Search Results (19)

An increasing lack of raw materials, resource depletion, environmental impacts and other concerns have changed the way the population faces garbage disposal and municipalities implement waste management strategies. The aggravated global rise in municipal solid waste (MSW) generation has led to a new stage in full development, with objectives and targets set by the European Union regarding reducing the production of MSW. The targets also include the increasing selective collection, reuse, recycling and recovery (organic and energetic) of the waste produced. At the same time, the European Union has also set caps for the greenhouse gas emissions and for increasing the use of alternative renewable energy sources. In this context, one of the sources of renewable energy that is beginning to be used to produce electricity in our country is biogas. Finally, AD promotes the development of a circular economy. The present study introduces the formalism for a computer application that simulates the technical–economic behaviour of the short-term management of biogas for the conversion of electricity, and the mathematical model is formulated as a mathematical programming problem with constraints. A simulation for a case study of short-term management is given using the real landfill data available. The case study proves the ability of the LandGEM, despite some authors’ support that the Tabasaran–Rettenberger model provided a more reliable estimate, especially when compared to actual landfill data. The present paper is a contribution to the optimisation of the management of electricity from the use of biogas, namely the second phase of the Strategic Plan for Urban Waste. In addition to complying with the legislation in force, the use of biogas to produce electricity is an added value for the concessionaires of waste treatment and final destination units, as this alternative energy source can provide not only self-sufficiency in electricity for these units but also the export of surplus energy to the National Electricity Grid, thus contributing to the self-sustaining management and energy flexibility that is intended for these infrastructures. Full article

Military ammunition and derivative materials that have reached the end of their service life are classified as hazardous waste due to the presence of explosives, necessitating proper decommissioning. Valorization of such materials through the reuse of energetic components offers a sustainable alternative, aligning with circular economy principles. This study aims to assess the environmental impact of civilian emulsion explosives (EEs) formulated with nitrocellulose powder derived from recycled ammunition, comparing these findings to traditional EEs and EEs containing standard nitrocellulose powder. The Life Cycle Analysis (LCA) was performed using the CML Baseline v3.07 methodology combined with the Ecoinvent 3.8 database, utilizing inventory data obtained from Polish sources. The results indicate that incorporating nitrocellulose powder into conventional EEs increases the overall environmental impact by 4.5%, while utilizing recycled nitrocellulose powder reduces the impact by 4.99%. This highlights the environmental benefits of recycling energetic materials for use in civilian applications, as it not only reduces hazardous waste and reliance on virgin materials but also supports the principles of the circular economy. By closing the loop on material use, this approach promotes environmental sustainability and resource efficiency, aligning with broader goals of sustainable development. Full article

A glycoluril-derived molecular-clip-based supramolecular organic framework (clip-SOF) with intrinsic porosity was prepared. The clip-SOF was used for the adsorption and removal of 2,4,6-trinitrotoluene (TNT) driven by noncovalent interactions. The efficiency of TNT removal by clip-SOFs is up to 88.5% in adsorption equilibrium, and the TNT adsorption capacity of clip-SOFs is about 40.2 mg/g at 25.0 °C. Clip-SOFs have good reusability, exhibiting almost no loss in performance in ten consecutive recycling tests. This work not only provides a new method for adsorbing energetic materials, but also promotes the application of supramolecular hosts in crystal engineering. Full article

A sudden increase in polyurethane (PU) production necessitates viable recycling methods for the waste generated. PU is one of the most important plastic materials with a wide range of applications; however, the stability of the urethane linkage is a major issue in chemical recycling. In this work, termination reactions of a model urethane molecule, namely methyl N-phenyl carbamate (MPCate), are investigated using G3MP2B3 composite quantum chemical method. Our main goal was to gain insights into the energetic profile of urethane bond termination and find an applicable chemical recycling method. Hydrogenation, hydrolysis, methanolysis, peroxidation, glycolysis, ammonolysis, reduction with methylamine and termination by dimethyl phosphite were explored in both gas and condensed phases. Out of these chemicals, degradation by H₂, H₂O₂ and CH₃NH₂ revealed promising results with lower activation barriers and exergonic pathways, especially in water solvation. Implementing these effective PU recycling methods can also have significant economic benefits since the obtained products from the reactions are industrially relevant substances. For example, aniline and dimethyl carbonate could be reusable in polymer technologies serving as potential methods for circular economy. As further potential transformations, several ionizations of MPCate were also examined including electron capture and detachment, protonation/deprotonation and reaction with OH⁻. Alkaline digestion against the model urethane MPCate was found to be promising due to the relatively low activation energy. In an ideal case, the transformation of the urethane bond could be an enzymatic process; therefore, potential enzymes, such as lipoxygenase, were also considered for the catalysis of peroxidation, and lipases for methanolysis. Full article

