Short rotation forestry
A short rotation plantation ( KUP, fast-growing plantation ) is to produce a planting of fast-growing trees or shrubs with the goal within a short rotations wood as a renewable raw material. If this is done solely for energy production, is also spoken by energy forest.
- 5.1 Germany
- 5.2 Austria
Tree species
In a short rotation plantation are fast-growing and decisive viable tree species, especially poplars ( Populus species ) and willows ( genus Salix ) are used. The research and breeding, focusing on tree species that are suitable for temperate climate.
Under the Poplars especially the balsam poplars as the Western balsam poplar and Populus maximowiczii and their hybrids and hybrids between balsam and black poplars are suitable. These are distinguished from pure black poplars and other tree species by the fact that they grow very quickly, do not need too much light and form a dense root system. More destinations in combination cultivars of poplar are the increase in biomass production, improve pest resistance, acceptance of higher planting density, high floor rash and rapid growth during the first years of development in order to shorten the harvest intervals. The fuel quality of wood is influenced by breeding, by forms with high efficiency of nutrient use and high, but nutrient-poor equity share will be selected.
Among the willows especially the basket Willow, the Kubler- or kitten - willow ( Salix × smithiana ) and the Filzast pasture are important. The cuttings of these species grow in safe and tend to mehrtriebigem ejection or to bush encroachment. Tree species, their suitability is discussed for short-rotation plantations, but is still poorly understood, the locust, the black alder and silver birch.
History and economic situation
A historical precursor has the short rotation plantation in low forest where trees on a regular basis, inter alia, for the production of firewood were placed on the floor.
The cultivation of fast-growing tree species for the material use for the production of wood-based materials has been successfully practiced in some European countries for many years. In Germany timber fields, however, are gone beyond the experimental stage of cultivation, although as early as 1974 in Hesse, the first research center was founded for fast-growing tree species since the 1970s. This is due in part to a previously limited availability of market for the final product wood chips. On the other hand, was for years the most economical fuel oil fuel for heat supply. In the wake of rising prices of fossil fuels, however, this situation is changing. Today, short rotation plantations are mainly grown for energy use.
Since about 1990, for example, willow clones are grown in large plantations. In Sweden, there are many years of experience with the cultivation of willow in the short term. 16,000 hectares were cultivated as early as 1999 there were in the marketing year 2005/2006 there about 15,000 acres timber fields in management. The yield could be increased massively in the newer varieties as compared to the first timber fields and is currently at an annual rate 8-12 tonnes of dry matter (absolutely dry) per hectare. In Germany, the area of short rotation plantations in 1996 was still only 80 hectares. However, plantations were increasingly applied to fields, ruderal or even on brownfield sites, particularly in recent years.
Wooden boxes are a very labor- extensive farming methods in the field of agricultural production. The majority of the work can perform their own machines, agriculture or forestry. Only for the planting and harvesting special machines are required, which are usually provided by service providers.
Use
In the short-rotation plantation tree saplings are planted in rows and, depending on the type and climate, harvested every 3 to 10 years by machine. The remaining plant residues in the soil have the ability to coppice, and takes place after harvesting a renewed sprouting of trees without having to be replanted. Under good conditions, short rotation plantations can average about 10 tons of dry matter per year and hectare produce, in very good conditions also doubled. After about 20 years the production of the plants waning, and the area should be created with further use.
Cultivation
With the investment of short-rotation plantations prior tillage is the rule. A result, the accompanying growth is displaced and loosened the soil for tree growth. This will improve the competitive situation of the power plants in the fouling phase and alleviates problems with mice or frost. Also the introduction of the cuttings is facilitated by loosening the soil.
