Origin of wood foam The development of wood foam, inspired by biomimicry principles, marks a significant stride towards sustainable materials in the construction industry. Traditionally, the sector has heavily relied on petrochemical plastics for insulation, contributing to environmental concerns. With a focus on renewable resources and reducing fossil fuel dependence, researchers at the Fraunhofer Institute …
Origin of wood foam
The development of wood foam, inspired by biomimicry principles, marks a significant stride towards sustainable materials in the construction industry. Traditionally, the sector has heavily relied on petrochemical plastics for insulation, contributing to environmental concerns. With a focus on renewable resources and reducing fossil fuel dependence, researchers at the Fraunhofer Institute for Wood Research in Germany turned to natural cellular structures, particularly those found in traditional wood products, for inspiration.
Wood foam is a multifunctional material derived entirely from lignocellulose, comprising 100% wood and a variety of biomass from the cell walls of trees and woody plants. Utilizing nanocrystals activated by hydrogen peroxide and foaming agents like CO2 or proteins, this material transforms from a viscous mass to a frothy foam that solidifies into odor-neutral hard foam boards or elastic foam. Technologies employed in its production ensure durability, flexibility for varied applications, and water resistance. Sustainable production is further guaranteed by incorporating organic substances and chemicals.
Two primary types of wood foam cater to different needs: strong, closed-cell foams for rigid insulation and packaging, and soft, open-cell foams for absorbing materials in hygiene products. Customization is achieved through various technologies like web formation, paper manufacturing, extrusion, and 3D printing.
Wood foam has found application in a range of products, including CLT and LVL wood foams, bioplastic composites, textile fibers, personal care items, hygiene products, filters, household items, foam tiles, protective and thermal packaging, thermal insulation, and soundproofing. Acoustic panels made from wood foam are particularly effective in treating spaces with excessive reverberation, such as living rooms, offices, and restaurants.
Compared to traditional PVC foams, wood foam offers advantages such as the ability to be stained and painted, uniform textures, and resistance to slipping and fading. Some variants match the durability of plastic foams while exhibiting resistance to deformation, collapse due to moisture, and pressure and humidity, all while maintaining thermal insulation, mechanical, and hydrodynamic properties. Wood foam emerges as a state-of-the-art solution meeting both customer needs and environmental standards in various industries.
Innovation of wood foam: technology and research
The innovation in wood foam production has seen the integration of chemistry, physics, and rheology sciences, leading to significant advancements in the hardening process and material properties. The utilization of specific chemical processes, leveraging natural substances within wood, has resulted in a lightweight base material with a porous, open-cell structure and low bulk density. Furthermore, improvements in sound absorption during production have been achieved through the exploration of diverse material mixtures and production methods, contributing to the overall sustainability of wood foam production.
Enhancements in strength have broadened the applications of wood foam. Innovations include blending wood foam with metal muscles, introducing functionalities like electrical conductivity while enhancing bending strength. Unique material mixes, such as the combination of lignin, wood fiber, and laponite, have yielded shock and humidity-resistant foams, presenting viable alternatives to traditional plastics.
Addressing a key concern in the wood-based composite industry—density reduction—technology has evolved to create ultra-low-density wood foams with an exceptional strength-to-weight ratio, attributed to anisotropic properties. Foam-forming technologies utilizing small air bubbles containing aqueous foam as a transporting medium have improved homogeneity and stability compared to conventional wood materials.
Challenges in wood foam production, particularly efficiency and scalability, have prompted research focusing on materials with unique rheological properties. This research has extended the relaxation time during the drying process, enabling scalable and flexible production. By manipulating elongated and closed bubble structures, an anisotropic film structure has been created, conferring superior directional strength per density, as well as insulation and shockproofing properties. This breakthrough positions wood foam as an advanced and versatile material, surpassing other bio-based foams and traditional cardboards in terms of performance and functionality.
ESG impacts of wood foam: the contemporary view
Wood foam stands out as a transformative material, particularly when compared to PVC foams, addressing a spectrum of economic, social, and environmental concerns. Researchers have meticulously addressed shortcomings related to weight, maintenance costs, fire resistance, weather resistance, durability, sound absorption, and insulation capabilities, making wood foam a game changer on multiple fronts.
Compared to glass fibers, wood foams offer advantages in availability from renewable resources, low weight, cost-effectiveness, and favorable mechanical properties. They cause minimal damage to processing equipment, have improved surface finish for molded parts composite, and pose fewer health hazards. Notably, the absence of adhesives in wood foam production contributes to health and environmental safety for users.
Wood foam solutions, exemplified by products like Nefab’s WoodFoam, boast health benefits over plastic-based and PU foams due to their fiber-based nature and lack of isocyanates and chemical additives. They are repulpable, recyclable, and FSC-certified, generating significantly fewer CO2 emissions than PU foams (Figure 1). Wood foam’s absorption properties enable the reuse of materials from natural resources, aligning with Environmental, Social, and Governance (ESG) principles. Wood foam has been compared intensively with PVC foams regarding weight and maintenance costs, capability of fire-resistance, self-extinguishing, weather, water, chemicals and vibration resistance, durability, strength, effectiveness at sound absorption, sound insulation, and thermal insulation. These shortcomings have all addressed by researchers, making wood foam a true game changer in all sense of economic, social, and environmental aspects.