This research explores the depolymerization of waste polymethyl methacrylate (PMMAW) from dental material in fixed bed semi-batch reactors, focusing on three production scales: laboratory, technical and pilot. The study investigates the thermal degradation mechanism and kinetics of PMMAW through thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, revealing a two-step degradation process. The heat flow during PMMAW decomposition is measured by DSC, providing essential parameters for designing pyrolysis processes. The results demonstrate the potential of DSC for energetic analysis and process design, with attention to standardization challenges. Material balance analysis across the production scales reveals a temperature gradient across the fixed bed negatively impacting liquid yield and methyl methacrylate (MMA) concentration. Reactor load and power load variables are introduced, demonstrating decreased temperature with increased process scale. The study identifies the influence of temperature on MMA concentration in the liquid fraction, emphasizing the importance of controlling temperature for efficient depolymerization. Furthermore, the research highlights the formation of aromatic hydrocarbons from the remaining char, indicating a shift in liquid composition during the depolymerization process. The study concludes that lower temperatures below 450 °C favor liquid fractions rich in MMA, suggesting the benefits of lower temperatures and slower heating rates in semi-batch depolymerization. The findings contribute to a novel approach for analyzing pyrolysis processes, emphasizing reactor design and economic considerations for recycling viability. Future research aims to refine and standardize the analysis and design protocols for pyrolysis and similar processes. Full article

The common use of tires is responsible for the production of large quantities of waste worldwide, which are landfilled or energetically recovered, with higher economical cost and known environmentally harmful consequences. This type of problem must be studied, and all efforts must be conducted to eliminate, or at least mitigate, such high costs. The use of thermochemical conversion processes, such as pyrolysis, can allow the recycling and the reuse of raw materials for the tire industry, namely, in the production of carbon black, usually produced using the controlled combustion of fossil fuels. This article reports the production of torrefied and carbonized waste tire samples using a laboratorial procedure, and their subsequent laboratory characterization, specifically the elemental and proximate analysis. This preliminary approach found that carbon concentration in the produced rubber char reached values higher than 75%, indicating the possibility of its reuse in the production of carbon black to in turn be used in the production of new tires or other industrial rubber materials. The possibility of using this rubber char for other uses, such as energy recovery, is still depending on further studies, namely, the evaluation of the amount of sulfur present in the final product. Full article

Raw earth is one of the oldest building materials of mankind. Almost a third of the world’s population is living in an earth-based house. However, their use remains low compared to conventional materials such as concrete, steel, and wood. Although these geosourced materials are abundant, recyclable, and have a low environmental footprint, their use is very limited in the construction sector. This can be explained by the lack of data regarding their hygrothermal behavior. In this context, the present work aims to highlight the properties of cob construction material with straw addition. An experimental characterization of hygrothermal and microstructural properties has been carried out. Thermal conductivity, specific heat, sorption isotherms, moisture storage capacity, moisture buffer value (MBV), and water vapor permeability are obtained experimentally. Then, the collected data are used as input parameters of a numerical prediction model to numerically assess the thermal and hygric behavior. Cob is then compared to other more commonly used materials to highlight the benefits of its use within the context of the energetic and environmental transition. Our results will allow better understanding of the behavior of the new geosourced material thanks to experimental and numerical investigation. Full article

