BOIS ENERGIE 2000
Wood –Energy Harvesting Techniques Ismo Nousiainen VTT Energy INTRODUCTION During last decade there is developed many new forest fuel production methods and equipment in Scandinavian. Many of these methods and equipment can be also applied in many other parts of Europe - not only in Scandinavian conditions. Presentation is diveded to six parts: • wood fuels in Finnish energy balance • production potential of forest fuels • wood fuel harvesting techniques • competitiveness of wood fuels • targets for the use of forest fuels • conclusions. VTT ENERGY VTT is an impartial and multidisciplinary expert organization. We promote technology dedicated to the improvement of a company’s competitiveness. Our man years are nowadays over 2 700, staff is over 2 900 and total turnover about 191 million Euros. Our work consist self-financed projects, jointly funded projects and commercial activities. About 30 % of our budget we get directly from the government. We have nine research units and one of these is VTT Energy. The Mission of VTT Energy is to carries out on high-level and impartial research and development work on energy production, transfer, distribution and use and also for process industry. Nowadays the research and development work on renewables energy sources and especially on wood fuels are very important part of our work. PRIMARY ENERGY SOURCES IN FINLAND Finnish energy demand is high because of a cold climate, long distances and energyintensive industry. Primary energy consumption in 1998 was totally 30.8 million tons of oil equivalent. At the same time, the indigenous energy sources, which include hydro and wind power, wood fuels and peat, are scarce and about 70 % of energy is imported. The use of wood derived fuels was 5.9 million tons of oil equivalent, which was 19 % of the total energy consumption and that’s ranks Finland at the top among the industrialized countries.
Until the end of 1990’s wood derived fuels were mainly by-products from our forest industry, like waste liquors from pulping industry and bark, sawdust and other wood wastes from sawmills and pulp and paper mills. The share of forest fuels - forest chips – was very low, in 1998 it was about 0.08 million tons of oil equivalent. The share of traditional firewood is naturally higher, about 1.1 million tons of oil equivalent. PRODUCTION POTENTIAL OF WOOD FUELS We have calculated that the total annual harvestable forest fuel potential varies between 21.8 – 31.6 TWh in the other words 1.9 - 2.8 million tons of oil equivalent. The main source for the forest fuel production is logging residues, top stem wood and branches, which we left in regeneration felling areas after harvesting of raw wood. This source is also the most attractive from the standpoint of harvesting techniques and harvesting costs. But why we then have not utilized these resources better for energy production. The main barrier has been too high production cost compared to the price of alternative fossil fuels. In the beginning of 1990’s the production costs of logging residue chips was about 62 FIM/MWh. At the same time the inland price of coal was 44 FIM/MWh. So, forest fuels was not competitive against fossil fuels. In this situation our answer was to develop production techniques of forest fuels so that we can lower the production costs to the competitive level. Of course we need also other promotion instruments, like taxes and investments subsidies to improve the competitiveness of forest fuels. PRODUCTION METHODS OF LOGGING RESIDUES In the beginning of 1990’s we started in Finland a large research and development work of forest fuel production methods and equipment. During this work we have get many different methods and equipment to commercial use. Commercial harvesting techniques are based on roadside chipping, on terrain chipping, on the use of so called multi-purpose chipper and combined chipper-lorry and on the chipping at the mill site. In addition we have also some new equipment in demonstration level. These methods are for the large scale-production of logging residue chips. In all these methods one important thing is integration the production of forest fuels to the harvesting of wood raw material. In this way we can get the best cost-effectiveness.
