Microbial fuel cells (MFCs) are regarded as an eco-friendly processes for bioelectricity generation and simultaneously treating wastewater. Nonetheless, MFCs have a significant limitation, constant supply of organics needed for microbial oxidation. In this context, plant microbial fuel cells (PMFCs) play an essential role in addressing this problem. Root exudates containing organic acids and sugars act as continuous electron donors that are metabolized by electrogenic microbes such as Geobacter to drive extracellular electron transfer, while nitrogen-transforming taxa such as Nitrosomonas link substrate oxidation with nitrogen cycling. The present review explores the multiple functions of PMFCs in the concurrent production of energy along with environmental restoration. It outlines the fundamental principles of PMFCs, emphasizing plant selection, microbial diversity, and electrode design as key factors affecting performance. The review also discussed about plant-microbe-electrode interactions in bioelectrogenesis, highlighting their potential in wastewater treatment, soil restoration, and precision agriculture. Furthermore, the review evaluates scalability challenges, including electrochemical limitations, design constraints, and field-level performance in pilot studies. By integrating renewable energy generation with ecosystem services, PMFCs align strongly with multiple United Nations Sustainable Development Goals (UN SDGs), particularly in clean energy, water purification, sustainable agriculture, and climate action. Future advancements in materials science, modular designs, and plant-microbe interactions are essential for translating PMFCs from laboratory prototypes into scalable, multifunctional systems for sustainable development.

As atmospheric COQ levels steadily rise, more effective carbon mitigation methods are needed to capture and convert COQ. Microbial electrosynthesis (MES) is a hybrid electrochemical system in which electro-autotrophic microorganisms utilize electrons from a cathode to convert COQ into multi-carbon compounds. This review provides a mechanistic overview of current advancements in MES, emphasizing electron transfer pathways, biocathode architecture, COQ mass transfer limitations, and essential techno-economic factors. The inherently poor solubility of COQ in water is a primary rate-limiting factor, inhibiting carbon transfer to the Wood-Ljungdahl pathway. Strategies such as gas diffusion electrodes (GDE), biofilm-enhancing surfactants, and pH gradient operation have demonstrated significant improvement in CO2 availability and electron uptake. Advances in 3D nanostructure cathodes, including carbon nanotube-modified carbon felt and metal oxide composites, have achieved good production rates. Techno-economic analysis of acetate production via MES remain constrained by high capital expenditure (CAPEX approximate to 5059 /tonne product) and the energy burden associated with multi-electron products such as ethanol. Integration of MES with COQ-rich industrial exhaust streams, renewable power inputs, and metabolic engineering of an electrotrophic framework is expected to reduce operational cost and to improve product selectivity. The review highlights future priorities including advanced kinetic modeling, improved electrode-microbe coupling, and reactor designs that decouple mass transfer from bio-catalytic limitations to accelerate MES towards scalable, carbon-negative bio-manufacturing. Overall, this review delineates the scientific, engineering, and economic levels that must be optimized to transition MES from laboratory systems to commercially viable COQ valorization technologies.

Sugarcane bagasse (SCB), a recalcitrant lignocellulosic biomass, necessitates pretreatment to enhance the release of soluble organics for effective utilization. This study evaluated three pretreatment methods including alkaline (ALK), acid (AC) and hydrothermal (HTL), to extract sugars from SCB, subsequently evaluating these hydrolysates as substrates for bioelectricity generation in dual-chamber microbial fuel cells (MFCs). The study was conducted in two phases. Phase I utilized tap water to dilute the SCB hydrolysate, while Phase II replaced tap water with sewage. Results from Phase I indicated that ALK hydrolysate yielded the highest current density (414.00 mA/m²), followed by AC (339.00 mA/m²) and HTL (316.13 mA/m²). The corresponding chemical oxygen demand (COD) degradation rates were 57.60% for ALK, 46.67% for AC, and 37.30% for HTL hydrolysates. Phase II introduced sewage as a diluent, enhanced HTL hydrolysate performance (415.05 mA/m²; 53.50% COD removal) due to improved ionic conductivity and nutrient availability, which fostered better biofilm formation and electron transfer. The blending of AC and ALK hydrolysates facilitated in-situ pH neutralization, optimizing substrate complexity and buffering stability, culminating in a peak specific power yield of 1011 W/kgCOD. Cyclic voltammetry (CV) confirmed the development of an electroactive biofilm, indicating effective electron mediation. The study demonstrated that integrating optimized pretreatment with cost-effective methodologies, such as sewage repurposing can amplify energy recovery from SCB. This approach not only improves green energy production but also aligns with circular bioeconomy principles by valorizing agricultural residues and wastewater, presenting a scalable model for sustainable bioenergy systems.

