Co-pyrolysis of plastic waste and eucalyptus waste wood for fuel pellets production: A study of fuel, mechanical, and combustion characteristics under varying binder proportion.

The study explores the effect of varying molasses proportions as a binder on the characteristics of densified char obtained through the slow co-pyrolysis of plastic waste and Eucalyptus wood waste (Waste low-density polyethylene - Eucalyptus wood (WLDPE-EW) and Waste Polystyrene - Eucalyptus wood (WPS-EW)). Pyrolysis was conducted at 500 °C with a residence time of 120 min, employing plastic to wood waste ratios of 1:2 and 1:3 (w/w). The focus was on how varying the proportion of molasses (10-30 %), influences the physical and combustion properties of the resulting biofuel pellets. Our findings reveal that the calorific value of the pellets decreased from 28.94 to 27.44 MJ/Kg as the molasses content increased. However, this decrease in calorific value was compensated by an increase in pellet mass density, which led to a higher energy density overall. This phenomenon was attributed to the formation of solid bridges between particles, facilitated by molasses, effectively decreasing particle spacing. The structural integrity of the pellets, as measured by the impact resistance index, improved significantly (43-47 %) with the addition of molasses. However, a significant change in the combustion characteristics depicted by lower ignition and burnout temperatures were observed due to decrease in fixed carbon value and increase in volatile matter content, as the proportion of molasses increased. Despite these changes, the pellets demonstrated a stable combustion profile, suggesting that molasses are an effective binder for producing biofuel pellets through the densification of char derived from the co-pyrolysis of plastic and Eucalyptus wood waste. The optimized molasses concentration analyzed through multifactor regression analysis was 16.96 % with 28 % WLDPE proportion to produce WLDPE-EW char pellets. This study highlights the potential of using molasses as a sustainable binder to enhance the mechanical and combustion properties of biofuel pellets, offering a viable pathway for the valorization of waste materials.

PDA-Fe3O4 decorated carbon felt anode enhancing electrochemical performance of microbial fuel cells: Effect of electrode materials on electroactive biofilm.

Anode modification is an effective strategy for enhancing the electrochemical performance of microbial fuel cell (MFC). However, the impacts of the modified materials on anode biofilm development during MFC operation have been less studied. We prepared a novel PDA-Fe3O4-CF composite anode by coating original carbon felt anode (CF) with polydopamine (PDA) and Fe3O4 nanoparticles. The composite anode material was characterized by excellent hydrophilicity and electrical conductivity, and the anodic biofilm exhibited fast start-up, higher biomass, and more uniform biofilm layer after MFC operation. The MFC reactor assembled with the composite anode achieved a maximum power density of 608 mW m-2 and an output voltage of 586 mV, which were 316.4% and 72.4% higher than the MFC with the original CF anode, respectively. Microbial community analysis indicated that the modified anode biofilm had a higher relative abundance of exoelectrogen species in comparison to the unmodified anode. The PICRUSt data revealed that the anodic materials may affect the bioelectrochemical performance of the biofilm by influencing the expression levels of key enzyme genes involved in biofilm extracellular polymer (EPS) secretion and extracellular electron transfer (EET). The growth of the anodic biofilm would exert positive or negative influences on the efficiency of electricity production and electron transfer of the MFCs at different operating stages. This work expands the knowledge of the role that anodic materials play in the development and electrochemical performance of anodic biofilm in MFCs.

From slag to green: Aided-phytoremediation as a sustainable tool to rehabilitate land contaminated by steel slag and assessment of CO2 sequestration.

