PRINTED FLOORS COULD LEAD TO LOW-WASTE BUILDINGS
A mixture of polylactic acid and wood flour is showing promise as a replacement for traditional steel and concrete, hinting at a greener future for modular construction.
Written by Nicole Imeson
Each floor cassette features structural bracing and cavities for plumbing and HVAC systems between two flat plates. Photo: Charissa King-O’Brien, ORNL
These cassettes are designed to have the same strength as a traditionally fabricated steel floor but are actually stiffer, providing an improved walking experience. Image: University of Maine/Assembly OSM
A RESEARCH TEAM AT OAK RIDGE NATIONAL LABORATORY (ORNL) has developed a bio-based composite that has been tested to be strong enough to replace carbon-intensive structural materials currently used in construction such as steel.
The result is 3D-printed floor assemblies or cassettes that can be used in modular building applications. They’re composed of polylactic acid (PLA), a thermoplastic monomer derived from renewable sources like corn starch and sugarcane, and wood flour, a refined form of sawdust from soft woods such as pine, spruce, and fir.
“We tested various natural, cellulose fibers, from nanoscale to millimeter-scale, experimenting with different formulations and fiber contents,” explained Halil Tekinalp, a senior R&D staff member with ORNL's SM2ART (Sustainable Materials & Manufacturing Alliance for Renewable Technologies) program. “Ultimately, softwood fibers provided consistency and reliability. Adjusting fiber size altered material properties and processing so we optimized for this source.”
The SM2ART team developed the bio-based floor cassette together with the University of Maine, Nature Works (a bio-based 3D-print manufacturer), Assembly OSM (a modular design-builder), and SHoP Architects. It was made possible by a public-private partnership to advance sustainable manufacturing with bio-based materials.
“Our goal is to create sustainable solutions using bio-based resources. Polylactic acid, the most common bio-based resin system, serves as our foundation. Collaborating with Nature Works, we refined this material for large-scale printing systems under development,” Tekinalp explained.
A unified component
The floor cassette design integrated structural bracing and cavities for plumbing and HVAC systems between two flat plates. Despite the cassette’s complexity, printing rather than assembling reduced the number of components down to one unified part.
A single cassette can be 3D printed in about 30 hours, resulting in a labor-savings of about 33 percent when compared to building a similar steel floor assembly by hand. Photo: Charissa King-O’Brien, ORNL
“We cut assemblies from 39 parts, 133 fasteners, and three materials to one and replaced concrete, metal, and plastics with a single bio-based material,” explained John Cerone, principal at SHoP Architects.
The team adjusted the cassette size based on application needs and 3D printer capabilities, with the current design measuring 7 feet 6 inches by 12 feet 10 inches. Multiple cassettes will form a single module’s floor. A large-scale 3D printer places the PLA/wood flour mixture in a precise, geometric shape, completing a single cassette in about 30 hours—equating to a labor savings of about 33 percent compared to making a steel floor assembly of the same size by hand, the researchers found.
Although the team focused on floor cassettes, the methodologies for incorporating 3D printing have the potential to be used for several other multi-part assemblies, such as ceiling cassettes, bathroom pod walls, and millwork elements.
“In traditional methods, design flexibility comes at a cost, driven by coordination and documentation. 3D printing provides seamless customization through direct-to-fabrication output from model-to-machine-to-product,” Tekinalp explained.
Typical modular building systems are built of a combination of hot-rolled and light gauge steel, which has reduced mass compared to a conventional concrete structure—the gold standard for the “feel” of walking in a high-rise building. A bio-based cassette introduces more mass and stiffness, approaching the feel of a concrete floor, while only placing material where structurally required. The resulting cassette meets the strength requirements of a floor in an assembly’s modular system. Early prototyping also revealed that users appreciated the floor cassette’s stiff feel, offering a comfortable walking experience more akin to concrete.
“Our goal is to create sustainable solutions using bio-based resources. Polylactic acid, the most common bio-based resin system, serves as our foundation. Collaborating with Nature Works, we refined this material for large-scale printing systems under development.”
—Halil Tekinalp, senior R&D staff member, SM2ART program, Oak Ridge National Laboratory Photo: Charissa King-O’Brien, ORNL
A large-scale 3D printer deposits the PLA/wood flour mixture into a precise, geometric shape. Image: Assembly OSM
Sustainability and efficiency
Fabricating the bio-based floor assemblies generates less carbon than traditional methods, while the use of wood products adds the benefit of carbon sequestration, enhancing the eco-friendly appeal. Additionally, building modules offsite in factories has the potential to reduce emissions by streamlining processes and cutting the energy demands of an active construction site, minimizing site disturbance, environmental impacts, and transportation-related emissions thanks to fewer jobsite visits.
The United States produces about three million tons of sawdust annually. Decades ago, industries recycled this byproduct into pulp, paper, or bio-energy facilities. As paper production declined, sawdust found fewer applications, with much of it ending up in landfills. But repurposing sawdust for modular housing creates products with reduced carbon footprints, often reaching carbon neutrality and sometimes nearing carbon negativity.
Meanwhile, despite its classification as plastic, PLA supports recycling and naturally decomposes, making it more sustainable. Its popularity in 3D printing stems from lower energy demands, reduced carbon emissions, and a lower melting point.
The PLA and wood flour mixture flows smoothly through 3D printers, maintaining its shape on the printing bed before curing into a durable structure. This efficiency and versatility makes PLA a top choice for sustainable manufacturing and rapid prototyping.
And as North America's housing crisis demands faster, more efficient solutions, modular construction has become increasingly popular as it streamlines the building process. Factories produce modular components while crews prepare sites, significantly cutting construction timelines. This parallel workflow enables faster delivery of homes and buildings.
“It’s time to embrace modern methods of building—using robotics, digitization, and precision manufacturing. Modular housing offers high-volume, high-quality production with minimal waste,” Ozcan explained. “This approach ensures control, efficiency, and sustainability in construction.”
Nicole Imeson is an engineer and writer in Calgary, Alta.
© 2025 The American Society of Mechanical Engineers. All rights reserved.