An increase in the demand for wood results in improved recovery and less residual biomass in the forests. Paradoxically, interest in forest residue as a renewable source of raw material seems to be in a reverse ratio to its availability in a certain area. Finland and Sweden are probably more dependent on forestry and forest in­ dustries than any other developed countries in the world. A sufficiency of raw ma­ terial for integrated forest industries is vital for the national economy of both countries, and a great deal of attention is being paid to the long-term potential of unutilized biomass left behind in logging operations. Furthermore, since these countries possess no reserves of fossil fuels, and since their per-capita consump­ tion of primary energy is exceptionally high, they also consider unmerchantable forest biomass a realistic source of indigenous energy. A joint Nordic research project on harvesting and utilization of logging residue was carried out in 1969-1976 under the auspices of the Nordic Research Council on Forest Operations. This fruitful cooperation soon gave rise to related national projects in Sweden, Finland, Norway, and Denmark, stimulating further research and producing practical applications. Concurrently, particularly after the worldwide energy crisis in 1973, research on all aspects of utilization of forest bio­ mass mushroomed in the United States, Canada, and the Soviet Union. An ex­ plosive increase occurred in both the number and diversity of biomass studies.

Inhalt

1 Introduction.- 2 Residual Forest Biomass as a Raw Material Reserve.- 2.1 Biomass Components of a Tree.- 2.1.1 Tree Crown.- 2.1.1.1 Development of the Crown.- 2.1.1.2 Foliage Mass.- 2.1.1.2.1 Moisture Content of Foliage.- 2.1.1.2.2 Vertical Distribution of Foliage Mass.- 2.1.1.2.3 Seasonal and Annual Variation in Foliage Mass.- 2.1.1.2.4 Effect of Tree Size on Foliage Mass.- 2.1.1.2.5 Effect of Crown Class on Foliage Mass.- 2.1.1.2.6 Effect of Tree Species on Foliage Mass.- 2.1.1.2.7 Effect of Atmospheric Pollution on Foliage Mass.- 2.1.1.3 Composition of Branch Mass.- 2.1.1.3.1 Moisture Content in Branches.- 2.1.1.3.2 Percentage of Bark in Branches.- 2.1.1.3.3 Dead Branches as a Biomass Component.- 2.1.1.4 Crown Mass.- 2.1.1.4.1 Crown Ratio.- 2.1.1.4.2 Vertical Distribution of Crown Mass.- 2.1.1.4.3 Effect of Tree Size on Crown Mass.- 2.1.1.4.4 Effect of Stand Density and Crown Class on Crown Mass.- 2.1.1.4.5 Effect of Tree Species on Crown Mass.- 2.1.2 Unmerchantable Top.- 2.1.2.1 Percentage of Bark in the Unmerchantable Top.- 2.1.2.2 Mass of Unmerchantable Top.- 2.1.3 Stump and Roots.- 2.1.3.1 Distribution of Stump-Root System Components.- 2.1.3.2 Percentage of Bark in Stump and Root Mass.- 2.1.3.3 Dry Mass of the Stump-Root System.- 2.2 Composition of Whole-Tree Biomass.- 2.3 Biomass of an Entire Stand.- 2.4 Forest Biomass Inventory.- 2.5 Quantity of Residue in Practical Logging Operations.- 2.5.1 Estimating the Quantity of Logging Residue.- 2.5.2 Examples of the Quantity of Logging Residue.- 3 Technical Properties of Residual Tree Components.- 3.1 Anatomical Structure of Residual Tree Components.- 3.1.1 Compression Wood in Softwood Branches.- 3.1.2 Tension Wood in Hardwood Branches.- 3.1.3 Juvenile Wood in Stem Tops.- 3.1.4 Anatomical Characteristics of Root Wood.- 3.2 Cell Dimensions in Residual Tree Components.- 3.2.1 Cell Dimensions in Branch Wood.- 3.2.2 Cell Dimensions in Stem Tops.- 3.2.3 Cell Dimensions in Stump and Root Woods.- 3.3 Chemical Composition of Residual Tree Components.- 3.3.1 Primary Constituents in Residual Tree Components.- 3.3.2 Extractives in Residual Tree Components.- 3.3.2.1 Extractives in Wood and Bark.- 3.3.2.2 Extractives in Foliage.- 3.3.3 Inorganic Materials in Residual Tree Components.- 3.4 Basic Density of Wood and Bark in Residual Tree Components.- 3.4.1 Basic Density of Wood and Bark in Branches.- 3.4.2 Basic Density of Wood and Bark in Stem Tops.- 3.4.3 Basic Density of Wood and Bark in Stumps and Roots.