Discussion on economy and energy balances of forest residues. for Bio-energy at Sano city, Tochigi prefecture in Japan

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1 Discussion on economy and energy balances of forest residues for Bio-energy at Sano city, Tochigi prefecture in Japan Kazuhiro Aruga; Associate Professor, Fac. of Agric., Utsunomiya Univ., Tochigi Reiko Yamaguchi, Chikara Nakahata, Ayami Murakami, Kaname Ito, Masashi Saito; Graduate Student, Fac. of Agric., Utsunomiya Univ., Tochigi ABSTRACT To discuss the harvesting system considering extracting forest residues for supplying to a biomass power plant, we estimated harvesting volumes and costs using GIS at Sano city, Tochigi prefecture in Japan. Forest-registration data (stand ages, tree species, and site indexes) and GIS data (information on roads and subcompartment layers) from the Tochigi Prefectural Government were used in the study, as were 50 m-grid digital elevation models (DEM) from the Geographical Survey Institute. As a result, the minimum and average costs of Cut-To-Length system with forwarders were 4,424 yen/m 3 and 8,206 yen/m 3, respectively. Only 0.08% of subcompartments were extracted as those costs below 4,500 yen/m 3. Energy input increases as harvesting volumes of forest residues increases. However, the maximum energy input, 0.08 GJ/m 3 was still lower than potential energy of wood, 4.06 GJ/m 3. Same with energy input, CO 2 emission increases as harvesting volumes of forest 1

2 residues increases. However, the maximum CO 2 emission, 6 kgco 2 /m 3 was still lower than sequestered CO 2 in wood, 576 kgco 2 /m 3. Therefore, this system would be energy-effective. In order to reduce costs, subsidy and whole tree logging system were considered. As a result, the average costs with subsidy were reduced to 5,719 yen/m 3 and 41% of subcompartments were extracted. The average costs of stem extraction without branches were also reduced to 7,995 yen/m 3. The minimum and average costs of whole tree logging system were significantly reduced to 1,182 yen/m 3 and 5,911 yen/m 3, respectively. Moreover, costs considering timbers extraction were also reduced. Therefore, the whole tree logging system could be more advantageous for extracting forest residues than the Cut-To-Length system. ($1=92.76 yen on March 28, 2010) Key Words: forest residues, harvesting systems, GIS, Subsidy, Whole tree logging INTRODUCTION Forest has important roles in realizing the low-carbon society in that forest sequesters carbon from the atmosphere and produces wood: one of typical renewable resource which stores sequestered carbon. Therefore, forest needs to be continuously and properly managed and the 2

3 use of wood, particularly domestic one, should be promoted. Forestry in Japan, which is necessary for forest management as well as wood production, faces many difficulties; shrinking domestic wood demand, declining wood prices and deteriorating profitability. If the situation remains unchanged, the population in mountainous areas is expected to decrease and become older, resulting in lack of proper forest management (Japan Forestry Agency 2009). Revenues increase from the sales of value-added wood products or the Domestic Credits and the Offsetting Credits (J-VER), as well as cost reduction at each stage from wood production to processing, might improve the profitability of forestry, revitalizing forestry industry and communities in mountainous areas. Proper care of forests in mountainous areas and effective wood use while revitalizing forestry industry and communities in mountainous areas are the keys to the realization of the low-carbon society (Japan Forestry Agency 2009). Woody biomass can be categorized into forest residues, sawmill residues and construction waste woods. Although the introduction of wood-fired boilers and generators and the production of wood pellet have been steadily increasing in recent years, large amount of woody biomass, in particular forest residues, still remains unused (Figure 1). In order to utilize forest residues as energy in a region where forestry is the major source of income, it is crucial to find out the relationship between the available amount and the procurement 3

