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Biomass-based composite material manufacturing technology is a new material manufacturing technology field that has gradually emerged through the introduction of advanced composite material manufacturing technologies and continuous development and innovation based on traditional wood processing technology. Traditional wood processing technology primarily uses tree trunks as raw materials, processing them into solid wood boards of various sizes through techniques such as sawing. This process produces a large amount of processing residues such as bark and sawdust, and the wood utilization rate is generally around 40%. "Wood-based composite material" manufacturing technology, on the other hand, utilizes these wood processing residues, as well as the large amount of logging residues such as branches and twigs generated during tree harvesting, and transforms them into board products of various sizes through a series of advanced composite processes. Using this technology, the wood utilization rate can reach over 90%. With the development of "composite material" manufacturing technology, its raw materials have gradually expanded to biomass resources such as bamboo and agricultural residues (agricultural straw), forming a new type of "biomass-based composite material manufacturing" that includes "bamboo-based composite material manufacturing technology" and "agricultural residue-based composite material manufacturing technology" that uses a variety of different biomass resources. With the continuous advancement of technology and industrial expansion, the "biomass-based composite materials manufacturing" technology system has now developed into one of the important industries of the national economy with an output value of trillions of yuan.
The precise output value of biomass-based composite materials, including wood, bamboo, and agricultural residues, across various industries, and their impact on downstream industries, is currently lacking unified data due to its vast scope and fragmented nature. Some technical areas, such as agricultural straw-based composite materials, are relatively new, so no statistical data is available. Furthermore, output value data for timber structures, timber (bamboo) plank roads, and bamboo-wood structural material landscapes are typically included in data for national forest parks and, to a lesser extent, real estate (community development), making it difficult to separate.
Some organizations do publish statistics on wood-based panels, but they aren't necessarily accurate. For example, Liu Nengwen, president of the China Timber Distribution Association, reported that my country's wood-based panel production in 2017 was 315 million cubic meters. Meanwhile, Qian Xiaoyu, vice president of the my country Forest Products Industry Association, reported 294.8 million cubic meters. With a discrepancy of over 20 million cubic meters, which one is more accurate?
Even the data released by the National Bureau of Statistics is subject to significant inaccuracies. Take plywood production, for example. Many plywood mills in my country don't produce veneer themselves, but instead purchase it from specialized veneer manufacturers. For example, veneer produced in Henan is shipped to Shandong to be manufactured into plywood. Therefore, when calculating the output and value of these companies, veneer is counted once (in Henan, the output and value of veneer mills are aggregated under the man-made board sector), and plywood is counted again (in Shandong, plywood production is actually already counted at the veneer stage). Besides plywood, veneer is also sold to flooring manufacturers for flooring, decorative board manufacturers for decorative panels, and wallboard manufacturers for wallboard. The credibility of these combined statistics is questionable.
Therefore, the purpose of giving a general estimate in this article is just to give everyone a macro concept. It is actually unnecessary to pursue a specific accurate value.
1. Scope and application areas of biomass-based composite materials technology system
Biomass-based composite material manufacturing technologies include the following: Processing and manufacturing technologies for solid wood-based composite materials using solid wood (sawn timber) as raw materials, such as CLT (cross-laminated timber) and glulam (glulam). Processing and manufacturing technologies for wood-based panels using wood materials in various component forms (veneer, fiber, and wood particle size) as raw materials, such as laminated veneer lumber (LVL), plywood, particleboard, oriented strand board (OSB), fiberboard, and blockboard. Manufacturing technologies for bamboo engineering materials using bamboo materials in various component forms as raw materials, such as reconstituted bamboo, bamboo bundle glued (laminated) boards, bamboo strip plywood, bamboo laminated glulam, bamboo strip plywood, (flattened) bamboo veneer plywood, bamboo particleboard, bamboo fiberboard, as well as bamboo/wood composite panels, bamboo fiber/synthetic fiber composites, and round bamboo building components. Processing and manufacturing technology of agricultural residue composite panels using agricultural straw as raw materials, such as wheat straw particleboard, cotton stalk chipboard, wheat straw fiberboard, rice straw bundle wall board, etc.