Resulting from the growing human population and the long dependency on fossil-based energies, the planet is facing a critical rise in global temperature, which is affecting all ecosystem networks. With a growing consciousness this issue, the EU has defined several strategies towards environment sustainability, where biodiversity restoration and preservation, pollution reduction, circular economy, and energetic transition are paramount issues. To achieve the ambitious goal of becoming climate-neutral by 2050, it is vital to mitigate the environmental footprint of the energetic transition, namely heavy metal pollution resulting from mining and processing of raw materials and from electronic waste disposal. Additionally, it is vital to find alternative materials to enhance the efficiency of energy storage devices. This review addresses the environmental challenges associated with energetic transition, with particular emphasis on the emergence of new alternative materials for the development of cleaner energy technologies and on the environmental impacts of mitigation strategies. We compile the most recent advances on natural sources, particularly seaweed, with regard to their use in metal recycling, bioremediation, and as valuable biomass to produce biochar for electrochemical applications. Full article

Novel polyurethane-based binders, specifically designed for environmentally responsible rocket propellant composites, were obtained by employing the polyester-polyols that resulted from the degradation of polyethylene terephthalate waste. A new class of “greener” rocket propellants, comprising polyurethanes (based on recycled PET) as the binder, phase stabilized ammonium nitrate (PSAN) as the eco-friendly oxidizer, and triethylene glycol dinitrate (TEGDN) as the energetic plasticizer, together with aluminum as fuel and Fe₂O₃ as the catalyst, is herein reported. The components of the energetic mixtures were investigated (individually and as composite materials) through specific analytical tools: ¹H-NMR, FT-IR, SEM-EDX, DTA and TGA, tensile and compression tests, DMA, and micro-CT. Moreover, the feasibility of this innovative solution is sustained by the ballistic performances exhibited by these composite materials in a subscale rocket motor, proving that these new formulations are suitable for rocket propellant applications. Full article

Buildings are responsible for 40% of the overall final energy consumption in the European Union. On the other hand, the construction, energy, and industry sectors generate around 50% of the waste produced in Europe, out of which a third part is construction and demolition waste (CDW). In recent years, many research works have been carried out to analyze the viability of incorporating waste, especially CDW, as a substitute for traditional raw materials with great environmental impact. However, most of the studies found cover only the mechanical characterization of the compound, and there are very few that analyze these materials in specific building applications. This research work evaluates the energy efficiency potential of recycled materials with CDW. After an exhaustive analysis of the main existing recycled materials, an energetic evaluation of several construction solutions is carried out, as well as a comparison with traditional solutions. The findings show that the incorporation of recycled materials in several building construction elements is a success, since it not only reduces the consumption of raw materials, but also reduces the energy consumption of the building. Energy savings using recycled materials can range from 8% in a warm region (such as Seville) up to 13% in cold regions (such as Soria), which are greater in heating than in cooling. Full article

The building sector continues to register a significant rise in energy demand and environmental impact, notably in developing countries. A considerable proportion of this energy is required during the operational phase of buildings for interior heating and cooling, leading to a necessity of building performance improvement. A holistic approach in building design and construction represents a step to moderate construction costs in conjunction with reduced long-term operating costs and a low impact on the environment. The present paper presents an experimental evaluation of the energy efficiency of a building under real climate conditions; the building, which represents a holistically designed modular laboratory, is located in a moderate continental temperate climate, characteristic of the south-eastern part of the Pannonian Depression, with some sub-Mediterranean influences. Considerations for the holistic design of the building, including multi-object optimization and integrated design with a high regard for technology and operational life are described. The paper provides a genuine overview of the energy efficiency response of the building during six months of operational use through a monitored energy management system. The energetic analysis presented in the paper represents an intermediary stage as not all the energetic users were installed nor all the energetic suppliers. However, the results showed a reliable thermal response in the behaviour of recycled-PET thermal wadding used as insulation material in the building and for the intermediary stage in which the building has only secondary energy users, the energetic balance proves its efficiency, keeping the buffer stock of energy high values over 90%. Full article

