Recycling waste vehicle tyres into crumb rubber and the transition to renewable energy sources: A comprehensive life cycle assessment

Waste tire valorization: Advanced technologies, process simulation, system optimization, and sustainability

The production of waste tires is steadily increasing, leading to challenges like slow degradation, severe environmental pollution, and significant land use. To address these issues, waste tire valorization has emerged as a crucial aspect of global environmental protection and sustainable development, garnering widespread attention and promotion. Innovative technologies are being leveraged to convert waste tires into valuable products and energy, promoting resource recycling and mitigating environmental harm. While existing literature has highlighted key technologies in the waste tire valorization process, this study aims to comprehensively review the current advancements in waste tire valorization from various angles, including processes, optimization, and evaluation, to support its sustainable development. Firstly, it outlines advanced technologies in the waste tire valorization process for producing value-added products, such as grinding, pyrolysis, and critical devulcanization stages. Secondly, it summarizes simulation and optimization techniques applied in waste tire valorization. Lastly, it discusses the application of sustainable assessment methods like techno-economic assessment, Life Cycle Assessment (LCA), and Sustainable Development Goals (SDGs) in waste tire valorization, proposing the establishment of a unified assessment system. The review findings suggest that (1) developing a super-structural waste tire valorization framework offers a promising path for technological enhancement and low-carbon sustainable transformation. (2) Integrating mechanism and data-driven method in simulation modeling enhances result accuracy and interpretability. (3) Creating a multi-objective optimization model to optimize waste tire valorization from economic, technological, social, and environmental perspectives can drive efficient and low-carbon development. (4) Establishing a unified sustainability assessment system will standardize the evaluation of waste tire valorization's sustainability.

Recent advances on waste tires: bibliometric analysis, processes, and waste management approaches

End of life tires (ELTs) are a pressing environmental concern due to their non-biodegradable nature and potential release of toxic chemicals, as confirmed by human health exposure studies. The expanding transport sector, driven by the automotive industry, has led to inadequate attention to safe tire disposal. This review extracted papers using keywords such as "waste tire rubber," "waste tire pollution," and "waste tire applications" from 2012 to 2023. Recycling publications have surged by 80% in the past decade, with China and the USA leading the research. Pyrolysis and devulcanization methods have emerged as key circular economy (CE) advancements, producing fuel and reusable rubber. Globally, 1.5 billion waste tires accumulate yearly, projected to increase by 70% in the next 30 years if unaddressed. Around 26 million tonnes of used tires are generated annually worldwide, while civil engineering and backfilling use 17 million tonnes of recycled rubber particles. These tires are complex polymer composites, primarily composed of natural and synthetic rubber. The amorphous nature of rubber results in a 50% loss of mechanical properties when exposed to chemicals and microbes, shortening its lifespan. This paper explores the applicability of waste tire rubber and polymer fabrication to offer eco-friendly and cost-effective solutions for proper disposal, mitigating environmental accumulation.

An integrated financial and environmental evaluation framework to optimize residential photovoltaic solar systems in Australia from recession uncertainties

This study assesses the financial viability and environmental evaluation of Photovoltaic (PV) panels from the perspective of the recent economic recession due to the Russia-Ukraine war. The financial viability of PV installation is calculated based on the estimated price, solar rebates, feed-in tariff, energy supply cost, and other evaluation parameters available at the assessment time. This calculation implicitly assumes variable discount rates (4%, 7%, and 12%) to show how the future will unfold and its correlations with design parameters. Details of economic appraisal integrating current inflation, rebates, and incentives of solar systems have been analyzed for the first time in this study. Financial indicators reveal the advantages of installing a grid-connected solar system (SS) over a solar battery storage system (SSWB). Compared to other installation systems, the lowest payback (PB) and highest internal rate of return (IRR) are observed for a 7 kW grid-connected solar system. Relative uncertainties of solar installation systems represent the necessity of government subsidies (r = -0.602) for solar storage batteries. LCA signifies the energy-intensive process of manufacturing metallurgical-grade (MG) silicon is the primary cause of significant greenhouse gas (GHG) emissions and cumulative energy demand (CED) for PV panels. A potential amount of metal and fossil fuels is depleted for interconnective components of solar installation systems. Amorphous solar panels exhibit lower impacts than polycrystalline, but further upgradation in service life is required to become cost-effective and cope with current inflation.

