The central challenge is that biomass is not a uniform feedstock. Agricultural residues and other plant materials can contain different proportions of cellulose, hemicellulose, lignin, minerals, and moisture, even when they appear similar. Their particle size and internal structure can also differ. During carbonization, these variations influence how the material decomposes and reorganizes, potentially producing differences in pore networks, surface chemistry, carbon ordering, electrical properties, and transport pathways. As corresponding author Yaning Zhang explained in the news release, “Biomass is not a uniform raw material. Even seemingly similar agricultural residues can behave very differently during carbonization.” The finding suggests that feedstock selection cannot be separated from the performance target: materials intended for supercapacitors, rechargeable batteries, carbon capture, catalysis, or contaminant removal may require different combinations of structure and chemical functionality.

Microwave-assisted pyrolysis is highlighted as a promising approach because microwaves can transfer energy directly into suitable materials. The review reports that this heating method may shorten processing times and improve control over carbon formation compared with conventional heating. The source also cautions against treating the technology as a complete solution. Uneven energy absorption, localized overheating, and variations among reactor designs can lead to inconsistent results. Reliable scale-up would therefore require careful temperature monitoring, accurate energy measurements, and standardized processing conditions. The review does not establish that microwave processing outperforms conventional heating in every application or provide a universally optimal production method; instead, it frames the approach as one part of a broader strategy for controlling material properties.

The analysis also finds that maximizing surface area alone does not guarantee high performance. Accessible pores, useful chemical groups, orderly carbon structures, and pathways that permit movement of charge or other substances must be matched to the intended application. A material with a large internal surface can still underperform if its pores are poorly connected or if its chemistry does not support the relevant reaction. The review’s integrated framework consequently connects four stages: the original feedstock, the manufacturing process, the structure and chemistry of the resulting carbon material, and the behavior required in an application. This relationship offers researchers a more structured alternative to trial-and-error development and could help them identify which precursor and processing combinations are most likely to meet a specified goal.

To improve reproducibility, the authors propose standardized methods for characterizing biomass and reporting experimental conditions. They further recommend combining detailed material measurements with machine learning and data-driven modeling, which may reveal relationships that conventional experimental approaches overlook. These recommendations are not presented as a validated predictive model, and the review does not report new machine-learning performance data. It instead argues that more consistent feedstock descriptions, processing records, and structural measurements could make results from different studies more comparable and more useful for designing carbon nanomaterials. Industrial assessment must also include production costs, energy consumption, and environmental impacts, because a laboratory material that cannot be manufactured reliably or sustainably may not be commercially viable. Taken together, the review presents a roadmap for developing biomass-derived carbon materials, but it does not demonstrate commercial deployment, clinical benefits, or a guaranteed improvement in any specific energy or environmental application.

Subject of Research: How biomass feedstock variability affects the structure and performance of biochar-based carbon nanomaterials

Article Title: From agricultural waste to advanced carbon materials: Scientists reveal why the starting material matters

Article References: From agricultural waste to advanced carbon materials: Scientists reveal why the starting material matters. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: biomass, biochar, carbon nanomaterials, agricultural waste, microwave pyrolysis, carbonization, energy storage, carbon capture, materials characterization, machine learning, agricultural, waste

The research team, led by Cynthia C. Nwaeju and Francis O. Edoziuno, collected raw crab shells from the seashore of the Kurutie River in the Gbaramatu Kingdom of Delta State. After separating the shells from the crabs, they brushed away flakes, washed the material thoroughly with distilled water to remove sand and mud, and sun-dried it for 48 hours. The shells were then oven-dried at 100 degrees Celsius and crushed in a planetary ball mill running at 200 revolutions per minute for one hour and 45 minutes. Sieving produced a uniform powder of 75 micrometer particles, a size the authors selected because it balances surface area against homogeneity: finer particles tend to agglomerate and weaken composites, while coarser ones create stress concentration points under mechanical loading.

Half of the powder was then carbonized in a muffle furnace, ramping from ambient temperature to 800 degrees Celsius at 5.5 degrees per minute and holding there for one hour under a high-purity nitrogen atmosphere. The uncarbonized particles, which the team labels UCSP, appeared off-white, reflecting their natural content of chitin and calcium carbonate. After carbonization, the particles, dubbed CCSP, turned a dark greyish-brown, a visible signature of thermal decomposition and the loss of volatile organic compounds. The measured moisture content of the raw shells was 9.78 percent and the ash content 16.25 percent, values the authors note are lower than those reported in related studies and within the range considered suitable for industrial use.

The heart of the study lies in a battery of characterization techniques. X-ray fluorescence revealed that calcium and oxygen dominate both particle types, with significant amounts of silicon, aluminum, phosphorus, iron, and trace elements including sulfur, chlorine, potassium, manganese, and magnesium. The dominant oxides were calcium oxide, silicon dioxide, aluminum oxide, and phosphorus pentoxide. Calcium content fell from 61.781 percent in the raw particles to 59.462 percent after carbonization, a decrease the researchers attribute to the decomposition of calcium carbonate into calcium oxide and carbon dioxide, along with the removal of volatile matter, which raised the relative concentrations of other elements.

