Waste Resource Recovery Research Articles

Pilot-scale, cost-effective waste resource recovery: Efficient reduction of trace Au(Ⅰ) from industrial wastewater via an adsorption and electrodeposition coupling process

Pilot-scale, cost-effective waste resource recovery: Efficient reduction of trace Au(Ⅰ) from industrial wastewater via an adsorption and electrodeposition coupling process

Characterization of biochar produced from paperboard sludge: A sustainable approach for waste management and resource recovery

The pulp and paperboard industry are a significant industrial sector that consumes large quantities of fresh water and generates substantial volumes of wastewater. Treating this wastewater produces a considerable amount of sludge, which poses serious environmental challenges. This study proposes a sustainable solution by converting paperboard sludge (PBS) into biochar through slow pyrolysis at temperatures ?00°C, offering an alternative approach to waste management and resource conservation. The physicochemical analysis of paperboard sludge biochar (PBSB) revealed a neutral pH of 7.49, electrical conductivity of 0.09 dS m-1, an organic carbon content of 38.12%, and a calcium carbonate (CaCO3) content of 24.5%. Proximate analysis of PBSB revealed an increased fixed carbon content of 10.27 %, total organic carbon (TOC) of 7.13%, and reduced volatile matter and moisture levels. Micronutrients viz., iron (Fe) (5.06 mg L-1), Manganese (Mn) (419.3 mg L-1), Copper (Cu) (26.3 mg L-1), and Zinc (Zn) (66.1 mg L-1), were also observed in PBSB. FTIR analysis identified various carbon-containing functional groups, including C-Cl, C-N, C-C, H-C=O, C-H, and -C?C-H, indicating substantial chemical transformations during pyrolysis. Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX) analysis revealed that PBSB consists of fine particles with a coarse, fluffy, spongy, porous structure, making it ideal for water adsorption. Elemental analysis through x-ray diffraction (XRD) showed high carbon and oxygen content and significant amounts of aluminosilicates, carbonates, and nutrients like phosphorus and potassium, suggesting PBSB as a potential slow-release fertilizer. This research highlights the potential of biochar derived from paperboard waste as a sustainable solution for effective waste management and resource recovery.

Nutritional, Antioxidant and Antimicrobial Properties of Citrus Peels: A Sustainable Valorization Approach

Background: Citrus peels are often discarded as waste despite being rich in bioactive compounds with potential health benefits. Traditional extraction methods for these compounds are not always sustainable and can lead to environmental harm. Using a sustainable vaporization approach, the bioactive compounds in citrus peels can be efficiently extracted and retained for various applications. Valorization strategies have been used for various waste streams, including agro-industrial by-products and olive mill wastewater. Aims: Using a sustainable vaporization method, this study seeks to examine the antibacterial, antioxidant, and nutritional qualities of citrus peels. Methods: waste valorization remains a promising approach for sustainable waste management and resource recovery. Quantitative studies and antimicrobial activities were carried out using peels of C. aurantifolia (Key Lime), C. maxima (Pomelo), C. sinensis (orange), Citrus limetta (Sweet Lemon), and C. reticulata. Citrus aurantiifolia is believed to be a hybrid of Citrus medica, Citrus grandis, and a Micro-citrus species, with significant antibacterial activity. Result: Citrus limetta Mosambi is gaining popularity due to its delicious taste and high vitamin-C content. Citrus sinensis is a small, spherical fruit rich in vitamin C and vitamin A. Pummelo, or Citrus maxima, is known for its large, sweet fruits with abortifacient and menstrual stimulant properties. Peels of C. maxima exhibit the highest amount of antioxidant activity equivalent to ascorbic acid and display significant antimicrobial activity against Klebsiella species. Citrus reticulata, found mainly in eastern India, has a maximum amount vitamin C among citrus species and exhibits high antimicrobial activity.

E-waste as a potential precursor for geopolymers

Abstract The rapid growth in electronics production and the shortening product lifespans have resulted in a growing problem of electronic waste (e-waste). E-waste is a complex mixture of organic and inorganic materials, making its recycling a challenge. This study explores the potential of powdered e-waste as a geopolymer precursor and investigates the geopolymerization of reactive phases in e-waste. Research techniques, including XRD, XRF, SEM/EDX, and FTIR, were used to characterize the e-waste and obtained geopolymers. Significant contents of reactive SiO2, Al2O3 and CaO components were detected in the e-waste which can participate in the formation of geopolymer gel. The present study elucidate the feasibility of utilizing e-waste as a geopolymer precursor, offering a potential for sustainable waste management and resource recovery in the electronics recycling industry.