4 (harvesting and transporting) cost of forest residues in the region. In this study, feasibility of the energy utilization of forest residues in a mountainous region in Japan is discussed with the aid of the GIS. To discuss the harvesting system considering extracting forest residues for supplying to a biomass power plant, we estimated harvesting volumes and costs using GIS at Sano city, Tochigi prefecture in Japan. Forest-registration data (stand ages, tree species, and site indexes) and GIS data (information on roads and subcompartment layers) from the Tochigi Prefectural Government were used in the study, as were 50 m-grid digital elevation models (DEM) from the Geographical Survey Institute. Then, in order to reduce costs, subsidy and whole tree logging system were considered. Finally, the energy balance and the carbon dioxide (CO 2 ) emission were analyzed using the method of a life cycle inventory. Figure 1 Sources and Utilization of Woody Biomass (Japan Forestry Agency 2009) 4

5 STUDY SITE AND DATA Study site is Sano City in Tochigi Prefecture, Japan (Figure 2). The gross area is 35,607 ha, the forest area is 21,839 ha (the percentage to the gross area is 61%). Most of the tree species are conifers; Japanese cedar and Hinoki cypress account for 39% and 23% of the trees, respectively (Figure 3). Most of conifers are within years old (Figure 4). According to site-index which indicates the order of the production capacity of the stands by three classes and the smaller number is, the larger production capacity is. Site-index 1 is 72%, Site-index 2 is 23%, and Site-index 3 is 5% (Figure 5). Most of forests are relatively steep and average inclination is 32 degrees (Figure 7). The density of the road network is relatively high, 53 m/ha. Forest-registration data (stand ages, tree species, and site indexes) and GIS data (information on roads and subcompartment layers) from the Tochigi Prefectural Government were used in the study, as were 50 m-grid digital elevation models (DEM) from the Geographical Survey Institute. Using these materials and the GIS, the available amount of forest residues was estimated and the distribution map was made based on sub-compartments which were usual operational units in Japan. 5

6 Figure 2 Study site Figure 3 Stand species 6

7 2,500 2,000 Area(ha) 1,500 1, Age-class Figure 4 Stand age class (5 years each class) Figure 5 Site index 7

8 METHODS Procurement costs Harvesting and transporting systems were shown in Figure 6. Table 1 lists the operation patterns of sub-compartments to be felled. Logging residues are considered as a by-product of conventional forestry. Therefore, the system boundary of logging residues starts with forwarding by forwarders (Figure 6). Table 2 shows the machine specification and Table 3 shows the equations for calculating the harvesting and transporting costs of logging residues whose variables are logging distance L Y (m), slope θ (degree), harvesting volumes per ha V (m 3 /ha), area A (ha), and transporting distance L T (m). Payloads are changed according to forwarding and transporting parts such as stems and branches (Table 4). Therefore, forwarding and transporting expenses are classified into three equations (Table 3). Felling by Chainsaw Processing by Chainsaw Forwarding by Forwarder Piling by Grapple-Loader Transporting by 8-ton Truck Figure 6 Harvesting system (Cut-To-Length system) 8

9 Table 1 Harvesting condition First (pre-commercial) thinning Second (commercial) thinning Clear cutting Age 25~39 40~59 60~ Cutting rate 25% 35% 100% Extracting rate 80% 111% * 111% * Logging residues rate 100% 55% 26% Timber rate 0% 45% 74% * including branches 9

10 Machine prices (thousan d Yen) Duration (Years) Table 2 Parameters for machine expenses Annual operatio n time (h/year) Depreciatio n rate Maintenanc e and repair rate Annual administratio n rate Fuel consumpti on(l/h) Productivity Chainsaw Felling Chainsaw Processi ng Forwarder Part 1 6, , ,191/Ly Grapple-Load er (m 3 /h) Part 2 5,254/Ly Part 3 15,168/Ly 9, , Ton Truck Part 1 10, , ,500/Lt Part 2 85,500/Lt Part 3 247,423/Lt Tractor 9, , ,440/Ly Tower-Yarder Small 6, ,080/(2Ly+80) Tower-Yarder Medium 36, ,860/(2Ly+243) Yarder 5, Ly Ly : Logging Distance (m), Lt : Transporting Distance (m) Part 1) Logging residues from First thinning, Part 2) Logging residues from Second thinning and Clear cutting, Part 3) Timbers Fuel unit expenses are assumed to be 80 yen/l. Oil expenses are assumed to be 20% of Fuel expenses

