The use of energy wood

Transcription

1 The use of energy wood The environmental and economical effects 1

2 Forest energy and the decision making environment Decision makers preferences forest owner Procurement companies Effects of forest energy utilisation Society: Goals, constraints and subsidies Alternatives Knowledge 2

3 Forest energy - decision criteria Recreation Silviculture Wood production Income & outcome Biodiversity Nutrients balance Wood ash recycling The utilisation of forest energy is a pure multicriteria decision making problem! 3

4 The effects of energy wood harvesting Silviculture Environment Economics The nutrient balance and growth influence 4

5 Silvicultural effects The use of forest energy has different silvicultural effects, which can have direct or indirect effects on forest owners economy by increasing or decreasing the forest productivity by influencing on costs of silvicultural actions by giving income from the sales The magnitude of different effects depends on many variables, such as labour costs and technology, and thus it is very difficult to estimate accurate values. However, it is possible to estimate if the effects are positive or negative. 5

6 Silvicultural effects Examples: 1. Forest regeneration % increased productivity of soil preparation (spot mounding with excavator) +0..5% increased productivity of manual planting work and % machine based planting work (Bräcke planting machine) Influences on forest regeneration are positive and savings in costs can be higher than the stumpage price paid for the energy wood 6

7 Silvicultural effects 2. Seedling/sapling cleaning The collection of logging residues will increase the amount of seedling via natural regeneration. This increases the need of seedling cleaning. On the other hand the need for replanting is smaller. The effect of energywood harvesting on seedling cleaning will cause some extra costs and thus the economical effect is negative. 7

8 Silvicultural effects Cost savings Forest regeneration Smaller risks for insect pests Quality of seedling Additional costs Seedling cleaning Growth losses Possible compensation fertilisation The positive effects are estimated to be higher than the negative effects from the economical point of view, even without the price of residues. 8

9 Silvicultural effects Net present value and cost influence of logging residue removal NPV (3%), /ha improved productivity of soil preparetion and planting improved spacing of seedlings faster regeneration increased removal of nutrients increased need for sapling clearing Total effect 9

10 Forest nutrient balance 10

11 Forest nutrient balance -The harvesting of energy wood will cause increased nutrient removals due extensive biomass removal -The loss of nutrients will have an effect on future growth of the forest -Especially harvesting of small-diameter wood in pre-commercial thinning is done in the phase where the need of nutrients is on the highest level within the forest stand -The most important nutrient for the forest growth on mineral soils is nitrogen, but also phosphorus, potassium, calcium and magnesium are important -The removal of nutrient-rich biomass compartments is not recommended on peat lands because there is usually lack of other nutrients than nitrogen as well. 11

12 Nutrient contents of biomass compartments 90- years old Norway spruce stand, total volume of stem wood 306 m 3 /ha kg/ha 250,0 200,0 150,0 100,0 N P K Ca Mg 50,0 0,0 Stem Living branches Dead Branches Needles Stump & roots 12

13 kg/ha 120 Energiapuun korjuun ravinnepoistumat - ensiharvennuskuusikko Typpi Fosfori Kalium Kalsium Magnesium runkopuu, kertymä 39 m3/ha kokopuu tuoreena, kertymä 70 m3/ha kokopuu kuivana, kertymä 59 m3/ha 13

14 kg/ha Energiapuun korjuun ravinnepoistumat - päätehakkuukuusikko Typpi Fosfori Kalium Kalsium Magnesium runkopuu, kertymä 278 m3/ha runkopuu + tuore hakkuutähde, kertymä m3/ha runkopuu + kuiva hakkuutähde, kertymä m3/ha kannot, kertymä 49 m3/ha 14

15 Forest nutrient balance -The nutrient removal with energy wood is highest on fertile forests, typically spruce stands, and thus the relative loss of increment is highest -On the other hand, fertile stands are more sustainable in the long term for extensive nutrient removal than the poor site types -The atmospheric nitrogen deposition compensates the removal of nitrogen. For instance, in Southern Finland the typical deposition is 3-5 kg/ha/year i.e kg during the 80 years rotation time, which compensates the nitrogen removal in the long run, and thus the most significant growth effects are only in the short term. -However, the removal of other nutrients have to be taken into consideration as well. 15

16 Forest nutrient balance The relative growth-level after whole-tree harvesting 1,05 1 0,95 Scots pine 0,9 0,85 0,8 0, years Norway spruce Nitrogen removal 70 kg/ha from spruce stand and 30 kg/ha from pine stand 16

17 Forest nutrient balance and productivity Example: combined energy wood and precommercial thinning VS. conventional precommercial thinning The combined energy and commercial wood harvesting will lead to increased nitrogen removal, approx. 300 kg/ha from Norway spruce stand and 100 kg/ha from the Scots pine stand during the rotation (pre-commercial thinning + logging residues from final felling) 17