Steel slag (SS) has many applications, but its immediate reuse is not possible due to its inherent swelling potential and presence of toxic metals. Therefore, it can only be used after the aging process, which can be either natural or artificial. While few large-scale steel plants afford artificial aging, many small-scale ones opt for natural aging through stockpiling of SS. This results in an increase in soil pH to over 12, thus damaging the ecosystem and making it unviable for plant growth. This research focuses on the reclamation of land affected by SS through the formation of a Phyto-barrier using 22 native plant species aided by the application of a 2 % (v/v) solution of the organic amendment. Furthermore, the superior performance of plants belonging to the Fabaceae family was ascertained, while establishing Sesbania grandiflora as an able species for aided-phytoremediation due to its remarkable growth (≈ 10 ft tall and 33 cm in circumference) during the study period. The CO2 sequestered by the plantation showed that maximum sequestration has been done by Sesbania grandiflora (49.96 kg CO2 / tree/ year), and least by Azadirachta indica (0.35 kg CO2/tree/year). The overall CO2 sequestered by the plantation stood at 3.85 tons/year. A cost-benefit analysis of using aided-phytoremediation indicates an expense of 90 $ per year as the recurring expense, while carbon credits if monetized, would yield 154 $ to 308 $ as returns. The investigations of this study established a new approach to vegetation over SS-affected land, through native species and the application of organic amendment.

Progress and perspectives on carbon-based materials for adsorptive removal and photocatalytic degradation of perfluoroalkyl and polyfluoroalkyl substances (PFAS).

Per- and polyfluoroalkyl substances (PFAS) (also known as 'forever chemicals') have emerged as trace pollutants of global concern, attributing to their persistent and bio-accumulative nature, pervasive distribution, and adverse public health and environmental impacts. The unregulated discharge of PFAS into aquatic environments represents a prominent threat to the wellbeing of humans and marine biota, thereby exhorting unprecedented action to tackle PFAS contamination. Indeed, several noteworthy technologies intending to remove PFAS from environmental compartments have been intensively evaluated in recent years. Amongst them, adsorption and photocatalysis demonstrate remarkable ability to eliminate PFAS from different water matrices. In particular, carbon-based materials, because of their diverse structures and many exciting properties, offer bountiful opportunities as both adsorbent and photocatalyst, for the efficient abatement of PFAS. This review, therefore, presents a comprehensive summary of the diverse array of carbonaceous materials, including biochar, activated carbon, carbon nanotubes, and graphene, that can serve as ideal candidates in adsorptive and photocatalytic treatment of PFAS contaminated water. Specifically, the efficacy of carbon-mediated PFAS removal via adsorption and photocatalysis is summarised, together with a cognizance of the factors influencing the treatment efficiency. The review further highlights the neoteric development on the novel innovative approach 'concentrate and degrade' that integrates selective adsorption of trace concentrations of PFAS onto photoactive surface sites, with enhanced catalytic activity. This technique is way more energy efficient than conventional energy-intensive photocatalysis. Finally, the review speculates the cardinal challenges associated with the practical utility of carbon-based materials, including their scalability and economic feasibility, for eliminating exceptionally stable PFAS from water matrices.

Effective method for upcycling construction and demolition waste into concrete: A life cycle approach.

Different property enhancement techniques have already been established to support upcycling of construction and demolition waste as aggregate in concrete. However, the most suitable and sustainable method is still unknown. Quality improvement of recycled coarse aggregate (RCA) after any treatment method and its environmental impact is estimated using life cycle analysis (LCA). This article compares the environmental impacts of such treatment methods on RCA and aims to find out the most suitable method with minimum impacts. The functional unit of this study is considered the preparation of 1 tonne of treated aggregate (recycled), considering reduction in water absorption after the treatment. An LCA is carried out using the SimaPro software (https://simapro.com/) followed by ISO 14040/44 guidelines. Based on the LCA environmental profiles, thermal treatment is the highest emission contributing removal method followed by mechanical grinding. In strengthening of attached mortar methods, accelerated carbonation process is the major emission contributing method followed by a specific microbial treatment. Moreover, a sensitivity analysis was performed by varying the energy mix with a focus on renewable-based energy mix. The sensitivity analysis shows a shift on selection for the suitable treatment method and other possibilities considering renewable-based energy mix. A preliminary assessment and probable impact prediction could be conceptualized before the adoption of any treatment method on RCA for a particular location.

