Search Results (18)

Anaerobic digestion (AD) is increasingly recognized as a key technology for renewable energy generation and sustainable waste management within the circular economy. However, its performance is highly sensitive to feedstock variability and environmental fluctuations, making stable operation and high methane yields difficult to sustain. Conventional monitoring and control systems, based on limited sensors and mechanistic models, often fail to anticipate disturbances or optimize process performance. This review discusses recent progress in electrochemical, optical, spectroscopic, microbial, and hybrid sensors, highlighting their advantages and limitations in artificial intelligence (AI)-assisted monitoring. The role of soft sensors, data preprocessing, feature engineering, and explainable AI is emphasized to enable predictive and adaptive process control. Various machine learning (ML) techniques, including neural networks, support vector machines, ensemble methods, and hybrid gray-box models, are evaluated for yield forecasting, anomaly detection, and operational optimization. Persistent challenges include sensor fouling, calibration drift, and the lack of standardized open datasets. Emerging strategies such as digital twins, data augmentation, and automated optimization frameworks are proposed to address these issues. Future progress will rely on more robust sensors, shared datasets, and interpretable AI tools to achieve predictive, transparent, and efficient biogas production supporting the energy transition. Full article

This study evaluates eight biodiesel blend types and determines the overall optimal blend by applying two established multi-criteria decision-making methods: the Analytic Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The selected blends represent widely produced and utilized feedstocks that are reported in the previous literature. In the proposed methodology, AHP is employed to determine the weights for both emissions-related subcriteria, quantified through Global Warming Potential scores and property-related subcriteria, thereby reducing the subjectivity often encountered in earlier studies. Furthermore, two boundary alternatives, defined as the “Best” and “Worst” based on international standards, are introduced to enhance the robustness of the normalization procedure. The weights determined via AHP are subsequently integrated into the TOPSIS framework to rank the biodiesel alternatives. This combined AHP-TOPSIS approach addresses a gap in the literature, as no previous study has compared the best performing blends from different sources to identify a single optimal alternative. The results indicate that a 20% sunflower biodiesel blend (SN20) achieves the highest ranking. Sensitivity analyses, including the incorporation of an additional economic criterion, consistently reaffirm SN20’s superior performance. This study offers a transparent and reproducible method that can guide future biodiesel blend evaluations and reduce subjectivity in comparative assessment. Full article

The deployment of Sustainable Aviation Fuels (SAFs) is central to decarbonizing aviation. However, diverse regulatory frameworks create complexity for SAF market deployment. Differing greenhouse gas (GHG)-reduction thresholds, feedstock eligibility rules and certification systems increase the compliance burden, especially for those operating across regional and international markets. This paper compares an example of regional approach (European) with the international ICAO sustainability certification. The comparison focuses on chain-of-custody models, substantiality principles, GHG accounting methodologies and approaches to ILUC. It highlights the need for harmonized GHG calculation rules, mutual recognition of certification schemes and interoperable traceability systems. Aligning these elements is critical for reducing administrative barriers, supporting market integration and enabling scalable SAF deployment. The analysis aims to assist policymakers, certifiers and producers in developing coordinated and transparent regulatory strategies. Full article

Sustainable aviation fuel (SAF) has demonstrated significant potential to reduce carbon emissions in the aviation industry. Multiple national and international initiatives have been launched to accelerate SAF adoption, yet large-scale commercialization continues to face technological, operational, and regulatory barriers. Industry 4.0 provides a suite of advanced technologies that can address these challenges and improve SAF operations across the supply chain. This study conducts an integrative literature review to identify and synthesize research on the application of Industry 4.0 technologies in the production and distribution of SAF. The findings highlight that technologies such as artificial intelligence (AI), Internet of Things (IoT), blockchain, digital twins, and 3D printing can enhance feedstock logistics, optimize conversion pathways, improve certification and compliance processes, and strengthen overall supply chain transparency and resilience. By mapping these applications to the six key workstreams of the SAF Grand Challenge, this study presents a practical framework linking technological innovation to both strategic and operational aspects of SAF commercialization. Integrating Industry 4.0 solutions into SAF production and supply chains contributes to reducing life cycle greenhouse gas (GHG) emissions, strengthens low-carbon energy systems, and supports the United Nations Sustainable Development Goal 13 (SDG 13). The findings from this research offer practical guidance to policymakers, industry practitioners, investors, and technology developers seeking to accelerate the global shift toward carbon neutrality in aviation. Full article