Sustainable humification of food waste slurry through thermally activated persulfate oxidation

This study introduces a thermoanalytical approach utilizing sodium persulfate (PS) to expedite the humification of food waste (FW) through advanced oxidation processes (AOPs). The method harnesses heat-induced free radicals to break down complex organic compounds into simpler forms, leading to the formation of humic substances. We conducted an analysis of changes in soluble chemical oxygen demand (SCOD), dissolved organic carbon (DOC), ammonia nitrogen, soluble proteins, and sugars, employing advanced techniques such as three-dimensional fluorescence spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). The findings indicate that the activation of PS at 70 °C effectively increases SCOD and DOC levels, converts proteins into soluble forms, and enhances NH4+-N content. This study, which focuses on the utilization of thermal methods, affirms that the thermal activation of persulfate (PS) significantly boosts the humification of food waste (FW), presenting a sustainable approach for waste management and resource recovery.

The Role of Bio-Based Innovations in Circular Economy: A Biochemical and Economic Perspective

The concept of the circular economy (CE) is gaining prominence as a sustainable alternative to the traditional linear economy. Bio-based innovations, which harness biological resources for production, offer promising solutions to resource depletion and environmental degradation. The increasing global emphasis on sustainable development has catalyzed the shift from traditional linear economic models towards a more sustainable and efficient circular economy. Within this transformation, bio-based innovations play a critical role, particularly in reducing environmental impact, enhancing resource efficiency, and stimulating economic growth. This research examines the biochemical processes underlying bio-based innovations and their potential economic benefits within a circular economy framework. It explores the significance of bio-based innovations from both biochemical and economic perspectives, examining their role in fostering a circular economy. The integration of bio-based materials and processes, which utilize renewable biological resources, not only reduces dependency on fossil fuels but also promotes the regeneration of biological systems. Economically, the bio-based sector contributes to job creation, GDP growth, and overall economic resilience. This study also analyzes how bio-based innovations can be harnessed for waste valorization, resource recovery, and environmental sustainability, culminating in a balanced approach to circular economy principles. Using case studies and statistical analysis, the paper presents a comprehensive view of the biochemical mechanisms and economic implications of bio-based innovations, with recommendations for policy and business strategies.

Innovative recycling and conversion of aluminum waste to hydrogen and aluminum chloride: Enhancing economic feasibility and sustainability in Saudi Arabia

The rapid industrialization and urbanization in Saudi Arabia have led to significant challenges in waste management, particularly in recycling aluminum waste. This study explores an innovative approach for converting aluminum waste, specifically beverage cans, into valuable products such as aluminum chloride (AlCl3) and hydrogen (H2). The process involves the chemical reaction of aluminum with hydrochloric acid (HCl), producing AlCl3 and H2, and is modeled using Aspen Plus software. Two scenarios are evaluated: one without recycling and one incorporating recycling processes. In the first scenario, the direct conversion process yields 355 tons of AlCl3 and 9 tons of H2 per day from 100 metric tons of aluminum waste. The minimum selling price (MSP) of AlCl3 is calculated to be $764 per ton, with an annual profit of $25 million, assuming a market price of $1000 per ton. However, the economic viability of this scenario is highly sensitive to conversion efficiencies and market conditions. The second scenario integrates a recycling loop, processing 90 % of the aluminum waste back into aluminum, significantly enhancing economic stability. This scenario produces 35 tons of AlCl3 and 1 ton of H2 per day, with an MSP of $1068 per ton. Despite the higher MSP, the inclusion of recycled aluminum, sold at $2400 per ton, results in a higher annual profit of $38 million, demonstrating greater economic resilience and sustainability. This study provides a comprehensive techno-economic analysis, highlighting the dual benefits of waste reduction and resource recovery. By optimizing reaction conditions and incorporating recycling, the proposed process aligns with Saudi Arabia's Vision 2030 sustainability goals, offering a viable pathway for enhancing economic feasibility and environmental sustainability in aluminum waste management.

