Graphene has generated significant interest as a material for a wide range of applications due to its exceptional strength, flexibility, and conductivity but it faces obstacles in supply and implementation within engineering composite materials. The energy use and climate impact of graphene production from mineral sources is significant. A renewable, plant-based graphitic nanoplatelet (pGNP) presents a more accessible and sustainable filler with properties comparable to mineral graphenes and a significant reduction in embedded emissions. In this study, a catalytic method for the production of graphitic carbon from biomass is studied and the impacts on process conditions and feedstock selection are examined. The impacts of catalyst loading, secondary catalysts and temperature are examined. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron microscopy (TEM) show highly disordered, pGNP with flakes 3-10 layers thick, lateral sizes from 200 to greater than 2000 nm, and which include epoxide and carboxyl functional groups. These functional groups play a key role in the dispersion of pGNP in suspensions as well as their interaction with thermoset plastics, as demonstrated by dynamic scanning calorimetry and rheology. Furthermore, Raman analysis was used to show the impact of pGNP addition to the polymer structure of epoxy and polyurethane (PU) resins. These interaction between thermosetting resins and pGNP allow for improved mechanical, electrical, and thermal properties of nanocomposites.

Although hydrothermal liquefaction (HTL) is the leading technology in converting wet biomass into bioenergy, the treatment of its toxic-laden aqueous phase wastewater presents a major challenge on its path toward commercial viability. This study presents the first-ever assessment of sewage sludge-fed HTL wastewater (SS-HTLWW) treatment and toxic compound removal using municipal activated sludge (AS) by optimizing its cultivation condition. It was found that AS with optimized pretreatment can remove up to 91.2% of the soluble chemical oxygen demand (sCOD) in SS-HTLWW, of which up to 82% can be attributed to biological mineralization and adsorption of sCOD by AS. Conventional bioprocess optimization techniques, including overliming, elevated temperatures, and nutrient supplementation, were found to raise the maximum rate of sCOD utilization (Rm) of AS treatment by 44%, 67%, and 45%, respectively. The variation in the maximum degradation potential (Dmax) after 23 days of treatment across all groups was negligible. Adjusting the SS-HTLWW dilution factor from 20× to 10× resulted in no significant difference in Rm or Dmax values due to the counteracting effects of high substrate and inhibitor concentrations. Additionally, AS was able to eliminate almost all N-heterocycles, phenolic compounds, and organic acids found in SS-HTLWW. This suggested that AS can both survive in and mitigate the high level of toxicity associated with SS-HTLWW; however, the high levels of recalcitrant COD after treatment may require further attention before it can be adequately discharged. The insights gained from this study are poised to interest engineers and treatment plant operators in search of efficient strategies for SS-HTLWW management and the broader application of HTL.

Storm events pose significant challenges to the stability and performance of a floating treatment wetland designed to cultivate aquatic plants. This study examines the resilience and ecological performance of a floating foam mat that harbors aquatic plants, serving multiple purposes: nutrient removal (e.g., nitrate and phosphate), carbon sequestration from the atmosphere, heavy metal removal, and biochar production. Plant growth trials were conducted in a watershed using 10 modular floating mats containing two aquatic macrophytes, common rush ( Juncus effusus ) and switchgrass ( Panicum virgatum ), from mid-June to December 2025 (6 months) to assess vegetation growth, biomass composition, and pyrolysis product yields. Biomass monitoring showed that common rush had a root length of 64 cm (2′1") and a stem length of 67 cm (2′2"), while switchgrass had the highest root length of 97.5 cm (3′2") and a stem length of 128 cm (4′2") over a five-month period. The plant survival rate for each mat ranged from 90% to 92% by the end of harvesting. The CHNS analysis revealed that switchgrass roots had the highest concentrations of nitrogen (2.2%) and sulfur (0.3%). The common rush stem had higher concentrations of carbon (~ 45%) and hydrogen (~ 6%), like switchgrass. Elemental concentrations showed high potassium (K) levels (> 10,000 ppm) in both biomasses. Furthermore, pyrolyzed biomass produced the highest biochar yield at CR-PR (0.48 g/g) and SG-WR (0.42 g/g), and the lowest at CR-WC (0.35 g/g) and SG-WS (0.39 g/g). These variations in pyrolysis product amount and elemental compositions highlight differences in biomass chemical composition across plant parts. This study offers practical insights into creating storm-resilient systems that support ecological restoration and biomass valorization into pyrolysis products, such as biochar and biooil, which can be used as soil amendments and biofuels, respectively.

