CO 2 -eq emissions and energy efficiency in forest biomass supply chains impact of terminals

Transcription

1 CO 2 -eq emissions and energy efficiency in forest biomass supply chains impact of terminals Heikki Ovaskainen

2 The aim of the study The aim of this study was to compare CO 2 -eq emissions and energy efficiency of work machines and transport vehicles in forest biomass supply chains. The study was part of the BEST research project, in which one of the key development targets was biomass terminals. Using biomass terminals in biomass supply chains is a typical and growing activity today. Consequently, in addition to direct supply chains, the transport of biomass through biomass terminals was central part of the supply chain comparisons. In this study, forest biomasses are meant to mean small-sized whole trees, stumps, logging residues and large-sized decayed wood. Due to the high level of insect replications of recent years, the supply chain examination of large-sized decayed wood was included in addition to traditional biomasses. 2

3 Proportions of forest biomass use in Finland in 2016 Logging residues 2.5 Mm 3 (34%) Small-sized trees 3.9 Mm 3 (52%) Stumps 0.8 Mm 3 (10%) Large-sized decayed wood 0.3 Mm 3 (4%) Source: Luonnonvarakeskus

4 Shares of comminution places of different biomasses in forest biomass supply chains in 2016 Source: Strandström 2017 Logging residues Small-sized whole trees 8 % 10 % 13 % 47 % 82 % 40 % Roadside chipping Terminal chipping Plant crushing Stumps Roadside chipping Terminal chipping Plant crushing Large-sized decayed wood 34 % 23 % 6 % 25 % 43 % 69 % Road side crushing Terminal crushing Plant crushing Roadside chipping Terminal chipping Plant crushing 4

5 Calculation assumptions To improve the comparability of supply chains, the study focused solely on truck transport based supply chains. The cubic meters presented in the calculation are solid cubic meters and the time consumption of work machines was gross effective time i.e. working hours include breaks up to 15 minutes. CO 2 -eq emissions and energy efficiency of the work phases have been calculated on the basis of the amount of fuel consumed, and therefore the quantities are directly proportional to each other. One diesel liter produces CO 2 -eq emissions g. CO 2 -eq differs from pure CO 2 in a way that it contains all emission compounds classified as greenhouse gases, which are generated by the use of diesel fuel. When considering the energy content of different biomasses, the values in Table 1 have been used. Table 1. Biomass properties in typical delivery moistures. Effective calorific value Typical delivery MWh/m 3 in dry matter, MJ/kg moistures, % Small-sized whole trees Stumps Logging residues Large-sized decayed wood

6 Calculation assumptions: cutting and stump lifting In the calculations, a small-sized whole trees were harvested by a single-grip harvester with a productivity of 5.4 m 3 /h. Stumps were lifted by an excavator with a productivity of 6.2 m 3 /h. Logging residues were piled on the stand at the same with the roundwood cutting. The productivity of logging residue piling was set to 5.6 m 3 /h. Large-sized decayed wood (ie. insect trees) was cut with a harvester and its productivity was set to 16 m 3 /h. 6

7 Calculation assumptions: forwarding All biomasses were transported by a forwarder from stand to the roadside. The productivities of forwarding used in the study were: 6.8 m 3 /h with small-sized whole trees 6.8 m 3 /h with stumps 9.1 m 3 /h with logging residues 12.0 m 3 /h with large-sized decayed wood 7

8 Calculation assumptions: long-distance transport and terminal operations in the supply chains Long-distance transport of biomasses took place in three different supply chain options, depending on the chipping location: Chipping on the roadside + transport of chip by chip truck from road side to the plant (= 60 km by empty truck + 60 km by loaded truck) Transport in uncomminuted form to the terminal by biomass truck + chipping at the terminal and transport of chips by chip truck to the plant (= biomass truck empty 60 km + biomass truck loaded 50 km + chip truck 10 km) Transport in uncomminuted form from roadside to the plant (= biomass truck empty 60 km + biomass truck loaded 60 km) + plant crushing In the calculation the load space of chip and biomass trucks was set to 150 m 3. The empty weights and payload weights of the vehicles used in the calculation are shown in Table 2. Table 2. Weights and payload weights of the trucks. Biomass truck Chip truck Roundwood truck Empty truck, t Loaded truck, t Empty truck, t Loaded truck, t Empty truck, t Loaded truck, t Small-sized whole trees Stumps Logging residues Large-sized decayed wood

