BUFFALO, N.Y. — Traditional forms of thermal insulation used to regulate temperatures in homes and commercials buildings are often energy-intensive to manufacture, resulting in significant greenhouse gas emissions.
An engineering professor at the University at Buffalo is pioneering an organic alternative that is much more sustainable: wheat straw.
“Unlike fossil fuels, which take millions of years to form, biomass materials, such as wheat straw, can be harvested and replanted regularly,” said Chi Zhou, PhD, associate professor and director of graduate studies in the Department of Industrial and Systems Engineering in UB’s School of Engineering and Applied Sciences. “This makes for an eco-friendlier insulation material.”
Zhou and a small research team began studying how to 3D print wheat straw-based insulation in 2022, with financial support from the Advanced Research Projects Agency-Energy (ARPA-E) within the U.S. Department of Energy.
Wheat straw is a waste product that is frequently burned after the wheat grain is harvested. As far as thermal insulation goes, Zhou and his team discovered that wheat straw insulates well, holds up under pressure, and is more flame retardant than other organic materials.
“The superior properties come from wheat straw’s unique structure, its natural fibrous and porous composition, which enhances thermal insulation,” Zhou explained.
The team processes the straw into fibers, which are then cross-linked via hydrogen bonding between an organic binder and hydroxyl groups in the straw’s cellulose. They formulate the straw fibers into 3D printable ink to be used in thermal insulation structures.
This method results in high mechanical strength and long-term durability, Zhou said.
An article detailing their work was published in the May print edition of the Journal of Manufacturing Science and Engineering. This paper marks the first work of 3D printing of wheat straw fibers for thermal insulation structures, Zhou added.
The other researchers are Jason Armstrong, PhD, professor of teaching and director of undergraduate studies in mechanical engineering at UB; Zipeng Guo, PhD, assistant professor of industrial and systems engineering at the Rochester Institute of Technology, who earned his doctorate at UB in 2023; Licheng Liang, a doctoral student in industrial engineering at UB; Aditya Chivate, PhD, assistant professor of industrial and manufacturing engineering at Cal Poly State University who recently earned his doctorate at UB; and Shenqiang Ren, PhD, professor of materials science and engineering at the University of Maryland, College Park.
The group is presenting the paper during the American Society of Mechanical Engineers (ASME)’s Manufacturing Science and Engineering Conference June 23-27 at Clemson University in Greenville, S.C.
Benefits of organic materials
Thermal insulation materials can generally be slotted into four main categories: inorganic materials, organic materials, composite materials, and advanced materials. Among them, inorganic materials such as glass wool and rock wool dominate the market due to their low thermal conductivity and cost-effectiveness. This makes them a preferred choice for many building applications. However, the extraction and manufacturing of these materials rely heavily on fossil fuels, Zhou said.
Wheat straw, on the other hand, is a natural fiber that is renewable and biodegradable, which offers significant environmental advantages.
The process involved pulping the fibers, which come from agricultural residues and wastes, into a slurry and drying them in molds. This creates a thick ink that can be used in a 3D printer to make the straw into insulation shapes.
“Their unique properties, such as low thermal conductivity and low density, make them valuable for a wide range of applications, especially in building insulation,” he said.
Another advantage is that wheat straw allows for custom-made parts such as kitchenware, footwear, furniture and decorative items. Because the material is sourced from agricultural waste, factories can be located near farms to reduce transportation emissions and support local economies.
Overcoming challenges
One obstacle to transforming agricultural waste into big thermal insulation panels is that standard 3D printing methods are very slow and small scale. The typical printer uses a round nozzle and prints one line at a time.
Zhou explained that the team was able to redesign the printer with a slot-die nozzle, which spreads material out more evenly and quickly over a wide area. They also used several nozzles at the same time and designed a special system to make sure the material flows evenly to all the nozzles, so the quality stays consistent.
The team developed a lab-scale, roll-to-roll system in UB’s Bell Hall to make prototype thermal insulation panels. According to Zhou, the methods and insights from this research can be readily scaled up for industrial manufacturing.
In the next phase, the team is hoping to collaborate with an industrial partner to perform tech-to-market analysis and translate the lab-scale success to real-world applications.
“If wheat straw were to be widely adopted,” Zhou said, “it not only would reduce greenhouse gas emissions, but it would also reduce agricultural waste and provide an environmentally friendly and affordable source of insulation for homes and commercial buildings.”
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