Hydrothermal liquefaction (HTL) of lignocellulosic biomass produces multiple product fractions, including solid residue (SR), heavy bio-oil (HBO), aqueous phase (AP), and light bio-oil (LBO). This study mainly applied principal component analysis (PCA) and regression modeling to predict AP solution weight, LBO weight and fuel characteristics, and HTL wastewater biodegradability, as well as to improve prediction accuracy for SR and HBO under various operating conditions (temperature: 250–350 °C, residence time: 5–60 min, and the combined solid loading of three batches: 15–45 g). A complementary relationship between SR and AP weights found in PCA enabled the estimation of AP weight based on predicted SR values in a regression analysis. A modified partition coefficient was introduced to link LBO weight with the carbon content of AP and was predicted, enabling accurate LBO yield estimation. Although LBO fuel characteristics could not be modeled reliably, those of SR and HBO were predicted with improved accuracy over prior kinetic models. The concentration of catechol in HTL wastewater (HTL-WW) was also modeled from operating conditions and linked to half-maximal inhibitory concentration (IC50) of R. jostii and A. niger as a biodegradability index. This work demonstrates the feasibility of predicting underrepresented HTL outputs using statistical approaches.

Fruit waste valorization offers sustainable way to unlock the hidden treasure stored in fruit processing industry. The present approach focuses on the extraction of pectin under optimal parameters by heating and ultrasound assisted extraction to attain maximum pectin yield from the lemon peels collected through local fruit juice shop of Kishangarh market (Rajasthan). The optimization process followed heating and ultrasound assisted extraction through varying reaction time (90-120 min and 30-50 min respectively), temperature (70-90 °C and 35-45 °C respectively) and solid solvent ratio (1:20-1:40 g/ml); Box Behnken Design (BBD) model was used and showed the statistically significant results. The extracted pectin was further analysed for physiochemical properties, functional properties, antioxidant property and instrumental characterization such as Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electon Microscopy (SEM), X-ray Diffraction (XRD), Thermogravimetric analysis (TGA), Differential Scanning Colorimetry (DSC) and zeta potential. The pectin extraction with ultrasound assisted and heating assisted extraction showed the maximum yield of 31 % and 29.8 % respectively. The functional properties includes ash content, moisture content, water holding capacity, oil holding capacity, emulsifying capacity and emulsifying stability observed is 4.6 ± 0.3 %, 3.91 ± 0.24 %, 7.39 ± 0.17 g/g, 2.27 ± 0.06 g/g, 46.17 ± 1.41 % and 87.76 ± 1.70 % of heating assisted extraction whereas 3.5 ± 0.3 %, 6.57 ± 0.35 %, 8.5 ± 0.31 g/g, 2.56 ± 0.16 g/g, 51.64 ± 1.46 % and 90.23 ± 1.41 % of ultrasound assisted extracted pectin respectively. The antioxidant activity observed to be 87.19 ± 0.30 % and 85.16 ± 0.70 % of ultrasound and heating assisted extraction respectively. This study revealed that within less time and temperature; ultrasound assisted extraction provides better yield as compare to heating assisted extraction instead of it the study also focuses on the circular solvent strategy used during the process.

In this study, hydrothermal liquefaction (HTL) of rice straw (RS) an abundant agricultural waste was carried out to produce bio-oil. Silica (SiO2)-rich ash derived from RS was used as a catalyst. Different reaction parameters such as reaction temperatures (230-270 degrees C), residence times (15-45 min), catalytic dosage (5-15 wt%) and different solvents such as water (H2O), Ethanol (EtOH), water-ethanol (H2O-EtOH), water-methanol (H2OMeOH), and water-isopropyl alcohol (H2O-IPA) solvent mixtures were employed. In non-catalytic HTL, the highest bio-oil yield (52.5 wt%) was obtained using an H2O-EtOH solvent mixture compared to H2O (14.75 wt %), EtOH (25.2 wt%), H2O-MeOH (45.7 wt%), and H2O-IPA (51.2 wt%) at temperature 250 degrees C for 30 min of reaction time. Using a SiO2-rich ash catalyst further improved the bio-oil yield to 59.16 wt% at 250 degrees C for 30 min under the H2O-EtOH solvent system. Catalytic HTL bio-oil showed a high content of phenolics (24.12 %), ketones/aldehydes (22.12 %), and hydrocarbons (18.61 %). The hydrogenation reaction was promoted in the presence of catalyst and the higher phenolic and hydrocarbon content was found in the catalytic bio-oil. The biooil obtained under catalytic conditions exhibited lower oxygen content (30.6 wt%) and a higher heating value (26.61 MJ/kg) compared to bio-oil obtained under non-catalytic reactions. This study highlights the potential of SiO2 rich ash catalysts from RS biomass for producing quality bio-oil.