Application of recycled crushed glass in road pavements and pipeline bedding: An integrated environmental evaluation using LCA

The study aims to conduct a comprehensive life cycle assessment (LCA) of mixed glass waste (MGW) recycling processes to quantify the environmental impacts of crushed glass as a partial substitute for virgin aggregate. Upstream washing, crushing, and sorting conducted at material recycling facilities (MRF) are the prime activities to assess whether reprocessed MGW in pavement construction is an alternate feasible solution. None of the previous studies explicitly account for the relative uncertainties and optimization of waste glass upstream processes from an environmental perspective. The study calculates environmental impacts using the LCA tool SimaPro considering design factors attributed to transportation, electricity consumption, use of chemicals, and water for reprocessing glass waste. Relative uncertainties of design variables and the national transition policy (2021-2030) from non-renewable to renewable energy sources have been validated by performing detailed Monte Carlo simulations. The correlation coefficients (r = 0.64, 0.58, and 0.49) of successive variables explain how the higher environmental gains of the glass recycling process are outweighed by diesel, energy consumption, and transportation distances. Compared to natural quarry sand, the recycled glass aggregate produced through crushing and recycling of its by-products reduces CO₂eq emissions by 16.2 % and 46.7 %, respectively. The need for a washing line at the plant, in addition to crushing, results in a higher environmental impact over natural sand by 90.1 % and emphasizes the benefits of collecting waste glass through a separate bin, hence avoiding contamination. The result indicates that the benefit of lowering emissions varies significantly when considering waste glass landfilling. Moreover, this study evaluates the potential impacts on asphalt and reinforced concrete pavements (RCP) with 5 %, 10 %, 15 %, and 20 % replacement of natural sand with recycled glass aggregate. The LCA emphasizes the limitations of energy-intensive waste glass reprocessing. The obtained results and uncertainty analysis based on primary MRF data and recycled product applications provide meaningful suggestions for a more fit-for-purpose waste management and natural resource conservation.

A review of waste-to-hydrogen conversion technologies for solid oxide fuel cell (SOFC) applications: Aspect of gasification process and catalyst development

In the twenty-first century, there has been an increase in energy demand and waste production, due to the rising population of the world. One good approach for satisfying the energy demand and overcoming the waste management issues is to convert waste to energy. Additionally, using waste biomass as the feedstock of waste-to-energy (WtE) conversion methods makes them renewable and green and also helps the environmental challenges and reduces the emission of greenhouse gases (GHGs). Gasification is a thermochemical WtE route, which can produce hydrogen-rich gaseous biofuel called synthetic gas (syngas), from wastes. In this paper, different aspects of gasification process are reviewed with greater focus on catalyst usage. Syngas processing steps, which increase the quality and H₂ content of the syngas to form bio-hydrogen, are discussed. Solid oxide fuel cell (SOFC) technology is one of the most promising techniques of renewable energy production due to their environmental cleanness characteristics and high efficiencies. Thus, one of the best ways to exploit the energy content of the bio-hydrogen product of gasification is to employ it in a SOFC. Therefore, waste biomass gasification process can be integrated with SOFCs to build high efficiency systems for production of clean and renewable energy from waste, which are called integrated gasification fuel cell (IGFC) systems. These systems provide the opportunity of further upgrading of syngas inside the SOFC. In this paper, we are going to briefly discuss fuel cell technology (especially SOFCs) and review SOFC applications from the aspect of integration with gasification process (IGFC system). Finally, the impacts and issues of gasification process and SOFC technology are considered.

Freeze/Thaw Resistance of Mortar with Recycled Tyre Waste at Varying Particle Sizes

There is a growing concern for finding alternative solutions to construction materials in order to minimise their environmental impact as well as enhancing their service life. This study investigated the durability of cementitious mortars prepared by replacing fine aggregate (sand) with recycled tyre shreds and crumbs, aiming at providing an alternative outlet to tyre waste disposal. Tyre shreds obtained at different particle sizes, from fibres of 0.5-5.0 mm to crumbs of 0.1-0.85 mm in diameter, were used as fine aggregate replacement at 20% by volume. The strength of the mortar samples, their thermal conductivity and their water absorption rate were tested at the age of 28 days and after 20 freeze/thaw cycles. The results showed that the mortar containing tyre crumbs at lower particle sizes resulted in negligible shrinkage, improved freeze/thaw resistance, a reduced water absorption by up to 52% and an improved thermal resistivity.