Processing Residues Research Articles

Metagenomes from microbial populations beneath a chromium waste tip give insight into the mechanism of Cr (VI) reduction

Dumped Chromium Ore Processing Residue (COPR) at legacy sites poses a threat to health through leaching of toxic Cr(VI) into groundwater. Previous work implicates microbial activity in reducing Cr(VI) to less mobile and toxic Cr(III), but the mechanism has not been explored. To address this question a combined metagenomic and geochemical study was undertaken. Soil samples from below the COPR waste were used to establish anaerobic microcosms which were challenged with Cr(VI), with or without acetate as an electron donor, and incubated for 70 days. Cr was rapidly reduced in both systems, which also reduced nitrate, nitrite then sulfate, but this sequence was accelerated in the acetate amended microcosms. 16S rRNA gene sequencing revealed that the original soil sample was diverse but both microcosm systems became less diverse by the end of the experiment. A high proportion of 16S rRNA gene reads and metagenome-assembled genomes (MAGs) with high completeness could not be taxonomically classified, highlighting the distinctiveness of these alkaline Cr impacted systems. Examination of the coding capacity revealed widespread capability for metal tolerance and Fe uptake and storage, and both populations possessed metabolic capability to degrade a wide range of organic molecules. The relative abundance of genes for fatty acid degradation was 4× higher in the unamended compared to the acetate amended system, whereas the capacity for dissimilatory sulfate metabolism was 3× higher in the acetate amended system. We demonstrate that naturally occurring in situ bacterial populations have the metabolic capability to couple acetate oxidation to sequential reduction of electron acceptors which can reduce Cr(VI) to less mobile and toxic Cr(III), and that microbially produced sulfide may be important in reductive precipitation of chromate. This capability could be harnessed to create a Cr(VI) trap-zone beneath COPR tips without the need to disturb the waste.

Ammonia production from microalgal biosystem: Present scenario, cultivation systems, production technologies, and way forward

Recent advancements in renewable energy technologies have increased the demand for ammonia production from a variety of biomasses due to biomass’s abundant availability. Many types of biomass are used to generate biofuels by thermochemical and biochemical methods. These include residues from farming and forests, municipal solid waste, energy crops, food processing residues, industrial organic effluents, and algae. Microalgae, among the biomasses, are a valuable resource for ammonia and hydrogen production because they have a higher biomass production rate than others. It is possible to use steam gasification, pyrolysis, catalytic pyrolysis, and steam catalytic gasification to move nitrogen from algal biomass to NH3. However, intensive investigation is required in new directions to develop a mature and cost-effective technology. This article closely examines the current production of ammonia and the feasibility of utilizing algal biomass for the production of hydrogen and ammonia through various biochemical and thermochemical routes. The study comprehensively addressed the characteristics of ammonia and the current status of its production across multiple countries. The subsequent section discusses the cultivation systems and life cycle assessment of algal biomass production for fuels. Furthermore, the ammonia/hydrogen production methods utilizing algal biomass are also listed and discussed.

Use of Residual Malt from an Artisanal Beer Brewing Process in the Biosynthesis of Silver Nanoparticles Mediated by Nucleating and Structure-Directing Agents.

Biosynthesized silver nanoparticles (AgNPs) are widely used in varied applications, which are morphology dependent. Consequently, a morphology-controlled synthesis is mandatory. Although there are several studies focused on the plant extract-based biosynthesis of metallic nanoparticles, the use of extracts obtained from agro-wastes is scant. Furthermore, information regarding morphology modification through the use of additional agents is even more scarce. Thus, in this study, AgNPs were synthesized using a malt extract (ME) obtained from an artisanal beer brewing process residue. Additionally, sodium chloride (NaCl), gum arabic (GA), and talc (T) were used in an attempt to modify the morphology of AgNPs. XRD, DLS, SEM, and TEM results demonstrate that stable AgNPs of different sizes and shapes were synthesized. FTIR, HPLC analysis, and the quantification of total proteins, free amino acids, reducing sugars, and total polyphenols before and after AgNPs synthesis showed that ME biomolecules allowed them to act as a source of reducing and stabilizing agents. Therefore, this study provides evidence that ME can be successfully used to biosynthesize AgNPs. Additionally, the antibacterial activity of AgNPs against Gram-negative and Gram-positive bacteria was evaluated. Results indicate that AgNPs show a higher antibacterial activity against Gram-positive bacteria.