Fourier-transform infrared spectroscopy mapped the functional groups on the particle surfaces. The uncarbonized shells showed absorption peaks at 3265.1, 2113.4, 1789.1, 1654.9, 1405.2, 1066.0, 1028.7, 872.2, and 711.9 inverse centimeters, corresponding to amine stretching, alkyne stretching, carbonyl groups, alkene and aromatic stretches, and the characteristic bands of calcite, the crystalline form of calcium carbonate. The presence of a carboxylic group signals an organic matrix within the raw particles, which earlier work suggests could act as a lubricant during sliding wear and improve corrosion resistance, both valuable traits in a reinforcement material. In the carbonized particles, the spectrum shifted: peaks at 2512.0, 2844.0, and 1790.6 inverse centimeters indicated overlapping hydroxyl vibrations, carbon-hydrogen bending, and carbonyl stretching, while bands at 1401.5 and 1043.7 confirmed aromatic and carboxylic acid groups. The team also observed evidence of interaction between calcite and magnesium in the carbonized material, meaning the calcite there is not entirely pure, unlike in the raw shells.

X-ray diffraction told perhaps the most dramatic story. In the uncarbonized particles, the dominant diffraction peak at 29.7426 degrees two-theta, with a d-spacing of 3.001 angstroms and full relative intensity, matched calcite, with additional reflections corresponding to aragonite, brushite, graphite, periclase, lime, quartz, and sylvine. Quantitative analysis confirmed calcite and brushite as the dominant phases. After carbonization at 800 degrees Celsius, the pattern transformed: peaks at 29.7160 and 29.8551 degrees two-theta confirmed calcium oxide, the product of the classic decomposition reaction in which calcium carbonate breaks down into calcium oxide and carbon dioxide. Residual calcium phosphate peaks survived the heat, and a major peak indexed as magnesium calcite, in which magnesium substitutes into the carbonate lattice, replaced the pure calcite of the raw material. The sylvine phase vanished entirely, having volatilized, while new low-angle peaks signaled the formation of graphitic or amorphous carbon from the partial decomposition of organic matter.

Scanning electron microscopy added the morphological dimension. The raw particles displayed a nodular crystalline structure with rough surfaces and uneven distribution, while the carbonized particles revealed large rod-like crystalline formations, likely corresponding to calcium-magnesium carbonate precipitates that grew in situ as volatile matter burned away. Rod-like calcium carbonate crystals are associated with orthorhombic calcite phases, corroborating the diffraction results. Energy-dispersive X-ray spectroscopy on both particle types showed strong peaks for calcium, carbon, oxygen, and magnesium, with calcium by far the most intense, confirming that crab shells are naturally calcium-rich materials. The team notes that this heterogeneous, nodular-and-rod morphology is conducive to mechanical interlocking, the physical gripping between reinforcement and matrix that underpins load transfer in particulate composites.

Why does any of this matter for engineering? In metal matrix composites, particularly aluminum matrix composites prized for their strength-to-weight ratio and corrosion resistance, the choice of reinforcement determines both performance and cost. Synthetic ceramics such as silicon carbide, alumina, and boron carbide work well but are expensive and energy-intensive to produce. Researchers have therefore turned to waste-derived fillers: palm kernel shell ash, rice husk ash, eggshells, coconut shell ash, fly ash, and glass powder have all been shown to boost the hardness, tensile strength, or wear resistance of aluminum alloys. Crab shells had largely been overlooked, with prior research focused on extracting chitin and calcium carbonate for biomedical devices and water purification rather than using the particles directly. The new study shows that the oxide chemistry of crab shell particles, dominated by calcium oxide with contributions from silica, alumina, and magnesia, closely resembles that of established agro-waste reinforcements. Calcium oxide is known to impede dislocation movement in metal matrices, enhancing strength and rigidity, while magnesium oxide acts as a grain boundary stabilizer that restricts grain growth, improves interfacial bonding, and enhances wettability between reinforcement and matrix.

The carbonized form emerges as the more promising candidate. Its conversion of calcium carbonate to calcium oxide enhances thermal stability and reactivity, and the presence of magnesium calcite has been linked in earlier literature to improved corrosion resistance. The authors conclude that carbonized crab shell particles, with their enhanced stability and mineral composition, are a viable eco-friendly reinforcement for composite applications. They also caution, implicitly, that this is a characterization study: the mechanical performance of actual aluminum composites containing these particles remains to be tested in follow-up work, as does the scalability of shell collection and processing.

Even so, the implications extend beyond one laboratory. Crab shells are generated in enormous quantities by seafood consumption, and their slow degradation and improper disposal contribute to genuine pollution problems in coastal communities. Redirecting even a fraction of that stream into composite manufacturing would exemplify circular economy thinking, converting a disposal liability into a raw material. The Nigerian study, funded through the Tertiary Education Trust Fund, demonstrates that a suite of standard characterization tools can rapidly vet a novel waste stream before any expensive composite synthesis begins. If subsequent mechanical testing confirms what the microstructure and chemistry promise, the humble crab shell, today ground into fishmeal or dumped on beaches, could one day find itself embedded in automotive components, structural panels, or lightweight machinery, a quiet transformation of marine waste into engineering value.