High-efficient synthesis of straw-derived carbon quantum dots for facilitating methanogenic performance in high-load co-digestion of food waste and excess sludge

Anaerobic digestion (AD), as a crucial technology for organic waste resource recovery, faces the challenge of low efficiency in converting high-load organic substance into biogas. In this study, high-load AD system with food waste and excess sludge as co-substrates was constructed. The effect and mechanism of carbon quantum dots (CQD) derived from straw in promoting the performance of AD systems have been studied. The oxidation pretreatment of straw with H2O2 and acetic acid increased the yield of hydrothermal synthesis CQD to approximately 40%. The effect of different CQD on CH4 yield performance was further explored. The cumulative CH4 yield performance of the fermenter was improved after adding CQD. The CQD synthesized from pretreated straw and the nitrogen-doped CQD synthesized using Chlorella as the nitrogen source showed competitive promotion performance, increasing cumulative CH4 yield by 17.71% and 8.87%, respectively. These CQD can effectively accelerate the degradation of dissolved organic matter and thus improve the CH4 yield performance, with the most significant effect of CQD synthesized from pretreated straw. Electrochemical analysis and the correlation analysis between microorganisms and performance parameters showed that these CQD established an electron conductive network to enhance the electron transfer of the system. This well conductive conditions enriched hydrogenotrophic methanogenic (Methanosarcina), electroactive bacteria (Clostridium_sensu_stricto_1), and hydrolytic-acidifying bacteria (norank_f__Bacteroidetes_vadinHA17). This study significantly enhanced the yield of straw-derived CQD through green methods, and deeply revealed the potential promoting mechanisms of biomass-derived CQD by investigating the correlation between system performance and microorganisms in high-load AD systems.

Enhanced hydrothermal liquefaction of tires using zinc and MoS2

This study introduces a novel approach for tire liquefaction employing zinc and unsupported catalyst MoS2 to mitigate oxygen, nitrogen, and sulfur content, while inhibiting poly-aromatic formation. Autoclave experiments were conducted under subcritical water conditions at 360 and 410 °C. Comprehensive characterization of char and oil was performed, encompassing elemental analysis, functional-group assessment, and composition analysis using gas chromatography-mass spectrometry (GC-MS) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). During the liquefaction, zinc metal pellets react with water to form ZnO and hydrogen, aiding hydrogenation, and MoS2 preserves its catalytic stability. ZnO shows a catalytic effect on deoxygenation, desulfurization, and denitrification reactions. However, the reaction between ZnO and H2S is not favorable under hydrothermal conditions. Zinc and MoS2 synergistically promote cracking of heavier compounds into lighter ones, particularly evident at higher temperatures, without diminishing the overall oil yield. Incorporating zinc pellets and MoS2 slightly facilitates sulfur and oxygen migration from liquid to solid and gas phases. FT-ICR MS analysis reveals oxygen, sulfur, and nitrogen-containing compounds in heavy fraction of oils. The oxygen-containing compounds, predominantly comprised of stearic acid and its derivatives, are identified. Concurrently, the nitrogen-containing compounds manifest primarily as basic nitrogen compounds. MoS2 possesses the capability of forming more N-containing compounds, leading to the generation of a broader spectrum of N-containing compounds. This work elucidates the synergistic role of zinc-assisted catalysis and MoS2, offering insights into tire liquefaction mechanisms and product composition, vital for sustainable waste management and resource recovery.

Efficiency of Penicillium sp. and Aspergillus sp. for bioleaching lithium cobalt oxide from battery wastes in potato dextrose broth and sucrose medium

Lithium-ion batteries, a primary power source, generate electronic hazardous waste at the end of their lifespan, which is a richer source of highly concentrated metals such as cobalt and lithium than those in natural resources. The waste is a potential renewable resource for the extraction of metals. Bioleaching, a process utilizing microbial activity, was used in this study to investigate the cobalt and lithium leaching efficiency from battery wastes. Two fungal strains, Aspergillus sp. strain JMET 15 and Penicillium sp. strain JMET 24 were used with different organic carbon sources (sucrose medium and potato dextrose broth) at 1 % pulp density. The sucrose medium derived a higher acid quantity and leached higher concentration of cobalt and lithium than in potato dextrose broth. Leaching efficiency by JMET 24 was higher than JMET 15. Cobalt (32.57 % and 27.19 %) and lithium (65.07 % and 40.58 %) were bioleached by JMET 24 and JMET 15, respectively, after 30 d cultivation in the sucrose medium. Lower pulp density was conducted to achieved higher leaching efficiency by JMET24, cobalt (77.87 % and 74.5 %) and lithium (99.88 % and 78.4 %) were bioleached at 0.1 % and 0.5 % pulp density, respectively. Cobalt oxide (Co3O4) was the product of the one-step recovery (leaching and precipitation) process. Cobalt was transformed from lithium cobalt oxide to cobalt phosphate-oxalate by JMET 24 in the sucrose medium. Thus, the potential of bioleaching as an effective method for recovering valuable metals from lithium-ion battery waste is demonstrated, presenting a promising approach for both waste management and resource recovery.