Exploiting Agri-Food Waste as Feed for Tenebrio molitor Larvae Rearing: A Review.

The agri-food industry generates substantial amounts of waste, including by-products and residues. The increasing demand for sustainable and eco-friendly practices in the agri-food sector has sparked an interest in finding alternative uses for such waste materials. One promising approach is the utilization of waste from the agri-food industry as feed for the rearing of mealworms (Tenebrio molitor). Since agri-food waste is rich in proteins, carbohydrates, lipids, and vitamins, as well as other bioactive compounds, all of which are essential for insect growth and development, incorporating such waste into the diet of mealworms promotes sustainable insect production, reducing the economic and environmental problems associated with waste disposal. This practice can also be beneficial for the rearing of mealworms since their nutritional value can also be enhanced. To this end, various waste materials, such as fruit and vegetable peels, spent grains, and food processing residues, have been investigated as potential feed sources, leading to increased mass production, lower cost, and enhanced nutritional value. This review aims to highlight the potential of agri-food waste as a feed source for mealworms, as well as their potential to enhance their nutritional value. Furthermore, the potential applications of mealworms reared on agri-food waste are highlighted, including their potential as a sustainable protein source for human consumption and as feed ingredients in the livestock and aquaculture sectors.

PHYSICAL AND CHEMICAL PROPERTIES OF SUBSTRATE DERIVED FROM COFFEE RESIDUE FOR SEEDLING PRODUCTION

The physical-chemical properties of substrates based on coffee residues for seedling production were analyzed. The production of seedlings is associated with the quality of the substrates used. The characterization of the physical-chemical properties is a fundamental part of components and their proportions in formulating substrate selection. Thus, the objective of this work was to analyze the physical-chemical properties of components and formulations based on agro-industrial residues. The quality of the use of three components, fresh coffee straw, carbonized coffee straw, and composted coffee straw, in 25 different formulations of substrates for seedling production were evaluated. The dry density, current humidity, total porosity, aeration space, easily available water, water retention capacity, electrical conductivity, and pH were evaluated. The experiment followed a completely randomized design with three replications, and the data obtained were analyzed by ANOVA and the Scott-Knott test (p<0.05). All substrates had statistical differences among themselves, for all variables studied. Coffee processing residue presented physical and limited electrical conductivity and pH characteristics. Formulated products have physical and chemical characteristics depending on their constituents and proportions. Three substrates stood out for presenting good chemical and physical characteristics, which were based on 30-40% carbonized or composted coffee straw. The results obtained here will work as an important tool to guide decision-making regarding the constituents and adequate proportions in formulating substrates for seedling production

Improved recovery of antioxidants from aronia juice processing residue via optimization of extraction variables based on multi-prediction models

Aronia melanocarpa, which has attracted attention for its outstanding antioxidant activity, is usually consumed as a juice, leaving considerable residue after processing into beverages. Recycling these by-products as feedstock for biorefineries is an important strategy for achieving a sustainable circular economy through biowaste management. In this study, the optimal extraction conditions for efficient antioxidant recovery from A. melanocarpa juice-processing residue (AJPR) were determined using statistical methods. Based on the Plackett-Burman design (PBD), four variables (shaking speed, solid loading, ethanol concentration, and total volume) were found to have significant effects on antioxidant extraction. The optimum points of the selected four variables were calculated by multi-regression models from response surface methodology (RSM), and the determined conditions were as follows:196.2 rpm, 71.3 g/L, 54.3% ethanol, and 137.8 mL of total volume. The DPPH• IC50 and ABTS•+ TEAC value of AJPR extracts were determined to be 2.02 mg/mL and 11.49 mg/mL, respectively, exhibiting promising potential as an antioxidant. The recovered polyphenol, flavonoid, and anthocyanin contents were 80.4, 42.5, and 14.1 mg/g-biomass, respectively. We show that bioengineering technologies can be used to achieve a circular economy by recycling discarded biowaste into value-added substances.