Maize residue is considered a significant feedstock for biogas production, especially in regions where it is abundantly cultivated. Maize ensilage undergoes chemical changes during the silage period, which positively impact biogas yield. This study investigates the impact of maize plant age, ensilage period, digestion temperature, substrate characteristics, biogas production, and substrate degradation rate on anaerobic digestion efficiency. Two samples of maize, differing in age by 20 days (Maize silage90 days) and (Maize silage110 days), were ensiled for 100 days, in a batch mode under mesophilic (35°C) and thermophilic (55°C) conditions for 60 days for anaerobic digestion. The results revealed that under thermophilic conditions, biogas production from Maize silage90 was 8.86% higher than from Maize silage110, while under mesophilic conditions, Maize silage90 produced 22.86% more biogas than Maize silage110. The rate of COD degradation reached 95.99% (Maize silage90) and 93.75% (Maize silage110) under thermophilic conditions, while 93.75% (Maize silage90) and 88.94% (Maize silage110) under mesophilic conditions. These results indicate that the younger maize plant, combined with appropriate silage and temperature, can substantially enhance biogas yield and substrate degradation, providing a basis for optimizing AD performance.

Anaerobic digestion of chicken manure (CM) with high-solid content is typically constrained by ammonia nitrogen accumulation, which influences the microbial activity and methane yield (MY). A strategy of recycling stripped biogas and co-digestion was developed to reduce ammonia nitrogen accumulation and increase MY in a semi-continuously-stirred tank reactor (semi-CSTR) using CM as feedstock (total solid, 10%). The experimental results demonstrate that the stripping strategy can improve hydrolysis efficiency and reduce total ammonia nitrogen, free ammonia nitrogen, and total volatile fatty acids concentrations by 11%, 14%, and 20%, respectively. The soluble chemical oxygen demand (SCOD) removal efficiency and MY were improved by 23% and 37%, respectively compared to the no-stripping operation. In the integrated in-situ ammonia stripping with co-digestion study, with the addition of co-substrate (glucose, sunflower oil, and peptone), which was optimized by a central composite design (CCD) model, resulted in increased biogas yield and MY yield by 39% and 21% over the no-stripping method. The process also evidenced a lower TVFA concentration than the control, inferring the efficient conversion of metabolites towards methane production. This technology could be utilised in high-ammonia waste/wastewater digestion.

Microbial fuel cells (MFCs) are sustainable energy technologies that could resolve pollution challenges brought by various activities. It can meet energy demand by producing bioelectricity through catabolizing organic matter. Over the past two decades, research on many microbes have been used in MFCs, which intrigued researchers to explore the underlying electron transfer mechanism between microbe and anode. Electron transfer between electrode and microorganism occurs via different pathways: direct, indirect electron transfer and interspecies electron transfer. Shewanella and Geobacter are well-known for microbe–electrode and microbe–microbe electron transfer. This review provides an overview of the significant varieties of microbes utilized in MFCs for simultaneous bioelectricity generation and wastewater treatment. Mechanisms of different modes of electron transfer involved during the oxidation of organic wastes in the anode section of MFCs are highlighted. Furthermore, this review also details some of the techniques to promote extracellular electron transfer efficiency which is important for the enhanced performance of MFC in terms of power, current generation and wastewater remediation. A perspective of challenges to be addressed for the effective functioning of these technologies, opportunities for MFC systems to be scaled up and associated techno-economic analysis are discussed. © 2024 Society of Chemical Industry (SCI).

Biopolymers are revolutionizing the materials landscape, driven by a growing demand for sustainable alternatives to traditional petroleum-based materials. Sourced from biological origins, these polymers are not only environment friendly but also present exciting solutions in healthcare, packaging, biosensors, high performance, and durable materials as alternatives to crude oil-based products. Recently, biopolymers derived from plants, such as lignin and cellulose, alongside those produced by bacteria, like polyhydroxyalkanoates (PHAs), have captured the spotlight, drawing significant interest for their industrial and eco-friendly applications. The growing interest in biopolymers stems from their potential as sustainable, renewable materials across diverse applications. This review provides an in-depth analysis of the current advancements in plant-based and bacterial biopolymers, covering aspects of bioproduction, downstream processing, and their integration into high-performance next-generation materials. Additionally, we delve into the technical challenges of cost-effectiveness, processing, and scalability, which are critical barriers to widespread adoption. By highlighting these issues, this review aims to equip researchers in the bio-based domain with a comprehensive understanding of how plant-based and bacterial biopolymers can serve as viable alternatives to petroleum-derived materials. Ultimately, we envision a transformative shift from a linear, fossil fuel-based economy to a circular, bio-based economy, fostering more sustainable and environmentally conscious material solutions using novel biopolymers aligning with the framework of the United Nations Sustainable Development Goals (SDGs), including clean water and sanitation (SDG 6), industry, innovation, and infrastructure (SDG 9), affordable and clean energy (SDG 7), sustainable cities and communities (SDG 11), responsible production and consumption (SDG 12), and climate action (SDG 13).