Subject of Research: Characterization of crab shell waste particles as sustainable reinforcement materials for composite applications

Article Title: Transforming marine waste into valuable resources: morphological and structural characterization of crab shell particles for composite applications

Article References: Nwaeju, C. C., Edoziuno, F. O., Okuma, S. O., & Tuaweri, T. J. (2025). Transforming marine waste into valuable resources: morphological and structural characterization of crab shell particles for composite applications. BMC Environmental Science, 2(1), Article 7. https://doi.org/10.1186/s44329-025-00023-9

Image Credits: AI Generated

DOI: 10.1186/s44329-025-00023-9

Keywords: crab shells, marine waste, composites, aluminum matrix composites, calcium carbonate, calcium oxide, X-ray diffraction, FTIR spectroscopy, SEM-EDS, carbonization, circular economy, sustainable materials

The review, led by Yan Zhang and Qiang Li of Huazhong Agricultural University together with colleagues at the International Centre for Bamboo and Rattan and the University of Tennessee, including noted lignin chemist Arthur J. Ragauskas, synthesizes the state of the art in lignin-based carbon fiber from molecular chemistry all the way to manufacturing. Its central message is sobering but constructive: lignin is abundant, renewable, and cheap, but the fibers made from it still fall short of the mechanical performance that commercial applications demand, and the bottleneck is not a single missing breakthrough but an incomplete scientific understanding of how precursor chemistry, processing, structure, and final properties are linked.

To understand why lignin is so attractive, it helps to know what it is. Lignin is one of the three major structural polymers in plant cell walls, alongside cellulose and hemicellulose, and it is essentially nature’s aromatic plastic: a complex, cross-linked network of phenylpropanoid units that confers stiffness to trees and resistance to decay. In the pulp and paper industry and in the emerging generation of cellulosic biorefineries, lignin is separated from carbohydrates in vast volumes, but most of it is burned for process heat rather than converted into higher-value products. Because carbon fiber is, at its core, a material made by aligning carbon-rich molecules and then driving off everything else, a feedstock that is already rich in aromatic carbon rings is an obvious candidate for the job.

The catch, as the review details, is that lignin’s natural complexity cuts both ways. Unlike polyacrylonitrile, which is a relatively uniform linear polymer engineered for consistency, lignin varies enormously depending on the plant species, the growing conditions, and above all the extraction process used to isolate it. Kraft lignin, organosolv lignin, lignosulfonate, and soda lignin each carry different distributions of molecular weight, different degrees of condensation, and different chemistries of the hydroxyl, methoxyl, and carbonyl groups decorating their aromatic rings. Those differences propagate through every downstream step. A precursor that spins poorly, stabilizes unevenly, or fuses during carbonization can often be traced back to molecular features fixed at the moment the lignin left the plant.

This is why the review devotes substantial attention to precursor chemistry as the true foundation of the field. Researchers have learned to tailor lignin through fractionation, which sorts the heterogeneous polymer pool by molecular weight or solubility; through chemical modification, such as acetylation, phenolation, or hydrogenation, which adjusts reactivity and thermal behavior; and through blending or copolymerization with synthetic polymers that lend the mixture the spinnability and orientation that pure lignin lacks. Each strategy reshapes the molecular structural features that ultimately determine whether the precursor fiber can survive the brutal thermal gauntlet ahead. The authors emphasize that understanding these molecular features, in the lignin itself, in the as-spun precursor fiber, in the carbonized fiber, and in the final graphitized fiber, is the scientific thread that ties the whole manufacturing chain together.

That chain begins with spinning, the step that converts a viscous polymer melt or solution into continuous filaments. Melt spinning, dry spinning, wet spinning, electrospinning, and centrifugal spinning each impose different demands on the precursor: melt spinning requires a lignin with suitable thermal flow and no premature cross-linking, while solution-based methods require solubility without degrading the aromatic backbone. The review systematically walks through the fundamental chemistry of each route, noting that the choice of spinning technology shapes fiber diameter, molecular orientation, and defect population, all of which are locked in before the fiber ever sees a furnace.

Next comes thermostabilization, widely regarded as the most unforgiving step in the entire process. During stabilization, the precursor fiber is heated slowly in an oxidative atmosphere so that its molecules cross-link into a network that will not melt, fuse, or shrink catastrophically when carbonization temperatures climb past a thousand degrees Celsius. For polyacrylonitrile, this chemistry is well mapped; for lignin, whose reactive hydroxyl and ether groups behave very differently, stabilization kinetics remain harder to predict and control. The review revisits the underlying oxidation and cross-linking chemistry, arguing that a firmer grasp of these fundamentals is what will allow manufacturers to shorten stabilization times, a key cost driver, without sacrificing fiber integrity.

Carbonization and graphitization then complete the transformation, burning off heteroatoms and reorganizing the remaining carbon into graphitic crystallites whose size, alignment, and connectivity dictate tensile strength and modulus. Lignin-derived fibers, the review notes, generally develop less ordered graphitic structures than their polyacrylonitrile counterparts, which is a major reason their mechanical performance lags. But the authors also survey how the molecular features established earlier, from aromatic content to cross-link density, influence the development of these carbon structures, offering a roadmap for designing precursors that graphitize more efficiently. High-lignin feedstocks with naturally aligned, less-condensed aromatic units, for example, may offer a shorter path to well-ordered carbon than heavily condensed technical lignins.

The review does not stop at the fiber itself. Surface processing, including oxidation, coating, and plasma treatment, receives its own systematic treatment, because the interface between carbon fiber and the surrounding polymer matrix often determines whether a composite realizes the fiber’s full potential. Poor adhesion at this interface produces composites that fail prematurely, no matter how strong the individual filaments are. The authors review how surface treatments modify the chemistry and topography of lignin-based carbon fiber surfaces to improve interfacial bonding, an area they identify as essential for moving these materials from laboratory curiosities toward load-bearing structural applications.