Changes in Physical Properties and Microstructure of Bamboo–Plastic Composites with Different Bamboo Powder/Polybutylene Succinate Ratios, Polypropylene, and Polyethylene

As the most promising biomass material, bamboo has been widely used, but at the same time, it is subject to many problems, such as processing residues and the failure of high-value utilization of residues. In this paper, bamboo powder and polybutylene succinate (PBS) were used as the main raw materials, and by changing the ratio of bamboo powder to PBS and adding polypropylene (PP) or polyethylene (PE) in combination with PBS, the effects of the ratio, as well as the effects of the use of PP and PE, on the physical–mechanical, thermal, and degradation properties of bamboo–plastic composites were investigated, and the microscopic changes of the materials were studied by chemical component analysis. The optimal formulation of bamboo powder/PBS composite material has been identified through experimentation, yielding a flexural strength of 24.87 MPa and a compressive strength of 29.74 MPa. This material can be used for outdoor furniture, wall panels, flooring, road barriers, and other applications, providing a new environmentally friendly approach to the consumption of residual bamboo materials.

Timber-framed exterior walls insulated with wood shavings: A field study in a nordic climate

Wood processing residues provide a possibility to produce thermal insulation material with low environmental impact. This paper deals with the hygrothermal performance of timber-framed exterior walls with wood shavings as insulation material. The presented study consisted of field measurements of five exterior wall structures with two different types of wood shavings insulation and three reference walls. The study was performed in cold Nordic climate, where hygrothermal conditions at outer parts of a wall structure are critical. Untreated wood shavings and wood shavings coated with pulverized clay were compared as insulation materials. Different wind barriers as well as a water vapour barrier and sheathing acting as vapour retarder were also used. Results indicated no suitable conditions for mould growth inside any wall. The thermal resistance of wind barriers as well as the clay-coating of wood shavings had positive effect on the hygrothermal performance of the test walls. Wood shavings proved to be suitable insulation materials for well-insulated structures from the hygrothermal point of view, when the overall design, construction and maintenance are carried out in a proper way.

Activated wood flour as adhesives for bonding activated wood veneer to produce sustainable wood composites

The use of biomass as a binder for the development of high-performance wood products has become a popular research topic in the context of sustainable development. In this work, wood flour obtained from agroforestry processing residues was used as an active functional filler. The wood flour was oxidized and chemically cross-linked with hyperbranched polyamines and used as a binder matrix. By applying the same oxidative treatment to the wood surface, a chemically activated bonding interface was formed. Analysis by FTIR, 13C NMR, XPS and XRD characterization showed that the key to the improved bonding property was the formation of multiple covalent cross-linked networks during hot pressing of the plywood. It is clear that the specimens with untreated wood surfaces showed no water resistance and the dry strength was only above the standard value. On the contrary, after activation of the veneer surfaces, the bond strength and water resistance were significantly improved, meeting the requirements of GB/T 17657–2013 for Class I panels. Activation of the chemically active adhesive interface by oxidation of wood materials is an effective means of improving the performance of plywood, and also provides a new idea for high-value utilization of biomass resources.

Detoxification of chromium slag using corn stalk for the hierarchical preparation of ultrafine aluminum hydroxide and iron hydroxide

The harmless treatment and resource utilization of chromite ore processing residue (COPR), a consequential byproduct of chromate production, carry profound significance. In this study, corn stalk, an agricultural waste, was used to generate reducing substances through high-temperature and vacuum treatments and was successfully used to detoxify COPR. The acid leaching method combined with multi-step purification was employed to extract iron and aluminum, two crucial metallic elements, from COPR. The successful preparation of iron hydroxide and ultrafine aluminum hydroxide (ATH) was achieved. The prepared ATH has an average particle size of 8.124 μm, with a highly uniform distribution, enabling it to be a promising environmentally friendly inorganic flame retardant. This study not only effectively addresses the issue of pollution caused by COPR but also presents a novel approach to utilizing industrial and agricultural wastes, thereby promoting the maximization of resource utilization.