Microbial electrolysis cells (MECs) offers a sustainable route for hydrogen production by decarbonizing global energy demands via transformation of biogenic waste/wastewater. Leveraging microbial metabolism, MECs contribute to the waste-to-energy nexus. The efficiency of MECs is significantly influenced by selection of electrode materials such as platinum, nickel, and stainless steel, which enhance the performance through their high surface area, chemical resilience, and effective hydrogen evolution reaction. MECs have been shown to generate 853 H2/m³/d using graphite brush (anode) and Pt-loaded carbon cloth (cathode). MECs were upgraded to 1000 l, having 24 modules with 144 electrode pairs. Key features of cathode materials and its advancements used in MECs are discussed in this review.

Aquatic plants are rich in biomass and they contain good amount of carbohydrates and proteins which are amenable for valorization to generate bioenergy. Duckweed is rich in proteins and carbohydrates that grow abundantly in contaminated waterbodies, it can be used as a substrate for biohydrogen production. Dark-fermentative hydrogen production was done by hydrothermal pretreatment of duckweed biomass under 15 lbs pressure, evaluated under three different operating temperatures that cover mesophilic (35 °C) and thermophilic conditions (50 and 55°C). The study resulted in the maximum hydrogen production rate of 0.97mmol/day in batch culture (160mL) from 55 °C that was found superior than 50 °C (0.84mmol/day) and 35 °C (0.38mmol/day) operations. From the 7 days of operation, under uncontrolled pH conditions, substrate (chemical oxygen demand, COD) utilization was 57.27%, which is higher than in mesophilic conditions (50.67%). Efficient hydrolysate conversion was noticed with thermophilic conditions, especially under operation at 55 °C (416mL H2/g of biomass) than mesophilic conditions (144mL H2/g of biomass) suggesting that duckweed biomass can be dependable biomass for hydrogen production, and the dark-fermentation can be an appropriate solution of aquatic weed biomass management in a sustainable approach.

The present research investigated the effect of two carbonaceous materials, multiwalled carbon nanotubes (MWCNTs), and graphene nanoparticles (GNPs), on biogas yield from food waste (FW) in an anaerobic digestion system for 30 days. Lab scale investigations were conducted in batch mode in 250 mL glass reactor bottles and the findings were compared to the control reactor. The performance of the experimental procedure was assessed in terms of biogas output and organic matter reduction. The addition of 100 mg/L multiwalled carbon nanotubes and 100 mg/L GNPs increased the cumulative biogas production (33.55% and 81.16%, respectively) while decreasing the total solid content (about 25.95% and 24.95%, respectively). However, increasing the concentration of both carbon nanomaterials from 100 mg/L to 500 mg/L reduced the total biogas production compared to the control, which can be attributed to cytotoxic effects. A microbial diversity study was performed using 16S amplicon sequencing to understand the changes occurring in the microbial ecology. The predominant phyla found during diversity analysis were Firmicutes, Proteobacteria, Actinobacteriota, and Bacteroidota. Finally, addition of carbonaceous nanomaterials to the anaerobic reactors favours organic matter degradation through the DIET mechanism. It improves the biogas production kinetics and productivity during the anaerobic digestion of FW up to a certain dose.

Pesticides are becoming more prevalent in agriculture to protect crops and increase crop yields. However, nearly all pesticides used for this purpose reach non-target crops and remain as residues for extended periods. Contamination of soil by widespread pesticide use, as well as its toxicity to humans and other living organisms, is a global concern. This has prompted us to find solutions and develop alternative remediation technologies for sustainable management. This article reviews recent technological developments for remediating pesticides from contaminated soil, focusing on the following major points: (1) The application of various pesticide types and their properties, the sources of pesticides related to soil pollution, their transport and distribution, their fate, the impact on soil and human health, and the extrinsic and intrinsic factors that affect the remediation process are the main points of focus. (2) Sustainable pesticide degradation mechanisms and various emerging nano- and bioelectrochemical soil remediation technologies. (3) The feasible and long-term sustainable research and development approaches that are required for on-site pesticide removal from soils, as well as prospects for applying them directly in agricultural fields. In this critical analysis, we found that bioremediation technology has the potential for up to 90% pesticide removal from the soil. The complete removal of pesticides through a single biological treatment approach is still a challenging task; however, the combination of electrochemical oxidation and bioelectrochemical system approaches can achieve the complete removal of pesticides from soil. Further research is required to remove pesticides directly from soils in agricultural fields on a large scale.