18 Forest nutrient balance and productivity The increased loss of nutrients will cause approximately 4 % (14 m 3 /ha) loss of productivity in a spruce stand and 0,5 % (1,5 m 3 /ha) loss in a pine stand, when compared to the normal commercial thinning and final felling without utilisation of energy wood. However, the pre-commercial thinning is a very important silvicultural action. The neglected pre-commercial thinning can cause even 10 % loss of income. The sales of energy wood could pay the expensive pre-commercial thinning and the economical result can be positive Total production in different management options, m 3 /ha precommercial thinning precommercial thinning + energywood no precommercial thinning TOTAL PRODUCTION, m3/ha logwood pulpwood energywood 105 tot revenues from sales (thining and clear cut) logwood pulpwood energywood tot. Net present value (3%) of sales of log- and pulpwood ENERGYW OOD PROD., t/ha thinning 23 clear cut 82 tot. rotation

19 Forest nutrient balance and productivity The profitability of energy wood production from the forest productivity point of view: If the net present value of income from energy wood sales exceeds the net present value of lowered sales of timber/pulp/other wood assortments due the loss of productivity, the energy wood utilisation is economically profitable in the long run /ha Forest owners discounted revenues (3% interest) with different price of residues ( /MWh), including growth influence (see table 1.) 0 0,5 1 1,5 2 2,5 /MWh In the example: 0,8 /MWh should be paid to forest owner to cover loss of future increment (ca. 1,6 /m 3 1,1 /m 3 )

20 How to influence nutrient balance? There are different ways to decrease nutrient losses 1. Compensation of nutrients with nitrogen fertiliser or wood ash (P, K, Ca and Mg) 2. Leaving some part of the energy wood to the forest, e.g. stem tops. The recommendation is to leave 30% of the total biomass of the residues to the forest to avoid too high nutrient removals. 3. Seasoning of the whole-tree stems or logging residue piles will cause the needles/leaves to drop to the ground. The needles and leaves are very nutrient rich 20

21 Environmental effects - general The use of forest resources has always an effect on the forest ecosystem dynamics so does forest energy harvesting. The utilisation of energy wood is usually made together with other silvicultural actions or together with commercial thinnings or regeneration Therefore it is important to understand which of the effects are due the general use of the forests and which of them are caused especially due the energy wood harvesting, and if the energy wood harvesting will have an extra effect on environment. 21

22 Environmental effects - biodiversity The evaluation of effects on biodiversity can be done for instance by Angelstam s classification: Size Quality Quantity Area Distance between habitats and the quality of intermediate areas are estimated. 22

23 Environmental effects - biodiversity When energy wood harvesting is combined with commercial thinning or regeneration: - The quantity and size of forest ecosystem habitats remains the same - It does not cause additional fragmentation of forests - The distance between habitat-types and the quality of the intermediate areas remains the same 23

24 Environmental effects - biodiversity The quality of habitats are changed with the logging residue extraction since the quantity of decayed wood is reduced. However, the residues after regeneration are mostly small diameter branches and stem tops which significance for biodiversity is smaller than large diameter decayed wood which should be left to forest stand in any case. 24

25 Environmental effects - biodiversity The important keyhabitats which are representing important forest nature types have to be left outside of forest energy utilisation. The deciduous trees and tree groups should be left outside of energy wood harvesting. This benefits also game species. Large diameter decayed wood should be left in the forest. 25

26 Environmental effects water systems and protection -Silviculture and regeneration loggings will have effects on water systems, if their protection is not taken into consideration -After thinning the remaining growing stock can utilise the nutrients released from the residues and the risk of leaching into water bodies is not very high -The regeneration, and especially clear cuts, are more problematic for nutrient and soil particle leaching -The collection of residues can prevent the leaching to some extent. 26

27 Environmental effects water systems and protection The following matters has to be taken into consideration: Always leave a filter buffer close to a water system, where the soil surface is untouched (ditches 2-3 m, creeks and springs 3-5 m and larger water systems 7-10 m from the edge) Collect the residues very thorough from the water system buffer areas to avoid leaching Don t make storages on ditches, if there is another options. Be sure that ditches are functioning also after operations 27

28 Environmental effects insect pests Energy wood harvesting does not increase the risk of insect pests or forest diseases. However, information of the long term experiments are not yet available. The risks of insect pests can be decreased by timing of logging and by following the rules for storage and transportation of the raw material. 28

29 Environmental effects Forest health The logging residue removal or young forest thinnings does not affect significantly on forest health issues, if the rules of storaging are taken into consideration. However some benefits can be achieved with stum removal: Hylobius abietis pine weevil Stump harvesting can reduce damages to seedlings since they grow in fresh stumps Heterobasidion annosum root rot Stump harvesting prevents the spread of root rot 29

30 Environmental effects scenery and multiple use of forests -Loggins have a clear influence on scenery (Finns like large diameter trees and clean sites - Germans like natural forests ) -Loggings have two contradicting effects on the beauty of the forest positive (better visibility) negative (logging residues) -By removing the logging residues the site looks more clean and it makes the use for recreation easier, it decreases the signs of harvesting operations 30

31 Environmental effects scenery and multiple use of forests Thinnings will improve the forest scenery which is easily seen in overdense young forest which are in need of thinning Stump harvesting decreases lignonberry yields but however, the yield of raspberry increases 31

32 A decision support tool for forest energy utilisation 32

33 Scenarios Baseline Green Brown Highlander EnerTree structure Stand level calculations General information Decision criteria economical ecological User interface Recommendations 33

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