Search Results (381)

Microbial fuel cells (MFCs) have attracted increasing attention due to their potential applications in renewable energy generation, waste utilization, and biomass upgrading, offering a promising alternative to traditional fossil fuels. By directly converting carbon-rich wastes into electricity, MFCs provide a unique approach to simultaneously address energy demand and waste management challenges. This review systematically examines the effects of various carbon-rich substrates on MFC performance, including lignocellulosic biomasses, molasses, lipid waste, crude glycerol, and C1 compounds. These substrates, characterized by wide availability, low cost, and high carbon content, have demonstrated considerable potential for efficient bioelectricity generation and resource recovery. Particular emphasis is placed on the roles of microbial community regulation and genetic engineering strategies in enhancing substrate utilization efficiency and power output. Additionally, the application of carbon-rich wastes in electrode fabrication is discussed, highlighting their contributions to improved electrical conductivity, sustainability, and overall system performance. The integration of carbon-rich substrates into MFCs offers promising prospects for alleviating energy shortages, improving wastewater treatment efficiency, and reducing environmental pollution, thereby supporting the development of a circular bioeconomy. Despite existing challenges related to scalability, operational stability, and system cost, MFCs exhibit strong potential for large-scale implementation across diverse industrial sectors. Full article

Urban tree-management operations generate substantial amounts of woody biomass that often remain underutilized despite their potential value as a local renewable fuel. This study investigates the possibility of using woodchips and sawdust delivered from municipal tree-cutting activities as boiler fuel, with a specific focus on how fuel moisture, particle size, and natural-fiber packaging influence combustion performance and emission characteristics. In collaboration with a municipal greenery-cutting company, representative batches of biomass were collected, characterized through proximate and ultimate analyses, and combusted in a small-scale boiler. Unlike conventional densification routes (pelletization/briquetting), the proposed approach uses combustible natural-fiber packaging to create modular ‘macro-pellets’ from minimally processed urban residues. The study quantifies how this low-energy packaging concept affects emissions and boiler efficiency relative to loose chips/sawdust at two moisture levels. The results demonstrate that packaging the fuel in jute bags markedly improved performance for both woodchips and sawdust by stabilizing the fuel bed, enhancing air distribution, and reducing emissions of incomplete combustion products. Boiler efficiency increased from approximately 60% for raw unpackaged fuels to 71–75% for the dried and jute-packaged variants. The findings highlight that simple preprocessing steps—drying and packaging in natural-fiber bags—can substantially enhance the energy recovery potential of urban green waste, offering a practical pathway for integrating municipal biomass residues into a sustainable fuel. Full article

The convergence of food insecurity, water scarcity, and environmental degradation has intensified the global search for sustainable agricultural models. Integrated Microalgal–Aquaponic Systems (IAMS) have emerged as a novel multi-trophic platform that unites aquaculture, hydroponics, and microalgal cultivation into a closed-loop framework for resource-efficient food production and water recovery. This critical review synthesizes empirical findings and engineering advancements published between 2008 and 2024, evaluating IAMS performance relative to traditional agriculture and recirculating aquaculture systems (RAS). Reported under controlled laboratory and pilot-scale conditions, IAMS have achieved nitrogen and phosphorus recovery efficiencies exceeding 95% while potentially reducing water consumption by up to 90% compared to conventional farming. The integration of microalgal photobioreactors enhances nutrient retention, may contribute to internal carbon capture, and enables the generation of diversified co-products, including biofertilizers and protein-rich aquafeeds. Nevertheless, significant barriers to commercial scalability persist, including the biological complexity of maintaining multi-trophic synchrony, high initial capital expenditure (CAPEX), and regulatory ambiguity regarding the safety of waste-derived algal biomass. Technical challenges such as photobioreactor upscaling, biofouling control, and energy optimization are critically discussed. Finally, the review evaluates the alignment of IAMS with UN Sustainable Development Goals 2, 6, and 13, and outlines future research priorities in techno-economic modeling, automation, and policy development to facilitate the transition of IAMS from pilot-scale innovations to viable industrial solutions. Full article