Algal-microbial fuel cells (A-MFC) offers a sustainable solution for wastewater treatment and energy recovery. The performance of a typical MFC is affected by the oxidative-reductive reactions occurring in it. The cathodic reduction is facilitated by electron acceptors such as oxygen and ferricyanide. However, higher operational cost is incurred from their application. Algae owing to its phototrophic metabolism, oxygenates the cathode photosynthetically and acts as a mediator for cathodic electron transfer. Mixotrophic metabolism of algae enable their adaptation and growth in pollutant-rich toxic environments, making them suitable for wastewater treatment and remediation. A-MFCs enable the generation of algal biomass, a rich source of carbohydrates, lipids, proteins, pigments, and many more for commercial applications. Algal-based CO2 sequestration, nutrient and heavy metal removal via assimilation and carbon capture pathways make A-MFC systems a promising approach for bioenergy generation and wastewater remediation. Hence, this review offers an overview on the principles and applications of A-MFC and their relevance in developing a waste-centered-circular economy.

The growing demand for sustainable energy sources has propelled research into innovative technologies that simultaneously address environmental challenges. Integrating microbial electrolysis cells (MECs) with wastewater management presents a promising avenue for sustainable hydrogen production. This innovative approach and synergistic capabilities of MECs, harness microbial activity to drive electrolysis and generate hydrogen gas. Wastewater, rich in organic matter, serves as a renewable and abundant substrate for microbial metabolism within the MEC, leading to efficient electron transfer and subsequent hydrogen production. Key factors influencing the performance of MECs in this context include electrode material, reactor configuration, and microbial community composition. This study highlights the significance of this integration in addressing the dual environmental challenges of wastewater treatment and clean energy production utilizing MECs allows for the efficient removal of organic contaminants from wastewater while also generating hydrogen, a clean, renewable energy source. Furthermore, the hydrogen produced can be utilized in various applications such as fuel cells, transportation, and industrial processes, contributing to decarbonization efforts and mitigating greenhouse gas emissions. This review explores the promising synergy between MECs and wastewater management for efficient hydrogen production. MECs harness the metabolic activities of microorganisms to facilitate the electrochemical conversion of organic matter in wastewater into hydrogen gas, presenting a dual benefit of clean energy generation and wastewater treatment.

The growing population and waste biomass accumulation are leading to increased environmental pollution and climate change. Waste biomass comprising of nutrient rich components has promising potential to produce value-added products for sustainable environmental solutions. This review explores the critical role of bio-based heterogeneous catalysts in enabling sustainable waste biomass utilization. In industrial chemical transformations, over 95% involve catalysts, with more than 90% being heterogeneous systems, prized for their robustness, ease of product separation, and reusability. Bio-based heterogeneous catalysts address the pressing need for sustainable waste biomass management, allowing the conversion of diverse waste biomasses into biodiesel as valuable products. Research on these catalysts, particularly for biodiesel production, has shown yields exceeding 90% with enhanced catalyst reusability. This surge in research is evident from the increasing number of published articles, notably in 2022 and 2023, highlighting growing interest and importance in the scientific community. The synthesis of these catalysts is examined, including novel approaches and techniques to enhance their efficiency, selectivity, and stability. The challenges with their feasible solutions of heterogeneous catalysts in catalyst-based processes are addressed. Altogether, this review underscores the immense potential of bio-based heterogeneous catalysts in sustainable waste biomass utilization, aligning with resource efficiency and environmental conservation goals while offering distinct insights and perspectives on the latest innovations in the field.

Over the years, extensive research has gone into fermentative hydrogen production using pure and mixed cultures from waste biomass with promising results. However, for up-scaling of hydrogen production mixed cultures are more appropriate to overcome the operational difficulties such as a metabolic shift in response to environmental stress, and the need for a sterile environment. Mixed culture biotechnology (MCB) is a robust and stable alternative with efficient waste and wastewater treatment capacity along with co-generation of biohydrogen and platform chemicals. Mixed culture being a diverse group of bacteria with complex metabolic functions would offer a better response to the environmental variations encountered during biohydrogen production. The development of defined mixed cultures with desired functions would help to understand the microbial community dynamics and the keystone species for improved hydrogen production. This review aims to offer an overview of the application of MCB for biohydrogen production.