What emerges from the synthesis is less a celebration than a research agenda. The authors are explicit that commercialization of lignin-based carbon fiber is still largely hindered by poor mechanical performance, and that the underlying science of the processing-structure-properties relationship, from precursor chemistry to manufacturing technologies, remains incompletely understood. By revisiting the fundamentals of spinning, thermal treatment, and surface engineering in one integrated framework, the review aims to inspire innovations that enhance performance and push the field toward industrialization. The work was supported by start-up funding from Huazhong Agricultural University and, in part, by the Center for Bioenergy Innovation at the US Department of Energy’s Office of Science. If that agenda succeeds, the payoff would be considerable: a structural material with the performance pedigree of carbon fiber, manufactured from a renewable stream that the bioeconomy currently produces in surplus, turning one of industry’s most abundant waste products into one of its most valuable.

Subject of Research: Lignin-based carbon fiber production from precursor chemistry to manufacturing

Article Title: Lignin carbon fiber: advancement from precursor chemistry to manufacturing

Article References: Zhang, Y., Xu, Y., Gao, H., Sun, F., Wei, S., Ragauskas, A. J., & Li, Q. (2026). Lignin carbon fiber: advancement from precursor chemistry to manufacturing. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02071-4

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02071-4

Keywords: lignin, carbon fiber, biopolymer, precursor chemistry, spinning, thermostabilization, carbonization, graphitization, surface treatment, composites, biorefinery, sustainable materials

Water hyacinth, Eichhornia crassipes, is a free-floating perennial macrophyte native to the Amazon Basin, and it is widely ranked among the ten worst weeds on the planet. In nutrient-enriched tropical and subtropical freshwater bodies, its growth is explosive: dense mats spread across the surface, blocking sunlight from penetrating to submerged vegetation and destabilizing entire aquatic food webs. As the enormous biomass dies and decomposes, microbial consumption of oxygen drives waters toward hypoxia, suffocating fish populations and eroding biodiversity. The plant also accelerates water loss through evapotranspiration and creates breeding grounds for mosquitoes and snails, the vectors of malaria, filariasis, and schistosomiasis, placing heavy public health burdens on lakeside communities.

The socioeconomic toll is equally severe. Infestations hinder fishing, obstruct irrigation canals, clog hydropower turbines, and restrict boat transport, while tourism suffers as scenic waterways disappear beneath a green carpet. In Ethiopia, the problem has become acute at Lake Abaya and Lake Chamo, where the weed threatens both aquatic biodiversity and the livelihoods of people who rely on the lakes. Decades of mechanical, chemical, and biological control have failed to deliver sustainable management, prompting researchers to reframe the invader as a potential bioresource. Its rapid growth, large biomass yield, and stress resilience make it attractive for phytoremediation, and studies have demonstrated its ability to accumulate heavy metals from industrial wastewater, including effluents from pulp and paper, textile, and dairy operations. That bioremediation capacity, combined with its potential for carbon sequestration and renewable energy generation, has fueled renewed interest in converting the weed into something useful.

The research team harvested mature water hyacinth stems from the shorelines of both lakes, with species identity confirmed by a plant taxonomist at Arba Minch University’s Botany Laboratory using standard botanical references. Roots and leaves were removed, the stems were chopped into small pieces, and the material was sun-dried for three weeks at the Abaya campus before being reduced to fragments less than one centimeter long and half a centimeter wide, ready for carbonization. The dried biomass was then carbonized in a barrel carbonizer maintained at an average temperature of 425 degrees Celsius, with surface temperatures monitored using a digital thermometer. The resulting charcoal was retrieved into a sealed steel container to cool, a step designed to prevent ash formation and preserve charcoal quality for the briquetting stage.

To shape the charcoal into usable fuel, the team built a manually operated piston-press briquette machine from metal, incorporating wrought iron, cast iron, and galvanized iron components. The device comprises a main stand, four compaction chambers where pistons compress the pulverized feedstock, a perforated base plate that drains excess water, pressure-transmitting piston cylinders welded to the plate, and a handle and bearing assembly that drives the screw shaft. Two organic binders were tested against the carbonized hyacinth: molasses obtained from the Wonji Shoa Sugar Factory of the Ethiopian Sugar Corporation, dissolved in water to the desired concentration, and plantain peel powder collected from the local community, washed, sun-dried for two weeks, and ground before mixing. Six formulations were produced at blending ratios of 60:40, 70:30, and 80:20 of water hyacinth to binder, labeled samples A through F.

The briquettes were then subjected to a battery of standardized tests following ASTM D1762-84 protocols, covering moisture content, volatile matter, ash content, and fixed carbon, alongside measurements of bulk density, compressive strength, burning rate, and emissions of fine and coarse particulate matter, carbon monoxide, hydrogen sulfide, and oxygen. Elemental composition was determined by X-ray fluorescence spectroscopy using an ORTEC multichannel analyzer with a silicon-lithium semiconductor detector and a plutonium-238 radionuclide source, with acquisition times fixed at 2000 seconds. Statistical analysis with XLSTAT software applied non-parametric Kruskal-Wallis tests followed by Dunn’s multiple pairwise comparisons, with significance set at P ≤ 0.05.

