The study, led by Andrea Feriancová of Alexander Dubček University of Trenčín together with colleagues at the Slovak Academy of Sciences and Comenius University in Bratislava, focused on the paper component of post-consumer Tetra Pak cartons. Rather than subjecting the waste to aggressive chemical pretreatments, which are common in cellulose extraction but carry their own environmental and economic costs, the researchers used a simple mechanical milling method to obtain a cellulose-rich paper pulp, which they designated PpCf. This choice matters. Mechanical processing avoids the solvents, acids, and energy-intensive steps that often undermine the environmental case for recycled fillers, and it produces a material that can be dropped directly into conventional rubber compounding workflows without retooling the factory floor.

Before the pulp could be trusted as a filler, the team needed to know exactly what it contained. Fourier transform infrared spectroscopy confirmed cellulose as the dominant component, with the characteristic C–O–C stretching bands appearing at 1205 and 1025 inverse centimetres, the spectroscopic fingerprints of the glycosidic linkages that hold the cellulose backbone together. Thermogravimetric analysis paired with differential scanning calorimetry revealed a four-step thermal degradation pattern, a profile consistent with the sequential loss of moisture, the breakdown of hemicellulose-like fractions, cellulose decomposition, and residual char formation. Energy-dispersive X-ray spectroscopy of the ash detected trace amounts of aluminium, calcium, and silicon, chemical echoes of the carton’s mineral coatings and the aluminium barrier layer, present only in quantities small enough not to disrupt the rubber matrix.

The central experiment was a hybrid filler strategy. The researchers incorporated the PpCf pulp at a loading of five parts per hundred rubber, the standard unit of measure in compounding known as phr, and used it to partially substitute carbon black in combination with kaolin, a soft aluminosilicate clay that has itself attracted attention as a more sustainable rubber filler. Three formulations were prepared and compared: a PpCf-only compound, and two hybrid compounds designated PpCf-5/3 and PpCf-5/10, in which the cellulose pulp was paired with different kaolin loadings. The logic of hybridization is well established in rubber science, since different filler geometries and surface chemistries can complement one another, with plate-like clays restricting polymer chain mobility while fibrous or irregular cellulosic particles contribute their own reinforcing network.

The processing results were among the most striking findings. Incorporating the waste-derived pulp improved the processability of the rubber compounds, reducing the mixing torque by more than twenty percent for the PpCf-5/10 formulation. In practical terms, lower torque means less energy consumed during mixing, less heat buildup in the compound, and easier flow through industrial equipment. Even more dramatic was the effect on curing: the optimum cure time dropped by more than thirty-four percent for the PpCf-5/3 formulation. The researchers attribute this acceleration to improved dispersion of the vulcanization agents, the sulfur-based chemicals that create the crosslinks giving rubber its elasticity. When those agents are distributed more uniformly, the crosslinking network forms faster and more evenly, a benefit that translates directly into shorter cycle times and lower energy demand on the production line.

Mechanical performance told a more nuanced story. Tensile strength decreased relative to the reference compounds, by 9.9 percent for PpCf-5, 7.1 percent for PpCf-5/3, and 17.9 percent for PpCf-5/10. This is the expected trade-off when a bio-filler replaces carbon black, whose finely tuned particle structure is exceptionally effective at load transfer in elastomers. Yet the losses were moderate, and one property moved decisively in the right direction: elongation at break increased from 257.6 percent to 311.0 percent for the PpCf-5/10 composite. Greater extensibility means the material can deform further before failing, a valuable attribute for applications where flexibility and toughness matter more than peak strength, such as seals, hoses, mats, and various non-tire rubber goods.

Dynamic mechanical analysis added another layer of insight. The composites showed increased damping at low temperatures, meaning they absorbed more mechanical energy in cold conditions, while the damping factor, expressed as tan delta, was reduced at sixty degrees Celsius, a temperature regime relevant to rolling resistance and heat generation in service. Lower damping at elevated temperature generally indicates less internal friction and therefore less heat accumulation, which can extend the service life of rubber components. These shifts in viscoelastic behavior reflect how the cellulose-kaolin hybrid alters the mobility of polymer chains near the filler surfaces, a microstructural effect that conventional bulk measurements can only hint at.

To probe that microstructure directly, the team turned to a technique rarely seen in rubber compounding studies: positron annihilation lifetime spectroscopy, or PALS. The method exploits the fact that positrons injected into a polymer form bound states with electrons, and the lifetimes of these positronium species correlate with the size and concentration of nanoscale free-volume holes in the material. The PALS measurements demonstrated a pronounced sensitivity to filler geometry, and the PpCf-5/3 formulation exhibited the most significant microstructural rearrangements, including a reduction in free volume after relaxation. In plain terms, the hybrid filler at that particular ratio packed the polymer network more tightly, restricting the voids between chains. This is exactly the kind of nanoscale evidence needed to connect filler architecture to macroscopic performance, and it validates PALS as a sensitive diagnostic tool for designing waste-derived filler systems.

The broader significance of the work lies in what it suggests about the circular economy of everyday packaging. Tetra Pak cartons have been the subject of numerous recycling approaches, from pyrolysis and hydrothermal treatment to solvent separation of the aluminium-plastic layers, but most of these routes are energy-intensive or yield low-value outputs. Converting the paper fraction into a functional rubber filler by simple milling sidesteps those difficulties and targets a market, carbon black substitution, with enormous volume. Carbon black is produced from fossil feedstocks at high temperatures, and its manufacture carries a substantial carbon footprint; every kilogram of it displaced by recovered cellulose represents both avoided emissions and diverted waste. The Slovak team’s results show that a five-phr substitution is achievable while maintaining satisfactory composite performance, with the added bonuses of faster curing and easier processing.

Challenges remain before such materials reach industrial adoption. The modest reductions in tensile strength will need to be weighed against application requirements, and questions of long-term durability, aging behavior, and batch-to-batch consistency of post-consumer waste will demand further study. Surface modification of the cellulose, a strategy the same research group has explored with other fillers, could improve interfacial adhesion and recover some of the lost strength. Still, the study demonstrates a credible and technically grounded pathway: a waste stream that is currently an economic liability can become a partial answer to one of the rubber industry’s most persistent sustainability problems. As regulators tighten extended producer responsibility rules and manufacturers search for lower-carbon inputs, the humble drink carton may find its most valuable afterlife not as packaging, but as the hidden skeleton inside the rubber products of tomorrow.