9 Calculation assumptions: chipping and crushing Chipping and crushing takes place either at the roadside, at the terminal or at the plant. All biomasses were mainly chipped, except stumps were crushed. At the plant it was always used crush to comminute materials. Productivities of comminution methods of different materials are presented in Table 3. The emissions of transportation of chipper or crusher to forest road side were added to roadside chipping or crushing chain emissions. Table 3. Productivities of chipping and crushing m 3 /h. Small-sized whole trees Productivity Logging residues Productivity Stumps Large-sized decayed wood Crushing at the road side Crushing at the terminal

10 Results: cutting and stump lifting In cutting and stump lifting, the emissions of different biomasses varied significantly (Figure 1). Logging residues can be collected without any additional work at the same with the roundwood cutting, whereas in the stump lifting considerable amount of energy is needed to lift the stumps off the ground. 9,00 8,00 7,00 8,06 kg CO 2 -eq/m 3 6,00 5,00 5,17 4,00 3,00 2,00 1,00 1,19 1,76 0,00 Small-sized whole trees Stumps Logging residues Large-sized decayed wood Figure 1. Emissions of cutting and stump lifting. 10

11 Results: forwarding In forwarding, the density of forwarder's load and hence the size of the load influenced fuel consumption per cubic meter (Figure 2). With large-sized decayed wood, the emissions were about half of the corresponding emission value of the stumps. 9,00 8,00 7,00 6,00 kg CO 2 -eq/m 3 5,00 4,00 3,91 4,50 3,36 3,00 2,00 2,22 1,00 0,00 Small-sized whole trees Stumps Logging residues Large-sized decayed wood Figure 2. Emissions of forwarding work. 11

12 Results: chipping and crushing Chipping and crushing may occur either at the roadside, at the terminal or at the plant (Figure 3). Chipping of logging residues caused the most emissions. It is explained by the low density of the material. With other materials, the emission levels were set to same. Small-sized whole trees Stumps Crushing at the road side Crushing at the terminal Logging residues Large-sized decayed wood kg CO 2 -eq/k-m 3 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 Figure 3. Emissions of chipping and crushing. 3,55 3,46 3,46 3,55 3,46 3,46 3,55 3,46 3,46 3,94 3,84 3,84 Metsätehon tuloskalvosarja 4a/

13 Results: moving of chipper and crusher Transferring crusher or chipper for grinding operations to forest to the roadside also causes emissions to the supply chains (Figure 4). If the material was processed at the terminal or at the factory, the emissions from the moving of the equipment were not taken into account. 0,60 0,50 kg CO 2 -eq/m 3 0,53 0,40 0,30 0,32 0,25 0,40 0,20 0,10 0,00 Small-sized whole trees Stumps Logging residues Large-sized decayed wood Figure 4. Emissions of moving of chipper and crusher. Metsätehon tuloskalvosarja 4a/

14 Results: long-distance transport The emissions of long-distance transport were significantly affected by the loose or chipped form of the material (Figure 5). In terminal chipping and plant crushing chains, the biomass is transported significantly in loose form. Handling of material at the terminal increases emissions in the supply chain through the emissions of the bucket loader. The transport chain was efficient from the terminal to the plant, because chips yielded a relatively high payload in the chip truck. Small-sized whole trees Stumps Crushing at the road side Crushing at the terminal Logging residues Large-sized decayed wood kg CO 2 -eq/m ,37 3,37 3,37 3,37 3,31 3,86 Figure 5. Emissions of long-distance transport. 7,08 7,00 7,13 7,07 7,08 7,00 14

15 Results: total emissions in the supply chains kg CO 2 /k-m 3 When looking at the total emissions of the supply chains, the lowest emissions were with a large-sized decayed wood (Figure 6). It is possible to achieve a high payload on the forwarder as well as on the timber truck with that biomass. Small-sized whole trees Stumps Crushing at the road side Crushing at the terminal Logging residues Large-sized decayed wood ,32 19,62 19,54 19,73 23,14 23,08 12,26 15,47 15,39 11,42 11,29 10,74 Figure 6. Total emissions in the supply chains. 15

