% repair and maintenance cost, /h-e Consumption, l/h: Fuel motor oil.1.1 gear oli.1.1 hydraulic oil.5.5 Cost, /l Fuel motor oil gear oli.1.1 hydraulic oil Higher purchase price includes additional tyres and rims for agriculture operations Table 6. Base information of the accessories for wood energy harvesting. Accessories for concept 1 Accessories for concept Wood energy harvesting head (accumulating felling head) Naarva-Grip -3E Naarva-Grip -3E Purchase price (VAT %), 6,97 6,97 Service life, machine hours 8, 8, Salvage-% of purchase price 5 5 Crane Kronos 5 Kronos Purchase price (VAT %), 13,967 9, Service life, machine hours,, Salvage-% of purchase price Trailer Kronos -wd Kronos H Purchase price (VAT %),,917 5,58 Service life, machine hours,, Salvage-% of purchase price 3 3 For both tractor concepts, three different working cases were analyzed. In the first case (Case 1) forestry equipped farm tractor was used purely in energy wood harvesting, where operating hours ranged from 15 hours up to 1,67 hours. In case two and three, in addition to wood energy harvesting, the tractor was used either 6 hours (Case ) or 1, hours (Case 3) in agriculture. Wood energy harvesting operations ranged from 15 to 1,5 hours in the Case, whereas in the Case 3 the range was 15 6 operating hours, respectively. Total machine hours did not exceed the work input of one shift work (8 h/d, d/m and 11 m/yr). In the analyses of the cases and 3, extra tyres with rims for agriculture use were included to base investment cost. Moreover, depending on the monthly use for forestry 19

20 works, the transposition of tyres and installation of accessories were set to hours per each month for the forestry use. Finally, three different working options of energy wood harvesting were included for all tractor conceptes and working cases. In the first option, tractor was used only in cuttings of energy wood, whereas second option consisted of forwarding of energy wood. The third option consisted both cutting and forwarding operations, thus, the tractor was used like a harwarder in energy wood harvesting. For the first working option (Cutting), the accessories were crane and energy wood harvesting head, whereas for forwarding (Forwarding) a crane and a trailer were included. In harwarder work (Harwarding), all the accessories for energy wood harvesting were needed. 3.3 Cost-competitive productivity level in energy wood harvesting The harvesting costs of energy wood harvesting from young stands referred from the latest study (Kärhä et al. 6) were determined as a reference cost levels. The reference cost level of energy wood cutting was based on the light thinning harvester, equipped with accumulating energy wood harvesting head. Correspondingly, the mid weight forwarder in forwarding of energy wood, and the forwarder based harwarder with energy wood harvesting head, were the machine concepts producing reference cost levels in energy wood forwarding and harwarding (cutting and forwarding). The costs and productivities were expressed in cutting and harwarding with the function of stem size, whereas the unit expressions in forwarding were with the function of forwarding distance. The theoretical productivity curves for forestry equipped farm tractors were calculated as follows: Farm-tractors hourly costs ( /h-e 15 ) were divided with the reference harvesting cost values of conventional forest machines ( /m³). Resulting productivity demand curve shows the cost-competitive productivity level for forestry equipped farm tractors to be targeted in energy wood harvesting in young stands. If the actual productivity of a far-tractor based system is above the productivity demand curve, the system is more economical, than forest machines in presented conditions. The hourly costs of the forestry equipped farm-tractor with the concepts 1 and as a function of used harvesting hours are presented in figures 9 and. With the dual use (agriculture and energy wood harvesting) of the farm-tractor, the hourly costs of energy wood harvesting could be reduced remarkably, when comparing to the farm-tractor use in wood energy harvesting. This would be the case when the wood energy harvesting will remain less than 5-7 hours. With the full annual one-shift use, the hourly cost of the energy wood harvesting is approaching close to euros in tractor concept 1, and