Subject of Research: Recycling Tetra Pak waste cellulose as a hybrid bio-filler for natural rubber composites

Article Title: Hybrid cellulose–kaolin reinforcement of sustainable natural rubber: a route for Tetra Pak waste valorisation

Article References: Feriancová, A., Švajdlenková, H., Šauša, O., Šulcová, J., Ďurišová, S., & Janík, R. (2026). Hybrid cellulose–kaolin reinforcement of sustainable natural rubber: a route for Tetra Pak waste valorisation. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13917-z

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13917-z

Keywords: Tetra Pak recycling, natural rubber, cellulose filler, carbon black substitution, kaolin, waste valorisation, rubber composites, vulcanization, positron annihilation lifetime spectroscopy, dynamic mechanical analysis, circular economy, sustainable materials

The research team systematically examined the scientific literature on the reuse and soil application of medicinal and aromatic plant residues, using the Web of Science database to capture studies reporting both the types of residues applied to soil and the resulting soil-related effects. After screening out studies that dealt with cultivation practices or with essential oils as main products rather than by-products, 39 studies were ultimately selected for detailed analysis. The review reveals a striking pattern: virtually no research existed on this topic before 2004, but interest has surged dramatically over the last five years, reflecting a broader shift toward circular economy thinking and waste valorisation across the agricultural sciences.

The bibliometric analysis showed that the People’s Republic of China contributed the largest number of publications on this topic, which aligns with the country’s well-established history of cultivating and utilizing medicinal and aromatic plants both in traditional medicine and modern applications. Considerable research interest was also evident in Mediterranean countries, a region characterized by high biodiversity of these plants and a long-standing tradition of using them for medicinal, culinary, and aromatic purposes. The review found that the plant families Asteraceae, Fabaceae, and Lamiaceae have received the greatest scientific attention, with European studies focusing mainly on Lamiaceae species while Asian investigations cover a wider range of families. Genera Mentha and Salvia attract high research interest worldwide.

The review identified four main categories of medicinal and aromatic plant waste used as soil amendments: fresh biomass, biochar, compost, and solid distillation residues. Each category carries distinct technical characteristics and produces different effects on soil properties and plant performance. The fresh biomass category involves incorporating aerial plant parts still rich in essential oils directly into soil, while biochar is produced through thermochemical conversion processes such as pyrolysis, gasification, and hydrothermal carbonization. Composting relies on microbial decomposition of organic waste into a stabilized material, and solid distillation residues are the lignocellulosic by-products left after essential oil extraction.

The effects of fresh biomass incorporation are particularly fascinating from a technical standpoint. Studies on spearmint, peppermint, Greek sage, and oregano showed that incorporating whole aboveground biomass into soil at rates of 2, 4, and 8 percent by weight produced measurable improvements in soil carbon-to-nitrogen ratio, boosted shoot length and plant dry weight in tomato seedlings, enhanced photosynthetic yield and chlorophyll content, and contained infections by Fusarium and Verticillium species. Spearmint application provided the best effects, especially at 4 percent by weight. However, rosemary exhibited negative impacts on plant growth, likely induced by compounds present in its essential oil, suggesting that microbe-mediated transformation of essential oil compounds appears necessary to achieve positive outcomes.

Perhaps the most commercially significant finding involves the exploitation of allelopathic metabolites, substances that influence the growth and development of neighbouring organisms and could help reduce reliance on synthetic herbicides. Apple mint residues showed adverse effects on germination and growth of dicotyledonous weed species such as Amaranthus retroflexus and Solanum nigrum, achieving nearly 100 percent inhibition rates, while also reducing monocotyledonous weeds like Digitaria sanguinalis by more than 95 percent and simultaneously increasing maize yield. Powdered leaf residues of Peganum harmala displayed potent herbicidal activity on seedling growth of Avena fatua and Convolvulus arvensis, alongside increases in soil electrical conductivity and available nitrogen, phosphorus, potassium, manganese, and copper content.

Pathogen suppression represents another critical dimension of this research. A pot experiment using dry biomass of Datura metel demonstrated that doses of soil amendment superior to 2 percent by weight completely controlled Southern blight of bell pepper caused by Sclerotium rolfsii. A mixed powder of Astragalus mongholicus roots, Epimedium acuminatum leaves, Atractylodes macrocephala rhizome, Cinnamomum verum bark, and Cnidium monnieri fruits reduced the disease index of ginseng root rot by 54.5 percent. Combined application of Xanthium strumarium biomass with two biofertilizers was found effective in increasing potato tuber yield and managing black scurf disease by increasing the activity of defence-related enzymes.

The composting pathway has received enormous attention, particularly regarding Chinese Medicinal Herbal Residue, the solid by-product generated after extraction of active pharmaceutical ingredients from medicinal plant materials. Key components of this herbal waste include carbohydrates, proteins, cellulose, polysaccharides, lignin, and nutrients essential for plant growth such as nitrogen, phosphorus, and potassium. Application of Chinese Medicinal Herbal Residue compost significantly increased cation exchange capacity, soil organic matter, total nitrogen, available potassium and phosphorus, and carbon-to-nitrogen and nitrogen-to-phosphorus ratios, indicating an overall improvement in soil fertility parameters. In trials with Chinese cabbage, maize, and tomato, plant growth parameters such as seedling height, stem diameter, root length, and aboveground and belowground biomass were positively affected, with 5 percent application rate increasing plant biomass production by 56 percent in tomato and 34 percent in cabbage.

Biochar derived from medicinal and aromatic plant distillation waste has also shown remarkable potential. Studies on biochar from Mentha arvensis distillation waste demonstrated that cation exchange capacity, pH, soil organic carbon, and nutrient availability increased with higher biochar application rates, while soil biological properties such as microbial biomass carbon and dehydrogenase activity improved in soil amended with both biochar and mint distillation waste. Researchers enriched biochar made from lemongrass distillation biomass with rock phosphate and waste mica minerals, significantly improving surface properties and nutrient content and showing positive impacts on Cassia angustifolia growth that were even more effective than conventional fertilizers in a highly weathered soil.

