The authors cast a wide net. Searching the Scopus and Web of Science databases, they identified 519 records related to sorghum biomass in construction applications. After removing duplicates, 334 unique records remained, and these were then screened according to the PRISMA 2020 reporting guidelines, the international standard for systematic reviews. In the end, 41 studies met the eligibility criteria and formed the evidence base for the detailed analysis. On top of the systematic screening, the team used VOSviewer, a widely adopted scientometric software package, to map the intellectual landscape of the field, tracking which research themes dominate, how they cluster together, and how the focus of the literature has shifted over time.

The scientometric results tell a story of a field in transition. Research activity has been steadily increasing, and the emphasis has moved away from purely academic curiosity toward industrial biomass valorization, the umbrella term for converting plant residues into higher-value products. Three application areas dominate the construction-related literature: polymer composites, in which plant fibers reinforce plastic matrices; wood–plastic composites, a hybrid class of materials that blends lignocellulosic filler with thermoplastics; and lignocellulosic boards, panel-type products made from pressed plant matter. This clustering suggests that sorghum is being evaluated most seriously as a substitute for wood fibers and synthetic fillers, materials whose supply chains face mounting environmental and economic pressure.

One of the review’s clearest findings is that virtually every fraction of the sorghum plant has been tested in building materials. The studies included in the review incorporated sorghum stalk, stem, straw, bagasse, the fibrous residue left after juice extraction, and husk into three broad families of materials: polymeric matrices, wood-based products, and mineral-based construction materials. In polymer systems, sorghum fibers have been compounded with matrices ranging from polypropylene and polyethylene, both high- and low-density, to polylactic acid, a biodegradable bioplastic, as well as polyvinyl chloride and even acrylonitrile styrene acrylate. In board products, the fibers have been bonded with conventional adhesives such as urea-formaldehyde and phenol-formaldehyde resins. In mineral systems, sorghum husk ash has been explored as a supplementary material, connecting the crop to the cement and concrete sector.

Performance, however, is far from automatic. The review found that the mechanical and physical properties of sorghum-based materials depend strongly on five interacting factors: which fraction of the plant is used, how much fiber is loaded into the matrix, how compatible the fiber is with the surrounding material, the conditions under which the composite is processed, and whether the fiber surface has been chemically or biologically treated. Fiber loading in particular presents a classic trade-off: increasing the share of renewable content can improve stiffness and sustainability credentials, but beyond an optimum it undermines dispersion and interfacial bonding, weakening the composite. Processing temperature and time matter too, since lignocellulosic fibers can degrade at the high temperatures used to melt thermoplastics.

Surface treatment emerged as one of the most powerful levers for improving performance. The review reports that alkali treatment with sodium hydroxide, silane coupling agents, enzymatic treatments, and organic acids such as citric acid generally improved the bonding between fiber and matrix, which translated into better mechanical performance and improved resistance to moisture. The chemistry is intuitive: natural fibers are hydrophilic, covered in waxes and hemicellulose that resist adhesion to hydrophobic polymer matrices. Alkali treatment strips away these weak surface layers and roughens the fiber, while silanes act as molecular bridges between the organic fiber and the synthetic matrix. Citric acid, a benign food-grade molecule, can esterify with both cellulose hydroxyl groups and matrix functional groups, offering a greener route to the same end. Analytical tools such as Fourier-transform infrared spectroscopy and scanning electron microscopy were routinely used in the underlying studies to confirm these chemical and morphological changes at the fiber-matrix interface.

Despite these successes, the authors are candid about the barriers. Moisture sensitivity remains the most persistent weakness: sorghum fibers, like most lignocellulosic materials, absorb water, which can cause swelling, dimensional instability, and degradation of mechanical properties over time. Feedstock variability compounds the problem, because the composition of sorghum biomass changes with variety, growing conditions, and harvest practice, making consistent product quality difficult to guarantee. The review also identified a shortage of durability data, meaning most studies report properties of freshly manufactured materials rather than aged, weathered, or long-serving ones. Inconsistent testing methods across studies, drawing on different standards such as European norms and Japanese Industrial Standards, further complicate comparisons and slow the accumulation of reliable design data.

The economic and environmental accounting is similarly incomplete. The authors found that comprehensive life-cycle assessments, which quantify environmental impacts from raw material to end of life, and techno-economic assessments, which evaluate whether a process can be profitable at scale, remain limited in the sorghum construction literature. Without these integrated evaluations, it is difficult to verify that sorghum-based panels or composites genuinely outperform conventional alternatives across their full life cycle, or to identify which conversion routes merit industrial investment. This gap matters for the circular bioeconomy ambitions that motivate much of the field, since a material that is renewable at the source may still carry hidden burdens in processing, transport, or adhesive chemistry.