21 33 euros in tractor concept, respectively. In addition, minor differences in hourly costs could be found between harvesting options, mainly due to different accessory set-ups. Cutting of energy wood Hourly cost, /h-e Energy wood harvesting hours Agriculture use of 6 h Agriculture use of h Only energy wood harvesting Forwarding of energy wood Harwarding of energy wood Hourly cost, /h-e Hourly cost, /h-e Energy wood harvesting hours Energy wood harvesting hours Figure 9. The hourly costs of forestry equipped farm-tractor (tractor concept 1) as a function of energy wood harvesting hours. 1

22 Cutting of energy wood 9 Hourly cost, /h-e Agriculture use of 6 h Agriculture use of h Only energy wood harvesting Energy wood harvesting hours Hourly cost, /h-e Forwarding of energy wood Hourly cost, /h-e Harwarding of energy wood Energy wood harvesting hours Energy wood harvesting hours Figure. The hourly costs of forestry equipped farm-tractor (tractor concept ) as a function of energy wood harvesting hours. The cost-competitive productivity levels in energy wood harvesting are presented in figure 11, when the agriculture use of farm-tractor is 6 hours per annum. Low use rate (less than 3 hours per annum) of the farm-tractor in energy wood harvesting requires comparatively higher productivity level, in order to reach the cost-competitiveness against conventional forest machines. Cutting of energy wood seems to be most feasible harvesting method for the forestry equipped farm tractors, whereas in forwarding of energy wood required productivity level is closer to the productivities of conventional forwarders. This finding can be noted in tractor concept 1, particularly. With the lighter and cheaper farm-tractor concept (concept ), the cost-competitive productivity could be reached in much smaller productivities, than with the bigger tractor concept. In energy wood cutting, the cost competitive productivities were about 8% higher for tractor concept 1, than for concept. Respectively, in energy wood forwarding the productivities were 33% higher, and in harwarding 5 3% higher than the productivities in concept.

23 1 Concept 1 Energy wood cutting 1 Concept Stem size, m³ Thinning harvester 15 h of EW cuttings 3 h of EW cuttings 5 h of EW cuttings 6 h of EW cuttings Stem size, m³ 1 Concept 1 Energy wood forwarding Concept Forwarding distance, m forwarder 15 h of EW forwarding 3 h of EW forwarding 5 h of EW forwarding 6 h of EW forwarding Forwarding distance, m 5 Concept 1 Energy wood harwarding 5 Concept 3 1 Harwarder 15 h of EW harwarding 3 h of EW harwarding 5 h of EW harwarding 6 h of EW harwarding Stem size, m³ Stem size, m³ Figure 11. Cost-competitive productivity levels (productivity demand curves) of forestry equipped farm-tractors (Concepts 1 and ) in energy wood harvesting, when tractors base use for agriculture work is 6 hours. As the comparable levels, the productivities of conventional forest machines are also presented. In the working case of 1, hours of agriculture work, the required productivity levels are lower (figure 1). Depending on the annual energy wood harvesting use, costcompetitive productivity levels were approximately 7 to 1% smaller, than in previous case of 6 hours of agriculture work. If the energy wood cutting was 6 hours, the cost-competitive productivity level for the tractor concept 1 was about 55% of thinning harvester s productivity. 3

24 1 Concept 1 Energy wood cutting 1 Concept Stem size, m³ Thinning harvester 15 h of EW cuttings 3 h of EW cuttings 5 h of EW cuttings 6 h of EW cuttings Stem size, m³ 1 Concept 1 Energy wood forwarding Concept Forwarding distance, m forwarder 15 h of EW forwarding 3 h of EW forwarding 5 h of EW forwarding 6 h of EW forwarding Forwarding distance, m 5 Concept 1 Energy wood harwarding 5 Concept 3 1 Harwarder 15 h of EW harwarding 3 h of EW harwarding 5 h of EW harwarding 6 h of EW harwarding Stem size, m³ Stem size, m³ Figure 1. Cost-competitive productivity levels (productivity demand curves) of forestry equipped farm-tractors (Concepts 1 and ) in energy wood harvesting, when tractors base use for agriculture work is 1, hours. As the comparable levels, the productivities of conventional forest machines are also presented. Correspondingly, with the cheaper tractor concept (Concept ), the cost-competitive productivity level was only 7% of thinning harvester s productivity. With the respective operating hours in energy wood forwarding, the cost-competitive productivity level was 69% of the forwarder s productivity in tractor concept 1 and 57% in tractor concept. Further, the cost-competitive productivity level in energy wood