The review concludes that medicinal and aromatic plant residual biomasses represent valuable soil amendments contributing to sustainable waste management and circular economy principles in the industry. However, the authors caution that further research is required to find a proper balance between herbicide and biostimulant effects and to optimize the use of these residues in soil, especially at field scale. Most experiments reported in the review were mainly conducted in pots, and future studies need to be carried out at field scale, assessing long-term effects on soil ecosystems and evaluating safety and efficacy across diverse cropping systems. The risk of accumulating contaminants from immature compost and causing soil salinization should also be taken into account, alongside the need to evaluate economic sustainability and develop practical guidelines for farmers to facilitate widespread adoption of these promising soil management practices.

Subject of Research: Agricultural Science

Article Title: Valorisation of medicinal and aromatic plant residues for soil amendment purposes

Article References: Berruto, F., Nebbia, M., Ghignone, S., Lumini, E., Scariot, V., & Bianciotto, V. (2026). Valorisation of medicinal and aromatic plant residues for soil amendment purposes. Discover Soil, 3(1), Article 188. https://doi.org/10.1007/s44378-026-00348-0

Image Credits: AI Generated

DOI: 10.1007/s44378-026-00348-0

Keywords: medicinal plants, aromatic plants, soil amendments, circular economy, biochar, compost, allelopathy, sustainable agriculture, waste valorisation, plant pathogens, Valorisation, medicinal

Mill scale is generated at roughly 1 to 3 percent of the mass of steel rolled, equivalent to about 22 to 40 kilograms per tonne. Applied to global crude steel production of 1,882.6 million tonnes in 2024, that implies something on the order of 19 to 56 million tonnes per year, consistent with two independent published estimates of approximately 37 and 39 million tonnes. Because concrete is produced at an even larger scale, even marginal substitutions of natural sand with mill scale could be consequential — and the material has attracted interest on three distinct grounds: as a partial replacement for fine aggregate, as a dense additive for heavyweight and radiation-shielding concretes, and, more speculatively, as a source of limited chemical reactivity in alkaline pore solution.

One of the review’s most striking technical contributions is resolving a confusion that has plagued the construction-materials literature for years. Studies reporting mill scale as “93 to 99 percent Fe2O3” and studies reporting it as roughly half wüstite (FeO) and half magnetite (Fe3O4) are not in conflict at all — they are simply using different measurement conventions. X-ray fluorescence returns elemental concentrations that are conventionally normalised and reported as oxides, with all iron reported arithmetically as Fe2O3 regardless of its actual oxidation state. X-ray diffraction with quantitative phase analysis, by contrast, resolves the actual crystalline phases present. The single quantitative phase analysis of as-received mill scale the authors located reports FeO at 47.81 percent, Fe3O4 at 51.34 percent and metallic Fe at 0.85 percent — magnetite marginally exceeding wüstite, with hematite not present as a major phase.

The review also documents that mill scale is a genuinely variable material with identifiable causes of variability. Steel grade and alloy content govern the trace-metal inventory; the process route — basic oxygen furnace versus electric arc furnace, hot rolling versus wire drawing — sets the thermal and mechanical history; coiling temperature and cooling rate control the eutectoid decomposition of wüstite below approximately 570 degrees Celsius and therefore the final phase assemblage; descaling method and water contact determine particle size distribution and surface hydroxide formation; and handling, storage and oil contamination introduce rolling oils and greases that can impair the paste-particle bond. Stockpile weathering causes progressive oxidation and hydration, arguing for per-batch characterisation.

When the authors mapped what the primary literature actually reports about mechanical, durability and environmental performance, they found the reported optimum replacement level is not consistent across the corpus. Eighteen primary studies met the eligibility criteria, spanning mortars, conventional and high-performance concretes, self-compacting concrete, geopolymer concrete and precast paving blocks at replacement levels from 5 to 100 percent. Four independent studies converge on approximately 15 percent by mass or volume as a strength optimum in mortar and self-compacting concrete — the strongest single pattern in the corpus. But several conventional concrete studies report optima at 50 to 60 percent, and at least two report monotonic strength loss. The review treats this discrepancy as a genuine open question, most likely reflecting the interaction between the fineness of the mill scale and the gradation of the sand it replaces.

Workability decreases with increasing mill-scale content, consistently across studies — the most reliably reported effect. One study quantifies a 74 percent slump reduction at 60 percent replacement. The mechanism combines the flake morphology and rough surface texture of mill scale, which increase internal friction, with surface hydroxide layers and any entrained rolling oil, which alter water demand and the paste-particle interface. Because workability was managed differently across studies — some held water constant, some held slump constant, some added superplasticiser — the strength results across the corpus are not comparable without accounting for this, which the review treats as a first-order confounder.

Durability evidence is thin and unevenly distributed. Post-fire residual performance, thermal behaviour and acid resistance are reported as favourable by more than one group. Chloride evidence exists but rests substantially on the rapid chloride permeability test, whose interpretation is questionable for a matrix containing an electrically conductive, iron-bearing phase — the test measures total charge passed, which is a function of pore-solution conductivity as well as pore structure. Carbonation depth and freeze-thaw performance are unreported in the entire corpus. Most consequentially, no electrochemical study of reinforcement corrosion in mill-scale concrete was located anywhere — an iron-bearing admixture in reinforced concrete raises a corrosion question that has not been asked, let alone answered, and the review places it first among research priorities.

Quantitative pooling across the literature is currently obstructed by six specific and documentable deficiencies: heterogeneous replacement bases (mass versus volume; aggregate versus binder), inconsistent curing ages and outcome definitions, uncharacterised variation in mill-scale provenance, near-universal absence of dispersion statistics and replicate counts, confounding of mill scale with co-additives such as graphite nano/microplatelets or steel fibres, and probable non-independence among studies from single research groups. Of the eighteen studies, only two companion papers from one campaign report replicate counts, error bars and inferential statistics. A random-effects meta-analysis cannot be estimated from a corpus in which the variance components are unrecoverable.