Looking forward, the review lays out a clear research agenda. The authors call for standardized durability testing protocols so that results from different laboratories can be meaningfully compared, long-term field validation to see how sorghum-based materials perform in actual buildings over years rather than weeks, harmonized testing methods across the international research community, and integrated environmental and economic assessment embedded from the earliest stages of material development. They also highlight opportunities in matrix compatibility engineering and in matching specific sorghum fractions to the applications where they perform best, for example husk ash in mineral systems and long stalk fibers in structural composites.

The broader significance of the study lies in its method as much as its findings. By pairing scientometric mapping with PRISMA-guided systematic review, Tufa and Pásztory provide both a bird’s-eye view of where the field has been and a granular synthesis of what 41 carefully selected studies actually demonstrated. Their overall verdict is cautiously optimistic: sorghum biomass shows promising potential as a renewable feedstock for sustainable, low-carbon construction materials, but realizing that potential will require the field to grow beyond small-scale laboratory specimens. If researchers and industry can close the durability, standardization, and assessment gaps identified in the review, the humble sorghum stalk, today a residue of grain production, could find itself pressed into panels, extruded into composite decking, and blended into concrete in the buildings of a decarbonizing world.

Subject of Research: Utilization of sorghum biomass as a renewable feedstock in sustainable construction materials

Article Title: An integrated Scientometric and systematic review of sorghum biomass utilization in sustainable construction materials

Article References: Tufa, M., & Pásztory, Z. (2026). An integrated Scientometric and systematic review of sorghum biomass utilization in sustainable construction materials. Discover Sustainability. https://doi.org/10.1007/s43621-026-05016-5

Image Credits: AI Generated

DOI: 10.1007/s43621-026-05016-5

Keywords: sorghum biomass, sustainable construction, agricultural residues, bio-based composites, wood-plastic composites, fiber surface treatment, life-cycle assessment, circular bioeconomy, lignocellulosic boards, scientometric analysis, moisture resistance, polymer composites

The raw materials could hardly be more mundane. Post-consumer PVC pipes were collected from a construction site at the university’s Department of Chemical Engineering in Nakhon Nayok, washed, dried at 30 °C for 48 hours, and ground into roughly one-centimeter particles. The cling film waste, supplied by a local retailer, contained 30 weight percent of the plasticizer DINCH, a detail that proved crucial: in earlier work by the same group, blending flexible and rigid PVC at a 50:50 ratio raised elongation at break from 25.3 percent for neat recycled rigid PVC to 206 percent, while lowering the glass transition temperature by 34.9 °C. That flexibility is exactly what a brittle recycled matrix needs. Teak sawdust from Ayutthaya was oven-dried, ground, and sieved to an average particle size of 197 micrometers, with a bulk density of 0.27 g/cm³ and moisture content of just 1.46 percent.

To create the cellular structure, the team turned to azodicarbonamide, a widely used chemical blowing agent known as AC. Thermogravimetric analysis showed that AC decomposes sharply between 190 and 200 °C in a single exothermic step, releasing roughly 240 milliliters of gas per gram, composed mainly of nitrogen (65 percent), carbon monoxide (24 percent), carbon dioxide (5 percent) and ammonia (5 percent). That decomposition window sits almost perfectly inside the molding temperature of 195 ± 5 °C used in the study, and well below the composite’s major degradation stage, which occurs between 314.5 and 318.0 °C. This thermal matching meant the blowing agent could generate gas efficiently without triggering significant thermal damage to the PVC matrix or the wood filler, a prerequisite for producing sound foam.

Processing followed a melt compounding and closed-mold foaming route. The PVC pipe particles, cling film and sawdust were blended on a two-roll mill at 165–180 °C, then compression molded. For the foamed versions, AC was added at loadings of 0.5, 1, 3 and 5 weight percent, and the mold was preheated at 120 °C for five minutes before ramping to the foaming temperature. A tightly controlled ten-minute cycle—three minutes for filling and compression, five for foam expansion and cell growth, and two for cooling—kept expansion in check and ensured dimensional uniformity. The closed mold restricted runaway expansion, producing specimens with a characteristic skin–core structure: a denser surface layer surrounding a porous interior.

The foaming results revealed a classic optimum. Density fell steadily as AC content rose, reaching its lowest value at 3 weight percent, where gas generation, melt viscosity and cell stabilization appeared perfectly balanced. Cell density, the number of cells per unit volume, peaked at the same loading, while average cell size shrank from 40.38 micrometers at 0.5 percent AC to just 24.16 micrometers at 3 percent, accompanied by the narrowest, most uniform cell size distribution. Scanning electron microscopy of cryo-fractured, gold-coated specimens showed no surface openings up to 3 percent AC, indicating gas was effectively retained. At 5 percent, however, excessive gas evolution ruptured cells and opened escape pathways, causing cell coalescence, surface defects and a slight rebound in density—a vivid demonstration that more blowing agent is not always better.