This work presents the experimental results of the mechanical and fracture behaviour of three polymeric blends prepared from two recycled plastics, namely polypropylene and opaque poly (ethylene terephthalate), where the second one acted as a reinforcement phase. The raw materials were two commercial degrees of recycled post-consumer waste, i.e., rPP and rPET-O. Sheets were manufactured by a semi-industrial extrusion-calendering process. The mechanical and fracture behaviours of manufactured sheets were analyzed via tensile tests and the essential work of fracture approach. SEM micrographics of cryofractured sheets revelated the development of in situ rPP/rPET-O microfibrillar composites when 30 wt.% of rPET-O was added. It was observed that the yield stress was not affected with the addition of rPET-O. However, the microfibrillar structure increased the Young’s modulus by more than a third compared with rPP, fulfilling the longitudinal value predicted by the additive rule of mixtures. Regarding the EWF analysis, the resistance to crack initiation was highly influenced by the resistance to its propagation owing to morphology-related instabilities during tearing. To analyze the initiation stage, a partition energy method was successfully applied by splitting the total work of fracture into two specific energetic contributions, namely initiation and propagation. The results revelated that the specific essential initiation-related work of fracture was mainly affected by rPET-O phase. Remarkably, its value was significantly improved by a factor of three with the microfibrillar structure of rPET-O phase. The results allowed the exploration of the potential ability of manufacturing in situ MFCs without a “precursor” morphology, providing an economical way to promote the recycling rate of PET-O, as this material is being discarded from current recycling processes. Full article

The article first summarizes case studies on the three basic types of treated water used in power plants and heating stations. Its main focus is Czechia as the representative of Eastern European countries. Water as the working medium in the power industry presents the three most common cycles—the first is make-up water for boilers, the second is cooling water and the third is represented by a specific type of water (e.g., liquid waste mixtures, primary and secondary circuits in nuclear power plants, turbine condensate, etc.). The water treatment technologies can be summarized into four main groups—(1) filtration (coagulation) and dosing chemicals, (2) ion exchange technology, (3) membrane processes and (4) a combination of the last two. The article shows the ideal industry-proven technology for each water cycle. Case studies revealed the economic, technical and environmental advantages/disadvantages of each technology. The percentage of technologies operated in energetics in Eastern Europe is briefly described. Although the work is conceived as an overview of water treatment in real operation, its novelty lies in a technological model of the treatment of turbine condensate, recycling of the cooling tower blowdown plus other liquid waste mixtures, and the rejection of colloidal substances from the secondary circuit in nuclear power plants. This is followed by an evaluation of the potential novel technologies and novel materials. Full article

Moisture of bulk material has a significant impact on energetic efficiency of dry grinding, resultant particle size distribution and particle shape, and conditions of powder transport. As a consequence, moisture needs to be measured or estimated (modelled) in many points. This research investigates mutual relations between material moisture and particle classification process in a grinding installation. The experimental setup involves an inertial-impingement classifier and cyclone being part of dry grinding circuit with electromagnetic mill and recycle of coarse particles. The tested granular material is copper ore of particle size 0–1.25 mm and relative moisture content 0.5–5%, fed to the installation at various rates. Higher moisture of input material is found to change the operation of the classifier. Computed correlation coefficients show increased content of fine particles in lower product of classification. Additionally, drying of lower and upper classification products with respect to moisture of input material is modelled. Straight line models with and without saturation are estimated with recursive least squares method accounting for measurement errors in both predictor and response variables. These simple models are intended for use in automatic control system of the grinding installation. Full article

In the last century, the economic growth has been accompanied by a worldwide diffusion of polymers for multiple applications. However, there is a growing attention to the environmental pollution and energy consumption linked to the unconditional use of plastic. In the present work, exergy is used as a measure of the resource consumption during the life cycle of polymers. Nine commercially diffused polymers are chosen, and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) is calculated as the sum of the contribution of each step of the chain, including the production process and the Exergy Replacement Cost (ERC) of the fossil fuel. Then, recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the crude polymeric material and the oil derivatives or structural molecules. The main results show that some commonly used polymers have a considerable impact in terms of EE (e.g., PET). Recycling indexes encourage the recycling processes, which are always energetically convenient (from 10% to 60% of exergy savings) compared with the production from virgin raw material. Results from EE calculation are used for the thermodynamic assessment of the plastic content of vehicle components, to obtain useful information for recycling practices development. Full article