To make future synthesis possible, the review specifies a pre-registered meta-analytic protocol — effect-size definition using Hedges’ g or raw mean difference, dose-response meta-regression, random-effects estimation with restricted maximum likelihood, heterogeneity quantification, pre-specified subgroup analysis, distributional diagnostics, sensitivity analysis and small-study-effect assessment — to be executed once the reporting deficiencies are remedied. It also proposes a minimum reporting standard for primary studies, requiring plant and process provenance, composition with the measurement technique named and the phase versus elemental basis stated explicitly, full particle size distribution, specific gravity, water absorption, chloride content, oil and grease content, complete mix proportions, and — for every outcome at every age — mean, standard deviation and number of specimens. Not mean alone. Not a bar chart without error bars.

What the evidence currently supports is cautious use of mill scale in non-structural and specialty applications. Four independent studies report shielding benefits attributable to mill scale’s density and iron content, including a linear attenuation coefficient of 0.085 per centimetre in a geopolymer composite and electromagnetic-interference shielding of 26.37 decibels at 11.82 gigahertz at 30 percent replacement in mortar. Notably, the shielding optimum lies at high replacement while the mechanical optimum in mortar lies near 15 percent — the two do not coincide, so a shielding mix must be designed against a strength requirement rather than assumed adequate. Radiation and EMI shielding, heavyweight and ballast concretes, mortars and renders at moderate replacement, and non-structural elements including paving blocks are the most defensible near-term applications. Structural reinforced concrete is not supported at any replacement level. The economics favour ready-mixed or precast operations near integrated steel plants, because the material is dense and transport cost scales with mass — the viable market is geographically bounded by its own density. The qualitative industrial-symbiosis case is strong; the quantitative case has not yet been made. But the reporting problem is solvable, and solving it is a precondition for the field to know what it collectively knows.

Subject of Research: Materials Science

Article Title: Steel mill scale in concrete and mortar: a critical review of the evidence base and a proposed framework for future quantitative synthesis

Article References: Loganathan, G., Senthil Pandian, M., & Deepa Nivethika, S. (2026). Steel mill scale in concrete and mortar: a critical review of the evidence base and a proposed framework for future quantitative synthesis. Frontiers in Built Environment, 12, Article 1932304. https://doi.org/10.3389/fbuil.2026.1932304

Image Credits: AI Generated

DOI: 10.3389/fbuil.2026.1932304

Keywords: steel mill scale, concrete, mortar, circular economy, construction materials, evidence synthesis, waste valorisation, durability, Steel, mill, scale, critical

The research, led by P. R. Rajimol of the CSIR-National Institute for Interdisciplinary Science and Technology in Trivandrum, began with marigold (Tagetes erecta) floral waste gathered from the Attukal Bhagavathy Temple in Kerala. Marigolds are rich in phytochemicals, including flavonoids such as quercetin and quercetagetin, carotenoids like lutein and zeaxanthin, and a variety of phenolic compounds. Rather than simply using a crude extract, the team pursued an activity-guided approach: they first identified which solvent extraction produced the most potent corrosion inhibitor, and then isolated the single molecule responsible for that activity. This distinction matters, because earlier studies of marigold as a corrosion inhibitor had stopped at the extract level without pinpointing or deploying the active compound in a controlled-release coating system.

The extraction itself was deliberately simple and green. Roughly 750 grams of dried petals were extracted at room temperature using two solvents of very different polarity: hexane, which pulls out nonpolar compounds such as carotenoids and steroids, and a 60:40 ethanol-water mixture, which captures polar species including flavonoids and phenolic acids. After concentration under reduced pressure and freeze-drying, the hexane route yielded about 26 grams of crude extract and the hydroethanolic route about 33 grams. When the two extracts were compared head-to-head in salt water, the hydroethanolic extract clearly outperformed its hexane counterpart, protecting mild steel more effectively in immersion tests lasting 14 days and in electrochemical measurements.

Those electrochemical tests provided the mechanistic clues. In electrochemical impedance spectroscopy, bare mild steel in 3.5 weight percent sodium chloride solution could be modelled with a simple circuit of solution resistance, double-layer capacitance, and charge transfer resistance. In the presence of the hydroethanolic extract, however, an additional film resistance and capacitance appeared in the fitted circuit, indicating that active molecules were adsorbing onto the metal surface and forming a protective layer. Potentiodynamic polarization told a complementary story: the hydroethanolic extract shifted the corrosion potential in the anodic direction and suppressed the corrosion current density, behaving as an anodic-type inhibitor, while the hexane extract acted predominantly on the cathodic reaction. Peak performance for both extracts occurred around 200 parts per million; at higher concentrations, the physically adsorbed layers apparently began to desorb or peel, slightly reducing efficiency.

With the hydroethanolic extract confirmed as the more active fraction, the researchers used column chromatography, eluting with mixtures of ethyl acetate and hexane, to isolate the marker compound. At 90 percent ethyl acetate, a pale-yellow solid emerged. High-resolution mass spectrometry assigned it the molecular formula C15H10O8, and proton and carbon nuclear magnetic resonance spectra confirmed its identity as quercetagetin, a hexahydroxyflavone. The molecule is, in electrochemical terms, almost ideally suited to corrosion inhibition: it carries a dense array of hydroxyl groups and a carbonyl group whose lone pairs can form coordinate bonds with metal ions, while its two aromatic rings, a double bond, and the carbonyl provide a delocalized pi-electron system that can also accept electrons back from the metal in retro-donation. In effect, quercetagetin and the metal surface behave as a Lewis acid-base pair, and this molecular handshake blocks the oxidation reactions that drive corrosion.

Immersion tests bore this out dramatically. Mild steel coupons soaked for 15 days in saline solutions at acidic, neutral, and alkaline pH developed heavy corrosion products, pits, and cracks when no inhibitor was present. In the presence of quercetagetin, the surfaces remained smooth and essentially damage-free, and elemental analysis showed far less oxide formation. The hydroxyl and carbonyl groups, by coordinating to the metal, simply deny corrosive chloride ions access to the surface.