Mechanically, the story was one of trade-offs and clever accounting. The unfoamed composite, with a flexural modulus of 2.71 GPa and flexural strength of 54.1 MPa, predictably outperformed the foams in absolute terms, since voids act as stress concentrators and reduce the load-bearing cross-section. Flexural properties fell to their lowest values at 3 percent AC (1.85 GPa and 32.90 MPa), and notched Izod impact strength dropped from 20.82 J/m for the unfoamed material to 13.33 J/m. But when properties were normalized by density, the picture reversed. Specific tensile modulus rose from 1.51 to 1.57 GPa·cm³/g, specific flexural modulus climbed from 2.04 to 2.23 GPa·cm³/g at 3 percent AC, and specific impact strength reached its maximum of 18.05 J·cm³/(m·g) at 5 percent AC. In stiffness- and strength-to-weight terms, the foams matched or beat the solid material—an essential criterion for lightweight construction.

Dynamic mechanical analysis added an unexpected bonus: superior vibration damping. All foamed composites showed tan δ values between 0.61 and 0.64, comfortably above the 0.3 threshold generally considered effective damping and approaching the 0.5 level classified as excellent, whereas the unfoamed composite managed only 0.43. The cellular architecture dissipates mechanical energy through cell-wall bending, friction at cell junctions, interfacial sliding and heterogeneous strain within the porous structure. The 3 percent AC formulation, with its maximum cell density and minimum density, delivered the greatest damping capacity. Glass transition temperatures of the foams, determined from tan δ peaks, ranged from 76.9 to 78.6 °C, slightly above the unfoamed material’s 70.8 °C, suggesting that cellular constraints subtly restrict segmental mobility of the PVC chains.

Thermal and moisture behavior rounded out the assessment. Differential scanning calorimetry confirmed the amorphous nature of the PVC matrix, with no melting peak and no change in transition pattern upon foaming, while the cling film’s plasticizer evidently acted as an internal plasticizing phase that eased foam formation. Thermogravimetry showed initial degradation temperatures declined modestly with AC content, from 240.2 °C for the unfoamed composite to 218.4 °C at 5 percent, but the major degradation temperatures remained essentially unchanged, and char residues of 26.5 to 27.9 percent matched the unfoamed value of 26.2 percent. Water absorption rose with the development of the cellular structure, peaking at 3 percent AC, yet thickness swelling after 60 days of immersion stayed between 3.88 and 7.07 percent—far below the 16.8 to 19.8 percent typical of particleboard and medium-density fiberboard after just 24 hours, thanks to the continuous polymer barrier around the wood particles.

The authors propose a three-stage deformation mechanism to explain how the foams fail under tension: an initial elastic stage in which spherical cells elongate into ellipses, a second stage of microcrack initiation at cell-wall junctions and wood–matrix interfaces, and a final stage of interfacial debonding, crack coalescence and cell collapse leading to fracture. Interestingly, at 5 percent AC, tensile and flexural properties partially recovered, apparently because over-foaming under the constrained mold caused localized densification and thicker cell walls that carried disproportionate load. The team is careful to note that a full life-cycle assessment, including recyclability and end-of-life management, remains future work. Still, the demonstration stands: three waste streams that would otherwise burden landfills can be merged into a single, foamed, dimensionally stable building material whose best formulation—3 weight percent AC—balances low density, fine uniform cells, strong density-normalized mechanics, excellent damping and good moisture resistance. It is a compelling case that the future of sustainable construction may be hiding in the demolition skip and the kitchen drawer.

Subject of Research: Upcycling mixed PVC waste streams and wood sawdust into foamed wood–plastic composites

Article Title: Toward sustainable wood–plastic composite foams fabricated via ternary blending of upcycled rigid poly(vinyl chloride) pipe, waste cling film and wood sawdust

Article References: Sukkaneewat, B., Sanetuntikul, J., Naknaen, P., Jansri, E., & Petchwattana, N. (2026). Toward sustainable wood–plastic composite foams fabricated via ternary blending of upcycled rigid poly(vinyl chloride) pipe, waste cling film and wood sawdust. Cleaner Engineering and Technology, 35, Article 101298. https://doi.org/10.1016/j.clet.2026.101298

Image Credits: AI Generated

DOI: 10.1016/j.clet.2026.101298

Keywords: wood-plastic composites, recycled PVC, cling film waste, polymer foams, chemical blowing agent, azodicarbonamide, circular economy, upcycling, wood sawdust, plasticizers, damping, sustainable building materials