- 3.5 Heating Value of Residual Tree Components.- 4 Recovery of Residual Forest Biomass.- 4.1 Harvesting Whole Trees.- 4.1.1 The Basis of Whole-Tree Harvesting.- 4.1.2 Felling for Whole-Tree Harvesting.- 4.1.2.1 Motor-Manual Felling.- 4.1.2.2 Mechanized Felling and Bunching.- 4.1.3 Off-Road Haulage of Whole-Tree Material.- 4.1.3.1 Off-Road Haulage with Skidders.- 4.1.3.2 Off-Road Haulage with Forwarders.- 4.2 Relogging Slash from Cutovers.- 4.2.1 Collection of Slash.- 4.2.2 Off-Road Haulage of Slash.- 4.3 Continuously Progressing Swath Harvesters.- 4.3.1 The Basis of Swath Harvesting.- 4.3.2 Operation of the Swath Harvesters.- 4.3.3 Swath Harvester Prototypes.- 4.4 Harvesting Stump and Root Mass.- 4.4.1 Logging Characteristics of Stump-Root Systems.- 4.4.1.1 Dimensions of Stump-Root Systems.- 4.4.1.2 Power Requirement of Stump Extraction.- 4.4.2 Extraction of Complete Trees.- 4.4.3 Separate Extraction of Stump-Root Systems.- 4.4.3.1 Stump Extraction by Blasting.- 4.4.3.2 Stump Extraction with Chassis-Mounted Equipment.- 4.4.3.3 Stump Extraction with Crane-Mounted Equipment.- 4.4.3.4 Splitting and Cleaning as Part of the Stump Harvesting Schedule.- 4.4.4 Off-Road Haulage of Stump and Root Mass.- 5 Comminution of Residual Forest Biomass.- 5.1 The Purpose of Comminution.- 5.2 The Techniques of Comminution.- 5.2.1 Portable Chippers.- 5.2.2 Portable Chunkers.- 5.2.3 Portable Hogs.- 5.3 Energy and Power Requirement in Comminution.- 5.3.1 Energy Consumption in Comminution.- 5.3.2 Power Requirement of Comminution.- 5.4 Position of Comminution in the Harvesting Schedule.- 5.4.1 Comminution in Terrain.- 5.4.2 Comminution at an Upper Landing.- 5.4.3 Centralized Processing of Residual Wood.- 5.4.3.1 Terminals for Large Trees.- 5.4.3.2 Terminals for Small Trees.- 5.4.3.3 Terminals for Residual Biomass.- 6 Trucking Residual Forest Biomass.- 6.1 Transport-Technical Characteristics of Residual Biomass.- 6.2 Improvement of Bulk Density by Compaction.- 6.3 Trucking Unlimbed Timber.- 6.4 Trucking Unprocessed Logging Residue.- 6.5 Trucking Comminuted Biomass.- 6.6 Alternatives to Trucking.- 7 Examples of Biomass Harvesting Systems.- 7.1 Whole-Tree Chipping Systems.- 7.1.1 Chipping Small Trees for Farm Heating.- 7.1.2 Chipping Small Trees for a 1-MW Heating Plant.- 7.1.3 Chipping Small Trees for a 3-MW Heating Plant.- 7.1.4 Chipping Small Trees for Pulping.- 7.1.5 Chipping Low-Quality Hardwoods for Pulping.- 7.2 Systems for Chipping Slash.- 7.2.1 Chipping Slash in Terrain for a Large Power Plant.- 7.2.2 Chipping Slash at Landing for a Large Power Plant.- 7.3 Systems for Integrated Recovery of Crown Mass and Conventional Timber.- 7.3.1 Biomass Recovery Based on the Tree-Section Method.- 7.3.2 Biomass Recovery Based on Centralized Processing of Large Trees.- 7.4 Systems, for Harvesting Stump and Root Mass.- 7.4.1 Relogging Stump and Root Mass for Pulping.- 7.4.2 Harvesting Stump and Root Mass with Conventional Timber.- 8 Utilization of Residual Forest Biomass.- 8.1 Use of Chips as a Solid Fuel.- 8.1.1 Techniques for Direct Combustion of Chips.- 8.1.2 Effect of Chip Properties on Direct Combustion.- 8.1.3 Energy Efficiency of Chip Combustion.- 8.1.4 Drying and Storage of Fuel Chips.- 8.1.4.1 Transpiration Drying of Small Trees.- 8.1.4.2 Storage of Fuel Chips.- 8.2 Use of Residual Biomass for Pulp and Paper Products.- 8.2.1 Strength Properties of Pulp and Paper.- 8.2.2 Appearance and Optical Properties of Pulp and Paper.- 8.2.3 Pulp Yield.- 8.2.4 Beatability and Drainage of Pulp and Paper.- 8.2.5 Consumption and Recovery of Chemicals.- 8.2.6 Wear and Tear of Equipment.- 8.2.7 Concluding Remarks.- 8.3 Use of Residual Biomass for Panel Products.- 8.3.1 Use for Fiberboard.- 8.3.2 Use for Particleboard.- 8.3.3 Use for Structural Flakeboard.- 8.4 Use of Residual Biomass as a Feedstock for Chemicals.- 8.4.1 Gasification of Forest Biomass.- 8.4.2 Pyrolysis of Forest Biomass.- 8.4.3 Direct Catalytic Liquefaction of Forest Biomass.-…