The next challenge was longevity. A free inhibitor dissolved in a coating would be consumed quickly and leach away, so the team loaded quercetagetin, and the whole hydroethanolic extract, into mesoporous silica nanoparticles synthesized by a template method using cetyltrimethylammonium bromide and tetraethyl orthosilicate. These nanocontainers are extraordinary sponges: nitrogen adsorption measurements showed a surface area of 729.67 square meters per gram and a pore volume of 0.68 cubic centimeters per gram. After loading the inhibitor at a 2:1 inhibitor-to-container weight ratio, the surface area dropped to 88.80 square meters per gram and pore volume to 0.12 cubic centimeters per gram, clear evidence that the organic molecules had filled the pores. Infrared spectroscopy confirmed that loading occurred by physisorption, with no chemical bonds formed or broken, so the inhibitor retains its full activity. Transmission and scanning electron microscopy showed spherical, slightly polydisperse particles whose surfaces became smoother and denser after loading, and thermogravimetric analysis revealed a bonus: the nanocomposite-filled epoxy was substantially more thermally stable than pristine epoxy, with the temperatures of 5 percent and 10 percent weight loss rising by 77 and 68 degrees Celsius respectively.

The coatings themselves were made by dispersing the loaded nanocontainers in a bisphenol A epoxy resin with a polyamine hardener, then dip-coating polished mild steel and aluminium-6061 panels and curing them at room temperature followed by a post-cure at 80 degrees Celsius. The average coating thickness was a modest 34 micrometers. Electrochemical testing in 3.5 percent sodium chloride revealed a clear optimum. For the whole extract, a 2 weight percent loading raised the charge transfer resistance of mild steel from 1,128 to 21,300 ohm square centimeters and cut the corrosion current density from 12.53 to 0.066 microamperes per square centimeter, an inhibition efficiency of 99.47 percent. The isolated quercetagetin did even better: at 3 weight percent, resistance climbed to 31,240 ohm square centimeters, corrosion current density fell to 0.0060 microamperes per square centimeter, and the corrosion potential shifted from minus 0.698 to minus 0.274 volts, yielding an inhibition efficiency of 99.95 percent relative to bare steel. Beyond that concentration, nanoparticles began to agglomerate, creating porous pathways that let electrolyte penetrate, so more was not better. The quercetagetin coating was also notably stable and non-hygroscopic, unlike the extract-loaded version at its highest loading. On aluminium-6061, the 3 percent quercetagetin coating raised resistance from 3,634 to 77,050 ohm square centimeters and delivered 99.67 percent inhibition by polarization measurements.

Perhaps the most remarkable results came from the coating’s responsive behavior. Because mesoporous silica releases its payload faster in acidic conditions, and because quercetagetin’s hydroxyl groups form more soluble anionic structures in alkaline media, the coating releases its inhibitor precisely where and when corrosion threatens, whether the environment is acidic, neutral, or basic. When the researchers scratched a coated aluminium panel with a razor blade and immersed it in salt water, scanning electron microscopy showed healing beginning within 3 hours and completing within 48 hours, with no corrosion products or leakage at the scratch site. Released quercetagetin fills the void, coordinates to the exposed metal, and hydrogen-bonds with the surrounding polymer, sealing the wound much as biological tissue repairs itself. The coating also proved self-sanitizing. In zone-of-inhibition tests, it produced a 3.0-centimeter inhibition zone against the gram-negative bacterium Escherichia coli and a 2.3-centimeter zone against the gram-positive Staphylococcus aureus, and quantitative testing under the AATCC-100 protocol showed 92 percent and 81 percent reductions in bacterial colonies respectively after one hour of contact. The stronger effect against gram-negative bacteria likely reflects differences in cell wall structure and their interaction with the flavonoid.

The significance of the work extends beyond the impressive numbers. Corrosion consumes an estimated 3.4 percent of global GDP each year, and the traditional inhibitors used to fight it, particularly hexavalent chromium compounds and heavy-metal complexes, are toxic, persistent, and carcinogenic, prompting tightening regulation under frameworks such as REACH. By converting temple flower waste, a documented source of water pollution, into a high-performance green inhibitor, the CSIR team addresses two environmental problems at once in a genuine waste-to-wealth strategy. The combination of passive barrier protection from the epoxy matrix and active, pH-triggered inhibition from the nanocontainers points toward a new generation of smart coatings for marine structures, healthcare surfaces, and industrial equipment, where a single layer of paint derived from discarded petals can resist rust, mend its own damage, and keep microbes at bay.

Subject of Research: Green multifunctional epoxy nanocomposite coatings from marigold floral waste for anticorrosive, antimicrobial, and self-healing metal protection

Article Title: Multifunctional epoxy nanocomposite coatings with anticorrosive, antimicrobial, and self-healing characteristics derived from floral biomass

Article References: Rajimol, P. R., Samuel, A. S., Ulaeto, S. B., & Rajan, T. P. D. (2026). Multifunctional epoxy nanocomposite coatings with anticorrosive, antimicrobial, and self-healing characteristics derived from floral biomass. Discover Electrochemistry, 3(1), Article 49. https://doi.org/10.1007/s44373-026-00122-5

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00122-5

Keywords: corrosion inhibition, quercetagetin, marigold floral waste, mesoporous silica nanoparticles, epoxy nanocomposite, self-healing coating, antimicrobial coating, green chemistry, mild steel, aluminium alloy, electrochemical impedance spectroscopy, waste valorisation

The research team, led by Snigdha Homroy and Rajni Chopra at the National Institute of Food Technology Entrepreneurship and Management in Kundli, Haryana, collected discarded Tagetes erecta flowers from a local temple within six to eight hours of generation and processed them within a day to minimise the loss of volatile phytochemicals. The flowers, which had a moisture content of approximately 88 percent, were gently crushed rather than milled to preserve the delicate glandular trichomes that house the oil-bearing volatiles. From this waste stream, the researchers extracted marigold essential oil using four different approaches: conventional hydro-distillation, ultrasound-assisted hydro-distillation, freeze-thaw-assisted hydro-distillation and solvent-free microwave extraction.