The imperative to decarbonize global energy systems and enhance energy security necessitates a transition towards ecofuels, broadly classified as biofuels, waste-derived fuels, and electrofuels (e-Fuels). The primary goal of this review is to provide a holistic and comparative evaluation of these three pivotal ecofuel pillars under a unified framework, identifying their strategic niches in the energy transition by critically assessing their interconnected technical, economic, and policy challenges. It offers a comparative dissection of inherent resource constraints, spanning biomass availability, the immense scale of renewable electricity required for e-Fuels, sustainable carbon dioxide (CO₂) sourcing, and the complexities of utilizing non-biodegradable wastes, identifying that true feedstock sustainability and holistic lifecycle management are paramount, cross-cutting limitations for all pathways. This review critically highlights how the current global reliance on fossil fuels for electricity production (approx. 60%) and the upstream emissions embodied in renewable energy infrastructure challenge the climate neutrality claims of ecofuels, particularly e-Fuels, underscoring the necessity for comprehensive well-to-wheels (WtW) lifecycle assessments (LCAs) over simpler tank-to-wheels (TtW) approaches. This perspective is crucial as emerging regulations demand significant greenhouse gas (GHG) emission reductions (70–100%) compared to fossil fuels. Ultimately, this synthesis argues for a nuanced, technologically neutral deployment strategy, prioritizing specific ecofuels for hard-to-abate sectors, and underscores the urgent need for stable, long-term policies coupled with robust and transparent LCA methodologies to guide a truly sustainable energy transition. Full article

This article considers modern approaches to obtaining synthetic oil from unconventional hydrocarbon feedstocks, including plastic waste, tires, biomass, coal, and extra-heavy oil. Particular attention is paid to multi-stage technologies, such as pyrolysis, catalytic depolymerization, gasification followed by Fischer–Tropsch synthesis, and hydrocracking of heavy residues. The important role of catalysts in increasing the selectivity and economic efficiency of processes is noted: nanostructured, bifunctional, and pollution-resistant systems are increasingly used. Economic factors influencing the competitiveness of this industry are considered, including the volatility of prices for traditional oil, government support measures, and the development of waste logistics infrastructure. It is emphasized that the strengthening of the position of synthetic oil is associated with the growth of environmental requirements stimulating the recycling of plastics, tires, and biomass; at the same time, compliance with high environmental standards and transparency of emission control play a critical role in the social aspects of projects. In addition to improving the environmental situation, the development of synthetic oil contributes to the creation of jobs, the resolution of problems of shortage of classical oil fields, and the increase of energy security. It is concluded that further improvement of technologies and integration into industrial clusters can turn this sphere into a significant component of the future energy sector. Full article

The negative environmental impacts of the current linear system of textile and apparel production are well-documented and require urgent action. The sector lacks an effective recycling system, resulting in massive waste and environmental pollution. This paper presents the results of qualitative research involving textile and apparel industry stakeholders, including representatives from brands and retailers, waste collectors, recyclers, non-profit organizations, academic institutions, and government agencies. Our research focused on stakeholder perceptions of the significance and importance of textile circularity, the challenges that exist for transitioning the textile and apparel industry from a linear system to a circular economy (CE), and resources that exist to support this transition. The results of this study call attention to the following urgent requirements: a consistent definition of CE to promote transparency and accountability and prevent greenwashing; improved systems for materials identification, sorting, and pre-processing of post-consumer textile waste to enable recycling; innovations in mechanical recycling technologies to maintain the value of recycled materials; and new, materials-driven approaches to design and manufacturing that are responsive to feedstock variability and diverse consumer needs. The research findings also suggest the need for flexible, regional CEs that are rooted in community partnerships. Full article

The Digital Product Passport (DPP) as a product-specific data set is a powerful tool that provides information on the origin or composition of products and increases transparency and traceability. This recycling case study accompanies the production of 2192 frisbees, which originated from collected beverage bottle caps. In total, 486.7 kg of feedstock was collected and transformed into 363.2 kg of final product with verified traceability through all process steps via a DPP, provided by the R-Cycle initiative and based on the GS1 standard. This demanded a generally agreed dataset, the availability of technical infrastructure, and additional effort in the processing steps to collect and process the data. R-Cycle offers a one-layer DPP where the data structure is lean and information is visible to everyone. This is beneficial to a variety of stakeholders in terms of transparency. However, it does not allow the sharing of sensitive information. On the one hand, the DPP has a high potential to be an enabler for customer engagement, origin verification, or as a starting point for more efficient and advanced recycling of plastics. On the other hand, the DPP involves a certain effort in data generation and handling, which must be justified by the benefits. For small, simple packaging items, the DPP may not be the perfect solution for all problems. However, with a broader societal mindset and legislative push, the DPP can become a widely used and trusted declaration tool. This can support the plastics industry in its journey towards a circular economy. Full article