Biomass-based composite materials are primarily used in the following areas: building materials, such as load-bearing materials for timber structures (glulam beams, purlins, rafters, and columns), enclosure materials (wall panels, floor panels, and roof panels), and cement formwork used in construction and infrastructure projects. Building decoration materials include interior roof and wall decoration, wardrobes, cabinets, flooring, and door panels. Outdoor building decoration materials include landscaping, outdoor flooring (boardwalks), and exterior wall panels. Furniture, including various panel and solid wood composite furniture, furniture for public spaces, various types of train car panels, container floors, and various packaging and heavy-duty packaging materials.
Despite rapid progress in my country's biomass-based composites industry, there is still a significant gap between industry development and national needs. Further efforts are needed, both in the technological research and development of existing industries and in the expansion of the product fields of these technologies.
2. Application progress of biomass-based composite materials technology system in the field of wooden structure construction
Wood-framed buildings have a history of thousands of years in my country. Traditional wood-framed buildings are primarily constructed using solid wood planks. These buildings, primarily constructed using solid wood planks, consume large amounts of high-quality wood and have low wood utilization rates. Currently, large-diameter, high-quality natural forest timber in my country is extremely scarce, and logging of the remaining large-diameter natural forest timber in major forest areas is prohibited. With the exception of a small number of solid wood residential structures in ethnic minority areas in certain provinces, traditional wood-framed buildings have been replaced by brick-concrete and steel-concrete structures. Building materials such as steel, cement, and clay bricks are high-carbon emitters, and their manufacturing processes emit significant amounts of carbon dioxide, which contributes to global warming. Therefore, the use of low-carbon "biomass materials" that sequester carbon dioxide, replacing high-carbon emitters like steel and cement, in wood-framed buildings has received significant national attention and is emerging as a new development direction for my country's construction industry.
Biomass-based composite materials have become a major building material in modern timber structures. For example, the main building envelope materials (wall panels, floor panels, and roof panels) used in modern timber structures in my country include oriented strand board (OSB), structural plywood, bamboo-wood composite panels, and bamboo-stripe plywood. The load-bearing materials (beams, purlins, rafters, and columns) used in Chinese timber structures include glulam (glulam), laminated veneer lumber (LVL), cross-laminated timber (CLT), and bamboo-stripe laminated timber. CLT, a material made by cross-gluing solid wood together, has also seen some development and application in high-rise hybrid (a combination of timber and steel-concrete structures) buildings.
One current problem is that my country still relies on imported high-quality wood for structural solid wood composite materials like glulam and CLT. This reliance on imported materials poses a significant risk to the development of my country's wood structure industry. If the international environment changes, raw material supply issues could impact the normal development of my country's wood structure industry. One solution to this development dilemma is to utilize domestic plantation timber and bamboo to produce load-bearing materials for building structures. The development of this new technology will also help promote the development of my country's timber and bamboo plantation industries and contribute to addressing employment issues for the rural population. my country has already made significant progress in technological research and development in this area. The manufacturing technologies for domestically produced building structural materials, such as bamboo laminated timber (glulam) made from bamboo strips, bamboo-wood composites made from plantation eucalyptus veneer and bamboo strip curtains, cross-laminated timber (CLT) made from bamboo strip laminated lumber and domestic plantation small-diameter pine boards, and reconstituted bamboo lumber, have reached maturity, and the industrialization of these technologies is progressing. With the application of these technologies in my country's wooden structure construction field, the problem of my country's wooden structure construction materials mainly relying on imported materials will gradually be alleviated.
3. Application progress of biomass-based composite material technology system in the field of wood-based panel manufacturing
Wood-based panel manufacturing technology, a system for producing "wood-based composite materials" using small-diameter timber and branches from my country's plantations as primary raw materials, is a key component of my country's forest products industry. Currently, it supplies over 300 million cubic meters of wood-based panel products annually to related industries (according to the China Timber Distribution Association, total wood-based panel production in my country reached 315 million cubic meters in 2017). This technology has also significantly boosted the development of my country's plantation industry.