Wastewater treatment with concurrent energy recovery plays a pivotal role in achieving sustainable development goals. Among emerging concerns, eutrophication remains a significant environmental threat, primarily driven by excess nutrient discharge into water bodies. Microbial fuel cells (MFCs) offer a promising solution by converting the chemical energy in organic matter directly into electricity. In this context, the present study investigates the integration of MFCs into constructed wetlands (CWs), resulting in Electro-Wetlands (EWs) hybrid systems engineered to achieve simultaneous nutrient removal and bioelectricity generation. Two identical CWs and EWs systems were designed and operated using institutional sewage to comparatively assess treatment efficiency and energy output. The EW units demonstrated enhanced nutrient removal (>90%) compared to CWs (75-85%), along with comparable fecal coliform reduction across both systems over a 60-day operational period. Hydraulic performance remained stable, with average evaporation rates of 0.99 L/day for EWs and 0.98 L/day for CWs, indicating minimal impact due to electrode integration. Electrochemical analysis of the EWs showed a consistent voltage output of 60-90 mV, current densities between 0.03-0.06 mA/cm(2), and power densities ranging from 1.5-3.0 mW/m(2), with peak values reaching 120 mV and 6 mW/m(2), respectively. The novelty of this study lies in the comparative evaluation of conventional CWs and Electro-Wetlands and the demonstration of a simple, cost-effective strategy for upgrading existing CWs to EWs with minimal structural changes. This makes the approach highly scalable and adaptable for decentralized wastewater treatment in institutional or community-based settings. Moreover, the study contributes to understanding the operational mechanism of CWs versus EWs, supporting future design improvements and broader implementation.

The search for renewable alternatives has turned attention to microalgae, which grow rapidly, achieve high biomass productivity, and accumulate substantial lipids. Unlike terrestrial feedstocks such as corn or sugarcane, microalgae can be cultivated on non-arable land using saline or wastewater streams, avoiding competition with food supplies. Wastewater cultivation is particularly compelling because municipal and agricultural effluents supply nitrogen, phosphorus, and organic carbon, while algal growth removes excess nutrients that would otherwise drive eutrophication; reported removal efficiencies often exceed 90 % under optimized conditions. Algal-bacterial consortia further enhance performance by generating oxygen through photosynthesis and capturing CO2, thereby lowering aeration costs. The major challenge lies not in cultivation but in conversion. Drying biomass is energy-intensive, whereas hydrothermal liquefaction (HTL) transforms wet algal slurries directly into biocrude at 250-350 degrees C and 10-20 MPa. Typical yields range from 30 to 50 % of dry weight, with an energy density of 38-41 MJ/kg, along with nutrient-rich aqueous fractions, gases, and char that can be recycled. Key barriers remain in lowering oxygen and nitrogen content, scaling reactors, and reducing upgrading costs. This review evaluates the integration of wastewater-based algal cultivation with HTL for renewable fuel production, examining wastewater characteristics, cultivation strategies, biomass yields, HTL fundamentals and process advances, product upgrading, and techno-economic and environmental aspects. By linking wastewater remediation with biofuel production, the review highlights opportunities for nutrient recycling, greenhouse gas mitigation, and circular-economy applications, while identifying the technical gaps that must be addressed for practical deployment.

The use of fossil fuels leads to greenhouse gas emissions and climate change. At the same time, the finite reserves of crude oil, natural gas, and coal necessitate a shift to alternative energy sources. Apart from the typical non-conventional energy sources, waste-to-energy routes are gaining popularity. Non-biodegradable plastic waste, which possesses a high amount of energy, can be thermo-chemically treated (pyrolysis or gasification) to generate fuel. On the other hand, biomass (BM) thermochemical conversion has the potential to emerge as a green energy source with proper forest management. Co-pyrolysis and co-gasification of plastic and BM show the potential for further improvement in fuel quality and quantity. The available research works involve a range of BM and plastic types, making it difficult to conclude a generalised trend of product generation. The current work systematically reviews the recent research data by categorising the results as per the type of feedstock used and the conversion processes. A general trend of fuel yield for various feedstock types and relative contents is summarised. The effects of various parameters – operating temperature, gasifying agent, blending ratio, reactor type, and use of catalysts are also discussed, along with an insight into the catalytic conversion mechanism. The review will be beneficial to get a broad picture of the recent progress in BM-plastic co-pyrolysis and co-gasification, associated challenges, and potential applications.