The choice of extraction route proved decisive. Hydro-distillation in a Clevenger-type apparatus for four hours yielded 0.0164 grams of oil per 100 grams of fresh flowers. When the flowers were first pre-treated with ultrasound at 500 watts and 20 kilohertz, acoustic cavitation, the violent formation and collapse of microscopic bubbles, tore open cell structures and improved solvent penetration, raising the yield by roughly 25 percent. A freeze-thaw pre-treatment, in which flowers were cycled between minus 80 degrees Celsius and room temperature three times, boosted the yield by about 17 percent, because ice crystals physically rupture cell walls and membranes during freezing, enlarging the porous network available to the extracting water.

Solvent-free microwave extraction, by contrast, performed poorly in this matrix, delivering a yield 85.3 percent lower than conventional hydro-distillation. The authors attribute this to the absence of added water and the limited intrinsic free moisture of the flowers, which restricted internal heating and volatilisation of the essential oil. The result is a useful reminder that green extraction technologies are not universally interchangeable: microwave methods that excel with aromatic herbs, as previous work on rosemary showed, can falter with high-moisture, fibrous floral waste. The relatively low absolute yields across all methods also reflect the use of whole flowers, which mix oil-rich tissues with fibrous, low-oil material, and the reporting of yields on a fresh-weight basis.

Chemical profiling by headspace gas chromatography-mass spectrometry identified 41 phytochemical constituents across the oils, with a profile rich in compounds prized for antioxidant, antimicrobial and anti-inflammatory activity. Nootkatone, limonene, tagetone, piperitone, ocimene, beta-caryophyllene and isoeugenol dominated, although their proportions shifted with the extraction method. Ultrasound-assisted hydro-distillation produced the highest overall content of key volatiles, enriching oxygenated sesquiterpenes and ketones such as nootkatone, which reached 11.15 percent, while freeze-thaw treatment similarly favoured sesquiterpenes. Microwave extraction skewed toward lighter hydrocarbons and phenolics, including isopentane and isoeugenol, which contribute aroma but are less relevant to oxidative protection.

The second half of the study tested whether this waste-derived oil could defend perilla seed oil, a cold-pressed, omega-3-rich oil whose high polyunsaturated fatty acid content makes it exceptionally vulnerable to rancidity. The researchers fortified the oil with marigold essential oil at 500, 1000 and 1500 parts per million and compared the results against 200 parts per million of tert-butylhydroquinone, or TBHQ, the synthetic antioxidant benchmark, and an untreated control. Samples were then subjected to a 20-day Schaal oven test at 60 degrees Celsius, an accelerated storage protocol that compresses months of ambient shelf-life degradation into weeks by speeding the same radical chain reactions that occur in normal storage.

Across every measure, the 1500 ppm marigold treatment performed impressively. Rancimat analysis showed a statistically significant, concentration-dependent extension of the induction period, indicating delayed oxidation onset. Viscosity, which climbs as oxidation generates polymeric degradation products, rose only to 37.1 centipoise in the marigold-fortified oil, compared with 40.3 centipoise in the untreated control. The untreated oil’s peroxide value, a gauge of primary oxidation, soared to 28.63 milliequivalents of oxygen per kilogram by day 20, whereas the marigold-supplemented oil held at 10.03 and TBHQ at 9.71. Acid value, p-anisidine value and conjugated triene content, which track hydrolysis and secondary aldehyde and ketone formation, followed the same pattern, with the highest marigold dose approaching TBHQ performance throughout.

Antioxidant capacity assays reinforced the picture. Untreated perilla oil lost radical-scavenging capacity rapidly, with DPPH inhibition falling from 84.42 to 74.35 percent and ABTS inhibition from 80.15 to 66.40 percent over the storage period. The 1500 ppm marigold sample, by contrast, retained 83.86 percent DPPH and 72.94 percent ABTS inhibition after 20 days, losses of less than seven percent, comparable to TBHQ-treated oil. The oil also preserved its golden carotenoid pigments better, retaining a yellow Lovibond value of 12.2 against 9.1 for the control. Hierarchical cluster analysis of all stability parameters grouped the control and 500 ppm samples together as low-stability outliers while placing the 1500 ppm marigold oil in the same high-stability cluster as TBHQ, a statistical confirmation that the floral waste extract can match a regulated synthetic preservative at its maximum permitted concentration.

The protective mechanism stems from the oil’s constellation of bioactive volatiles, which scavenge free radicals, chelate pro-oxidant metals and interrupt lipid peroxidation chain reactions, with synergy among compounds such as beta-caryophyllene, nootkatone and isoeugenol likely amplifying the effect. The study’s significance extends beyond food chemistry. It couples two sustainability goals at once: diverting a vast, culturally generated waste stream from landfill and offering food manufacturers a clean-label alternative to synthetic antioxidants such as BHA, BHT and TBHQ, whose potential carcinogenic, genotoxic and endocrine-disrupting effects have drawn increasing scrutiny in animal and mechanistic studies. The authors note that future work should clarify the underlying preservation mechanisms and extend testing to other oxidation-sensitive oils such as flaxseed and chia. If those trials succeed, the garlands left behind at temples across India could become a genuine industrial resource, turning ritual offerings into shelf life for the world’s healthiest cooking oils.

Subject of Research: Extraction of essential oil from marigold floral waste and its use as a natural antioxidant to stabilise polyunsaturated fatty acid-rich perilla seed oil.

Article Title: Valorisation of marigold floral waste for essential oil extraction and its application in stabilisation of PUFA rich perilla seed oil

Article References: Homroy, S., Madan, H., Sharma, S., Chopra, R., & Kumari, R. (2026). Valorisation of marigold floral waste for essential oil extraction and its application in stabilisation of PUFA rich perilla seed oil. Discover Green Chemistry, 1(1), Article 16. https://doi.org/10.1007/s44509-026-00015-1

Image Credits: AI Generated

DOI: 10.1007/s44509-026-00015-1

Keywords: marigold floral waste, Tagetes erecta, essential oil, hydro-distillation, ultrasound-assisted extraction, solvent-free microwave extraction, perilla seed oil, natural antioxidants, oxidative stability, TBHQ, omega-3, waste valorisation

The research team, led by Wojciech Jerzak of AGH University of Krakow, pyrolyzed both materials at 700, 800 and 900 degrees Celsius in a fixed-bed reactor flushed with high-purity nitrogen. Each 1.5-gram sample was held at the target temperature for one hour, after which the resulting chars were ground, sieved and subjected to a battery of analytical techniques including Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and nitrogen sorption analysis. Carbon dioxide uptake was then measured at 20 degrees Celsius across pressures ranging from 0.5 to 110 kilopascals.