Currently, the primary use of wood-based panel products in my country is in interior building decoration and furniture manufacturing. Due to the use of free-formaldehyde adhesives such as urea-formaldehyde glue in wood-based panel manufacturing, formaldehyde pollution in my country's indoor living environment caused by these products has long been a pressing pain point for this product. Using formaldehyde-free adhesives to manufacture wood-based panels and their products is a fundamental approach to addressing formaldehyde pollution. Currently, the technology for producing formaldehyde-free wood-based panel products using formaldehyde-free adhesives is largely mature in my country. Formaldehyde-free wood-based panel products manufactured using formaldehyde-free materials such as thermoplastic resins, soy protein, and isocyanates as adhesives have entered the Chinese market for interior building decoration and furniture manufacturing (particularly children's furniture), achieving significant economic and social benefits.
Regarding the innovative development of my country's wood-based panel products, developing new "low-density, high-strength" and "high-density, high-strength, high-weather-resistant" wood-based panel products to further expand their applications in automotive, rail transit, outdoor landscaping, and exterior decoration is also a key area of development. Developing "low-density, high-strength" wood-based panel products, which have a lower density than standard wood-based panels (low density) but meet or exceed the strength requirements of standard panels, will not only further reduce raw material consumption, but their application in automotive and rail transit applications will effectively reduce vehicle weight, thereby reducing vehicle energy consumption. Developing specialty wood-based panels with "high-density, high-strength, and high-weather-resistant" properties, such as high-density, high-strength plywood for use on liquefied natural gas (LNG) carriers, and developing "ultra-high-density," highly weather-resistant fiberboard for use in high-rise building exterior curtain walls and as decorative materials for high-humidity environments, will further expand the application areas of my country's wood-based panel products.
4. Application progress of biomass-based composite material technology system in the field of new bamboo engineering material manufacturing
The innovative development of new bamboo engineering material manufacturing technologies has always been a key development direction for my country's "biomass-based composite materials" manufacturing technology industry. In recent decades, my country has made significant progress in the development of the bamboo engineering material industry. Its products have found widespread application in architecture, building materials, interior decoration, outdoor landscape architecture, furniture, and carriage and container floors. my country's bamboo engineering material manufacturing technology is already at the forefront of the world. A new development direction for bamboo engineering material manufacturing in my country is to leverage bamboo's high strength-to-weight ratio and good flexibility to develop "3D special-shaped material" manufacturing technology. This technology can produce a variety of high-performance special-shaped composite materials with complex shapes, expanding their application in automotive, drones, rail transportation, missiles, aviation, and shipbuilding.
5. Application progress of biomass-based composite material technology system in the field of agricultural straw composite material manufacturing
Agricultural straw composite material manufacturing technology is one of the new biomass-based composite material manufacturing technologies developed in my country in recent decades. Using agricultural straw as a raw material to manufacture composite materials, such as wood-based panels, not only addresses my country's biomass raw material shortage but also helps address the environmental pollution caused by the burning of large quantities of agricultural residues. Currently, the application of agricultural straw-based composite materials in my country is limited, primarily due to the material's performance failing to fully meet application requirements and the relatively high production cost. In addition to addressing issues such as product performance and production cost, further developing new material manufacturing technologies and expanding new applications based on the characteristics of agricultural straw are also key areas of research for this field. Leveraging the relatively low specific gravity of agricultural residues, the development of lightweight insulation materials for building exterior walls, combining them with other inorganic materials to create new modular building walls, and developing lightweight wood-based panel products are all promising research directions.
Biomass materials such as wood, bamboo, and agricultural straw are among the world's most abundant natural resources. Their renewable and sustainable nature offers broad potential for the development of biomass-based composite materials manufacturing technology. Continuously developing new technologies and expanding new application areas to provide new impetus for low-carbon development in my country's industrial system should be our enduring goal.
Author profile: Wang Zheng, researcher at the Wood Research Institute, Chinese Academy of Forestry.
Source: Forestry Committee of the China Association of Senior Professors; Forestry Branch of the China Engineering Science and Technology Knowledge Center