Sustainable Energy Application of Pyrolytic Oils from Plastic Waste in Gas Turbine Engines: Performance, Environmental, and Economic Analysis

The rapid accumulation of polymer waste presents a significant environmental challenge, necessitating innovative waste management and resource recovery strategies. This study investigates the potential of chemical recycling via pyrolysis of plastic waste, specifically polystyrene (PS) and polypropylene (PP), to produce high-quality pyrolytic oils (WPPOs) for use as alternative fuels. The physicochemical properties of these oils were analyzed, and their performance in a gas turbine engine was evaluated. The results show that WPPOs increase NOx emissions by 61% for PSO and 26% for PPO, while CO emissions rise by 25% for PSO. Exhaust gas temperatures increase by 12.2% for PSO and 8.7% for PPO. Thrust-specific fuel consumption (TSFC) decreases by 13.8% for PPO, with negligible changes for PSO. The environmental-economic analysis indicates that using WPPO results in a 68.2% increase in environmental impact for PS100 and 64% for PP100, with energy emission indexes rising by 101% for PS100 and 57.8% for PP100, compared to JET A. Although WPPO reduces fuel costs by 15%, it significantly elevates emissions of CO2, CO, and NOx. This research advances the understanding of integrating waste plastic pyrolysis into energy systems, promoting a circular economy while balancing environmental challenges.

Micro-wave induced pyrolysis of low density polyethylene (LDPE) and biodegradation of resulting wax in soil and by defined microbial consortia is closing the loop towards LDPE upcycling

Plastic has become essential in daily life, replacing traditional materials like glass and wood due to its flexibility, durability, strength, and cost-effectiveness. However, the global plastic production surged to nearly 400 million tons in 2020, causing significant environmental accumulation. Polyethylene (PE), a ubiquitous polymer, poses recycling challenges due to its stability and widespread use in layered products, contributing to long-term pollution. This study focuses on PE degradation challenges, advocating for integrated chemical and biological treatments. Chemical methods like pyrolysis show promise but aren't fully eco-friendly. Microwave-induced pyrolysis emerges as a viable alternative, offering faster, targeted heating with lower energy consumption. Using microwave-absorbent materials such as silicon carbide, this method efficiently breaks down even challenging low-density PE (LDPE), yielding wax products of 68–91 % yield, with reduced molecular weight suitable for further biological degradation. Biodegradation experiments demonstrated over 95 % degradation by defined microbial consortia and considerable degradation in soil without bioaugmentation. The Rhodococcus consortium showed exceptional potential, degrading 90 % of LDPE-wax as a carbon source within 28 days, particularly strain CHBE-144 achieving 98 % degradation in just 14 days. Genomic analysis revealed enzymes crucial for alkane and plastic breakdown, with strains capable of producing biosurfactants, suggesting up-cycling potential for PE-derived materials into value-added products. Integrating microwave-induced pyrolysis with microbial biodegradation offers a promising pathway for managing PE waste sustainably, potentially reducing environmental impact while creating valuable resources from plastic waste. Further research is warranted to optimize these processes and scale them for practical application in waste management and resource recovery efforts globally.