Synthesis and commercialization of bioplastics: Organic waste as a sustainable feedstock.

Substituting synthetic plastics with bioplastics, primarily due to their inherent biodegradable properties, represents a highly effective strategy to address the current global issue of plastic waste accumulation in the environment. Advances in bioplastic research have led to the development of materials with improved properties, enabling their use in a wide range of applications in major commercial sectors. Bioplastics are derived from various natural sources such as plants, animals, and microorganisms. Polyhydroxyalkanoate (PHA), a biopolymer synthesized by bacteria through microbial fermentation, exhibits physicochemical and mechanical characteristics comparable to those of synthetic plastics. In response to the growing demand for these environmentally friendly plastics, researchers are actively investigating various cleaner production methods, including modification or derivatization of existing molecules for enhanced properties and new-generation applications to expand their market share in the coming decades. By 2026, the commercial manufacturing capacity of bioplastics is projected to reach 7.6 million tonnes, with Europe currently holding a significant market share of 43.5 %. Bioplastics are predominantly utilized in the packaging industry, indicating a strong focus of their application in the sector. With the anticipated rise in bioplastic waste volume over the next few decades, it is crucial to comprehend their fate in various environments to evaluate the overall environmental impact. Ensuring their complete biodegradation involves optimizing waste management strategies and appropriate disposal within these facilities. Future research efforts should prioritize exploration of their end-of-life management and toxicity assessment of degradation products. These efforts are crucial to ensure the economic viability and environmental sustainability of bioplastics as alternatives to synthetic plastics.

Composite of graphitic carbon nitride and TiO2 as photo-electro-catalyst in microbial fuel cell.

The widespread application of surfactants and their subsequent discharge in the receiving water bodies is a very common issue in developing countries. In the present investigation, a composite of graphitic carbon nitride (GCN) and TiO2 was used as a photo-electro-catalyst in a microbial fuel cell (MFC)-based hybrid system for bio-electricity production and simultaneous pollutant removal (organic matter and sodium dodecyl sulphate, SDS). The GCN: TiO2 composite with a ratio of 70:30 (by wt. %) revealed a better electrochemical response; thus, it was used as a photo-electro-catalyst in MFC. Additionally, the photochemical characterization indicated a decrease in the band gap and charge recombination of GCN-TiO2 composite compared to standalone TiO2, which indicated a conducive effect of GCN addition. Further, on the actual use as a photo-electro-catalyst, the GCN-TiO2 catalysed MFC attained 58.2 ± 9.6% and 86.5 ± 7.1% of COD and SDS removal; while simultaneously harvesting a maximum power density of 1.07 W m-3, which was higher than standalone TiO2-catalysed MFC. The follow-up treatment in the charcoal bio-filter and photo-cathodic chamber of the hybrid system further improved the overall COD and SDS removal efficiency to 92.1 ± 2.7 and 95.6 ± 1.5%, respectively. The electro-catalytic performance of the GCN-TiO2 can be attributed to the presence of nitrogen-active species in the composite. The results of this investigation demonstrated a potential MFC-based hybrid system for the simultaneous secondary and tertiary treatment of municipal wastewater. Consequently, the outcome of this investigation indicates an innovative research direction in the field of photo-electro-catalyst, which can fit into the role of a photo-catalyst as well as an electro-catalyst.

Life Cycle Assessment of Microbial 2,3-Butanediol Production from Brewer's Spent Grain Modeled on Pinch Technology.