The consumption of fossil fuel sources and in particular, the emerging lethal issues connected with global warming triggered by consumption of petroleum products have set off dynamic research in finding alternate and eco-friendly energy sources. In this regard, algae are viewed as the most versatile feedstock materials for the development of sustainable power sources and producing green biorefinery. Algae have a high obsession pace of atmospheric carbon dioxide which supports to rapid development rate with high efficiency per unit area as sustainable algal biomass. This review presents an extensive details of the sustainable process of microalgae biomass in biorefinery applications. The pre-treatment strategies and bioconversion of algae biomass into biofuel are also highlighted in this review. A detailed survey was encompassed on different microalgae harvesting techniques, transesterification process and biofuel production. This review further focuses on metabolic engi-neering methodologies accessible for altering the pathway in algal species for expanding biomass and biofuel production. The present article put forth the modern biotechnology tool to produce biofuel from microalgae biomass. At last, techno-economic analysis, manageability, difficulties and future points of view in algal development and pretreatment process were examined exhaustively for making an environmentally viable algal biofuel.

Sustainable technologies pave the way to address future energy demand by converting lignocellulosic biomass into fuels, carbon-neutral materials, and chemicals which might replace fossil fuels. Thermochemical and biochemical technologies are conventional methods that convert biomass into value-added products. To enhance biofuel production, the existing technologies should be upgraded using advanced processes. In this regard, the present review explores the advanced technologies of thermochemical processes such as plasma technology, hydrothermal treatment, microwave-based processing, microbial-catalyzed electrochemical systems, etc. Advanced biochemical technologies such as synthetic metabolic engineering and genomic engineering have led to the development of an effective strategy to produce biofuels. The microwave-plasma-based technique increases the biofuel conversion efficiency by 97% and the genetic engineering strains increase the sugar production by 40%, inferring that the advanced technologies enhances the efficiency. So understanding these processes leads to low-carbon technologies which can solve the global issues on energy security, the greenhouse gases emission, and global warming.

Glycoconjugates are the ubiquitous components of mammalian cells, mainly synthesized by covalent bonds of carbohydrates to other biomolecules such as proteins and lipids, with a wide range of potential applications in novel vaccines, therapeutic peptides and antibodies (Ab). Considering the emerging developments in glycoscience, renewable production of glycoconjugates is of importance and lignocellulosic biomass (LCB) is a potential source of carbohydrates to produce synthetic glycoconjugates in a sustainable pathway. In this review, recent advances in glycobiology aiming on glycoconjugates production is presented together with the recent and cutting-edge advances in the therapeutic properties and application of glycoconjugates, including therapeutic glycoproteins, glycosaminoglycans (GAGs), and nutraceuticals, emphasizing the integral role of glycosylation in their function and efficacy. Special emphasis is given towards the potential exploration of carbon neutral feedstocks, in which LCB has an emerging role. Techniques for extraction and recovery of mono- and oligosaccharides from LCB are critically discussed and influence of the heterogeneous nature of the feedstocks and different methods for recovery of these sugars in the development of the customized glycoconjugates is explored. Although reports on the use of LCB for the production of glycoconjugates are scarce, this review sets clear that the potential of LCB as a source for the production of valuable glycoconjugates cannot be underestimated and encourages that future research should focus on refining the existing methodologies and exploring new approaches to fully realize the potential of LCB in glycoconjugate production.

Nitrogen is essential for life and to produce food. Still, nitrogen loss of the unused nitrogen in wastewater, air, freshwater, and oceans has caused nitrogen pollution, which impacts the environment and leads to eutrophi-cation, climate change, biodiversity loss, and ozone depletion. It also causing cardio respiratory issues in humans. Anthropogenic activities such as food processing, fertilizer production, mining, and other impacting the global biogeochemical nitrogen cycle. Autotrophic ammonia-oxidizing microbial moieties such as ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and anaerobic ammonia-oxidizing bacteria (AnAOB) are being extensively used to remove nitrogen (present in the ammonia and ammonium forms). The conventional nitrogen removal process, "nitrification and denitrification," has been highly used in wastewater treatment plants by employing a various bacterial communities. Since it required high organic compounds and an energy -intensive process, new strategies were being developed to reduce carbon footprint. "Anammox," "Feammox," and "Comammox" are a few processes that utilize specific bacterial moieties and do not require organic carbon. Among these, Anammox has become the most potential nitrogen removal system. In various studies, the com-bined Anammox and partial nitrification (PN/A) have shown the maximum nitrogen removal rate (NRR). This review discusses the applications of autotrophic ammonia oxidizers in agriculture, wastewater treatment plants, and engineered ecosystems. We have also addressed various stress impacts on ammonia oxidizers.