Circular bioeconomy ecosystems: Hydroxyapatite from fish waste at Rio de Janeiro

AbstractThe transition to a low‐carbon economy endangered the revenues of many oil‐dependent regions. This is the case in Rio de Janeiro state, Brazil, which has become highly dependent on oil and gas royalties since the 1970s. At the same time, the circular blue bioeconomy has emerged as a pathway for environmentally sound socioeconomic development. In such a context, a biological resource in many oil‐dependent regions is fish processing residue, from which high added‐value compounds can be obtained, such as collagen, hydroxyapatite, gelatin, lipids, enzymes, hydrolysates, and bioactive peptides. The present study aims to understand the potential for a future fish waste hydroxyapatite (FHAp) market in the state of Rio de Janeiro (SRJ). The methodological approach integrates technology roadmapping with market and innovation ecosystem assessment. We found that the main techniques for obtaining FHAp were chemical hydrolysis and calcination, and the most innovative and value‐added applications were biomaterial for tissue regeneration (BTR) and physical sunblock (PS). The mapping of SRJ companies showed that the state has qualified players in cosmetic and biomedical industries that could develop innovations in BTR and PS made of FHAp. However, the mapping also showed a gap in the FHAp extraction stage, which is essential for the value chain. To find and encourage players to compound this innovation ecosystem, the public power can therefore act as an articulator, providing financial incentives and creating infrastructural conditions, such as a waste pretreatment plant next to the state fishing pole.

Antioxidant and Anticancer Activity of Pericarp Water Extracts of Mediterranean Ancient Chestnut Accessions

The residue of chestnut processing generates a large amount of waste material, a resource not adequately exploited. The antioxidant and antitumoral properties of cold and hot water extracts from discarded pericarp of four chestnut Sardinian accessions and one marron variety were studied. The antioxidant capacity of the extracts was determined by spectrophotometric and electrochemical tests. The 1,1-diphenyl-2-pic-rylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) results were highly correlated with each other; likewise, a good correlation was found between Ferric Reducing Antioxidant Power (FRAP) and cyclic voltammetry (CV) values, both based on the direct transfer of electrons. The antiproliferative effect on normal cells (fibroblasts), and on colon (RKO and SW48) and breast (MCF7) cancer cells was evaluated. Additionally, this paper marks the first application of chestnut extracts to investigate their effects on melanoma (B16F10) cells. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test demonstrated that temperature and different extraction times significantly influenced the growth of cells, both normal and tumor. The fibroblast growth was significantly inhibited by moderate doses of cold extracts, while the GI50 values calculated for hot extracts were high, regardless of the accession or cultivar. An even more marked inhibitory action of the cold extracts was observed both on the growth of RKO and SW48 cells and on B16F10 melanoma cells. Otherwise, an extract concentration, both cold and hot, of no less than 243 µg mL−1 is required to achieve a 50% inhibition of MCF7 cell growth.

Contamination Characteristics and Ecological Risk of Antibiotics in Contaminated Sites of Typical Pharmaceutical Factories in China

To understand the contamination characteristics and ecological risk of antibiotics in contaminated fields of pharmaceutical plants， samples of the surface soil， soil column， wastewater treatment process water， ground water， and residue dregs were collected from two typical antibiotic pharmaceutical plants in South and North China. A total of 87 commonly used antibiotics were quantified using ultrasound extraction-solid phase extraction and ultra-high performance liquid chromatography-mass spectrometry. The results showed that a total of 31 antibiotics of five classes were detected in all types of samples， and the maximum concentrations at each sampling point in the surface soil， soil column， residue dregs， wastewater treatment process water， and groundwater were 420 ng·g-1， 595 ng·g-1， 139 ng·g-1， 1 151 ng·L-1， and 6.65 ng·L-1， respectively. Most of the antibiotics were found in the surface soil， showing a decreasing trend with the depth of the soil column. The ecological risk assessment indicated that sulfamethazine， sulfaquinoxaline， tetracycline， chlorotetracycline， and D-sorbitol were at higher risk. Improving the efficiency of antibiotic removal from pharmaceutical wastewater and preventing production shop leaks are effective measures of controlling antibiotic contamination into and around fields in pharmaceutical plants.

The Bioenergetic Potential from Coffee Processing Residues: Towards an Industrial Symbiosis

Coffee processing generates a large amount of organic waste, which has the potential for energy use through biogas production. Although Brazil dominates world coffee production, treating its residue with biogas technology is not a practice, especially due to this product’s seasonality, which hampers continuous digester operation. The implementation of biogas production from coffee residues in a concept of industrial symbiosis could overcome this. This work evaluates the biogas energy potential from the main liquid residues of coffee processing (i.e., mucilage and wash water) and their integration with glycerin and cattle manure. Around 2773 m3 biogas day−1 would be produced (75% CH4), used as biomethane (734 thousand m3 year−1), or thermal energy (23,000,000 MJ year−1), or electricity (2718 MWh year−1), which could supply, respectively, all the liquefied petroleum gas (LPG) and diesel demands of the farm, all the thermal energy demands of the grain drying process, as well as electricity for 30 residences. Considering the short coffee season, the results have a broader context for the application of biogas production on coffee processing farms, envisaging that the Agroindustrial Eco-Park concept has the potential to integrate various agroindustrial sectors for energy production, residue exchange, and water recirculation.