Microbial production of 2,3-butanediol (BDO) has received considerable attention as a promising alternate to fossil-derived BDO. In our previous work, BDO concentration >100 g/L was accumulated using brewer's spent grain (BSG) via microbial routes which was followed by techno-economic analysis of the bioprocess. In the present work, a life cycle assessment (LCA) was conducted for BDO production from the fermentation of BSG to identify the associated environmental impacts. The LCA was based on an industrial-scale biorefinery processing of 100 metric tons BSG per day modeled using ASPEN plus integrated with pinch technology, a tool for achieving maximum thermal efficiency and heat recovery from the process. For the cradle-to-gate LCA, the functional unit of 1 kg of BDO production was selected. One-hundred-year global warming potential of 7.25 kg CO2/kg BDO was estimated while including biogenic carbon emission. The pretreatment stage followed by the cultivation and fermentation contributed to the maximum adverse impacts. Sensitivity analysis revealed that a reduction in electricity consumption and transportation and an increase in BDO yield could reduce the adverse impacts associated with microbial BDO production.

Biochar-mediated removal of pharmaceutical compounds from aqueous matrices via adsorption.

Pharmaceutical is one of the noteworthy classes of emerging contaminants. These biologically active compounds pose a range of deleterious impacts on human health and the environment. This is attributed to their refractory behavior, poor biodegradability, and pseudopersistent nature. Their large-scale production by pharmaceutical industries and subsequent widespread utilization in hospitals, community health centers, and veterinary facilities, among others, have significantly increased the occurrence of pharmaceutical residues in various environmental compartments. Several technologies are currently being evaluated to eliminate pharmaceutical compounds (PCs) from aqueous environments. Among them, adsorption appears as the most viable treatment option because of its operational simplicity and low cost. Intensive research and development efforts are, therefore, currently underway to develop inexpensive adsorbents for the effective abatement of PCs. Although numerous adsorbents have been investigated for the removal of PCs in recent years, biochar-based adsorbents have garnered tremendous scientific attention to eliminate PCs from aqueous matrices because of their decent specific surface area, tunable surface chemistry, scalable production, and environmentally benign nature. This review, therefore, attempts to provide an overview of the latest progress in the application of biochar for the removal of PCs from wastewater. Additionally, the fundamental knowledge gaps in the domain knowledge are identified and novel strategic research guidelines are laid out to make further advances in this promising approach towards sustainable development.

Valorization of wastewater: A paradigm shift towards circular bioeconomy and sustainability.

Limitation in the availability of natural resources like water is the main drive for focussing on resource recovery from wastewater. Rapid urbanization with increased consumption of natural resources has severely affected its management and security. The application of biotechnological processes offers a feasible approach to concentrating and transforming wastewater for resource recovery and a step towards a circular economy. Wastewater generally contains high organic materials, nutrients, metals and chemicals, which have economic value. Hence, its management can be a valuable resource through the implementation of a paradigm transformation for value-added product recovery. This review focuses on the circular economy of "close loop" process by wastewater reuse and energy recovery identifying the emerging technologies for recovering resources across the wastewater treatment phase. Conventional wastewater treatment technologies have been discussed along with the advanced treatment technologies such as algal treatment, anammox technology, microbial fuel cells (MFC). Apart from recovering energy in the form of biogas and biohydrogen, second and third-generation biofuels as well as biohythane and electricity generation have been deliberated. Other options for resource recovery are single-cell protein (SCP), biopolymers as well as recovery of metals and nutrients. The paper also highlights the applications of treated wastewater in agriculture, aquaponics, fisheries and algal cultivation. The concept of Partitions-release-recover (PRR) has been discussed for a better understanding of the filtration treatment coupled with anaerobic digestion. The review provides a critical evaluation on the importance of adopting a circular economy and their role in achieving sustainable development goals (SDGs). Thus, it is imperative that such initiatives towards resource recovery from wastewater through integration of concepts can aid in providing wastewater treatment system with resource efficiency.

Char from the co-pyrolysis of Eucalyptus wood and low-density polyethylene for use as high-quality fuel: Influence of process parameters.