Hydrodynamic cavitation (HC) is a green and readily scalable platform for the recovery and upgrading of bioactives from agri-food and forestry byproducts. This expert-led narrative review examines HC processing of citrus and pomegranate peels, softwoods, and plant protein systems, emphasizing process performance, ingredient functionality, and realistic routes to market, and contrasts HC with other green extraction technologies. Pilot-scale evidence repeatedly supports water-only operation with high solids and short residence times; in most practical deployments, energy demand is dominated by downstream water removal rather than the extraction step itself, which favors low water-to-biomass ratios. A distinctive outcome of HC is the spontaneous formation of stable pectin–flavonoid–terpene phytocomplexes with improved apparent solubility and bioaccessibility, and early studies indicate that HC may also facilitate protein–polyphenol complexation while lowering anti-nutritional factors. Two translational pathways appear near term: (i) blending HC-derived dry extracts with commercial dry protein isolates to deliver measurable functional benefits at low inclusion levels and (ii) HC-based extraction of plant proteins to obtain digestion-friendly isolates and conjugate-ready ingredients. Priority gaps include harmonized reporting of specific energy consumption and operating metrics, explicit solvent/byproduct mass balances, matched-scale benchmarking against subcritical water extraction and pulsed electric field, and evidence from continuous multi-ton operation. Overall, HC is a strong candidate unit operation for circular biorefineries, provided that energy accounting, quality retention, and regulatory documentation are handled rigorously. Full article

This study investigates the accumulation potential of Brassica napus L. and Zea mays L. cultivated on soils contaminated with Zn, Cd, Cu and Pb, using HEDTA—Hydroxyethyl Ethylenediamine Triacetic Acid—to enhance metal mobility. The research addresses a gap in the literature regarding the dual-purpose use of energy crops for assisted phytoextraction and bioenergy recovery. Two pot experiments were conducted on soils of different textures, with HEDTA applied at 2.5 and 5 mmol·kg⁻¹. Metal concentrations in soil and plant tissues were measured, and indices such as the geoaccumulation index (Igeo), bioconcentration factors (BCF), translocation factor (TF), metal tolerance index (MTI), crop growth rate (CGR) and higher heating value (HHV) were calculated. Results showed that HEDTA significantly increased Cd and Zn mobility, leading to higher accumulation in rapeseed shoots. Maize demonstrated phytostabilization by retaining metals in roots. Rapeseed biomass exhibited a higher HHV (up to 20.6 MJ·kg⁻¹) and greater carbon and hydrogen content, indicating suitability for thermochemical conversion. Maize, with lower ash content, showed potential for bioethanol production. The findings support the integration of chelate-assisted phytoextraction with energy recovery from biomass. Full article

Indonesia faces growing pressure to strengthen waste management while expanding renewable energy generation, particularly from high-moisture biomass such as palm oil mill effluent (POME) and the organic fraction of municipal solid waste (OFMSW). Anaerobic digestion technology (ADT) is technically suitable for both feedstocks; however, its deployment depends on broader operational, financial, social, and institutional conditions. This study evaluates ADT readiness for biomass waste-to-energy (BWTE) development in Indonesia using a multistakeholder Japanese Technology Readiness Assessment (J-TRA) framework. The results and discussion are supported by a literature review, secondary data analysis, and interviews with government agencies, industry actors, financiers, non-governmental organizations, and researchers. The results reveal a clear divergence in readiness outcomes. POME-based ADT reaches Technology Readiness Levels (TRLs) of 6–8, supported by a stable and homogeneous feedstock supply, established industrial operations, and corporate incentives to mitigate methane emissions. Key remaining constraints relate to high capital costs for smaller mills, low electricity purchase tariffs, and competing export incentives for untreated POME. In contrast, OFMSW-based ADT remains at TRL 2–4, constrained by inconsistent waste segregation, insufficient operation and maintenance capacity, limited municipal budgets, residential safety concerns, and fragmented governance across waste and energy institutions. Across both cases, readiness is shaped by five interacting forces. The first three are technical: feedstock characteristics, operations and maintenance (O&M) capability, and financial certainty. The remaining two are enabling conditions: social acceptance and institutional coordination. This study concludes that Indonesia’s BWTE transition requires integrated technological, behavioral, and policy interventions, supported by further research on hybrid valorization pathways and context-specific life-cycle and cost analyses. Full article