The starting materials could hardly have been more different. Chicken manure, collected from a poultry farm in southern Poland, contained just 8 percent fixed carbon but a hefty 26.4 percent ash, along with 4.1 percent nitrogen. Onion peels from a processing facility in the Kuyavian-Pomeranian Voivodeship were richer in combustible material, with 56.4 percent volatile matter, 14.9 percent fixed carbon and a lignocellulosic structure containing substantial cellulose and hemicellulose. X-ray fluorescence showed that calcium oxide dominated the ash of both feedstocks, at 48.8 percent for the manure and 40.8 percent for the peels, but the manure also carried elevated potassium, phosphorus, magnesium and sulphur, while the peels were unusually rich in silica at 33.8 percent.

As pyrolysis temperature climbed, both feedstocks lost mass, moisture and volatile components while their ash fractions concentrated in the solid residue. Manure biochar ash content soared from 26.4 percent in the raw material to 65.2 percent at 900 degrees Celsius, while onion peel biochar ash rose from 14.9 to roughly 41.8 percent. Hydrogen contents in both biochars fell below 1 percent, and nitrogen in the manure chars dropped from 4.1 to between 1.1 and 1.8 percent, reflecting the thermal cracking of volatile compounds and the release of small nitrogenous molecules. Onion peel biochars, by contrast, concentrated carbon to around 50 to 52 percent, more than the manure chars managed, thanks to their lower initial mineral burden.

Spectroscopy traced the chemical evolution in fine detail. Infrared spectra showed the progressive disappearance of hydroxyl, aliphatic and carbonyl bands with rising temperature, signalling dehydration, decarboxylation and the growth of a condensed aromatic carbon matrix. Yet phosphate and carbonate signals persisted in the manure-derived chars, underscoring the thermal stability of their inorganic constituents. X-ray diffraction revealed dramatic mineral reorganisation: at 700 degrees Celsius the manure char held quartz, portlandite and rutile, but by 800 and 900 degrees Celsius the ash had transformed into calcium oxide, whitlockite-type calcium-magnesium phosphates, magnesite, oldhamite and eventually sulfoapatite. The onion peel chars followed a different path, developing graphitic carbon alongside quartz, kalsilite, sodium carbonate and, at the highest temperature, the stable alkali aluminosilicate sanidine.

Electron microscopy captured the morphological consequences. Manure biochars remained dense, heterogeneous aggregates with no well-defined pore network, their high mineral content apparently filling or masking the developing carbon porosity. The onion peel chars told a more elegant story: at 700 degrees Celsius they retained elongated, layered fragments of the original plant tissue, and at 800 degrees Celsius they developed a striking channel-like structure the authors liken to a fish skeleton, with aligned, interconnected spaces carved out by devolatilisation. At 900 degrees Celsius, however, that ordered architecture began to fragment and partially collapse, a warning that excessive heat can destroy the very structure adsorbent designers hope to build.

Porosity measurements quantified these visual impressions. The onion peel biochar produced at 900 degrees Celsius achieved the highest specific surface area of the entire study, 109.8 square metres per gram—more than three times that of its 800-degree counterpart and nearly 6.5 times that of the 700-degree sample—with micropores contributing up to 60 percent of the internal surface in the intermediate-temperature samples. Manure biochars reached more modest areas between 14.0 and 36.2 square metres per gram, but their average pore diameter also shrank steadily with temperature, indicating progressive micropore refinement.

The carbon dioxide adsorption results upended the expectation that bigger surface area always means better capture. Among the onion peel chars, the 700-degree sample—despite its modest 17 square metres per gram—delivered the highest uptake, 26.6 cubic centimetres per gram at 100 kilopascals, while the 900-degree sample with the largest surface area actually adsorbed less. The researchers attribute this to pore widening and a shrinking population of narrow ultramicropores, those cavities below 0.7 nanometres whose dimensions closely match the kinetic diameter of CO2 and which nitrogen adsorption at cryogenic temperatures cannot fully resolve. Residual oxygen-containing surface groups may also enhance CO2-surface interactions in the cooler char.

The manure biochars behaved in almost mirror-image fashion, with CO2 uptake rising steadily as pyrolysis temperature increased, tracking the growth of microporosity and surface area. But texture alone could not explain the performance of the 900-degree manure char, which captured substantial CO2 despite a smaller surface area than its onion peel rivals. X-ray diffraction and fluorescence pointed to the missing piece: calcium oxide and calcium-rich phosphate phases that furnish basic adsorption sites with a strong affinity for acidic CO2 molecules, potentially even fixing some of the gas chemically as carbonate or bicarbonate species. In these mineral-rich chars, capture is a partnership between physical pore-filling and mineral-assisted interaction.

The practical lesson is that biochar design must be matched to feedstock chemistry. For lignocellulosic wastes like onion peels, the goal should be preserving narrow micropores rather than maximising total surface area, and avoiding the pore widening and structural collapse that come with excessive heat. For manures, engineers should exploit the inherent calcium, magnesium and potassium phases that add a chemical dimension to capture. Converting two problematic wastes into tailored carbon sorbents in a single thermal step offers a double dividend—waste valorisation and carbon management—grounded not in exotic chemistry but in a careful reading of what heat does to the organic and mineral halves of agricultural residue.

