Sustainability

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13 pages, 2188 KiB

Open AccessArticle

Solvolysis of Nylon: A Pathway to Sustainable Recycling and Circular Economy

by Nuno Gama, Jéssica Araújo, Bruno Godinho, Artur Ferreira and Ana Barros-Timmons

Sustainability 2024, 16(22), 9725; https://doi.org/10.3390/su16229725 - 8 Nov 2024

Cited by 1 | Viewed by 1862

Abstract

Polyamides (PAs) are extensively utilized across various applications, yet the accumulation of PA residues presents significant ecological and environmental challenges. Given that a substantial portion of fishing nets are composed of nylon, a type of PA, this material’s disposal raises environmental concerns impacting [...] Read more.

Polyamides (PAs) are extensively utilized across various applications, yet the accumulation of PA residues presents significant ecological and environmental challenges. Given that a substantial portion of fishing nets are composed of nylon, a type of PA, this material’s disposal raises environmental concerns impacting marine life and the global ecosystem. Therefore, to enhance sustainability, they could be collected and recycled. This study introduces a method for the chemical recycling of PA waste using hydrochloric acid (HCl). Through solvolysis, a PA was depolymerized, and the effect of various reaction conditions on the depolymerization yield was analyzed, being the best conditions established in this work (100 °C, 4 h, and an HCl/PA ratio of 11:1, wt.wt⁻¹). Next, a novel separation methodology was employed to isolate recycled products from salts formed during neutralization. Subsequently, these recycled products were incorporated as a partial substitute (up to 10% wt.wt⁻¹) for a conventional PA in a new material production. The results indicate that the presence of recycled products enhances material stiffness due to crystallinity differences compared to the virgin matrix. In turn, the introduction of lower-molecular-weight species increases the materials’ glass transition temperature (Tg) and their melt flow index (MFI). This research underscores a sustainable pathway for PA recycling aligned with circular economy principles, contributing positively to environmental conservation efforts. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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25 pages, 10520 KiB

Open AccessArticle

Waste-Cooking-Oil-Derived Polyols to Produce New Sustainable Rigid Polyurethane Foams

by Miriam Cappello, Sara Filippi, Damiano Rossi, Patrizia Cinelli, Irene Anguillesi, Caterina Camodeca, Elisabetta Orlandini, Giovanni Polacco and Maurizia Seggiani

Sustainability 2024, 16(21), 9456; https://doi.org/10.3390/su16219456 - 31 Oct 2024

Cited by 1 | Viewed by 4099

Abstract

Polyurethanes (PUs) are one of the most versatile polymeric materials, making them suitable for a wide range of applications. Currently, petroleum is still the main source of polyols and isocyanates, the two primary feedstocks used in the PU industry. However, due to future [...] Read more.

Polyurethanes (PUs) are one of the most versatile polymeric materials, making them suitable for a wide range of applications. Currently, petroleum is still the main source of polyols and isocyanates, the two primary feedstocks used in the PU industry. However, due to future petroleum price uncertainties and the need for eco-friendly alternatives, recent efforts have focused on replacing petrol-based polyols and isocyanates with counterparts derived from renewable resources. In this study, waste cooking oil was used as feedstock to obtain polyols (POs) for new sustainable polyurethane foams (PUFs). POs with various hydroxyl numbers were synthesized through epoxidation followed by oxirane ring opening with diethylene glycol. By adjusting reagent amounts (acetic acid and H₂O₂), epoxidized oils (EOs) with different epoxidation degrees (50–90%) and, consequently, POs with different OH numbers (200–300 mg KOH/g) were obtained. Sustainable PUFs with high bio-based content were produced by mixing the bio-based POs with a commercial partially bio-based aliphatic isocyanate and using water as the blowing agent in the presence of a gelling catalyst and additives. Various water (4, 8, 15 php) and gelling catalyst (0, 1, 2 php) amounts were tested to assess their effect on foam properties. PUFs were also prepared using EOs instead of POs to investigate the potential use of EOs directly in PUF production. Characterization included morphological, chemical, physical, thermal, and mechanical analyses. The rigid PUFs exhibited high density (150–300 kg/m³) and stability up to 200 °C. The combined use of bio-based polyols with partially bio-based isocyanate and water enabled PUFs with a bio-based content of up to 77 wt.%. EOs demonstrated potential in PUF production by bypassing the second synthesis step, enhancing sustainability, and significantly reducing energy and costs; however, PUF formulations with EOs require optimization due to lower epoxy ring reactivity. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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15 pages, 2203 KiB

Open AccessArticle

Investigating the Potential Use of End-of-Life Fire Extinguisher Powder as a Soil Amendment in Different Soil Types: A New Approach Following a Circular Economy Model

by Ioanna Tsigka, Nikolaos Kiatikidis, Panagiotis K. Tsolakis, Nikolaos Stergiou and Evangelia E. Golia

Sustainability 2024, 16(20), 8913; https://doi.org/10.3390/su16208913 - 15 Oct 2024

Viewed by 1865

Abstract

A first attempt to assess the potential alternative use of fire extinguisher filler powder after its exhaustion has been investigated in the present research. The chemical composition of fire extinguisher filler powder, specifically type ABC 40%, consists of monoammonium phosphate and ammonium sulfate. [...] Read more.