Hydrothermal liquefaction (HTL) offers a promising pathway for producing high-quality bio-oil, which can serve as a renewable source of chemicals and fuels. This study explores the potential of rice straw (RS) hydrothermal liquefaction for synthesizing phenolic compounds rich bio-oil under different reaction temperatures, retention times, and catalysts. The use of K2CO3 and solid catalysts (Kaolin (KA), Fe/KA, Ni/KA, and Ni-Fe/KA) promoted the HTL of RS. Maximum bio-oil yield (23.91 wt%) was obtained with Ni/KA and K2CO3 catalysts, compared to bio-oil yield of 10.8 wt% under non catalytic condition as well as under catalytic conditions using with KA (21.21 wt%), Fe/KA (19.1 wt%), and Ni-Fe/KA (19.5 wt%) at 270 degrees C with retention time of 30 min. Bio-oils were characterized using various analytical methods such as GC-MS, FT-IR, NMR, TGA, UV-Vis and CHNS analysis. Alkaline salt, in the presence of the Ni/KA catalyst, promoted the cleavage of C-O bonds of lignin present in RS biomass, resulting in higher yields of phenolic compounds compared to the non-catalytic and other catalytic conditions. Syringyl-type (S-type) phenols were highest with KA and Fe/KA, while Ni/KA showed a lower amount of phenols. Guaiacyl-type (G-type) phenols were produced in higher amount using Fe/KA, whereas Ni/ KA yielded the highest p-hydroxyphenyl-type (H-type) phenols. Furthermore, high higher heating value (HHV) and lower oxygen content of bio oil were also achieved with Ni/KA catalyst.

Agricultural biomass residues represent a substantial underutilized resource, and their conversion into biochar offers a practical approach for sustainable waste management, renewable energy production, and carbon sequestration. The present study was conducted to evaluate the physicochemical properties of biochar produced from four locally available agricultural biomass feedstocks, namely cotton waste, pigeon pea, rice husk, and pruned wood, using the developed farmer-friendly natural draft biochar kiln. The selected biomass feedstocks were initially characterised for their physicochemical properties and were then carbonised under three air opening conditions (100% closed, 100% opened, and 50% opened). The produced biochar was subsequently analysed for proximate composition, ultimate composition, calorific value, and pH. A two-factor Completely Randomised Design (CRD) was used to evaluate the effects of biomass type and air opening treatment. Among the biomass feedstocks, pigeon pea recorded the highest volatile matter (82.58%) and carbon content (67.50%), whereas rice husk exhibited the highest ash content (15.48%) and fixed carbon content (16.47%). The physicochemical characteristics of the produced biochar varied significantly with biomass type. Rice husk biochar recorded the highest fixed carbon content (72.80%) and carbon content (77.19%), while pruned wood biochar recorded the highest calorific value (28.72 MJ kg⁻¹). The pH of the biochars ranged from 8.44 to 10.11, indicating their alkaline nature and suitability for soil amendment applications. Statistical analysis revealed that biomass type significantly influenced all evaluated physicochemical properties, whereas air opening treatment had a significant effect only on biomass moisture content and showed limited influence on the quality of the produced biochar. Overall, the developed farmer-friendly biochar kiln successfully converted locally available agricultural biomass into quality biochar suitable for renewable energy, carbon sequestration, and sustainable agricultural applications. The findings further indicate that biomass selection plays a more important role than air opening conditions in determining biochar quality.

