Anaerobic digestion (AD) is a widely applied technology for renewable energy generation, environmental impact mitigation, and nutrient recycling. Despite its potential, critical gaps exist in modeling AD processes, particularly in understanding and predicting the fates of carbon (C), nitrogen (N), and phosphorus (P)—essential elements for advancing circular nutrient management. This review addresses two key questions: What are the limitations of current AD models in simulating nutrient fates, and how can future models improve these predictions? Our findings indicate that most AD models emphasize methane production, while models addressing nutrient transformations remain limited due to the complex biochemical interactions in AD systems. Mechanistic models, such as the Anaerobic Digestion Model No. 1 (ADM1), provide a foundational framework but are constrained by their complexity and the need for precise calibration, which limits scalability in larger applications. Emerging advances in artificial intelligence, particularly machine learning, offer promising solutions by enhancing model accuracy and predictive capabilities. AI-driven models enable real-time optimization and adaptive decision-making, which can expand AD applications at industrial scales. Future research should focus on integrating nutrient fate predictions with AI-driven methods to address these challenges, enhancing the role of AD in sustainable waste treatment systems.
Oil spills are of great concern because oily wastewater disrupts the aquatic ecosystem, causes mutations in animals, contaminates surface water resources, and causes diseases such as cancer in humans. Current efforts are geared towards recovering spilled oil from aquatic environments and ensuring the effective separation of oil and water in the collected emulsion. After oil separation from the emulsion, a polishing step is required to treat the residual oil in the water before discharging the effluent into the aquatic environment. Oily wastewater treatment methods such as electrochemical treatment, membrane filtration, flocculation, membrane bioreactor, and advanced oxidation processes are intricate, costly, and achieve varying removal efficiencies. Adsorption using environmentally friendly and cost-effective adsorbents is seen as an attractive option. This paper provides an overview of oily wastewater treatment using adsorption. Recent adsorption studies have focused on optimizing parameters such as adsorbent dosage, pH, initial oil concentration (IC), and contact time (CT) to enhance treatment efficiency. Principal component analysis was conducted based on previous studies to understand the key parameters influencing adsorption and gain insights into the interactions between these operating variables. The findings indicated a strong positive correlation between the first principal component (PC1) CT and IC, with coefficients of 0.704 and 0.702, respectively. This suggests that positive values of CT and IC significantly contribute to the variance in PC1, meaning that the variation in PC1 is closely linked to the variation in CT and IC. New materials could be produced to enhance selectivity to target specific pollutants in oily wastewater.
The adverse consequences of hazardous environmental contaminants, at minimal concentration also constitute a major threat to both human health and the ecosystem. Multiple techniques are investigated to remove contaminants. Among these techniques, microbial bioremediation has emerged as an appealing method because of its removal efficacy, affordability, and environmental friendliness. This review is an overview of the major environmental pollutants such as plastics, heavy metals, and dyes with their source and toxicity towards both humans and the environment. The summary of the beneficial microbes like bacteria, fungi, and algae that employ remediation techniques like biosorption, bioaccumulation, bioleaching, biodeterioration, bio-fragmentation, and biotransformation to convert the toxic compounds to non-toxic compounds has been discussed. During the degradation process factors like temperature, pH, initial concentration, O2 concentration, N2 addition, soluble salts, pollutants both chemical and physical structure, and hydrophobic properties play a major role. The enzyme present in the microbes helps in the quick and complete breakdown of the pollutants, emerging advancement techniques like genetic engineering are implied to generate desired compounds or enzymes to attain pollutant removal. As with other removal techniques, like immobilization, the recent advancements are also explained. The review majorly states the efficiency of microbial remediation toward environmental sustainability.
This work aims to propose earth-abundant materials for CO2 photoreduction to generate renewable solar fuels to provide practical solutions to global warming. The selected material in this case is cuprous oxide (Cu2O), one of the most promising photocatalysts for CO2 photoreduction due to its high affinity to solar radiation and electronic properties. Cu2O nanoparticles (NPs) were synthesized using Psidium guajava residue for the photocatalytic CO2 reduction. The aqueous residue of the Psidium guajava fruit proved to be suitable for stabilizing and acting as a reducing agent for the synthesis of Cu2O NPs. The XRD analysis confirmed the formation of the cubic structure of Cu2O. The nanoparticles absorb light from 430 nm with a direct bandgap value of around 1.8 eV. Cu2O NPs exhibited activity for CO2 photoreduction, whose efficiency was optimized by an orthogonal Taguchi L9 design. The factors studied were catalyst loading, air flow, and temperature. During the use of Cu2O NPs in the CO2 photoreduction HCOOH was identified as the main product, with an optimized production of 103.4 µmol h−1 under visible light. Also, it was demonstrated the photocatalytic activity of the Cu2O NPs for H2 evolution by water splitting.