This study investigates the selective dissolution of manganese from a manganiferous iron ore using nitric acid (HNO₃) in the presence of various organic reductants. A series of leaching experiments was performed to evaluate the effects of temperature, reductant type, and leaching time on Mn recovery, with particular emphasis on biomass (horse dung) and tartaric acid as novel reducing agents. The dissolution behaviour of Fe, Mn, Mg, Ca, and Al was systematically examined, revealing that Mn extraction was strongly enhanced in the presence of reductants, while Fe dissolution remained below 10% under all conditions. The maximum Mn dissolution exceeded 90% at 90 °C using biomass and reached nearly 85%–90% with tartaric acid at elevated temperatures. Kinetic studies were conducted by applying reaction order models and the shrinking core model. The results indicated that Mn dissolution in HNO₃ medium is predominantly controlled by surface chemical reaction, with Arrhenius analysis yielding activation energies of 27.74 kJ/mol for biomass and 21.26 kJ/mol for tartaric acid. These relatively low values confirm the efficiency of organic reductants in facilitating Mn reduction and dissolution. To sum up, comparison of reductant efficiency revealed that, at the lowest concentrations, the dissolution of Mn followed the sequence glucose > sucrose > oxalic acid > tartaric acid > maleic acid > biomass > citric acid > acetic acid. At the highest concentrations, the trend shifted, with citric acid emerging as the most effective, followed by tartaric acid > oxalic acid > glucose > sucrose > maleic acid > biomass > acetic acid. Full article

The growing demand for palladium (Pd) necessitates the development of sustainable and efficient recovery methods. This work presents a green, one-step synthesis of activated carbon (AC) from winemaking waste (grape seeds) via direct pyrolysis, eliminating the need for separate, energy-intensive activation. Remarkably, the AC synthesized at the lowest temperature of 400 °C exhibited the highest Pd(II) adsorption capacity (16.20 mg/g at 50 °C), performing comparably to many literature-reported ACs that underwent complex activation processes. Characterization revealed that this optimal material possessed a favorable point of zero charge (PZC 7.78) and the lowest ash content (4.66%). Higher pyrolysis temperatures (400–800 °C) progressively increased surface basicity (PZC up to 11.00) and carboxylic group content (reaching 0.565 mmol/g at 800 °C). A comprehensive life cycle assessment (LCA) demonstrated the significant environmental advantage of this method, showing a 74% lower total environmental impact and a 92% reduction in acidification potential compared to commercial coal-based AC. These results prove that highly effective Pd(II) recovery can be achieved through a simplified, direct pyrolysis process, offering a sustainable and practical approach for precious metal recycling from waste biomass. Full article

The transition toward a circular bioeconomy requires efficient conversion of biogenic wastes and biomass into renewable fuels. This study explores the gasification potential of wastewater sludge (WWS) and food waste (FW), representing high moisture-content biowastes, compared with softwood (SW), a lignocellulosic biomass reference. An Aspen Plus equilibrium model incorporating the drying stage was developed to evaluate the performance of air and steam gasification. The effects of temperature (400–1200 °C), equivalence ratio (ER = 0.1–1), and steam-to-biomass ratio (S/B = 0.1–1) on gas composition and energy efficiency (EE) were examined. Increasing temperature enhanced H₂ and CO generation but reduced CH₄, resulting in a maximum EE at intermediate temperatures, after which it declined due to the lower heating value of the gases. Although EE followed the order SW > FW > WWS, both biowastes maintained robust efficiencies (60–80%) despite high drying energy requirements. Steam gasification increased H₂ content up to 53% (WWS), 54% (FW), and 51% (SW) near S/B = 0.5–0.6, while air gasification achieved 23–27% H₂ and 70–80% EE at ER ≈ 0.1–0.2. The results confirm that wet bio-wastes such as WWS and FW can achieve performance comparable to lignocellulosic biomass, highlighting their suitability as sustainable feedstocks for waste-to-syngas conversion and supporting bioenergy integration into waste management systems. Full article