Circular economy, turning decay into magic: heparin extraction from pig viscera

The transformation of industrial waste into valuable resources is an increasingly important concept. At Taiwanâ–™s National Cheng Kung University a multi-disciplinary team has been working towards the 17 Sustainable Development Goals (SDGs) adopted by the United Nations member states in 2015 and has developed a method of extracting a valuable medical drug called heparin from agricultural waste. The researchers have combined the advantages of chemical engineering and biotechnology to effectively improve the extraction efficiency and purity of heparin and protected it with technology patents. This exciting innovation could solve the problem of waste disposal from pork production while creating a high-medical value resource from that waste and the residue of the production process could be transformed into fertiliser and animal feed. As such, the researchers believe the application of this technology will help improve the economic productivity of pig farmers and promote environmentally sustainable farming. The value of Chiangâ–™s research are the anticoagulant benefits heparin offers to patients, and also providing new techniques that offer a sustainable and stable supply of the drug. He and the team have taken an innovative approach to extracting heparin sodium, which is the heparin precursor, from pig viscera waste by using dual hydrogen peroxide oxidation methodology and microbial monitoring to enhance the purity of the extracted heparin sodium, creating a higher-quality product for medical applications.

Production of biological hydrogen from Quinoa residue using dark fermentation and estimation of its microbial diversity

Although they are one of the world's environmental problems, agricultural wastes or residues are carbohydrate-rich and low-cost, so they are used as raw materials for the manufacture of biohydrogen (bio-H2). Among biological hydrogen manufacture methods, the dark fermentation method is suitable for processing waste or residues. In this regard, no study has been found in the literature on determining the potential of biological hydrogen manufacture from quinoa residue by the dark fermentation method. This work was carried out in a dark room at 36 ± 1 °C under different operating conditions in anaerobic batch bio-reactors fed with thermally pretreated anaerobic mixed bacteria + raw quinoa or quinoa extract liquid + nutrients. In the study, gas analyses were performed and biohydrogen production was detected in all the bio-reactors. Besides, taxonomic content analyses and organic acid analyses were executed. Maximum bio-H2 production was found as follows: at pH 4.5, 14,543.10−4 mL in the bio-reactor fed with 1.00 g quinoa/L and 1880.10−4 mL in the bio-reactor fed with 0.50 g quinoa extract/L, and at pH 4.0, 61,537.10−4 mL in the bio-reactor fed with 1.00 g quinoa/L and 1511.10−4 mL in the bio-reactor fed with 0.75 g quinoa extract/L. In the bio-reactors fed with raw quinoa residue, Clostridium butyricum and Hathewaya histolytica were detected as the most dominant bacteria at pH 4.5 and 4.0, respectively, whereas in the bio-reactors fed with quinoa extract liquid, Fonticella tunisiensis were detected as the most dominant bacteria at both pH 4.5 and pH 4.0.

Anaerobic fermentation of poplar processing residue to produce methane by alkaline hydrogen peroxide (AHP) pretreatment

ABSTRACT The study evaluated the effects of alkaline hydrogen peroxide (AHP) pretreatment on poplar processing residue for methane production. The delignification of poplar processing residue was used as the basis for evaluation. The experiment considered the pretreatment time (0 h-24 h), the hydrogen peroxide (H2O2) concentration (0.5%-2.0%), and potassium hydroxide (KOH) concentration (1.0%-3.0%) at a temperature of 70°C. Subsequently, anaerobic fermentation experiments were conducted using the pretreated biomass with sludge as the inoculum under mesophilic temperature conditions (37 ± 1°C). The initial feedstock (poplar processing residue) contained 40.31 ± 0.06% cellulose, 31.17 ± 1.59% lignin, and 14.85 ± 0.38% hemicellulose. The AHP pretreatment caused changes in the lignocellulosic content of the feedstock, particularly affecting the lignin structure compared to cellulose and hemicellulose. At a pretreatment time of 18 hours, temperature of 70°C, and concentrations of 2.0% H2O2 and 1.0% KOH, the AHP pretreatment resulted in a higher methane production of 237.4 mL per gram. These findings demonstrate that AHP pretreatment is an effective strategy for enhancing methane production from poplar.