In general, wood fields are applied in early spring ( March to early April). When planting material are often 2.50 meters long rods that are cut for planting in about 20 centimeter long cuttings. The cultivation of short rotation plantations from seed is not performed, as the seeds of poplars and willows can not be stored, and often after only a few weeks are no longer viable. A much more expensive alternative to the cuttings, which are obtained by high-yielding mother plants, is the use of tissue culture propagation. This is not profitable currently and is accordingly used only in research. The wooden boxes are created using a planting machine. The plant spacing depends on the species, the planned product (energy or industrial wood) and the track widths of the machinery to be used. A now- common plant spacing for the production of willow wood energy is the system of double rows with 70 to 75 cm distance, which can be detected by the harvester in a single pass. Clearance for the wheels of the harvesting machine must be sufficient to be present between the double rows. This is about 2 m. The distance between the plants in the row is typically 60-65 inches. Plant according to densities of 5,000 to 10,000 plants per hectare, can be realized.
Plant protection
In short rotation plantations occur on the same problems as in forest plantations. In addition to general hazards play primarily on individual species specialized pests a certain role.
The problem in the cultivation of short rotation plantations is the low genetic variability of plants, resulting from the vegetative propagation of cuttings, as well as the crowding of the plants. This makes the total stocks susceptible to pests, which so far only led the attack by rust fungi of the genus Melampsora and by poplar leaf beetle ( Chrysomela populi ) to stronger earnings.
In addition to mechanical plant protection methods such as fencing around the cuttings against deer browsing herbicides are used in the cultivation of grain. For pesticide applications on non-indexed cultures is needed in Germany according to § 18 b Plant Protection Act, a certificate of exemption by the competent authorities. This is issued without any problems usually because wood chips do not enter the food chain.
Under certain conditions, it is necessary to dispense with the use of herbicides in whole or in part. For example, in water protection zones or in organic farming the case. For some alternative measures offer: Through early and multiple mechanical maintenance and use of mulch films of the manager can prevent excessive accompanying vegetation. Mulch films reduce the maintenance measures and offer the tree protection and significant growth advantages. Pastures as a quick starter are particularly suitable because they get along unlike poplars rather without care measures. Against Mice damage help mulching between the rows and raptor perches on the surface.
Harvest
Short-rotation plantations are perennial crops that can be used up to 20 years with an average of 3 to 6 crop rotations usually. The harvest takes place over several years Umtrieb, the stock has reached a height of 6-8 meters at harvest time. Yields of balsam poplars are doing 10 to 15 tonnes per hectare per year, at Willows at 5 to 10 tonnes per hectare per year. The harvest time is optimal in the winter after leaf drop, as this is a large part of the nutrients may remain in the fields. As harvesters high-powered, self-propelled forage harvester with low wood collection are in short rotation usually used, besides also Anbaumähhacker. Holzvollernter ( Harvester ) and coordinators from the forest technology can also be used in higher-yielding crops, and with longer rotation periods. It is important not to over compact the soil so the trees can stand in a well-aerated soil.
Fresh wood chips generally have a water content of 50 to 60% and must be pre-dried for use. This occurs during storage of the chips in the open or in compressed bales. For burning they should have a maximum water content of 30%. Important is a coarse chopping of wood, since fine wood chips are bad for storage. The chips can be stored as rent or burned as needed, gassed or processed into pellets. The willow- after harvest again. Depending on the soil can be useful after harvest fertilization of 50 to 70 kg N / ha.
Economy
Compared to established annual field crops KUP require relatively high investment in inventory reasons and a relatively long production period and produce irregular cash flows. Finally, the costs of reconversion of the area must be calculated for agricultural use (removal of rhizomes ) at the end of its useful life. KUP therefore present greater business risk than for annual crops; a cultivation appears economically viable only at fixed purchase contracts with binding prices.
To compare the efficiency of SRC with the annual crops is recommended to refer to the dynamic investment calculation instead of contribution margin; as the irregular cash flows can be converted into a constant annual annuity. The calculated annuity can be directly compared with the contribution of annual plants. According to various studies, the annuity of poplars and willows can lie around € 250 to 500 per hectare per year under favorable conditions, can in many cases also be negative. The higher the number of rotations is, with a rotation period of three to four years, the more positive annuities can be achieved.