In the context of the zero-carbon transition, this article provides a comprehensive review of Organic Rankine Cycle (ORC) technologies for low-grade heat recovery and conversion to power. It surveys a wide range of renewable and waste heat sources—including geothermal, solar thermal, biomass, internal combustion engine exhaust, and industrial process heat—and discusses the integration of ORC systems to enhance energy recovery and thermal efficiency. The analysis examines various configurations, from basic and regenerative cycles to advanced transcritical and supercritical designs, cascaded systems, and multi-source integration, evaluating their thermodynamic performance for different heat source profiles. A critical focus is placed on working fluid selection, where the landscape is being reshaped by stringent regulatory frameworks such as the EU F-Gas regulation, driving a shift towards low-GWP hydrofluoroolefins, natural refrigerants, and tailored zeotropic mixtures. The review benchmarks ORC against competing technologies such as the Kalina cycle, Stirling engines, and thermoelectric generators, highlighting relative performance characteristics. Furthermore, it identifies key trends, including the move beyond single-source applications toward integrated hybrid systems and the use of multi-objective optimization to balance thermodynamic, economic, and environmental criteria, despite persistent challenges related to computational cost and real-time control. Key findings confirm that ORC systems significantly improve low-grade heat utilization and overall thermal efficiency, positioning them as vital components for integrated zero-carbon power plants. The study concludes that synergistically optimizing ORC design, refrigerant choice in line with regulations, and system integration strategies is crucial for maximizing energy recovery and supporting the broader zero-carbon energy transition. Full article

The urgent need for cleaner energy sources has driven exploration into innovative and sustainable solutions. This study investigates the potential of the invasive aquatic plant, the water hyacinth, to contribute to energy recovery and support the preservation of blue carbon ecosystems through biomass removal. Employing slow pyrolysis, this study examines the influence of temperature (300–500 °C) and residence time (30–90 min) on bio-oil and biochar production in a fixed-bed reactor. Results revealed that residence time was the key operational parameter significantly influencing total liquid condensate yield, which peaked at 34.34 wt% at 400 °C after 90 min. Moisture content reveals an actual organic bio-oil yield of approximately 3.4–4.8 wt%. In contrast, biochar yield (max. 43.74 wt%) was not significantly affected by the tested parameters. The resulting bio-oil exhibited a high heating value of up to 25.84 MJ/kg, suggesting its potential as a renewable fuel. This study concludes that slow pyrolysis of invasive water hyacinth provides a dual-benefit pathway: it co-produces renewable bio-oil for energy recovery alongside a stable biochar, offering a tangible route for blue carbon sequestration. This integrated approach transforms an environmental liability into valuable resources, contributing to a cleaner environment and a more sustainable future. Full article

Bioethanol can be efficiently produced from lignocellulosic biomass via two-phase processes, consisting of enzymatic hydrolysis and fermentation. To enhance economic and energy efficiency, a system combining separate hydrolysis and fermentation of biomass with a direct-ethanol solid oxide fuel cell (SOFC) is proposed in this work. The system comprises six units: a pretreatment reactor unit, a conditioning unit, a high-solids hydrolysis unit, a seed train unit, an ethanol recovery unit, and an SOFC unit. Exergy analysis based on a thermodynamic model indicates a total exergy efficiency of approximately 0.72. Within the high-solids hydrolysis unit, one piece of equipment exhibits the lowest exergy efficiency of 0.21, at a biomass flux of 71,510 kg/h. The other main exergy destruction exists in the conditioning unit and is followed by seed train unit, accounting for 5.61 and 2.77 of total exergy destruction ratios, respectively. In addition, the tentative parametric analysis for reaction kinetics is performed with varying reaction orders. The results indicate that ammonia gas in a specific unit can follow first- or second-reaction order, whereas acetic acid and sulfuric acid exhibit zero-reaction order, due to the gradual conversion of cellulose to glucose. This work provides key insights for the practical design and operation of the proposed separate hydrolysis and fermentation–SOFC system. Full article