16 Emissions in relation to the amount of energy obtained from biomass kg CO 2 -eg kg/mwh Differences in biomass were equalized when the emissions were compared to the typical amounts of energy from biomass units (Figure 7). Small-sized whole trees Stumps Crushing at the road side 7,32 8,80 8,76 8,62 At the plant, the quality of stump biomass is generally dryer than other materials, which reduces its emissions compared to other biomasses. Crushing at the terminal Logging residues 5,60 7,07 7,03 10,11 10,08 Large-sized decayed wood 4,99 4,93 4,69 Figure 7. Emissions in relation to the amount of energy obtained from biomass. 16

17 Energy efficiency of the supply chains Input MWh/Output MWh Energy efficiency describes how much one (fossil) input energy unit produces bioenergy output energy units. One input MWh gives 26.2 to 56.4 output MWh depending on the biomass and supply chain. The amount of input varies between 1.8% to 3.8% of output in percentage. Small-sized whole trees Stumps Crushing at the road side Crushing at the terminal Logging residues Large-sized decayed wood ,17 30,10 30,22 30,73 26,20 26,27 47,29 37,47 37,67 53,08 53,71 56,43 Figure 8. Energy efficiency of the supply chains. 17

18 Discussion This study took account harvesting, chipping/crushing and long-distance transport of various biomasses, as well as possible unloading and loading at the terminal as well as chipper/crusher transfers in roadside comminution. In addition to direct supply chains, alternative supply chains using biomass terminals or plant crushing were examined. The essential distance variables were set to constant to improve the comparability of the supply chains. The basis for calculation was partly obtained from a study of Kariniemi et al. (2009). The average productivity figures and fuel consumptions were updated to correspond present level. This study did not take into account the emissions of the entire purchasing activities, for example the emissions caused by the moving of managerial operator persons. The energy efficiency calculations did not either take into account the operating efficiency of engines or combustion techniques. 18

19 Conclusions Terminals or comminution at the plant did not prove to be effective methods compared to direct supply chains from the point of view of emissions and energy efficiency. However, there are many streamlining and rationalizing benefits achievable in terminal-based supply chains (Virkkunen et al. 2015). Emission comparisons are in line with the results of Kariniemi et al. (2009). However, Kariniemi did not study large-sized decayed wood, which is a material close to round wood and thus it is very energy-efficient material compared to other forest biomasses. The calculation of emissions of certain fixed supply chains is challenging and therefore such a review should be made with the delivery volumes and distributions of the whole supply area. Simulation of the procurement of wood in the procurement area with spatial data would also be a viable research method to study the topic more comprehensively. This would also allow the valuation of the other benefits of terminal operations. 19

20 Literature Alakangas, E., Hurskainen, M., Laatikainen-Luntama, J. & Korhonen, J Suomessa käytettävien polttoaineiden ominaisuuksia. VTT Technology Kariniemi, A., Kärhä, K., Heikka, T. & Niininen, M Feedstock Supply Chain CO2-eq Emissions A Case Study on Forest Biomass to Liquid Traffic Fuel. Metsätehon tuloskalvosarja 7/ p. Luonnonvarakeskus Suomen virallinen tilasto (SVT): Puun energiakäyttö. [Online page]. Helsinki. Strandström, M Metsähakkeen tuotantoketjut Suomessa vuonna Metsätehon tuloskalvosarja x/2017. (Will be published later and updated thereafter here, too.) Virkkunen, M., Kari, M., Hankalin, V. & Nummelin, J Solid biomass fuel terminal concepts and a cost analysis of a satellite terminal concept. VTT Technology 211. Espoo: VTT Technical research centre of Finland. 70 p. 20

21 BEST thanks This work was carried out in the Sustainable Bioenergy Solutions for Tomorrow (BEST) research program coordinated by CLIC Innovation with funding from the Finnish Funding Agency for Innovation, Tekes. 21

22 Update Slides 12 and 13 added. Slides 15 and 16 updated. Metsätehon tuloskalvosarja 4a/