25 harwarding was 6% of the forwarder based harwarder s productivity in tractor concept 1 and 5% in tractor concept, respectively. 1 Concept 1 Energy wood cutting 1 Concept Stem size, m³ Thinning harvester 6 h of EW cuttings 9 h of EW cuttings h of EW cuttings 15 h of EW cuttings Stem size, m³ 1 Concept 1 Energy wood forwarding Concept Forwarding distance, m forwarder 6 h of EW forwarding 9 h of EW forwarding h of EW forwarding 15 h of EW forwarding Forwarding distance, m 5 Concept 1 Energy wood harwarding Concept Harwarder 6 h of EW harwarding 9 h of EW harwarding h of EW harwarding 15 h of EW harwarding Stem size, m³ Stem size, m³ Figure 13. Cost-competitive productivity levels (productivity demand curves) of forestry equipped farm-tractors (Concepts 1 and ) in energy wood harvesting. The tractor was used only for harvesting, and the annual working hours ranged from 6 to 1,5. As the comparable levels, the productivities of conventional forest machines are also presented. 5

26 The figure 13 presents the productivity demand curves for a farm-tractor, when it is used only for harvesting operations. The cost-competitive productivity level of forestry equipped farm-tractors starts to saturate, when the annual use in energy wood harvesting approaches the full one-shift operating level. With the annual 1,5h work load of tractor concept 1, the cost-competitive productivities were 56% in cutting, 7% in forwarding, and 6% in harwarding of the corresponding productivity levels of conventional forest machines. The corresponding values for the tractor concept were about % units lower than the concept 1 had. 6

27 . Conclusions Wood ash recycling back to the peatland forest reveals to be a fesible and profitable method to utilisate the combustion waste from energy wood as a fertilizer. Granulating or pelletizing wood ash improves remarkably the handling of ash over the recycling process. In Finland, there are three large wood ash refining companies, of which two are located in North Karelia. Even though ash spreading using helicopter based system is somewhat three times more productive method, than ground based spreading with a forwarder system, the spreading with the forwarder is noticeably cheaper. While the spreading distance ranged from 5 to, metres, the spreading costs of granulated wood ash done with the forwarder system was /ton, whereas spreading with helicopter system was 6 /ton. For improving the economy of wood ash recycling back to peatlands, according to this study, following factors should be considered: Ground based spreading of granulated ash should be emphasized and, therefore, a comprehensive planning for selection of the stands, and for adequately large operational units, is needed. In contrast to helicopter spreading, forwarder spreading requires strip roads, and in peatlands, frozen ground. Operationally feasible and economical size of the spreading area for forwarder spreading shoud be at least hectares, and for helicopter spreading 3 to hectares, at minimum. From the forest owner s point of view, fertilizing of peatland forest with wood ash seems to be a very profitable silvicultural investment. By using the average annual growth increase (3m³/ha/year) influenced by wood ash fertilizing in N-rich type peatlands, the internal rate of return (IRR) of the fertilizing investment was.7% for helicopter spreading, and even 1.5% for forwarder spreading. KEMERA (state) subsidy and tax deduction were taken into account on the profitability calculations. The utilization of farm-tractors in energy wood harvesting, especially in young stands, has increased steadily in Finland. Energy wood harvesting with forestry equipped farmtractors can be a feasible and profitable business opportunity for farmers having seasonal agriculture works, and for contractors operating year round in energy wood harvesting. According to the productivity analyze of two different sizes of farm-tractors, cutting operations could provide the best possibilities to compete with the economy against conventional forest machines in energy wood harvesting. In forwarding and in harwarder-type of use the competitiveness is weaker. Moreover, if the annual use of the tractor in energy wood harvesting can be increased close to 5 hours and more in dual works (agriculture and forestry works), and up to 1, hours solely in energy wood harvesting, hourly costs of tractors are settled down to economical level. 7