11 Table 3 Operation expenses Machine Operation Part Expenses(Yen/m 3 ) Felling and Chainsaw 1,212 Processing Forwarder Forwarding Ly +2,845+27,510e 0.117θ /V Ly +2,845+27,510e 0.117θ /V Ly +2,845+27,510e 0.117θ /V Grapple-Loader Piling Ton Truck Transporting Lt Lt Lt +778 Tractor Skidding 1.031Ly +1,669+27,510e 0.117θ /V Tower-Yarder(Small) Yarding Ly ,207,500/LyV Tower-Yarder(Medium) Yarding 8.369Ly +1,108+3,786,750/LyV Yarder Yarding Ly ,271,752/LyV +104,009/V Landing-establishment expenses ,211/VA Ly : Logging Distance (m), θ : Inclinations of Operation sites (degree), V : Harvest Volumes (m 3 /ha), A : Area (ha), Lt : Transportation Distance (m) Part 1) Logging residues from First thinning, Part 2) Logging residues from Second thinning and Clear cutting, Part 3) Timbers, Underlines indicate logging trail establishment expenses, and Yarding set up expenses, respectively. Table 4 Payloads (m 3 ) Part Extracting part Stems Stems and Branches Stems Logging Transportation Part 1) Logging residues from First thinning, Part 2) Logging residues from Second thinning and Clear cutting, Part 3) Timbers The following items on topography were processed on the GIS software. The average angle of inclination of each sub-compartment was estimated (Figure 7). Logging distances were 11

12 estimated as average distances from landings to all grids within sub-compartments (Figure 8). Landings were set within grids in such a manner as to minimize distances from roads, centers of gravity in sub-compartments, and log market. The log market managed by a Forestry Cooperative was selected in the analysis. As simply method, transportation distance was supposed to be calculated with a straight line distance from landing in each sub-compartment to chip factory or log market using detour ratio (Figure 9). Detour ratio is different from the physiographic division (Kobayashi 1997). The terrain of the study site is relatively steep. Therefore, detour ratio was set to 0.4. By applying the topographical data on each sub-compartment to the equations listed in Table 3, procurement costs from all sub-compartments in the region can be estimated. Figure 7 inclination (degrees) Figure 8 logging distance (m) 12

13 Chip Production Factory Log Market Figure 9 Transporting distance (km) to chip factory (left) and to log market (right) Volumes The volume for each sub-compartment was estimated using yield tables (Table 5, Forestry examination plantation of The Forestry Agency, 1955 and 1962) with stand species, ages, and site indexes in the present forest registration (Figure 10). We set out to study only Japanese cedar and Hinoki cypress, which are major species in Japanese plantation forests. 13

14 Table 5 Yield Table Volume (m 3 /Ha) Age Cedar Hinoki Cedar Hinoki Cedar Hinoki Site Index 1 Site Index 2 Site Index

15 Chip Production Factory Log Market Figure 10 harvesting logging residues (left) and timber (right) potential on each sub-compartment (m 3 ) Energy balance Only operation energy was considered as the energy input into the system in this study although the energy input into the system should consist of the equipment and operation energies over the entire life cycle of the plant (Yoshioka et al 2005). Operation energy was defined as the energy necessary for operating a system and is composed of the fuel consumption of forestry machines. The quantity of required fuel is calculated from the fuel consumption of each machine, the productivity of each machine, and harvesting volumes of logging residues (Table 2). The 15

16 gasoline is used for fuel of chainsaw and light oil is used for fuel of other machines. Energy densities of gasoline and light oil are 34.6 MJ/L and 38.2 MJ/L, respectively (Ministry of the Environment 2005). In addition, the CO 2 emissions from all the processes of the system were examined. The CO 2 emissions are estimated from energy input into each process and the CO 2 emission per unit energy of each energy resource. The CO 2 emissions from gasoline and light oil per unit energy are kgco 2 /GJ and kgco 2 /GJ, respectively (Ministry of the Environment 2005). RESULTS Economic balance The minimum and average costs of Cut-To-Length system with forwarders were 4,424 yen/m 3 and 8,206 yen/m 3, respectively (Figure 11). Only 0.08% of subcompartments around the chip factory were extracted as those costs below 4,500 yen/m 3 which was the target price of the chip factory (Figure 12). 16