This work aims at preliminary evaluating the techno-economic feasibility of a biolubricant production process starting from lignin and waste cooking oil, to be integrated in a lignocellulosic biorefinery. A phenyl-branched FAMEs mixture is obtained, which exhibit improved lubricity and oxidative stability compared to standard FAMEs-based biolubricants. The product is obtained exploiting aromatic hydrocarbons from lignin, generated via hydrothermal liquefaction followed by selective hydrodeoxygenation. The economic analysis compares the minimum ethanol selling price (MESP) of a generic U.S. biorefinery processing 2000 tonne/day of corn stover with and without the integration of biolubricant production. Results indicate potential improvement in the biorefinery economic performance, with MESP decreasing from $0.798/L in the reference case (ethanol production only) to $0.697/L when the biolubricant process is included. Reduction in the price of waste cooking oil improves the performances, although the biolubricant selling price has a large impact on the economic profitability of the process.

This study investigated a green chelation strategy for deashing algal biomass using nitrilotriacetic acid (NTA) and deionized water (DI) to enhance its suitability for biofuel and bioproduct applications. Solid-state algal turf scrubber (SS ATS), green algal turf scrubber (ATS), and Scenedesmus were analyzed, with Scenedesmus selected for detailed evaluation due to its high ash removal efficiency. The objective was to optimize a purification process that minimizes ash and heavy metal content while preserving biochemical integrity. Algal biomass underwent sequential washing with DI, NTA, and NTA+DI under varying temperatures (90-130 °C). Analytical techniques including Fourier Transform Infrared (FTIR) spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and CHN (carbon, hydrogen, nitrogen) elemental analysis were employed to assess changes in ash content, metal ion concentration, elemental composition, and biochemical properties. The NTA+DI treatment was the most effective, lowering the ash content in Scenedesmus from 15.2% to 3.8% and decreasing lead (Pb) and copper (Cu) levels below detectable limits. Ash removal was greatly aided by temperature reaching a high efficiency of 83.07% at 130 °C owing to enhanced calcium, magnesium, and potassium solubilization and chelation. Successive NTA recycling led to a decline in efficiency by the third cycle, indicating chelating agent saturation. Despite ash reduction, the ultimate analysis showed minimal changes in CHN composition (C: 45.2%, H: 6.0%, and N: 7.1%), ensuring the retention of organic matter. These findings established NTA+DI treatment as an effective and sustainable method for deashing algal biomass while maintaining its biochemical integrity. This optimized process enhances the feasibility of Scenedesmus-derived biofuels improving combustion efficiency and reducing inorganic fouling in biorefineries and thermochemical conversion systems.

Floating treatment wetlands (FTWs) are engineered systems that utilize floating platforms planted with aquatic vegetation to treat polluted water such as stormwater, agricultural runoff, and wastewater. FTWs have emerged as promising and environmentally sustainable solutions for water purification. This review synthesizes the current knowledge on FTW design, plant selection, and performance evaluation. It highlights key factors influencing nutrient and heavy metal removal, including the hydraulic retention time, mat thickness, and types of plant species. Recent findings on the roles of root architecture, microbial interactions, and seasonal variability in treatment efficiency are also discussed. Additionally, the review explores advanced analytical methods for monitoring water quality and assessing plant growth and contaminant uptake. Case studies from both laboratory- and field-scale experiments illustrate how variation in FTW configurations impacts pollutant removal efficiency. The review concludes by identifying critical research gaps, including the need for standardized monitoring protocols, strategies to enhance long-term performance, and the integration of FTWs with complementary treatment technologies to improve effectiveness across diverse aquatic environments.

The hydrothermal liquefaction (HTL) process offers an energetic advantage over pyrolysis because it does not require prior drying of the biomass feedstock. However, there are significant challenges in simultaneously estimating both the yields and characteristics of products from the HTL of biomass with theoretical support. This study developed a unique element-based kinetic model to predict the yields, higher heating values, and fuel characteristics of solid residue and heavy bio-oil, based on the temperature, residence time, solid loading, and elemental composition (C, H, N, and O) of corn stover. Furthermore, the model predicted the weights of dissolved carbon and nitrogen in the aqueous phase. HTL experiments were conducted using corn stover at temperatures ranging from 250 to 350 °C for residence times between 5 and 60 min. The resulting solid and liquid products were analyzed for the elemental composition and ash content. The experimental data and MATLAB program were used to predict the products. The fuel characteristics derived from predicted elemental weight data of solid residues followed the trend line of the observed data on the van Krevelen diagram. In those of heavy bio-oil, the H/C atomic ratio of the average predicted data matched the one calculated from the observed data. Additionally, power function relationships between the amounts of corn stover and obtained product fractions were identified under identical temperature and residence time conditions by varying solid loading, providing insights into the partial nonlinear behavior of the reaction system.