Patent Application
20250128450
This disclosure relates to building materials and, in particular, to wood building materials.
Wood engineering towards high mechanical strength includes two general strategies: (1) wood composite, and (2) direct treatment of wood to minimize its porosity with preserved wood load-bearing structure. However, conventional wood composite materials typically require chipping and shredding of wood. Wood chips have high volume and a damaged structure, which often requires additional polymers, fillers, and other additives. Direct wood treatment, on the other hand, often requires heavy use of chemicals with a large carbon footprint due to the difficulty in the uniformity of chemical treatment of wood blocks.
The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.
Living trees sequester carbon by pulling CO2 from the atmosphere and storing it as woody biomass. However, once processed as building materials, natural wood loses its carbon capturing capacity and becomes vulnerable to microbial decomposition and weathering. These processes generate cracks and failures, shorten service life, and limit the use of wood-based materials as building elements, especially in tall buildings. The development of strong wood materials with low carbon footprint and improved performance metrics has the potential to render significant carbon storage in new and retrofitted buildings. Wood engineering towards high mechanical strength includes two general strategies: (1) wood composite 3-5, and (2) direct treatment of wood to minimize its porosity with preserved wood load-bearing structure 1,6-9. However, conventional wood composite materials typically require chipping and shredding of wood. Wood chips have high volume and a damaged structure, which often requires additional polymers, fillers, and other additives. Direct wood treatment, on the other hand, often requires heavy use of chemicals with a large carbon footprint due to the difficulty in the uniformity of chemical treatment of wood blocks.
The methods described herein provide “living wood” by harnessing the natural activities of microbes and their interaction with wood scaffolds to fundamentally change how the wood will be processed and engineered for sustainable construction. Microbes are used to significantly reinforce the wood composite through three-fold functions: 1) Microbial infiltration and growth within the composite matrices. 2) In situ production of bonding biomaterials within the porous space of the wood scaffold to provide a natural carbon sink and self-healing capacity. (3) In situ activation of other mineralization reactions, as needed to further reinforce the material and modulate its properties to expand manufacturing opportunities. The microbes are incorporated during the manufacturing process of the wood composite as bioinks. Such direct microbe-based bioink modification strategies on natural wood transform the dead wood into a new living, strong, carbon capturing and self-healing composites to replace the materials currently used as non-renewable structural components in buildings (e.g. steel and concrete). The method described herein also overcomes the manufacturing barrier in making scalable wood composite with intact wood scaffold with minimum CO2 generation.
The method described herein harnesses the activities of living microbes to rapidly infiltrate the natural pores in wood (40% to 80% by volume in wood are hollow wood channels) and fill the void spaces with carbon-rich, bonding fillers. Carbon negativity is ensured with the carbon stored in wood and microbial networks as well as with the continued carbonation process enabled by the in situ synthesis of biofillers. Notably, the method described herein enables the use of local wood species with lower cost and lower energy/chemical consumption. Even after the new wood composite is applied as in buildings, the mineralization activities of microorganisms can still be used for continued carbonation. The microbe assisted infiltration and in situ mineralization concurrently address challenges in scaling up and market penetration, and optimizing materials properties in a cost-effective manner.
Compared with direct wood modification methods, the living wood described herein addresses the fundamental limit in the non-uniformity of chemical treatment by employing living systems as active and smart fillers of the wood scaffold. Compared with wood-mineral composite that incorporate wood particles as an aggregate in the mineral matrix, the living wood preserves natural wood's multiscale aligned structure for structural/load-bearing applications with the active pore filling with living microbes, which will lead to improved mechanical strength, uniform reaction and fewer technical barriers when scaling up. Compared with natural fungal mycelia, which lacks a load-bearing matrix, living wood can provide guided growth of the bionetwork into an interconnected and strong backbone
Then, the wood is sterilized. For example, the wood may be sterilized in a malt extract broth (e.g. 1%).
Sequential inoculation strategies are employed to enhance the co-existence of fungi and bacteria. Fungi are first inoculated to establish a mycelial scaffold, followed by bacterial infiltration to fill the remaining spaces with bacterial cellulose. Techniques like passive infiltration and vacuum assisted infiltration may be used to ensure uniform penetration of microorganisms throughout the wood's structure. Fungi are introduced first because their mycelial networks can effectively penetrate and colonize the porous structure of wood. The mycelium forms a complex, fibrous network referred to as a mycelial scaffold 106 that binds to the cell walls of the wood and occupies a significant portion of the wood's pores. Once the mycelial scaffold 106 is established, bacteria are introduced to fill the remaining spaces with biopolymers and/or biominerals. Several infiltration techniques are employed to optimize microbial colonization including passive infiltration and vacuum-assisted infiltration.
Biopolymers are natural polymers produced by living organisms. They include monomeric units that are covalently bonded to form larger structures. An example of a biopolymer is bacterial cellulose, which is produced by certain bacteria and consists of glucose units that form long, strong fibers. Other examples include chitin and the long-chain polymers found in mycelium produced by fungi. Biominerals are inorganic compounds produced by biological organisms, often serving structural or protective functions. For instance, calcium carbonate (CaCO3) produced by bacteria is a common example of a biomineral.
For each step of infiltration, the wood is incubated at optimal conditions for microbes' growth, typically at room temperature for 1-2 weeks. During the first period, the fungi grow and colonize the wood's internal structures, forming a mycelial network. This mycelial network, created by the fungal hyphae, serves as a scaffold that supports the subsequent infiltration and colonization by bacteria. During the second growing period, the bacteria are later introduced to fill the remaining spaces with bacterial cellulose, further reinforcing the wood's structure. The growth stops when the pours and interior channels are filled.