Figure 1. Carbon footprint of different foams. Adapted from Nefab LCA models for packaging materials verified by Pre-Sustainability.
The innovative supply chains associated with wood foam embrace circular thinking and sustainable business strategies. These chains not only contribute to waste and resource management research but also provide economic, social, and environmental benefits. In contrast to Styrofoam’s long-lasting environmental impact, wood foam products break down in soil within a few weeks while maintaining their packaging and insulation properties.
Wood foam products offer an alternative to traditional air conditioning, consuming less electricity and acting as thermal insulation. They reflect sunlight and emit absorbed heat back into the atmosphere, contributing to energy efficiency for cooling and heating needs. The blending of wood and metal in recent developments has shown promising results, reducing cooling costs and minimizing waste.
Wood foam’s potential extends to smart buildings and offices, serving as building elements for roofs and exterior walls. Moreover, it plays a role in mitigating climate disasters, especially in hurricane-prone areas, due to its wind-uplift capacity on wood roof-sheathing panels. Structural retrofits with wood foam can enhance wind-uplift capacity, addressing challenges related to the wind resistance of older roof designs.
The utilization of wood left in harvested forests reduces the potential fuel for devastating wildfires, showcasing wood foam’s contribution to environmental resilience. Overall, wood foam emerges as a versatile, sustainable, and impactful material with far-reaching implications across various industries and applications.
Future of wood foam as a game-changer material
The development of wood foam technology is advancing through innovative approaches in thermo-mechanical pulping, heating, and grounding of wood chips. Scientists in Braunschweig are exploring specific tree species, primarily beech and pine, to identify the optimal raw materials for wood foam production, with a focus on scaling up the process for industrial applications.
Expanding the scope of wood foam materials, researchers are exploring the integration of non-wood fibers and lignocellulosic fibers from agricultural waste, including carrot, lingonberry, cranberry, beetroot powder, and carbon. This diversification aims to enhance the sustainability and performance of wood foams in various impact categories, aligning with European Union standards.
Leading companies like Stora Enso are at the forefront of bio-based materials, introducing wood foams such as Fibrease and Papira (Figure 2). These products excel in damping, resilience, and insulation capacity, particularly in protective and thermal packaging. Stora Enso’s commitment to sustainability includes customization options in rigidity, density, flexibility, fiber type, and content level, along with certifications for recyclability and biodegradability. The production process prioritizes sourcing from sustainably managed forests, FSC certification, and using air and water for foaming without solvents or hazardous chemicals.New technologies are being developed for thermo-mechanical pulping, heating and grounding of wood chips for the foam base and the physical anchorage and entanglement between strands of fibre. As their ESG benefits are better recognised in the application of wood foams, Braunschweig-based scientists continue to search for the tree species exclusively of beech and pine that would provide the best raw materials for wood foam and identify suitable processes for mass production on an industrial scale.
Figure 2. Stora Enso wood foam. Photo: Magnus Glans, via Stora Enso photo library.
The performance of wood foams extends to ultralight particleboards, demonstrating positive environmental impacts throughout their life cycle. Reduced use of adhesives and lighter weight for transportation contribute to their competitiveness in the market.
Life cycle assessments are crucial in evaluating the environmental benefits and drawbacks of wood foam. Researchers are actively engaging in attributional and consequential assessments, addressing product and process development issues and benchmarking parameters at both operational and policy levels.
Ongoing research aims to enhance the hygric, thermal insulation, and moisture-related characteristics of wood foams. Challenges related to stability, fibrillation in fluctuating temperatures, and resistance to pressure and humidity are being addressed to meet insulation material standards.
In a noteworthy development, researchers from Aalto University in Finland have integrated artificial intelligence (AI) into wood foam technology (Figure 3). They have successfully created wood foam that is resistant to humidity, fire-safe, and maintains strength, flexibility, and light weight. This advancement opens new possibilities for the application of wood foam in various industries, showcasing its potential for multifaceted improvements through technology integration.
Figure 3. Wood foom developed with AI by Aalto University. Picture: Mikko Raskinen.
You might be interested in learning more:
Hudert, M., Pfeiffer, S. 2019. Rethinking Wood: Future Dimensions of Timber Assembly. https://doi.org/10.1515/9783035617061
Verkerk, P.J., Hassegawa, M., Van Brusselen, J., Cramm, M., Chen, X., Maximo, Y. I., Koç, M., Lovrić, M., Tegegne, Y. T. 2022. The role of forest products in the global bioeconomy – Enabling substitution by wood-based products and contributing to the Sustainable Development Goals. Rome, FAO. https://doi.org/10.4060/cb7274en
More research could be done following the questions:
- Can we use the current assembly to upscale the PVC foams into bio-based foams from different materials and wastes?
- How can manufacturers switch into the foam forming process and technologies from their current systems?
- How can wood foam perform better? From releasing the heat passively to the environment to dissolving the heat into new energy alternatives and solutions?
- How can it be circular: sourcing non-biodegradable materials and industrial wastes after their disposal at the end of the production line into a new production of wood foam?
Featured photo copyright Fraunhofer WKI / Manuela Lingnau