[en] Most stands in Denmark are planted, but a tendency to use natural regeneration during reforestation can be noted. This means, however, that cleaning is not usually a problem. A first thinning is carried out in two steps with initial row thinning followed by a selective thinning. Pulpwood prices are so low that chipping the wood for energy is the only economical alternative, where a positive net return per hectare can be achieved. Research questions are no longer focused on improving productivity of the chipping operation, but should now be focused on the consequences of harvesting fuel chips. These consequences are: soil fertility, humus layer and ground pressure problems. Also the problems connected to returning of wood ash to the forest should be investigated 4 refs

[en] There are currently no precommercial thinning operations on harvesting of wood fuels in New Zealand. Precommercial thinning of New Zealand's planted production forests for wood fuel could, however, provide over 7 % (about 400 PJ) of New Zealand's energy needs between the years 2000 and 2010. The dispersed nature of the resource, the likely environmental impacts (nutrient removal and soil damage), availability of substantial quantities of lower cost residue from cleafell harvesting operations and the competition for the resource from conventional fiber users may result in the potential not being quickly realized 13 refs

[en] Precommercial thinning and plantation cleaning offer opportunities for increasing the availability of wood fuel in Canada. In 1992, approximately 130 000 ha were treated with precommercial thinning or stand cleaning. Manual methods predominate in these silvicultural activities; however, at stand densities greater than 10 000 - 15 000 stems/ha, mechanized systems are more economical. Recovering this biomass for wood fuel would require changes to silvicultural systems and harvesting technology

[en] Cleaning is carried out in order to influence the competitive situation of controlling the distribution of volume growth and the quality of timber. today, cleaning is conducted on about 200 000 ha per year in Sweden, most if which is cleaned motor-manually. The degree of mechanization is less than 1 % of. The biomass content of a cleaned stand is generally low, ranging from 1 to 2 tons dry matter per ha, but in some stands it can amount to over 20 tons per ha. The main motivation for removing biomass from a cleaned stand is the possibility of reducing overall cleaning costs. Few studies have been made on the environmental effects of the biomass removal in connection with cleaning. Studies made in connection with thinning, primarily conifers, indicate that the negative effects, such as increased soil acidification, reduced pools of base cations and nitrogen losses, can occur. It should be possible to compensate these undesirable effects through measures such as fertilization or ash recycling. Estimates of impacts on the flora and fauna suggests that effects are small and reversible. However, certain biotopes require special attention. Cost and performance studies indicate that it can be profitable for individual landowners to remove biofuel from very tall, dense stands, whereas better technology is required for more commercial operations. The development of such techniques is under way today. For large-scale removal of biofuel in connection with cleaning, simple forecasting tools will have to be developed that can help in determining when and where biomass should be removed. The decision should be based on economic, ecological and technical considerations. Furthermore, thorough analyses of the effects on the nutrient balance need to be made, and any reductions in the quality and growth of timber need to be quantified 21 refs

[en] This paper summaries the results of an international of wood fuel from early thinning and plantation cleaning. The economic and biological benefits from early thinning have been well documented. However, removing forest biomass during early stages of stand development from sites which are low in one or more nutrients may contribute a loss of nutrients and organic matter. Depending on the pre-thinning density and the thinning intensity, the potential yield of wood fuel from early thinning may be as much as 79 dry tons per hectare. Thus, wood fuel from the thinnings could be an important source of revenue to forest owners and would contribute to domestic energy requirements. Motor-manual felling predominates in early thinning, mainly due to the lack of appropriate technology for thinning small trees. However, the productivity of motor-manual felling is greatly affected by the initial stand density and declines dramatically at densities greater than 10 000 stems per ha. Under these conditions, purpose-built wood fuel harvesters with small-tree harvesting capability offer the greatest potential for increasing felling productivity and reducing the cost of wood fuel. The cost of wood fuel from early thinnings varies widely between countries from USD 25.00 - 87.50 per dry ton depending on stand conditions, harvesting system, transport distance, domestic tax rates, and stumpage prices. At the low end of this range, wood fuel chips from early thinning are competitive with wood fuel produced from mill waste, the residues from clearfell operations, or from later thinnings

[en] Discussions regarding the use of wood fuels for commercial energy production in the Netherlands began in the 1990's. The main reasons for using wood fuel are: the political demand for using renewable energy, the need to reduce CO₂ emissions, and the lack of markets for surplus timber. Only 10 % of the area of Holland is forested. Therefore, early thinning and cleaning are important management tools for improving growth and producing better quality timber. The energy potential from early thinning and plantation cleaning could be between 400 000 and 570 000 dry tons annually. The Netherlands has not experience in harvesting energy wood. However, through the International Energy Agency/Bioenergy Agreement, knowledge gained in other countries, especially Denmark, Sweden and Finland, is being transferred to Holland. In 1996, there have been made field tests with Danish equipment. Although there are few technical barriers to wood fuel in the Netherlands, the economics of wood fuels consumption are affected by the low costs of fossil fuels and the high natural gas reserves. This is changing however, due to political concerns over the balance of greenhouse gases. In 1996, a small energy tax on fossil fuels was introduced and electricity suppliers are now selling an environmentally friendly 'green electricity'. Energy wood has a future in the Netherlands, although the total forest reserves would satisfy only a small percentage of energy requirements 5 refs

[en] The paper deals with the biomass potential, silvicultural considerations, cost of recovery and environmental aspects in conjunction with the energy use of small trees from plantation cleanings and early thinnings in Finland. Repeated thinnings from below are an essential characteristic of the Finnish forest management system. Due to high operational costs, plantation cleanings and first commercial thinnings are currently a critical link in the management chain. These young forests possess a high potential as a source of renewable energy, 4 to 6 million m³ or 8 to 12 TWh per year. Utilization of small-tree biomass for energy is constrained by the high costs compared to peat, coal, oil or even wood chips produced from residues such as bark, sawdust or logging slash from clearcuts 3 refs

[en] Activities 1.2 (Forest management) and 1.2 (Harvesting) of Task XII/IEA Bioenergy Agreement carried out an international review of wood fuel from plantation cleaning and early thinning. The participating countries were Canada, Denmark, Finland, the Netherlands, New Zealand, Sweden and the United Kingdom. The individual country reviews and an international summary are presented in this paper. Each report gives country-related background information on forestry and wood utilization, energy potential from plantation cleaning and early thinning, environmental considerations from the viewpoint of wood fuel recovery, silvicultural systems and methods, cost of wood fuel, and knowledge gaps and problems

[en] There is little wood fuels harvested on a commercial scale in Great Britain presently. This is likely to change in the future as a result of Government legislation. The results of Aberdeen University harvesting trials into wood fuels from early thinnings found that terrain-based whole-tree comminution gave the lowest harvesting costs, with landing-based whole-tree comminution being the next most cost effective method. Integrated harvesting systems are generally the highest cost system for harvesting wood fuel in early thinnings. Once a stable market requiring a constant supply for wood fuel has been established within Great Britain, it is likely that the wood fuel will be sourced from clearfell operations rather than from thinning operations due to lower harvesting costs and the subsequent reduction in future restocking costs