The wood is then post-processed. For example, the wood may be oven banked where the sample is dried with convection, such as in a forced air convention oven. Alternatively or in addition, the wood may be hot pressed where a sample is first hot pressed in a fixed thickness model (i.e. stainless steel), and then transferred to a convention oven for cooling curing.
Various fungal and bacterial may be used depending on the design goal for achieving compatibility with wood, carbon conversion efficiency, and ability to increase wood strength:
The fungi may include White-rot Fungi (Lignin degradation). White-rot fungal species are known for their ability to degrade lignin, a key component of wood, making it more porous and suitable for microbial colonization. This lignin reduction allows better integration of the mycelium, which acts as a fiber network inside the wood structure. The mycelium fibers enhance the mechanical properties of the wood, increasing tensile strength and toughness. The fungi also assist in reducing wood's natural carbon emissions by converting ambient carbon into fungal biomass.
For example, the fungi may include Ganoderma spp. Ganoderma lucidum and Ganoderma sessile: were tested and selected for their lignin degradation capacity and ability to create strong mycelial networks. Ganoderma species can penetrate deeply into wood structures, providing mechanical benefits while aiding in carbon fixation through fungal biomass production. Other possible white-rot fungi species for achieving lignin degradation include Phanerochaete chrysosporium, Trametes versicolor
The fungi may include Brown-rot Fungi (Cellulose preservers). For example, the fungi may include Gloeophyllum trabeum. While it targets hemicellulose and lignin, G. trabeum leaves the cellulose content relatively intact. This property may be beneficial in applications where maintaining cellulose is critical for strength while reducing lignin for microbial colonization.
Alternatively or in addition, the fungi may include Postia placenta: Another brown-rot fungus, P. placenta is known for its rapid wood degradation but selective targeting of non-cellulose components. It is a candidate for enhancing porosity and preparing wood for bacterial colonization without compromising overall structural strength.
The fungi may include other species suitable for mycelium fiber production. For example, the fungi may include Pleurotus spp. Commonly known as oyster mushrooms, these species form extensive mycelial networks, which can act as scaffolds in wood. These networks not only enhance the wood's mechanical properties but also provide a foundation for further bacterial colonization.
Alternatively or in addition, the fungi may include Schizophyllum commune: This fungus is known for its ability to form durable mycelial fibers that increase tensile strength. Its biotechnological applications, including enzyme production and biofiller potential, make it a versatile candidate for wood treatment.
The bacteria may include bacteria which facilitates Carbon capture and/or biomass production. Bacteria, specifically cellulose-producing strains such as Komagataeibacter xylinus, are introduced after fungal infiltration. They attach to the pre-existing mycelium fibers and produce bacterial cellulose, which acts as a biofiller within the wood's pores. This filling of pores with bacterial cellulose strengthens the wood and can contribute to calcite formation if carbon sources like CO2 are present. The bacteria's ability to attach and fill the spaces depends on the mycelial structure laid down by the fungi, allowing for synergistic enhancement.
For example, the bacteria may include Komagataeibacter spp. Komagataeibacter hansenii and Komagataeibacter xylinus were tested and selected. Known for high cellulose production, particularly in wood environments. Alternatively or in addition, the bacteria may include Pseudomonas spp. Known for its metabolic versatility, eg: P. putida can utilize various carbon sources, including ambient CO2, making it a potential candidate for biofiller production in wood.
A key to enhancing the mechanical properties of wood through microbial treatments lies in the synergistic combination of fungal mycelium and bacterial cellulose. These components work together to fill the wood's natural pores, increasing its strength and toughness.
In multiple trials with red oak, mechanical tests showed that the living wood samples achieved a tensile strength of 161.97 MPa compared to 55.91 MPa in untreated wood-representing a more than 200% increase in strength. The post-infiltration samples also showed a reduction in lignin content and an increase in cellulose content, further supporting the idea that these microbial treatments enhance the overall material properties of wood.
As illustrated in Table 1 and Table 2, the cellulose-to-lignin ratio in the treated wood was observed to shift from ˜1.7 to over 2.6, further contributing to the strength enhancement after post processing. This change is crucial because a higher cellulose content correlates with increased mechanical strength, while the reduction of lignin indicated for successful microbial inoculation.
The first peak in the DTG curve corresponds to the degradation of cellulose, while the second peak represents the degradation of lignin. In the treated wood, the shift toward a higher weight loss rate at the first peak indicates an increase in cellulose content, which is attributed to the bacterial cellulose produced during the treatment process.
The reduction in lignin content is evidenced by the shift to a lower temperature at the second peak, along with a broader zone between the first and second peaks. This confirms the successful degradation of lignin by the selected fungi, making the wood more porous and facilitating microbial colonization.
To clarify the use of and to hereby provide notice to the public, the phrases “at least one of <A>, <B>, . . . and <N>” or “at least one of <A>, <B>, . . . <N>, or combinations thereof” or “<A>, <B>, . . . and/or <N>” are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, . . . and N. In other words, the phrases mean any combination of one or more of the elements A, B, . . . or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed.
While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.
This application claims the benefit of U.S. Provisional Application No. 63/545,115 filed Oct. 20, 2023, the entirety of which is hereby incorporated by reference.
This invention was made with government support under DE-AR0001638 awarded by the Department of Energy. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63545115 | Oct 2023 | US |