Geotechnical investigations of lead-silver ore processing residues at the Auzelles site, Auvergne (France)

<p>Mining operations generate a significant quantity of mining waste in the form of sterile rocks and processing residues. These mining wastes are typically placed on the surface and can cause geotechnical and geochemical disturbances, as well as contaminants in surface water (through runoff) and groundwater (through infiltration), thus posing environmental risks. This article aimed to characterize the geotechnical properties of lead-silver ore processing residues at the Auzelles site in order to assess their stability and propose recommendations for their management and rehabilitation. The adopted methodology included in situ tests (such as density measurement and permeability) and laboratory analyses (grain size distribution, moisture content, methylene blue test, direct shear test, and standard Proctor test). The results showed a wet density of 1.63 g/cm<sup>3</sup> for the residues compared with 1.65 g/cm<sup>3</sup> for the waste rock, as well as a permeability of the residues measured at 5.5 × 10<sup>-5</sup> m/s, indicating significant drainage capacity. Laboratory analyses revealed that the samples were primarily composed of very silty sands and gravel, classified as B5 according to the Guide to Road Settlements. The cohesion of the residues was found to be zero, while the internal friction angle varied between 28° for the residues and 30° for the foundation soils. These geomechanical properties, particularly density, lack of cohesion, and friction angle values, raise concerns about the long-term stability of the residues. Due to their high permeability and lack of cohesion, the residues are susceptible to mass movement and erosion, which may exacerbate contamination risks. Therefore, it is essential to integrate these parameters into any potential residue stability analysis. Proactive management, based on these results, requires the implementation of appropriate rehabilitation techniques, such as drainage optimization and incorporation of vegetation covers, to minimize environmental impacts and ensure the long-term sustainability of mining waste structures.</p>

Analysis of raw material sources for a plant-based milk alternative from almonds

Plant-based alternative milks are mainly obtained by dry and wet grinding of raw materials. In both cases, it is extracted with water and filtered to remove large particles and residues of the technological process. Although there are many differences and changes in the technological processes in the production of plant milks, the traditional process on an industrial scale is the same as above. In this article, the importance and prospects of milk alternatives based on plant sources are discussed, and the raw material potential of almonds used in the production of plant milks in Uzbekistan is studied. In this research work, the 7 cheapest local varieties of almonds in the local markets were selected. Also, the properties of common almond varieties in the country were studied and optimal varieties were selected for obtaining almond milk. The chemical properties of selected promising varieties were studied in laboratory conditions and the obtained results were discussed. The physical and chemical characteristics of local varieties studied for obtaining almond milk are presented in the tables.

Utilization of Rubber Waste for Manufacture of Rubber Conical Bonded

Rubber Conical Bonded (RCB) is a component that connects the wheel with the train bogie, which functions to dampen vibration and noise. This RCB is made of rubber. In this research, RCB vulcanizate will be made with a mixture of natural rubber (RSS 1) and rubber waste. Rubber waste is the residue from the production process of technical rubber goods or rubber technical goods that are no longer used. This rubber waste goes through a devulcanization process to be reused as a raw material. In this study, rubber waste derived from the residue of the production process was varied with the phr ratio as follows: RSS 1 / Rubber waste / Devulcanized rubber waste (RCB0: 100/0/0; RCB10: 90/10/0; RCB30: 70/30/0; RCB50: 50/50/0; RCB10X: 90/0/10; RCB30X: 70/0/30). The vulcanizate obtained was then subjected to physical characterization (before and after aging 24 hrs; 70oC) and compared with the technical specifications of the RCB. Physical characterization includes Tensile Strength (min 14 N/mm2), Tear Strength (min 26 N/mm2), Hardness Shore A (50±5), Elongation at Break (min 400%), and Compression Set (max 30%). The results show that all variations meet the specifications for tensile strength, tear strength, and hardness.