Subject of Research: Thermal conversion of chicken manure and onion peels into biochars for carbon dioxide adsorption

Article Title: Effect of thermal treatment on the structure and CO2 adsorption capacity of biochar from chicken manure and onion peels

Article References: Jerzak, W., Dutka, B., Sokołowski, K., Wilk, A., Chwiej, J., Gajek, M., Kalemba-Rec, I., Cierpińska, M., & Magdziarz, A. (2026). Effect of thermal treatment on the structure and CO2 adsorption capacity of biochar from chicken manure and onion peels. Clean Technologies and Environmental Policy, 28(10), Article 244. https://doi.org/10.1007/s10098-026-03598-2

Image Credits: AI Generated

DOI: 10.1007/s10098-026-03598-2

Keywords: biochar, pyrolysis, CO2 capture, chicken manure, onion peels, carbon adsorption, microporosity, mineral phases, waste valorisation, X-ray diffraction, Raman spectroscopy, surface area

The scale of the problem is considerable. Around 95,000 tonnes of salty whey are generated in the United Kingdom every year, largely from the production of cheddar and similar hard cheeses. Whey is the liquid that separates from the curds during cheese making, and while sweet whey from some processes has long found uses in food ingredients and animal feed, the salty variety presents a far more difficult proposition. Its combination of milk sugars and high salt content makes it expensive to treat, unsuitable for many conventional applications, and environmentally problematic when discharged.

A single dairy producer can generate tens of thousands of litres of salty whey every week, creating simultaneous environmental and economic pressures. Disposal typically involves costly treatment or transport, and the salt load can disrupt anaerobic digestion systems and wastewater infrastructure. For an industry already operating on thin margins, the burden of managing this by-product has become an increasingly urgent concern, prompting the search for alternatives that treat the liquid not as a liability but as a resource.

That is precisely the philosophy that Take Root Bio brings to the problem. The company’s origins lie in biosphere engineering, the discipline concerned with closed-loop systems in which every resource is kept in use for as long as possible and the output of one process becomes the input of the next. In the systems the company develops, nothing is simply thrown away. It is an approach born of the constraints of space habitation, where astronauts must grow and recycle food with near-total efficiency because resupply is impossible, but the underlying principles translate remarkably well to industrial ecology on Earth.

Heriot-Watt University proved a natural partner for the project. The university has taught and researched brewing and distilling since 1903 and is home to the International Centre for Brewing and Distilling (ICBD), an institution with deep expertise in fermentation science. Its scientists specialise in finding new value in food and drink by-products, using biological processes to convert difficult materials into usable resources. Fermentation, the same biochemical engine that turns grain sugars into whisky and beer, can just as readily convert the lactose in whey into ethanol, provided the technical obstacles, chief among them the salt, can be overcome.

At the heart of the collaboration was the demonstration that the sugars locked in salty whey could indeed be transformed through a bio-based process into bioethanol. Just as significantly, the process leaves behind a secondary stream that could potentially be recovered and reused, extending the circular logic of the system further. Rather than a single extraction of value followed by residual waste, the approach envisions a cascade in which multiple components of the original by-product find successive uses, mirroring the closed-loop architecture of the space-inspired systems from which the concept emerged.

Kirk Siderman-Wolter, founder of Take Root Bio, explained the thinking behind the project. “We’ve always been interested in what happens when you stop looking at something as waste and start asking what else it could become,” he said. “The company began by looking at how people might grow food in space, where every resource matters and nothing can be thrown away. The same principles apply surprisingly well here on Earth. Salty whey is produced in huge volumes and can be difficult to deal with, so we wanted to find out whether there was a better use for it.” He added that converting a material that currently costs money to manage into something with real value represents a positive outcome for both dairy producers and the environment.

The commercial logic of the project extends beyond the fermentation itself. Take Root Bio is exploring whether mobile production units could be deployed close to the dairies where salty whey is generated, reducing transport requirements and making the concept easier to scale. Decentralised processing of this kind could allow even smaller producers to capture value from their waste streams without the capital investment of dedicated facilities, while cutting the emissions associated with hauling thousands of litres of liquid waste across the country. For producers, the prospect is twofold: reduced disposal costs and a new revenue stream from the resulting fuel.

Researchers at Heriot-Watt see the work as part of a much broader agenda in waste valorisation. Dr Jane White, an expert in the field at the university, noted that food and drink manufacturing produces a huge range of by-products, many of which still contain valuable components but can be challenging to manage. “That makes them interesting candidates for bio-based processes that can recover value from materials that might otherwise be treated as waste,” she said. Dr Shiwen Zhuang, who specialises in fermentation development, described the project as an opportunity to explore whether bio-based solutions could unlock value in salty whey while reducing disposal pressures, calling it exactly the kind of upcycling approach that could strengthen sustainability across the food and drink sector.

The collaboration also reflects the university’s wider institutional ambitions. Research at ICBD feeds into Heriot-Watt’s focus on the circular economy and resource efficiency, both key strands of iNetZ+, the university’s Global Research Institute for Net Zero and Beyond. The university is additionally developing plans for a new Centre for Sustainable Brewing and Distilling, intended to give the sector access to low-carbon testbeds, support for bringing new products to market, and training for the next generation of industry talent. At IBioIC, which connected the two organisations through its industry network, director of impact and deputy CEO Dr Liz Fletcher said one of the biggest opportunities in industrial biotechnology lies in finding new uses for materials currently treated as waste, and that projects combining businesses with academic expertise can deliver both environmental and commercial benefits. She highlighted the project’s fresh angle on a familiar problem as precisely the sort of innovation the centre wants to support.

Looking ahead, the partnership is investigating whether similar techniques could be applied to other food and agricultural by-products, including waste from fruit and vegetable processing. The company is also exploring ways to capture gases generated during fermentation, such as methane and hydrogen, for use in future food production systems, potentially closing the loop even further. If salty whey, one of the dairy industry’s most intractable liabilities, can be reliably converted into fuel and recoverable co-products, the project offers a template for how space-age systems thinking, academic fermentation expertise and industrial biotechnology can together reshape the economics of waste across the entire food and drink sector.

Subject of Research: Bio-based conversion of salty whey dairy waste into bioethanol through fermentation

Article Title: Heriot-Watt scientists turn dairy waste into fuel

Article References: Heriot-Watt scientists turn dairy waste into fuel. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: salty whey, bioethanol, dairy waste, fermentation, circular economy, industrial biotechnology, Heriot-Watt University, Take Root Bio, IBioIC, waste valorisation, brewing and distilling, net zero