Providing a valuable application to the under-utilized solid residue of co-pyrolysis of biomass and plastics could substantially improve economic and environmental sustainability of the process, thereby fostering circular economy. This study focuses on the variation of thermal and physiochemical characteristics of solid char, produced from the co-pyrolysis of waste low-density polyethylene (WLDPE) and Eucalyptus wood with varying pyrolysis temperatures from 300 to 550 °C, residence times of 90-150 min, and relative percentage of 33% and 25% (w/w) WLDPE in the feedstock. The highest values of yield (37%), energy density (1.25) and high heat value (31 MJ/Kg) were observed with the char produced at 300 °C. The physical inhibition caused by the overlaying plastic coating on the surface of the char below 450 °C resulted in the same. However, with the increase in temperature, increase in fuel ratio by 78-79% and fixed carbon content by 68-69% were observed. The highest concentrations of fixed carbon (39%), fuel ratio (0.81) along with the lowest O/C and H/C ratios (0.07 and 0.13) were observed with the chars produced above 450 °C depicting their high degree of carbonization. The fuel value indices of all the chars were > 500 GJ/m3 indicating their suitability as high-quality fuels. Significant influences of residence time and feedstock ratio were also observed on properties of the char. The analysis of variance and principal component analysis also depicted significant variations in the properties of the char produced below and above the temperatures of 450 °C due to the inhibitory and synergetic effects. While the chars produced at 300-350 °C could be used for combustion/co-combustion in coal-fired boilers, chars produced above 450 °C can be opted as household fuel due to their low losses of energy, water vapour, and smoke during combustion.

Landfill leachate as an alternative moisture source for hydrothermal carbonization of municipal solid wastes to solid biofuels.

Hydrothermal carbonization (HTC) of yard waste (YW) and food waste (FW) was performed in landfill leachate (LL) to overcome the unnecessary exploitation of our limited natural resources. The physicochemical properties and combustion behavior of the resulting hydrochars were compared with those obtained using distilled water (DW) as reaction medium. Although performing HTC in LL led to lower hydrochar mass yields (43% YWH and 36% FWH) than DW (47.1% YWH and 41.5% FWH), it had minimal impact on the fuel characteristics of the hydrochars. Notably, the higher heating value of the hydrochars prepared in LL (22.8 MJ kg-1 for YWH and 30.2 MJ kg-1 for FWH) is comparable to that of conventional solid fuels, and may, therefore, be considered as inexpensive alternatives to fossil fuels. Overall, the results of this study conclusively suggest that the use of LL as an alternative moisture source can significantly improve the sustainability of HTC technology.

Porous media transport of iron nanoparticles for site remediation application: A review of lab scale column study, transport modelling and field-scale application.

Injection of surface modified zero valent iron nanoparticles for in situ remediation of soil, contaminated with an array of pollutants has attracted great attention due to the high reactivity of zero valent iron towards a broad range of contaminants, its cost effectiveness, minimal physical disruption and low toxicity. The effectiveness of this technology relies on the stability and mobility of injected iron nanoparticles. Hence the development of a modelling tool capable of predicting nZVI transport is indispensable. This review provides state of the art knowledge on the mobility of iron nanoparticles in porous media, mechanisms involved in subsurface retention of nZVI based on continuum models and field scale application. Special attention is given to the identification of the influential parameters controlling the transport potential of iron nanoparticles and the available numerical models for the simulation of laboratory scale transport data.

Electrochemical pretreatment of yard waste to improve biogas production: Understanding the mechanism of delignification, and energy balance.

In the present study, electrochemical pretreatment with a pair of graphite electrode was conducted to pretreat yard waste prior to anaerobic digestion. The Response Surface Methodology was employed to optimize the pretreatment conditions. To determine the mechanism of delignification physical and chemical properties of untreated and pretreated yard waste were investigated. In the subsequent anaerobic digestion of pretreated yard waste, the ultimate biogas production of 446 mL/g VS was achieved in comparison to the untreated yard waste of 287 mL/g VS on 35th day of anaerobic digestion. A net energy gain of 4.75 kJ/g VS (Output energy of 5.73 kJ/g VS - Input energy of 0.98 kJ/g VS) and net profit of 518 rupees (US$ 7.4) per 1 ton of yard waste indicates the applicability of electrochemical pretreatment for pilot scale.