Poly(lactic acid) (PLA) and Poly(butylene succinate) (PBS) were chosen as raw materials and melt blended by a twin screw extruder and pelletized; then, the pellets were extruded into filaments; after that, various PBS/PLA blending samples were prepared by Fused Deposition Molding (FDM) 3D printing technology using the filaments obtained and the effect of the dosage of PBS on technological properties of 3D-printed specimens was investigated. For comparison, the PLA specimen was also prepared by FDM printing. The tensile strength, tensile modulus, thermal stability, and hydrophilicity became poorer with increasing the dosage of PBS, while the flexural strength, flexural modulus, impact strength, and crystallinity increased first and then decreased. The blend containing 10% PBS (10% PBS/PLA) had the greatest flexural strength of 60.12 MPa, tensile modulus of 2360.04 MPa, impact strength of 89.39 kJ/m², and crystallinity of 7.4%, which were increased by 54.65%, 61.04%, 14.78%, and 51.02% compared to those of printed PLA, respectively; this blend also absorbed the least water than any other specimen when immersed in water. Different from the transparent PLA filament, 10% PBS/PLA filament presented a milky white appearance. The printed 10% PBS/PLA specimen had a smooth surface, while the surface of the printed PLA was rough. All the results indicated that the printed 10% PBS/PLA specimen had good comprehensive properties, including improved mechanical properties, crystallization performance, and surface quality than PLA, as well as proper wettability and water absorption. The prominent conclusion achieved in this work was that 10% PBS/PLA should be an ideal candidate for biodegradable feedstock among all the PBS/PLA blends for FDM 3D printing. Full article

Stereolithography processes such as lithography-based ceramic manufacturing (LCM) are technologies that can produce centimeter-sized structures in a reasonable time frame. However, for some parts specifications, they lack resolution. Two-photon-polymerization (2PP) ensures the highest geometric accuracy in additive manufacturing so far. Nevertheless, building up parts in sizes as large as a few millimeters or even centimeters is a time-consuming process, which makes the production of 2PP printed parts very costly. Regarding feedstock specification, the requirements for 2PP are different to those for LCM, and generally, feedstocks are designed to meet requirements for only one of these manufacturing technologies. In an attempt to fabricate highly precise ceramic components of a rather large size, it is necessary to develop a feedstock that suits both light-based technologies, taking advantage of LCM’s higher productivity and 2PP’s accuracy. Hybridization should bring the desired precision to the region of interest on reasonably large parts without escalating printing time and costs. In this study, specimens gained from a transparent feedstock with yttria stabilized zirconia (YSZ) particles of 5 nm at 70 wt% were presented. The resin was originally designed to suit 2PP, while being also printable with LCM. This work demonstrates how hybrid parts can be sintered into full YSZ ceramics. Full article

Despite being a promising feedstock for food, feed, chemicals, and biofuels, microalgal production processes are still uneconomical due to slow growth rates, costly media, problematic downstreaming processes, and rather low cell densities. Immobilization via entrapment constitutes a promising tool to overcome these drawbacks of microalgal production and enables continuous processes with protection against shear forces and contaminations. In contrast to biopolymer gels, inorganic silica hydrogels are highly transparent and chemically, mechanically, thermally, and biologically stable. Since the first report on entrapment of living cells in silica hydrogels in 1989, efforts were made to increase the biocompatibility by omitting organic solvents during hydrolysis, removing toxic by-products, and replacing detrimental mineral acids or bases for pH adjustment. Furthermore, methods were developed to decrease the stiffness in order to enable proliferation of entrapped cells. This review aims to provide an overview of studied entrapment methods in silica hydrogels, specifically for rather sensitive microalgae. Full article