This study presents the first comprehensive investigation of direct supercritical water oxidation (SCWO) of microalgae biomass integrated with photobioreactor oxygen recovery for sustainable energy production. Laboratory-scale experiments were conducted on Nannochloropsis gaditana at optimized conditions (650 °C, 24 MPa, 1 min residence time), achieving extraordinary conversion efficiency of 99.99% at biomass concentrations as low as 0.5 wt%. Process simulation using Aspen Plus demonstrated that this integrated photobioreactor-SCWO system can recover oxygen produced during photosynthesis, reducing compressor energy demands by 10–15% compared to conventional air-fed systems. The coupled system achieved net thermal power outputs of 47–66 kW from a 1 kg/min microalgae feed at 5–10 wt% biomass concentration, corresponding to an overall system thermal efficiency of approximately 18%. CO₂ recovery via mono-ethanolamine absorption enabled 70–80% carbon cycle closure, while simultaneous nutrient recycling through the aqueous phase supports sustainable circular economy principles. This coupled photobioreactor-SCWO process represents an efficient pathway for energy recovery from wet microalgae biomass, eliminating the energy-intensive drying requirement (typically 60–70% of conventional processing energy) and achieving complete mineralization of organic compounds. The system demonstrates technical and energetic viability for scaling to pilot demonstration scale. Full article

This study explores the decarbonization of the district heating network in Riva del Garda. The existing system (baseline) was modeled in EnergyPLAN, and future configurations were optimized using a Multi-Objective Evolutionary Algorithm (MOEA) to minimize both CO₂ emissions and annual costs. Nine decision variables were assessed under defined boundary conditions to generate alternative future scenarios grouped into five types. In Type A, a large deep geothermal cogeneration plant combined with a small biomass boiler achieved the only zero-emission solution, with lower annual costs than the baseline but high capital needs. Excluding deep geothermal cogeneration (Type B) led to dominance of the biomass boiler and waste heat recovery from the Alto Garda Power (AGP) plant; full decarbonization remained possible only with extensive biomass use at a higher cost. Removing biomass (Type C), the solar thermal plant, and the shallow geothermal heat pump enabled deep but costly decarbonization, including grid electricity dependence. Types D and E, dominated, respectively, by shallow geothermal heat pump and electric boiler, provided moderate emission reductions and further increase in costs. Across all types, thermal storage improved operational flexibility. These analyses were also extended to assess potential district heating network expansions within Riva del Garda and into the neighboring municipality of Arco. Full article

Lithium-ion batteries (LIBs) have become the leading energy storage technology because of their high specific energy, excellent efficiency, and longer lifespan. This review offers a comprehensive overview of the lithium battery industry, covering lithium materials and the global supply chain, as well as examining traditional and sustainable extraction methods. The discussion includes the technical and environmental challenges of each extraction method, with particular emphasis on feedstock selection, which greatly influences lithium recovery efficiency, yield, and ecological impact, and capital and operating expenditures. It also investigates the growth of the global battery recycling industry and provides an outlook on innovations in this area. These innovations include recycling systems, a case study on Biomass Energy Systems Inc., and the battery chemistries needed to support a circular economy. The review highlights industrial applications of LIBs in sectors such as automotive, consumer electronics, and aerospace. Finally, it addresses supply chain and recycling challenges related to LIBs, positioning cost, environmental footprint, and regulatory compliance as central considerations for the future of the battery industry. Full article