Thermal activation of basic oxygen furnace slag as a heterogeneous catalyst in transesterification: Characterization and catalytic activity studies

The valorization of industrial by-products has garnered significant attention in recent years due to its potential to enhance sustainability and economic efficiency within various sectors. Basic Oxygen Furnace slag (BOF-S), a by-product generated in the steelmaking process characterized by its complex composition, presents an opportunity for waste management and resource recovery. This study investigates the potential of BOF-S as a catalyst in converting waste cooking oil to biodiesel via the transesterification reaction. To improve its efficiency, BOF-S was calcined at 850 °C (BOF-S 850), and 1000 °C (BOF-S 1000), for 5 h. The BOF-S was characterized using XRF, N2 sorption, XRD, TGA-DSC, SEM-EDS and FTIR. The characterization techniques showed that the BOF-S 850 had superior characteristics as a catalyst: rough surface, increased pore size and more active basic sites compared to the BOF-S and the BOF-S 1000 slag samples. The transesterification reaction was conducted at a methanol: oil ratio of 20:1, a catalyst loading of 20 wt %, a reaction time of 12 h, a reaction temperature of 60 °C, and a stirring speed of 750 rpm. The findings established that the BOF-S 850 was the best catalyst, with a 90.77 % biodiesel yield and was able to sustain a maximum of two transesterification cycle runs.

Optimization of Leaching Recovery of Zinc, Iron and Manganese from Selected Solid Waste Ashes in Zaria, Kaduna State, Nigeria

The increasing environmental burden of toxic heavy metal-concentrated ash from solid waste incineration, particularly from burnt tires and contraband drugs, poses significant challenges for waste management and resource recovery. This study aims to optimize the leaching recovery of zinc, iron, and manganese from these solid waste ashes in Zaria, Kaduna State, Nigeria, using Response Surface Methodology (RSM). The ashes were analyzed for their metal content using atomic absorption spectroscopy (AAS), with additional characterization by X-ray diffraction (XRD) and X-ray fluorescence (XRF). Among the leaching agents tested, hydrochloric acid (HCl) exhibited the highest efficiency, particularly under optimized conditions determined through central composite design (CCD). The optimal conditions for leaching from burnt tire ash were found to be 2.97 mol/l acid concentration, 97.7 minutes leaching time, and 68.85°C temperature, yielding recoveries of 32,009 mg/kg zinc, 4,553 mg/kg iron, and 137 mg/kg manganese. For contraband drug ash, the optimal conditions were 2.83 mol/l acid concentration, 97.7 minutes leaching time, and 68.85°C temperature, resulting in recoveries of 70.55 mg/kg zinc, 5,771 mg/kg iron, and 676 mg/kg manganese. This study successfully developed a multiple linear regression model to express the relationship between the leaching parameters and metal recovery, providing a reliable and sustainable method for metal recovery from solid waste ashes. The findings offer valuable insights into waste management practices, contributing to the circular economy and reducing the environmental impact of waste disposal.

Experimental investigation on a solar-powered oxy-hydrogen gas system for enhanced plastic pyrolysis

The escalating environmental concerns associated with plastic waste have intensified the search for sustainable waste management solutions. Plastic dispersion in the environment poses severe threats to ecosystems, human well-being, and agriculture. Consequently, addressing plastic pollution stands as a pressing ecological concern. In contrast, the adoption of sustainable solar energy is harnessed for the production of HHO (Oxy-Hydrogen) gas, offering a promising avenue for clean energy generation. Gas production is achieved through the process of electrolysis, utilizing solar panels as the primary energy source. To address storage challenges, a spiral pipe configuration is employed for the interim containment of the generated HHO gas. Given the highly flammable nature of HHO gas, stringent safety protocols are imperative throughout the production and storage phases. To ensure the safe handling of HHO gas, a sophisticated MQ-8 Sensor is employed for real-time leak detection within the gas containment system. This sensor plays a critical role in maintaining operational safety by promptly identifying and addressing any potential gas leaks that may arise within the tubing infrastructure. The HHO gas, generated through the electrolysis process, serves as the primary fuel for the pyrolysis of plastic. This optimization is crucial to maximize the efficiency of the pyrolysis process. As a result of the pyrolysis process, crude oil is produced as an intermediary product. This crude oil holds the potential for subsequent refinement, offering versatility for various applications and end uses. Hence, the integration of solar energy-driven HHO gas in the pyrolysis of plastic demonstrates a promising avenue for mitigating plastic waste and contributing to environmental cleanliness. The intricate technological aspects, ranging from gas production through electrolysis, leak detection, optimized combustion, to crude oil production and refinement, collectively establish a comprehensive framework for sustainable waste management and resource recovery.