28 Farm-tractor based harvesting of energy wood is an attractive option in cases, where it is difficult to achieve a full work load for a forest machine based supply chain within a reasonable operational area. This can be the case, for example, in areas with low percentage of forest area, or areas in which the energy wood markets and mechanized harvesting of young stands is emerging. Lower investment and productivity means also lower risk, together with lower demand for work opportunities. These advantages are emphasized, if farm-tractor has complementary work opportunities for example in agriculture. Energy wood harvesting contractors, which operate with the forestry equipped farmtractors, could set the productivity demand curves presented in this case study as a minimum target, to be able to compete with conventional forest machines. One has to keep in mind that, even though, the more expensive farm-tractor concepts requires higher productivity levels for competing in economy, these bigger machines are often more feasible for forestry operations than cheaper forestry use farm-tractors. In difficult terrains (high slopes, rocky terrains and terrains with low bearing capacity) the feasibility of farm-tarctor based harvesting is more vulnerable, than of purpose built wheeled forest machines or excavator based harvesters. 8

29 References Energiateollisuus ry. 3. Sivutuotteiden hyötykäyttöaste. Energiateollisuus Ry. Available: [Read ] Eriksson, J. & Börjesson, P Vedaska i skogen. En literaturstudie. Vattenfall. FUD- Papport 1991/6. 77 p. Finnish Forest Industries. 5. Ympäristönsuojelun tilastot. Massa-, paperi- ja puutuoteteollisuus. 5. Finnish Forest Industries. Available: [Read ]. Hakkila, P Tuhkan kierrätyksen tekniikka. In publication of: Finér, L. Leinonen, A. and Jauhiainen, J. (editors). Puun ravinteet tuhkana takaisin metsään?. Metsäntutkimuslaitoksen tiedonantoja 599. Joensuun tutkimusasema pp Hakkila, P.. Puuenergian teknologiaohjelma , metsähakkeen tuotantoteknologia loppuraportti, teknologiaohjelmaraportti 5/ TEKES. Hakkila, P. & Kajala, H Puu- ja kuorituhkan palauttamisen tekniikka. Summary: The technique of recycling wood and bark ash. Folia Forestalia 55: pp Kaunisto, S Suometsien ravinnetalouden erityispiirteet ja puutuhkan käyttömahdollisuudet. Teoksessa: Nurmi, J., Hytönen, J. & Polet, K. (toim.) Energiapuusta puutuhkaksi. Metsäntutkimuslaitoksen tiedonantoja 66: 1 Koponen, R Tuhkan itsekovetus. In publication of: Anttila, P. & Korpilahti, A. (editors). Tuhkahankkeen väliseminaari. Metsätehon raportti 5. Metsäteho Ltd. pp. -5. Korpilahti, A Varastointi ja levitys sekä hyöty- ja kustannustarkastelu. In publication of: Anttila, P. & Korpilahti, A. (editors). Tuhkahankkeen väliseminaari. Metsätehon raportti 5. Metsäteho Ltd. pp Kärhä, K., Keskinen, S., Liikanen, R. & Lindroos, J. 6. Kokopuun korjuu nuorista metsistä. Metsätehon raportti 193 Lauhanen, R., Moilanen, M., Silfverberg, K., Takamaa, H. & Issakainen, J Puutuhkalannoituksen kannattavuus eräissä ojitusaluemänniköissä. Summary: The profitability of wood ash-fertilizing of drained peatland Scots pine stands. Suo 8(3): Malmström, C Svenska gödslingsförsök för belysade av de näringsekologiska villkoren för skogsväxt på torvmark. Comm. Inst. For. Fenn. (17): pp Paavilainen, E Tuloksia vanhoista tuhkanlannoituskokeista. Muhoksen tutkimusaseman tiedonantoja : pp. -7. Palmberger, B., Ståhl, K. & Widegren-Dafgård, K Askåterföringssystem, tekniker och möjligheter. Sydkraft, Nutek, Vattenfall. Rapport 3. p. Pekkarinen, J Tuhkan rakeistus. Anttila, P. & Korpilahti, A. (editors). Tuhkahankkeen väliseminaari. Metsätehon raportti 5. Metsäteho Ltd. pp

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