The results delivered a clear verdict on binder choice. Molasses-bound briquettes, samples A, B, and C, showed substantially lower moisture content, ranging from 30.97 to 37.12 percent, compared with the plantain peel formulations, which ranged from 66.54 to 87.48 percent. Ash content followed the same pattern: molasses briquettes registered 27.09 to 28.83 percent, while plantain peel briquettes climbed to 34.97 to 36.38 percent. Because moisture and ash act as impurities in solid biofuel, absorbing heat during combustion and physically obstructing oxygen flow, their reduction translated directly into better burning performance. The molasses-bound samples achieved fixed carbon levels of 20.48 to 25.75 percent and burning rates of 101.61 to 133.14 grams per minute, dwarfing the plantain peel counterparts, which managed only 3.75 to 7.57 percent fixed carbon and burning rates between 4.85 and 10.52 grams per minute. Sample A, with 60 percent water hyacinth and 40 percent molasses, posted the highest burning rate and the highest bulk density at 0.59 grams per cubic centimeter, while sample F, at 80 percent hyacinth with plantain peel, recorded the lowest values across the board.

Emissions testing in a closed room using a QRAE II multi-gas detector revealed important nuances. Sample D, rich in plantain peel, produced the highest concentrations of PM2.5 at 86.33 micrograms per cubic meter, PM10 at 251.00 micrograms per cubic meter, and carbon monoxide at 34 parts per million, while sample C, 80 percent hyacinth with 20 percent molasses, was the cleanest performer. The elevated particulate loads in the plantain peel formulations correlated strongly with their higher concentrations of inorganic elements. X-ray fluorescence analysis showed that calcium, iron, potassium, and sulfur were all more abundant in samples D, E, and F, with calcium reaching tens of thousands of parts per million in the plantain peel briquettes compared with roughly 1,200 to 2,200 ppm in the molasses samples. The researchers traced a strong positive relationship between potassium and calcium levels and particulate emissions: potassium volatilizes during combustion and condenses as fine particles that contribute heavily to PM2.5, while less volatile calcium generates fly ash and coarser PM10 fractions as its minerals decay. Encouragingly, carbon monoxide levels across all samples remained well below the Occupational Safety and Health Administration’s permissible exposure limit of 50 ppm over an eight-hour workday, oxygen concentrations stayed within the safe indoor combustion threshold of 19.5 percent, and no hydrogen sulfide was detected in any sample, marking the briquettes as comparatively clean and health-friendly fuels.

The elemental chemistry also shaped the study’s practical recommendations. Moderate calcium content may improve thermal reflectivity and combustion efficiency, but excessive calcium signals ash formation that complicates residue management and stove maintenance. Elevated iron in the plantain peel samples, peaking at 5,873.73 ppm in sample D, may further correlate with the higher particulate emissions recorded for that group, since metals in fly ash influence both the physicochemical properties of emissions and their potential health impacts. Sulfur, which can generate sulfur dioxide during combustion, was lowest in sample A and highest in sample F, again favoring the molasses-bound formulations. The findings align with prior literature showing that high concentrations of alkali and alkaline earth metals in biomass can degrade combustion performance and increase emissions, and they echo earlier work on water hyacinth molasses blends and on briquettes derived from banana peels, pineapple peels, and other agricultural residues.

Taken together, the study positions water hyacinth briquetting as a strategy that attacks an invasive species problem from two directions at once. Removing biomass from Lake Abaya and Lake Chamo directly combats blooming and its ecological and public health consequences, while the harvested material displaces conventional wood fuel, easing pressure on forests and providing an affordable energy option for developing regions. The superior performance of molasses-bound briquettes underscores that binder selection is as decisive as feedstock in densified biofuel design, and the researchers emphasize that continued advances in this area could deliver energy that is affordable, environmentally sound, and socially responsible while simultaneously addressing waste management concerns. For the communities around Ethiopia’s Rift Valley lakes, the message is striking: the weed that has long defined their waterways may yet become a resource that helps restore them.

Subject of Research: Conversion of invasive water hyacinth biomass from Ethiopian lakes into charcoal briquettes as an alternative energy source

Article Title: Utilization of water hyacinth briquette as an alternative energy source to combat blooming in Abaya and Chamo Lakes, Ethiopia

Article References: Debel, G. L., Ibrahim, R., Mamo, A., Zewdie, Y., Lema, N. K., Syraji, Y., Fetane, S., & Fekadu Andeta, A. (2026). Utilization of water hyacinth briquette as an alternative energy source to combat blooming in Abaya and Chamo Lakes, Ethiopia. BMC Environmental Science, 3(1), Article 5. https://doi.org/10.1186/s44329-025-00044-4

Image Credits: AI Generated

DOI: 10.1186/s44329-025-00044-4

Keywords: water hyacinth, briquettes, invasive species, bioenergy, Lake Abaya, Lake Chamo, Ethiopia, carbonization, molasses binder, particulate matter, combustion, renewable energy

The research, led by Lukas Fliri of Aalto University and BOKU University together with colleagues at Aalto and VTT Technical Research Centre of Finland, focused on fibers spun with the Ioncell technology, a process that dissolves pre-hydrolyzed kraft birch pulp in a superbase-derived ionic liquid and dry-jet wet spins it into filaments. Unlike the native cellulose I allomorph found in wood and cotton, these regenerated fibers crystallize in the cellulose II form, the same allomorph that matters for carbon fiber production. Yet, as the authors point out, nearly all of the fundamental mechanistic data on cellulose pyrolysis has been gathered on cellulose I, while studies on cellulose II have mostly reported end-material properties without the underlying physics and chemistry. That gap made it difficult for the team to compare their own carbonization experiments with the literature, so they decided to build the reference dataset themselves.

