Pulpwood
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
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 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 : 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.
Softwood applications
Softwoods come from gymnosperm trees that consists of needles and cones. When a sample of softwood is observed under a microscope, they appear to have no pores because of the presence of tracheids. Tracheids are a primitive element of xylem. They consist of a single elongated cell and a secondary cellulosic wall containing a thick layer of lignin. Medullary rays and tracheids transport water and produce sap. Approximately 80% of timber comes from softwood, such as cedar trees, Douglas fir, juniper, pine, and many more.Although they are called 'softwood,' trees, they are not actually softer in comparison to hardwood trees. The term just refers to wood that comes from gymnosperms or conifers. Some hardwood trees are even softer than specific softwood tree species.
Softwoods are used in wood manufacturing as well, and are sometimes preferred over hardwoods depending on the product being constructed. An important characteristic that softwoods have that make them a suitable pulpwood to build with, is that they can easily absorb any kind of finish. They can become very resistant and last for a long time. Softwoods tend to be cheaper than hardwood due to their growth rate and development being faster. They are versatile, strong, and can be managed easily. Some of the biggest softwood forests can be found in Canada, Scandinavia, and Russia.
Types of softwoods
Cedarwood: One of the most resistance and durable softwoods. Cedarwood is originally from the Mediterranean area and is highly resistant to water, bacteria, fungi, and insects. Their impressive resistance ability comes from the woods natural scent, which is sweet and pleasant. Its insect-repellent properties make cedar-wood ideal for the manufacturing of internal furniture, such as chests, boxes, and closets. The woods insulating properties make it suitable to be used for roofing material. Western Red Cedar is used to make musical instruments such as guitars and violins, due to its colour and resistance to warping and cracking.Pinewood: Mostly found in the Northern Hemisphere, this type of wood is mainly used for domestic applications. It is resistance to shrinkage, swelling, and warping. It is used for outdoor wooden projects, such as decks. A disadvantage of pinewood is that over time, the wood could splinter, and items constructed from the specific type of pinewood used for making outdoor furniture/decks should be checked annually to prevent any risks to the people using them.
Firwood: This type of wood comes from Douglas Fir trees, and can be found in North America, Europe, North Africa, and Asia. It is strong and resistant to abrasion, and can be used for a diverse array of products. Some include furniture, doors, windows, and larger-scale items such as bridge parts, log homes, and commercial buildings. It can also be used for boat-building and aircraft construction, due to its sturdy and stable nature.
Redwood: This is mainly used for outdoor applications because of its resistance to weather conditions, insects, and rot. As a result of these characteristics, it is a premium building wood. It is another type of wood used to build decks, because of its natural strength, stability, and lifespan.
Products
Pulpwood can be used for a multitude of different uses, some of them already mentioned above. Some of the main products it is used for is listed below.Paper
Paper production is the most common and main use for pulpwood. Paper can be produced from both hardwood and softwood trees, and each species for both types of trees have specific and unique properties that make the type of paper and other products produced differ. The short fibres of hardwoods trees produce smoother and more uniform paper, like printing paper. Softwood trees have longer fibres that produce industrial papers like newsprint.Wood is broken down mechanically or chemically. After the breakdown process, fibres and lignin are leftover. Lignin is the glue or cement that holds the fibres in wood together. Simply putting it, wood pulp is a large amount of individual wood fibres with the lignin removed. Wood pulp is naturally between dark brown to light grey in colour. Dark brown wood pulp is used for paper bags and boxes, and bleaching the pulp produces higher grades of paper.