A future bioeconomy pursues the transformation of the resource base from fossil to renewable materials in an effort to develop a holistic, sustainable production and provision system. While the significance of this change in the German context is not yet entirely explored, scenarios analysing possible pathways could support the understanding of these changes and their systemic implications. Bioeconomy in detail depends on respective framework conditions, such as the availability of biomass or technological research priorities. Thus, for scenario creation, transferable methods for flexible input settings are needed. Addressing this issue, the study identifies relevant bioeconomy scenario drivers. With the theoretical approach of narrative analysis, 92 statements of the German National Bioeconomy Strategy 2020 have been evaluated and 21 international studies in a STEEPLE framework were assessed. For a future German bioeconomy 19 important drivers could be determined and specific aspects of the resource base, production processes and products as well as overarching issues were exploratively characterised on a quantitative and qualitative basis. The developed method demonstrate an approach for a transparent scenario driver identification that is applicable to other strategy papers. The results illustrate a possible future German bioeconomy that is resource- and technology-driven by following a value-based objective, and which is supplied by biogenic residue and side product feedstocks. As such, the bioeconomy scenario drivers can be used as a starting point for future research like scenario development or modelling of a future German bioeconomy. Full article

Mullite (3Al₂O₃·2SiO₂) is an aluminosilicate characterized by excellent physical properties, which makes it an important ceramic material. In this way, ceramics based on mullite find applications in different technological fields as refractory material (metallurgy, glass, ceramics, etc.), matrix in composite materials for high temperature applications, substrate in multilayer packaging, protective coatings, components of turbine engines, windows transparent to infrared radiation, etc. However, mullite is scarce in nature so it has to be manufactured through different synthesis methods, such as sintering, melting-crystallization or through a sol-gel route. Commonly, mullite is fabricated from pure technical grade raw materials, making the manufacturing process expensive. An alternative to lowering the cost is the use of mining waste as silica (SiO₂) and alumina (Al₂O₃) feedstock, which are the necessary chemical compounds required to manufacture mullite ceramics. In addition to the economic benefits, the use of mining waste brings out environmental benefits as it prevents the over-exploitation of natural resources and reduces the volume of mining waste that needs to be managed. This article reviews the scientific studies carried out in order to use waste (steriles and tailings) generated in mining activities for the manufacture of clay-based ceramic materials containing mullite as a main crystalline phase. Full article

The potential use of elm wood in lignocellulosic industries has been hindered by the Dutch elm disease (DED) pandemics, which have ravaged European and North American elm groves in the last century. However, the selection of DED-resistant cultivars paves the way for their use as feedstock in lignocellulosic biorefineries. Here, the production of cellulose nanofibers from the resistant Ulmus minor clone Ademuz was evaluated for the first time. Both mechanical (PFI refining) and chemical (TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation) pretreatments were assessed prior to microfluidization, observing not only easier fibrillation but also better optical and barrier properties for elm nanopapers compared to eucalyptus ones (used as reference). Furthermore, mechanically pretreated samples showed higher strength for elm nanopapers. Although lower nanofibrillation yields were obtained by mechanical pretreatment, nanofibers showed higher thermal, mechanical and barrier properties, compared to TEMPO-oxidized nanofibers. Furthermore, lignin-containing elm nanofibers presented the most promising characteristics, with slightly lower transparencies. Full article

Polylactic acid (PLA) is one of the most promising biodegradable and recyclable thermoplastic biopolymer derived from renewable feedstock. Nanocellulose reinforced PLA biocomposites have received increasing attention in academic and industrial communities. In the present study, cellulose nanofibrils (CNFs) was liberated by combined enzymatic pretreatment and high-pressure homogenization, and then subsequently incorporated into the PLA matrix to synthesize PLA/CNF biocomposite films via solution casting and melt compression. The prepared PLA/CNF biocomposite films were characterized in terms of transparency (UV-Vis spectroscopy), chemical structure (attenuated total reflectance-Fourier transform infrared, ATR-FTIR; X-ray powder diffraction, XRD), thermal (thermogravimetric analyzer, TGA; differential scanning calorimetry, DSC), and tensile properties. With 1.0–5.0 wt % additions of CNF to the PLA matrix, noticeable improvements in thermal and physical properties were observed for the resulting PLA/CNF biocomposites. The 2.5 wt % addition of CNF increased the tensile strength by 8.8%. The T_onset (initial degradation temperature) and T_max (maximum degradation temperature) after adding 5.0 wt % CNF was increased by 20 °C, and 10 °C, respectively in the nitrogen atmosphere. These improvements were attributed to the good dispersibility and improved interfacial interaction of CNF in the PLA matrix. Full article