The experimental design deliberately echoes a classic: the influential 1960s work by Tang and Bacon on the carbonization of Fortisan cellulose II fibers. Fliri and colleagues heated Ioncell fibers from room temperature up to 1100 degrees Celsius under helium in a simultaneous thermal analyzer coupled to a mass spectrometer, using heating rates spanning 2.5 to 40 kelvin per minute. Tiny samples of around 3.5 milligrams minimized heat and mass transfer distortions, and the evolved gases, water, carbon monoxide and carbon dioxide, were quantified through a calibration procedure based on calcium oxalate monohydrate. In parallel, batch carbonizations were carried out in a tubular furnace under nitrogen at nine target temperatures between 300 and 1100 degrees Celsius, with no thermostabilization pretreatment and no tension applied to the fibers, so that the intrinsic behavior of the material could be observed without process tricks that boost yield.

The thermal analysis revealed the familiar fingerprint of cellulose pyrolysis: a violent mass loss concentrated in a window of only 70 to 100 degrees, with onset temperatures between 288 and 322 degrees Celsius depending on heating rate. At the peak of this event, cellulose chains depolymerize and expel levoglucosan, the sugar anhydride that dominates the volatile stream, alongside furans, dehydrated sugars, water and carbon oxides. Crucially, the slower the heating, the more char survived. Char yield at 1100 degrees Celsius fell log-linearly as the heating rate rose, and the combined yields of water and carbon dioxide tracked the char yield almost perfectly. This is exactly what the two-competing-pathway model of cellulose pyrolysis predicts: long residence times below 300 degrees favor dehydration reactions that lock carbon into char precursors, while rapid heating funnels the material toward volatilization as levoglucosan instead.

The kinetic analysis added quantitative teeth to this picture. Using Friedman’s isoconversional method, the team found that the apparent activation energy of Ioncell fiber pyrolysis sits in a narrow band of roughly 190 to 220 kilojoules per mole up to about 80 percent conversion, consistent with a single dominant step: the rupture of the beta-O-4 glycosidic bond that links the glucose units of cellulose. Beyond that conversion level, the activation energy climbs sharply, signaling a shift from depolymerization to reactions within the solid carbonaceous residue. A first-order kinetic model, fitted with activation energies of 227 to 231 kilojoules per mole and pre-exponential factors matching literature values for cellulose I, described the mass loss curves well, but the authors caution that this is a phenomenological description of the main mass loss step, not proof of a simple one-step mechanism, and the parameters should not be extrapolated to isothermal treatments or temperatures above about 600 degrees.

One of the more surprising results concerns heat. The apparent heat of pyrolysis, measured by integrating the differential scanning calorimetry signal, came out between roughly 180 and 250 kilojoules per kilogram across all heating rates, in close agreement with decades of measurements on microcrystalline cellulose and filter paper. When the team ran control experiments on pure levoglucosan, the heat of its thermal evaporation matched the apparent heat of cellulose pyrolysis almost exactly. The implication is striking: the endothermic demand of cellulose pyrolysis is largely just the energy needed to evaporate levoglucosan. From a process engineering standpoint, this reaction heat is small compared with the roughly 650 kilojoules per kilogram of sensible heat required simply to bring the fibers up to their degradation temperature, a fact that matters for anyone designing industrial carbonization furnaces.

The batch carbonization experiments then traced how the fibers’ properties evolve with the final heat treatment temperature. Yields dropped steeply between 300 and 500 degrees and then plateaued between 6.8 and 9.4 percent by weight. Elemental analysis showed hydrogen and oxygen draining away as carbon accumulated, and a van Krevelen plot revealed two distinct linear regimes: below about 400 degrees the hydrogen-to-carbon and oxygen-to-carbon ratios follow a slope of roughly two hydrogens per oxygen, the signature of dehydration, while above that temperature decarboxylation and decarbonylation take over. Notably, oxygen loss largely stops above 600 degrees, and X-ray photoelectron spectroscopy confirmed that thermally stable oxygen functionalities remain embedded in the carbon even at 1000 degrees. These trapped oxygen atoms, the authors argue, act like reticulation agents, promoting five- and seven-membered rings that curve and distort the growing aromatic network and prevent the formation of a graphite-like structure, a key reason cellulose-derived carbons are non-graphitizing.

Morphology told a parallel story. The round cross-section of the Ioncell filaments survived carbonization intact, but the diameter shrank by roughly 60 percent by the time the fibers reached 600 degrees, after which further shrinkage was minimal. Fiber diameter correlated linearly with carbon content and log-linearly with carbonization yield, and the team interprets the shrinkage as the surface degradation of oriented cellulose microfibrils followed by their coalescence into denser cross-linked furanic and polyaromatic structures. Raman spectroscopy completed the picture: a polyaromatic network was already detectable at 400 degrees, and the ratio of the disorder-induced D band to the graphitic G band jumped from 0.59 to 0.93 between 600 and 700 degrees, then climbed more slowly toward 1100 degrees. The D-to-G intensity ratio correlated linearly with the hydrogen-to-carbon ratio above 600 degrees, indicating that large aromatic domains grow through dehydrogenation and radical condensation of smaller ring systems. Estimated in-plane aromatic cluster sizes grew from about 1.0 to 1.4 nanometers between 600 and 800 degrees and then stalled.