The seedling of Nicotiana tabacum L. (N. tabacum) holds strategic and economic importance in the product chain due to its vital contributions to agronomical yield and the characteristics of the final product. This study assessed the environmental life cycle impacts of three technologies for N. tabacum seedlings (traditional seedbed, technified, and tray-based). This assessment considered the main activities within the studied system boundaries, insecticides, fertilizers, fungicides, infrastructure, energy, seedling and composting, irrigation, and land use. In this context, relevant scenarios were examined for the Cuban context. The findings reveal that tray-based technology exhibited lower environmental burdens due to reduced consumption of insecticides, fungicides, and fertilizers in N. tabacum phytotechnology, as well as lower diesel consumption in water pumping for irrigation. Energy consumption was the highest contributing factor in 10 out of the 18 impact categories (with values of up to 90%), associated with the emissions from electricity consumption in a fossil fuel-based energy matrix. Additionally, Seedling and composting showed higher impacts in five impact categories (with values of up to 99.8%) due to emissions of nitrogen oxides and acephate into the air. The implementation of cleaner production strategies resulted in a significant reduction of impacts compared to the baseline scenario, particularly through a combination of photovoltaic energy generation for water irrigation pumping and optimized soil tillage (reducing diesel consumption), leading to a reduction of up to 73%. These results not only benefit researchers and farmers but also provide valuable insights for decision-makers, supporting the implementation of renewable energy sources in agriculture.
The widespread use of acrylonitrile (Acyrlonitrile) and crude C4 across industries has significantly boosted global manufacturing of these energy-intensive petrochemicals. A life cycle assessment was employed to evaluate the environmental impact of Acyrlonitrile and C4 production, aiming to promote sustainability in the petrochemical supply chain. Modeling integrated refinery-petrochemical plant operations in Türkiye revealed that Acyrlonitrile production emitted 7.46 kg CO2eq./kg, while C4 production emitted 1.62 kg CO2eq./kg. The Acyrlonitrile production was found to be more environmentally polluting, especially in terms of acidification potential, photochemical smog potential and eutrophication potential with 4.5 kg SO2eq., 3.88 kg C2H4eq. and 2.39 kg PO4eq. per kg Acyrlonitrile respectively. Waste disposal, natural gas use, propane and nitrogen emission have been the major hotspots of Acyrlonitrile production, while natural gas use and lubricant oil for C4. On average, the production stage emerged as the primary hotspot, for Acyrlonitrile production contributing 58% to overall impacts. The results of water footprint identified 3.13 L per kg Acyrlonitrile and 0.99 L per kg C4 production, with aromatics and ethylene plants being the key contributors. Adoption of energy efficiency measures and circular economy principles is recommended to mitigate environmental impacts. This study sheds light on the resource-intensive petrochemical supply chain, offering valuable insights into environmental impact assessment in this sector.
The marketing of pyrolysis oil derived from plastic waste is impeded by oil instability, influenced by the wax formation. It is essential to identify the wax source and determine the fuel types produced from various plastic waste. This research aims to investigate the outcomes of pyrolysis conducted at 450 °C using bentonite catalyst. Wax formation and pyrolysis oil stability were analyzed across different storage temperatures (16–42 °C). The result revealed that each type of plastic waste has its own characteristics. Pyrolysis of PS and PP without catalyst produced almost wax free oil and completely wax free oil using catalyst. HDPE and LDPE non-catalytic pyrolysis produced entirely waxy pyrolysis oil (melting point at 38 °C). The utilization of a catalyst does not significantly alter the melting point. PC and PVC plastics are not advisable for large-scale pyrolysis oil conversion due to their low yields, high char, and substantial energy requirements. The highest oil yield was achieved in PS pyrolysis (97.62 wt%), followed by LDPE (77.66 wt%), PP (74.98 wt%), and HDPE (65.82 wt%). The application of catalyst reduces the liquid yield and increases the gas yield for PS, PP, and LDPE pyrolysis. The highest gasoline fraction was predominantly obtained from PS pyrolysis without catalyst (56.43 wt%), while the highest diesel from PS with catalyst (37.09 wt%). PS, PP, HDPE, and LDPE are recommended for conversion into pyrolysis oil. Further research on catalysts is required to prevent and process the waxy pyrolysis oil into marketable fuels in the second stage of catalytic cracking.