Pulpwood can be defined as timber that is ground and processed into a fibrous pulp. It is a versatile natural resource commonly used for paper-making but also made into low-grade wood and used for chips, energy, pellets, and engineered products. Pulpwood can be derived from most types of trees. Categorizing trees into hardwood and softwood is the easiest way to characterize types of paper produced from pulpwood. Hardwoods are raw material that are preferred for pulp used in printing papers. It has small dimensions in its fibres, which can be useful for small-scale uniformity, opacity, and surface smoothness, all important for printing paper. Softwoods are the preferred raw material for strong papers, due to the length and slimness of the fibres. Low-density softwoods, such as firs with thin-walled fibres are preferred for papers with high demands for bonding-related strength characteristics. Some of these characteristics include tensile, burst, and surface strength. Trees raised specifically for pulp production account for 15% of world pulp production, while old growth forests account for 9% and second/third plus generation forests account for the balance.
Hardwood applications Hardwood has anatomical structural differences to softwood, which influences physical properties, durability, workability, and bonding. Different types of cells complete the three main tasks in hardwoods compared to softwoods. The main tasks include stabilization, water conduit, and storage.
Hardwood applications can be sectioned into four areas:
Solid wood products Wood-based materials Use after modification Supplemental services
Solid wood products Hardwoods (such as oak) are the preferred raw material for joists, roof structures and timber frames. The use of solid hardwoods has decreased during the last couple centuries, most likely due to the development of wood-based materials that allow for larger constructions not limited to the size of trees. Trees of any size can be used for pulpwood, but trees that are 5–9 inches in diameter at breast height are normally used. These trees are cut after a saw timber harvest or as a separate operation to thin a crowded stand. Low-quality stands are completely harvested for pulpwood to regenerate the forest to more desirable species, as well as larger trees with disease or defects that prevent their use for lumber. Additional fields of application include playgrounds, wood-facings, railway sleepers, bridges, and more. Furniture is another application of hardwood. Furniture made of pure solid wood is relatively rare. Most parts of furniture such as table boards, shelves or cabinet doors belong to wood-based materials because of their glued components. Solid wood can be used for chairs, tables, beds, upholstery frames, sideboards, cabinets, bathtubs, and more. Hardwood is also used for interior work, such as parquet flooring, doors, and windows. Hardwood is especially preferred for parquet flooring. Tree species in darker colours are commonly used to give the flooring a "used look," for visual appeal. Solid wood is used for front doors and windows, while internal doors are mainly made of wood-based panels.
Wood-based materials Wood-based materials can be separated into a few different types. These include solid wood, ply, particle, and fibre materials. Solid wood materials are used as beam or panels. Typical tree species used for solid wood materials include beech, oak, birch, alder and chestnut. Hardwoods are commonly used for nonstructural products such as plywood. Structural products such as cross laminated timber, are mainly composed of softwoods. Particle materials are ideal to use low-rate timber assortments and saw mill waste. Types of particle materials include particle board, mineral-bonded wood composites, oriented strand board, laminated strand lumber, and oriented strand lumber. Fibre materials include fibreboards, insulating fibreboards, wood particle mouldings and wood plastic composites. The quality and processing of fibreboards and insulating fibreboards are influenced by the fibre percentage, the geometrical structural of the fibre, and the specific chemical composition of wood. The fibres of hardwoods are short, smooth and thin, and are suited for the dry production process because they do not mat. Ironically, hardwoods are barely used for fibreboards and insulating fibreboards.
Use after modification The purposes of wood modification are dimensional stabilization and resistance increase. Wood can be modified in a multitude of ways, including but not limited to: chemical modification, heat treatment, ammonia treatment, electrodialysis, and more. Chemical modification, heat treatment, and impregnation (with salts, metals, monomers and polymers) are the most used methods.
Supplemental services Hardwood can be used in other ways outside of physical wood structures and paper. It can be used as a substance, such as through food production. The sawdust of beech and oak is used to grow edible mushrooms. Oak, beech and maple are used to cure meat or fish, while oak staves, chips and powder add aroma to wine. The sawdust of oak and robinia can be used to filter elements such as copper, nickel, zinc and cadmium. It can also be added to plastics. 60% of linoleum flooring consists of sawdust. Wood can also be used as an energy source, with sawmill waste and low-rate timber. Combustion, wood gasification, and production of bioethanol are the three main ways hardwood is used for energy. Combustion: split billets, chips and wood pellets. High-density wood species burn down slower, and the heat value depends on wood moisture content. Burning rate decreases with increasing density. Wood gasification (synthetic natural gas and biomass to liquid): synthesis gas production is done by wood smouldering. Bioethanol: start off by the splitting of cellulose and hemicelluloses in sugar by enzymes and acids, then the fermentation of the sugar with the aid of microorganisms. Lastly, the distillation and dewatering creates the bioethanol.
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