Perhaps the most consequential conclusion is what the study did not find. Older carbon fiber literature, still frequently cited, holds that the cellulose II crystal structure follows a special carbonization mechanism tied to the recondensation of four-carbon intermediates. The new data show no evidence of such a peculiarity: the pyrolysis behavior of Ioncell fibers matched the classic two-pathway models, and the high-temperature evolution agreed with general models for non-graphitizable carbons. The authors also observed an unexplained systematic mass loss above 800 degrees, but only at the slowest heating rate of 2.5 kelvin per minute, a phenomenon not previously reported that they flag for further confirmation. By identifying the temperature windows where dehydration, volatilization, dehydrogenation and aromatization each dominate, the dataset gives carbon fiber researchers a practical map for optimizing thermostabilization and carbonization schedules, and a common reference point for comparing cellulose II precursors of every kind. For a field trying to make carbon fiber cheap, renewable and strong enough for the mass market, that map may prove as valuable as the fibers themselves.

Subject of Research: Pyrolysis dynamics and physicochemical property development during the carbonization of Ioncell regenerated cellulose II fibers for carbon fiber production

Article Title: Tracking carbonization in Ioncell cellulose II fibers: pyrolysis dynamics and development of the physicochemical properties

Article References: Fliri, L., Yildirim, Z., Meinander, K., Guizani, C., & Hummel, M. (2026). Tracking carbonization in Ioncell cellulose II fibers: pyrolysis dynamics and development of the physicochemical properties. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13716-6

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13716-6

Keywords: carbon fibers, cellulose II, Ioncell, pyrolysis, carbonization, levoglucosan, char yield, Raman spectroscopy, thermogravimetric analysis, biobased materials, turbostratic carbon, kinetic modeling

The study, published in the Journal of Saudi Chemical Society, describes ZIF-8/CA composite porous carbons: materials built by combining zeolitic imidazolate framework-8, a metal-organic framework prized for its ultrahigh surface area, with cellulose acetate, the biocompatible and biodegradable polymer that already dominates commercial cigarette filter manufacturing. The research was led by Wei-li Xu, Pei-jian Sun and Cong Nie of the Key Laboratory of Tobacco Chemistry at the Zhengzhou Tobacco Research Institute of CNTC, working with colleagues from China Tobacco Shaanxi Industrial and China Tobacco Shandong Industrial. Their central insight is deceptively simple: the ratio in which the two ingredients are mixed before carbonization decides everything about how well the final carbon can grab benzene molecules from a moving gas stream.

To build the composites, the team turned to a dual emulsion-solvent evaporation method, a technique borrowed from soft-matter chemistry that is rarely applied to metal-organic framework composites. First they synthesized ZIF-8 powder by mixing zinc nitrate hexahydrate with 2-methylimidazole in water at a precisely controlled molar ratio and stirring the milky suspension for 24 hours. They then created a primary emulsion by injecting an aqueous internal phase containing ammonium bicarbonate into a solution of cellulose acetate dissolved in dichloromethane, adjusting the ZIF-8 to cellulose acetate mass ratios to 3/7, 4/6, 6/4 and 7/3. Droplets of this emulsion were dispersed into a dilute polyvinyl alcohol solution to form a secondary emulsion. As the solvent evaporated over six hours of stirring, uniform composite microspheres formed. The final and most transformative step was pyrolysis: heating the microspheres to 950 degrees Celsius at 5 degrees per minute under nitrogen and holding them there for two hours, converting the polymer-framework hybrid into porous carbon.

Why go to such lengths? The answer lies in the complementary weaknesses of existing adsorbents. Conventional activated carbon, the workhorse of volatile organic compound control, suffers from a moderate specific surface area, irregular pore structures and weak affinity for benzene at low concentrations. ZIF-8, by contrast, offers exceptional microporosity, strong pi-pi interactions with aromatic molecules and a gate-opening flexibility that accommodates bulky guests like benzene and toluene — but the raw powder is notoriously difficult to process, tends to agglomerate, and cannot easily be shaped into practical devices such as filter cartridges. Cellulose acetate solves the processability problem: its hydroxyl and acetyl groups form hydrogen bonds with ZIF-8, promoting even dispersion and mechanical stability, while its carbonization generates additional pores. What remained unknown, and what this study set out to map systematically, was how the ZIF-to-polymer mass ratio shapes the full hierarchy of pore sizes and, in turn, the benzene uptake.

The characterization data tell a striking story of structural optimization. Scanning electron microscopy revealed spherical particles between 100 and 500 micrometers in diameter, but their internal architecture varied dramatically with composition. At the 3/7 ratio, excess cellulose acetate caused the polymer matrix to aggregate, producing a dense, nearly pore-free cross-section. Pushing ZIF-8 content too high, at 6/4 and 7/3, triggered the opposite failure: agglomerated carbon particles and larger but poorly distributed pores. The sweet spot arrived at 4/6, where the surface roughened into uniform microscale protrusions and the cross-section displayed a beautifully interconnected porous network. Nitrogen physisorption measurements confirmed the visual evidence: the 4/6 composite achieved a Brunauer-Emmett-Teller specific surface area of 1380 square meters per gram and a mesopore volume of 0.77 cubic centimeters per gram, far exceeding the 577, 657 and 796 square meters per gram recorded for the other formulations. All samples showed Type IV isotherms with H4 hysteresis, a fingerprint of mesoporosity, with mesopores concentrated near 2.5 nanometers.