Scientists at the University of Halle noted that not all short-rotation plantations are economically viable. They assume that short-rotation plantations could be operated profitably indeed, but compared to imported food crops einbrächten lower profits and therefore were not competitive. An alternative they only represented for remote small and splinter surfaces, since they rarely need to be approached.
The total cost for the establishment of a short rotation plantation are about 3,000 to 4,000 euros per hectare. The first harvest of poplar and willow plantations will usually produce slightly lower income than it does in the following years, because the roots are not yet completed and the coppice is still missing.
For the cultivation of SRC for use as a renewable resource on non- set-aside land for energy crops premium could be claimed under certain conditions until 2009.
In the heat market wood chip furnaces are economically because of the sharp rise in prices for fossil fuels at higher investment costs for the incineration and feed technology. The average energy content is 15.5 to 18.5 MJ / kg at harvest and crushing about 0.06 MJ / kg are consumed, so that the energy balance is very good. It should be noted, however, that fast growing plants have a lower specific energy content, so that the volume to be processed the raw materials rises sharply. For example, an area meter firewood of oak about 1890 kWh, fast-growing poplar only 1110 kWh. This is not clear in the calorific value, since it refers to the mass and not volume.
Terms of Use
Germany
Since the amendments to the Federal Law on Forests ( BWaldG ) 2010 is clearly established that short-rotation plantations do not belong to the forest. Previously, it was disputed whether the investment of short-rotation plantations subject to forest law or not.
Short-rotation plantations are classified as agricultural perennial crops, where the rotation period is not longer than 20 years. The areas eligible for aid under EC Regulation 1120/2009.
Prior to the amendment of the BWaldG short rotation plantations were in Germany under the "Law on Equality of disused and agricultural land " is created. This allows explicitly to designate areas for the cultivation of short rotation forests in the context of set-aside. This can occur, for public support, if these areas meet the requirements for the set-aside. In addition, " remains the right to use such areas after completion of the decommissioning period in the same manner and to the same extent as at the time before the closure, untouched ", but only for 20 years.
The EC Regulation 1120/2009 carries the nation states to establish a priority list of allowed woody species. In Germany, willow, poplar, locust, birch, alder, and the common ash stem, grape and red oak were admitted.
Austria
In Austria, conversions and new plantings should be approved by the respective district headquarters. The decision follows the management policy in the cultural area protection law. Moreover, the European Regulation 1586/97, the Austrian Forest Act, the Fertilizers Act and the Water Act must be observed. In principle, the cultivation of short rotation plantations on both arable and on set-aside land is possible; must be considered a minimum distance to other cultures between three and ten meters to prevent damage to neighboring fields by root penetration and shading.
Short-rotation plantations devastated and urban areas
The global food price increases in 2007 and 2008 has led to a discussion of whether and to what extent the production of renewable resources for energy production this increase has abetted. For this reason, pilot projects were started to plant short-rotation plantations on land that is not in competition with food production. These experiments in devastated areas vormaliger opencast mines and urban areas are emphasized. The latter were 2007/2008 started from the town hall on economic land that was formerly cultivated with residential buildings which have been demolished as part of the so-called " urban renewal East" in Halle ( Saale).
Impact on biodiversity
In the evaluation of the influence of short-rotation plantations on biodiversity is critical, it is assumed from which the reference system. Most studies come to the conclusion that the short-rotation to intense agricultural use positive effect on the (vegetable ) Biodiversity works, but compared to semi-natural forest is an impoverishment. NABU finds that the investment of SRF contributes in farming regions to structure the landscape and the creation of habitats and stepping stones for species of plants. Yet still lacked reliable studies for a comparison against the use of grassland. For biodiversity in terms of species KUP had, however, no great importance, since endangered species in intensively farmed regions are little to non-existent. However KUP would bring animal ecological advantages because animals to annual field crops benefited from a longer ground rest, lower fertilizer and pesticide use and less overall interference.