Effect of the ICT‐enabled reclaimer system on the informal waste recycling system in Cape Town, South Africa: The Regenize model

AbstractThe impact of information and communication technology (ICT)‐enabled waste management systems on municipal solid waste, waste reclaimer integration, and resource recovery is critical, particularly in the informal recycling sector. This study investigates the effects of the ICT‐enabled waste management system in Cape Town, South Africa, with a focus on the Regenize model. Leveraging digital technologies, the Regenize model aims to improve waste picker integration and resource recovery within the local waste management system. A qualitative research methodology involving semi structured interviews with key stakeholders in Cape Town's ICT‐enabled waste reclaimer system, data triangulation, and thematic content analysis was employed to investigate the system's transformative potential. Preliminary findings indicate the Regenize system's alignment with extended producer responsibility (EPR) principles and its embodiment of local entrepreneurial innovation. Waste pickers' active participation as cocreators of waste management mobile platforms has transitioned them from traditional waste collectors to technological contributors, enhancing their role in the waste management ecosystem. Furthermore, the ICT‐enabled waste reclaimer system has significantly regularized the status of foreign waste pickers, providing them with essential rights and access to banking services through mobile platforms. By utilizing Internet and Communication Technologies (ICTs) and the Internet of Things (IoT), the Regenize model not only improves resource recovery but also promotes sustainable waste management practices. This represents a substantial step towards inclusive urban waste management in Cape Town. The study's implications extend beyond Cape Town, offering valuable insights for enhancing waste management practices and promoting sustainability across South Africa's broader waste management landscape.

Optimizing Hard Carbon Anodes from Agricultural Biomass for Superior Lithium and Sodium Ion Battery Performance.

Biomass-derived carbon materials are gaining attention for their environmental and economic advantages in waste resource recovery, particularly for their potential as high-energy materials for alkali metal ion storage. However, ensuring the reliability of secondary battery anodes remains a significant hurdle. Here, we report Areca Catechu sheath-inner part derived carbon (referred to as ASIC) as a high-performance anode for both rechargeable Li-ion (LIBs) and Na-ion batteries (SIBs). We explore the microstructure and electrochemical performance of ASIC materials synthesized at various pyrolysis temperatures ranging from 700 to 1400 °C. ASIC-9, pyrolyzed at 900 °C, exhibits multilayer stacked sheets with the highest specific surface area, and the least lateral size and stacking height. ASIC-14, pyrolyzed at 1400 °C, demonstrates the most ordered carbon structure with the least defect concentration and the highest stacking height and an increased lateral size. ASIC-9 achieves the highest capacities (676 mAh/g at 0.134 C) and rate performance (94 mAh/g at 13.4 C) for hosting Li+ ions, while ASIC-14 exhibits superior electrochemical performance for hosting Na+ ions, maintaining a high specific capacity after 300 cycles with over 99.5 % Coulombic efficiency. This comprehensive understanding of structure-property relationships paves the way for the practical utilization of biomass-derived carbon in various battery applications.

Solid waste management and resource recovery during the 4-crew 180-day CELSS integrated experiment

In order to explore the management and treatment methods of solid waste in the Controlled Ecological Life Support System (CELSS) of future lunar bases, during the 4-crew 180-day integrated experiment, the Solid Waste Management and Treatment System (SWMTS) was built, in which the treatment of recyclable solid waste such as inedible plant parts and human excrement was completed through a combination of biological aerobic composting and high-temperature oxidation. Basic data on the types and amounts of solid waste generated during the 4-crew 180-day experiment mission were obtained. There were six types of solid wastes, including the work support wastes, the household support wastes, the plant cultivation wastes, the plant-based wastes, and crew feces. The daily average production was 0.67, 1.4, 0.32, 8.48, 0.534 kg/d, respectively. The proportion of plant-based wastes was high as 74.3 %, indicating that it was the most important part. By closed-loop air drying and graded crushing, all 1526.97 kg of plant-based waste was treated, with water recovery (about 1163.87 kg), as well as volume reduction and stabilization treatment. By incineration and aerobic composting treatment, 67.3 % (244.4 kg) of the plant-based wastes (dry weight) and all of the feces (96.26 kg) were converted, providing 339.54 kg carbon dioxide for plant growth. And 90.6 kg organic fertilizer was obtained. The fertilizer was highly mature, met safety requirements, and effectively improved lettuce yield. The recycling rate of renewable solid waste during the experiment reached 89.8 %. The efficient circulation of solid waste had been achieved during the 4-crew 180-day integrated experiment. The long-time experimental results have shown that the established solid wastes management and treatment system can timely treat biomass solid waste such as inedible parts of plants and crew feces, achieve timely recovery of water in such solid waste, and recycle carbon and other elements, which effectively improved the material closure of the system and ensured the successful 4-crew 180-day experiment. This work also maybe lay the foundation for the construction and operation of an ecological life support system for future lunar bases.