Mercury intrusion porosimetry added the final piece of the hierarchical puzzle, probing pores far too large for nitrogen adsorption to detect. The dominant macropore diameter increased progressively with ZIF-8 content, a trend the researchers attribute to gas evolution — carbon dioxide and nitrogen released as the framework decomposes — which inflates and expands the pores during carbonization. This revealed an elegant division of labor: cellulose acetate carbonization builds mesopores and surface area, while ZIF-8 decomposition carves macropores. The two effects compete, and the 4/6 composition strikes the optimal balance between abundant mesoporous adsorption domains and macroporous highways for rapid molecular transport. Many high-surface-area carbons perform poorly in dynamic adsorption because blocked channels or excessive micropores strangle diffusion; this composite avoids both traps by design.

Dynamic benzene vapor adsorption tests brought the structure-property relationship into sharp focus. In breakthrough experiments with a benzene stream flowing at 100 milliliters per minute through a thermostatted column at 25 degrees Celsius, the saturation adsorption capacity traced a volcano-shaped curve across the composition series, peaking at 235.0 milligrams per gram for the 4/6 sample — well above its siblings and competitive with previously reported adsorbents. To dissect the kinetics, the team fitted the breakthrough curves with two classical fixed-bed models. The Apiratikul-Chu model reproduced the entire breakthrough curves with correlation coefficients exceeding 0.99, capturing the asymmetric tailing that arises from internal diffusion through tortuous pore networks. The 4/6 composite also displayed the highest rate constant, at 65.2 per minute, thanks to plentiful active sites and macropores that slash mass-transfer resistance. The Adams-Bohart model, applied to the initial stage of adsorption, delivered correlation coefficients above 0.97, confirming that surface adsorption and external mass transfer govern the onset of uptake.

The chemistry behind the capture is as important as the physics of the pores. Both the graphitic carbon formed from cellulose acetate and the residual framework structure of ZIF-8 are rich in delocalized pi-electrons, which form strong pi-pi stacking interactions with the aromatic ring of benzene — an affinity that physical adsorption alone cannot provide. Meanwhile, the graded pore hierarchy produces a confinement effect: micropores and mesopores physically trap benzene molecules, while interconnected channels accelerate their diffusion toward those sites. Macropores lower external diffusion resistance, mesopores and micropores dominate intraparticle diffusion, and the result is a material whose adsorption rate is as impressive as its capacity.

The most headline-grabbing result came when the material faced its intended real-world challenge: actual cigarette smoke. Using a custom-built apparatus connected to an SM-450 smoking machine operating under the ISO standard protocol — 35-milliliter puffs drawn over two seconds with 60-second intervals — the researchers loaded 10 milligrams of adsorbent into each cigarette filter and analyzed trapped benzene by gas chromatography-mass spectrometry. The ZIF-8/CA 4/6 composite removed 49.0 percent of benzene from mainstream smoke, dramatically outperforming a ZIF-8/polylactic acid control composite prepared under identical conditions, which managed only 20.7 percent. Even in the chemical chaos of real smoke, where countless gaseous components compete for adsorption sites, the hierarchical pore structure and pi-pi selectivity for aromatic compounds allowed the composite to maintain high benzene capture. The authors note that only benzene was quantified in this study, with multi-component analysis and regeneration and long-term cycling tests planned for follow-up work, and that static adsorption isotherms will be examined in future research.

Beyond the laboratory numbers, the study delivers a genuinely versatile design principle. By simply tuning a mixing ratio before a single carbonization step, researchers can dial in a micro-meso-macroporous architecture tailored to a target pollutant — a rational, adaptable strategy that could extend well beyond cigarette filters to industrial off-gas treatment, indoor air purifiers and protective respirators. The rigid carbon skeleton also promises structural stability for cyclic use. For a compound as pervasive and as dangerous as benzene, a scalable material that more than doubles the removal efficiency of a comparable commercial polymer composite represents meaningful progress — and a reminder that sometimes the biggest advances in environmental health come not from exotic new chemistry, but from getting the architecture of familiar ingredients exactly right.

Subject of Research: Hierarchical pore engineering of ZIF-8/cellulose acetate composite porous carbon for benzene vapor adsorption and cigarette smoke purification.

Article Title: Hierarchical pore structure modulation of ZIF-8/CA composite porous carbon for efficient benzene vapor adsorption

Article References: Xu, W.-L., Sun, P.-J., Sun, X.-H., Wang, Y.-P., Li, J.-L., Ge, C., Liu, Q., Zhou, J., Yang, F., Song, X.-H., & Nie, C. (2026). Hierarchical pore structure modulation of ZIF-8/CA composite porous carbon for efficient benzene vapor adsorption. Journal of Saudi Chemical Society, 30(4), Article 56. https://doi.org/10.1007/s44442-026-00098-2

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00098-2

Keywords: ZIF-8, cellulose acetate, porous carbon, benzene adsorption, volatile organic compounds, hierarchical pores, metal-organic frameworks, cigarette smoke filtration, air purification, carbonization, adsorption kinetics, breakthrough curves