ROADSIDE CHIPPING METHOD In Scandinavian the harvesting of raw wood is based on short-wood method. In the traditional cutting method in final felling the harvester operator fells the trees on either one or both side of the strip road. After felling he moves trees in the front of machine and delimbes and bucks trees to timber assortments. As the harvester is moving to next working spot logging residues is trampled under the tires. Naturally this kind of traditional logging method mean that logging residue is difficult to harvest and the harmful soil material is easily collected with it. If we want to harvest logging residues after cutting of raw wood, we must modified cutting method. We have developed the cutting method where we pile logging residues on side of the harvester in conjuction of cutting. In this way we can increase the productivity of logging residue harvesting and improve the quality of chips. Adopting this new cutting method is easy for the harvester operator because the changes from tradional method are minor. Also the effects to the productivity of cutting are small. After the forest haulage of saw logs and pulpwood we use load carrying tractors equipped with special logging residue grapple and enlarged load space for the forest haulage of logging residues to the roadside. At the roadside we can supply logging residues and when we need them we chip them by truck mounted drum chipper straight to load space of trucks and transport chips to power or heating plant. This truck mounted chipper is build especially for the chipping of logging residues and its productivity varies between 40 to 80 loose-m3/effective hour. It means that annual capacity can be about 100 000 loose-m3. TERRAIN CHIPPING METHOD Terrain chipping of logging residues requires also the piling of logging residues. In this method a single unit performs the chipping at the stand and off-road transport of chips to a roadside when the chip container is full. The chip container is emptied by tipping it sideways. The company Logset have developed the new type of terrain chipper where the drum chipper is located in the front of machine. The company Bruks is the largest manufacturer of terrain chippers in Scandinavian. MULTI-PURPOSE CHIPPER One developed equipment is also so called multi-purpose chipper, which is a combined chipper and chip lorry. For operation, a forwarder is used to build a preminary pile of logging residue on the cutting area or at roadside. The off-road capable MOHA then chips the logging residues in a 35 m3 demountable container that it carries. The container
can be transported directly to the end use facility by same unit. This unit is especially competitiviness when the road transport distance to the plant is under 30 km. COMBINED CHIPPER-LORRY To this method we have also developed other type of combined chipper-lorry. This unit is not off-road capable, but this equipment make it possible to achieve the optimum flexibility in chipping at logging sites of different sizes. This combination is particularly suitable for small logging sites. Nowadays we have one this kind of unit in commercial use in Finland. CHIPPING AT THE END USE FACILITY Chipping at the end site offers advantages over other production methods. In this way we can avoid the problems of the hot chain between chipper and lorry and chipping can be implemented more economically at the end site than at the stand or at the roadside. However the problem with this method lies in the lorry transport of logging residue. Without compacting the logging residue the load would remain very small and transport cost will be too high. This chain have been studied and developed intensively in Sweden. To compacting the logging residue to the load space have developed special compacting equipment and logging residue grapples. In this way we can increase the density from 15 % to 30 %. For this method the newest idea is to bundle logging residues. For this purpose is developed special equipment in Sweden. When we use bundling, we can use the normal load carrying tractors and trucks for the forest haulage and road transportation of logging residues. Bundles are also easier to supply than logging residues. INTEGRATION TO PEAT PRODUCTION Peat is very significant energy source in Finland. In peat production we use strong tractors. When the whether condition are not suitable for peat production we can use these machines for other purposes. So we have developed forest fuel methods where we use these machines and peat production areas effectively. For this method we have developed tractor-trailer, which has compacting device. By this trailer we transport logging residues to the peat production areas, where we dry them in the piles. In the winter time we can chip them by tractor forced chippers and transport them to the end use site by lorries which we use also in peat transportation.
SMALL SCALE PRODUCTION Small scale forest fuel production in Finland is generally based on heating entrepreneurship, where the contractor is taking care of both wood fuel production and heat production. These wood fuel production methods are usually based on manual felling and the use of farm tractors for the forest haulage, road transport and chipping. PRODUCTION COSTS OF LOGGING RESIDUE CHIPS 1985-1998 What kind of effects these new developed methods and equipment has then to the competitiveness of forest fuels. After the beginning of 1990 when we started a large research and development work we have lower the production cost level by 20 %. These costs represent cost of the best available technology in optimal conditions. So we can say that nowadays logging residue chips are competitive in many places and the use of forest fuels are growing nowadays very fast. Our government has also set target to the use of forest fuels in the future in the promotion program of renewable energy sources in Finland. The total target is to increase the use of renewables 3 million tons of oil equivalent and this will be nearly totally from wood fuels. The share of forest fuel will be 0.9 million tons of oil equivalent and rest will be by-products and other wood wastes CONCLUSIONS Forest fuels are nowadays competitive in many cases and it’s energy use is growing fast. In long term the best way to improve the competitiveness of forest fuels is research and development work on production methods, handling systems and boilers.