Thermokinetic study of tannery sludge using combustion and pyrolysis process through non-isothermal thermogravimetric analysis

Sludge from the tannery is produced in enormous amount. This work has investigated the thermal analysis behaviour of the tannery sludge by use of the thermogravimetric analysis (TGA). The TGA experiments is carried out in both air and nitrogen environment at the varied heating rates of 5, 10, 20 and 40 °C/min from the temperature range of 30–900 °C. In the assessment of kinetic parameters, the model fitting (Combined kinetics) method was employed. It was investigated that thermal degradation of the tannery sludge sample occurred in three stages. Majorly the conversions were observed in stage II for both in air and nitrogen environment. The activation energy (Ea) value for the combustion is 165.9 kJ/mol while for the pyrolysis the Ea value is obtained as 65.2 kJ/mol from the conversion range between 0.2 and 0.8 which is a promising approximation supported by a strong R2 value of 0.9719 and 0.93 for combustion and pyrolysis respectively. It is estimated from the master plots that six ideal models A1/2, A1/3, A1/4, F3, F4 and D5 were probably in approximation with the linear fitted data for both air and nitrogen. Various thermodynamic parameters which include the ΔH, ΔG and ΔS are also complimented that indicates the formation of activated complex and non-spontaneity of the reaction. The detailed thermokinetic study of the tannery sludge in combustion and pyrolysis offers a novel approach to understanding how this waste material decomposes under different temperature conditions. This holistic perspective contributes valuable insights into waste management practices, environmental impacts, resource recovery, and process optimization within the leather industry. Furthermore, the optimization of leather production processes on a large scale can minimize waste generation and enhance energy efficiency, strengthening the competitiveness and sustainability of the leather industry.

Integrated circular economic approach of solid waste management and resource recovery: Poultry feather-based keratin extraction and its application in leather processing

The tanning industry faces considerable environmental challenges due to effluent load and hazardous chemical generation during processes like tanning and retanning. Therefore, this research work addresses these issues focusing on the pilot scale extraction and application of poultry feather-based keratin hydrolysate (KH) in leather manufacturing. Through pilot-scale experiments, optimal parameters for NaOH concentration, reaction temperature, and time were used to extract KH effectively. The study explored KH's potential application in chrome tanning and retanning stages as a chrome exhaust aid and keratin filler, respectively. During basification, KH was introduced to enhance chromium uptake by creating additional sites through the provision of crosslinking with collagen (modifying collagen) for better interaction and formation of complex with chromium, which not only streamlined the process by reducing the need for additional chemicals but also improved the thermal stability of the resulting leather product and enhance, the quality of leather. The shrinkage temperature of experimental wet blue leather was recorded to be above 107oC compared to the control wet blue leather which start to shrink at 104oc. Similarly, the percentage chromic oxide content of the experimental wet blue leather was observed to be significantly higher (3.89±0.20%) than that of the control wet blue leather (2.59±0.15). Furthermore, KH replaced commercial protein fillers during retanning, resulting in leathers with enhanced mechanical strength and organoleptic properties. The experimental crust leather treated with keratin solution at pH (5.5) was determined to have better tensile strength (23.4 N/mm2) and tear load (38.7 N/mm) than the control leather with tensile strength and tear load of 19.4 N/mm2 and 29.1 N/mm, respectively. Analytical techniques such as FTIR and XRD confirmed the presence of essential functional groups and protein structures in the KH solution, respectively. Leathers treated with 100 % KH substitution at pH value of 5.5 exhibited superior properties, including increased mechanical strength and thermal stability. Environmental impact assessments revealed a significant reduction in total dissolved solids in the spent liquor when KH replaced conventional fillers. Overall, this research demonstrates the potential of poultry feather-based keratin as an efficient, environmentally friendly filler in leather manufacturing, offering promising results in improving product quality and reducing environmental pollution.