17 12,000 10,000 First thinning Expenses(Yen/m 3 ) 8,000 6,000 4,000 2, Cumulative Harvest Volimes(thousand m 3 ) Second thinning Clear cutting Average Average-Logging expenses Average-Transportation expenses Average-Landing establishment expenses Figure 11 Direct costs of extracting logging residues Chip Production Factory Figure 12 Extracted sub-compartments (Red) and the closeup around the factory 17

18 Energy balance Energy input increases as harvesting volumes of logging residues increases (Figure 13). However, the maximum energy input, 0.08 GJ/m 3 was still lower than potential energy of wood, 4.06 GJ/m 3. Same with energy input, CO 2 emission increases as harvesting volumes of logging residues increases (Figure 14). However, the maximum CO 2 emission, 6 kgco 2 /m 3 was still lower than sequestered CO 2 in wood, 576 kgco 2 /m 3. Therefore, this system would be energy-effective Energy input (G J/m 3 ) Felling and Processing by C hainsaw Forw arding by Forwarder Piling by G rapple-loader Transporting by 8-ton Truck Total Cumulative H arvesting Volum es of Logging residues (thousand m 3 ) Figure 13 Energy input 18

19 6 CO2 em issions (kgc O 2/m 3 ) Felling and Processing by C hainsaw Forwarding by Forwarder Piling by G rapple-loader T ransporting by 8-ton Truck Total Cumulative H arvesting Volum es of Logging residues (thousand m 3 ) Figure 14 CO 2 emissions DISCUSSIONS In order to reduce costs, subsidy and whole tree logging system were considered. Subsidies were assumed 201,872 yen/ha for 25 year-old forests and 198,912 yen/ha for year-old forests at the first thinning. In addition, logging trail establishment expenses were assumed to be covered by subsidies at the second thinning and the clear cut. As a result, the average costs with subsidies were reduced to 5,719yen/m 3, and 41% of subcompartments were extracted (Figure 15). As for the whole tree logging system, tractors (skidders), tower yarders (mobile yarders), and yarders were assumed to be used for the skidding/yarding process (Figure 16-18). Since the system boundary of logging residues starts with piling by grapple-loader (Figure 16), the 19

20 minimum and average costs of whole tree logging system were significantly reduced to 1,182yen/m 3 and 5,911yen/m 3, respectively (Figure 19). Moreover, costs considering timbers extraction were also reduced. Therefore, the whole tree logging system could be more advantageous for extracting logging residues than the Cut-To-Length system. Chip Production Factory Figure 15 Extracted subcompartments (Red) with Subsidies Felling by Chainsaw The whole tree logging Processing by Chainsaw Piling by Grapple-Loader Transporting by 8-ton Truck Figure 16 Harvesting system (Whole tree logging system) 20

21 Figure 17 Logging machine selection Figure 18 Selected machines 21

22 18,000 16,000 14,000 Expenses(Yen/m 3 ) 12,000 10,000 8,000 6,000 4,000 2, Cumulative Harvest Volumes(thousand m 3 ) Logging residues and Timbers from Cut- To-Length system Logging residues and Timbers from Whole tree logging system Logging residues from Cut-To-Length system Logging residues from Whole tree logging system Figure 19 Direct costs of extracting logging residues and timbers REFERENCES KOBAYASHI, H., (1997): Forest Infrastructure Plan Theory. Nihon Ringyo Kyokai, Tokyo, 205pp (in Japanese) Japan Forestry Agency (2009) Annual Report on Trends on Forest and Forestry. Ministry of the Environment (2005) Guideline for the method to calculate GHG emissions from organizations. 83pp, Ministry of the Environment, Tokyo. YOSHIOKA, T., ARUGA, K., NITAMI, T., KOBAYASHI, H. and SAKAI, H. (2005) Energy and carbon dioxide (CO 2 ) balance of logging residues as alternative energy resources: System analysis based on the method of a life cycle inventory (LCI) analysis. Journal of Forest Research 10: 125~

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