A first attempt to assess the potential alternative use of fire extinguisher filler powder after its exhaustion has been investigated in the present research. The chemical composition of fire extinguisher filler powder, specifically type ABC 40%, consists of monoammonium phosphate and ammonium sulfate. As its nitrogen and phosphorus content is particularly high, the thought of its possible use as a fertilizer and/or a soil amendment is a challenge. For this purpose, a pot experiment was carried out and two leafy vegetables (spinach and lettuce) were used as biomarkers. Two soil samples from rural areas, one acidic (pH = 5.8 ± 0.1) and one alkaline (pH = 8.2 ± 0.7), were selected for the experiments. Filler powder from a used fire extinguisher was added to the soil samples in two levels (1 and 2% v/v). It was found that the addition of fire extinguisher filler powder caused no toxicity to either of the two plants studied. On the contrary, an increase in their above-ground biomass was observed, proportional to the amount of powder added. It was established that in the pots where the powder was added, in both plant species observed, the plant height, root length, and chlorophyll content of leaves increased, the total antioxidant capacity was enhanced, and the concentrations of nitrate and phosphate in the leaves and roots of plants also increased, compared to the soil without the addition of fire extinguisher powder. The early signs appear to be encouraging, as an increase was observed in almost all aspects. The mandatory end of the life cycle of the powder as a fire-extinguishing agent and its disposal is also a challenge in the context of the circular economy, as reducing the energy requirements for fertilizer production is one of the objectives of sustainable development. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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19 pages, 2686 KiB

Open AccessArticle

Efficiency Assessment of the Production of Alternative Fuels of High Usable Quality within the Circular Economy: An Example from the Cement Sector

by Mariusz Niekurzak, Wojciech Lewicki and Jacek Wróbel

Sustainability 2024, 16(20), 8762; https://doi.org/10.3390/su16208762 - 10 Oct 2024

Cited by 2 | Viewed by 1557

Abstract

This article aims to present the mechanisms regulating the waste management system of one of the European countries that affect the cement industry. This publication analyses the possibility of using selected fractions of municipal and industrial waste as alternative fuels, including an analysis [...] Read more.

This article aims to present the mechanisms regulating the waste management system of one of the European countries that affect the cement industry. This publication analyses the possibility of using selected fractions of municipal and industrial waste as alternative fuels, including an analysis of ecological costs and benefits. The methodology includes the analysis of production data and the calculation of savings resulting from the use of alternative fuels. On this basis, ecological aspects were also indicated that should be taken into account when analyzing the profitability of the investment. Production data from an example Polish cement plant were used to analyze the research problem. Based on the guidelines of environmental standards and technical specifications, the parameters that PASr alternative fuels should meet were calculated in the company laboratory. This fuel type was then calculated in terms of emission intensity and production efficiency. The research results obtained in this paper study emphasize that the change in cement clinker production technology toward the use of waste raw materials and secondary fuels does not lead to an increase in heavy metal emissions to the extent that would justify qualifying cement as a material requiring systematic control of its harmful impacts on humans and the natural environment. The conclusions show that the use of alternative fuels reduces CO₂ emissions and production costs, without negatively affecting the efficiency and production volume. The average energy requirement for the production of 1 ton of cement is approximately 3.3 GJ, which corresponds to 120 kg of coal with a calorific value of 27.5 MJ per kg. Energy costs account for 30–40% of the total cement production costs. Replacing alternative fuels with fossil fuels will help reduce energy costs, providing a competitive advantage for cement plants that use it as an energy source. The presented considerations can provide an answer to all interested parties, including representatives of the executive and legislative authorities, on what path the sector should follow to fit into the idea of sustainable building materials and the circular economy. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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18 pages, 596 KiB

Open AccessArticle

Exploring Determinants of Second-Hand Apparel Purchase Intention and Word of Mouth: A Stimulus–Organism–Response Approach

by Olga Tymoshchuk, Xingqiu Lou and Ting Chi

Sustainability 2024, 16(11), 4445; https://doi.org/10.3390/su16114445 - 24 May 2024

Cited by 3 | Viewed by 4305

Abstract

The U.S. second-hand clothing industry is experiencing rapid growth, driven by increasing environmental awareness among consumers. However, there is a gap in understanding the driving forces behind this trend. This study aims to investigate the impact of external factors, including product quality, information [...] Read more.

The U.S. second-hand clothing industry is experiencing rapid growth, driven by increasing environmental awareness among consumers. However, there is a gap in understanding the driving forces behind this trend. This study aims to investigate the impact of external factors, including product quality, information quality, and service quality, on consumers’ internal emotions and examines how these emotional states, encompassing hedonic value, utilitarian value, environmental value, functional risk, aesthetic risk, and sanitary risk, influence their purchase intentions and word-of-mouth recommendations. Data were collected from 448 consumers who have shopped for second-hand clothing through an online survey conducted on Qualtrics. Multiple regression was applied to test the hypotheses. The findings indicate that product quality, information quality, and service quality enhance consumers’ perceived hedonic, utilitarian, and environmental values. Furthermore, service quality significantly reduces consumers’ perceived risks in terms of functionality, aesthetics, and sanitation. Additionally, consumers’ purchase intentions and word of mouth regarding second-hand clothing are positively influenced by their perceived hedonic, utilitarian, and environmental values. This research enriches the understanding of consumer behavior in the second-hand marketplace and offers insightful implications for retailers and marketers in the second-hand clothing industry. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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15 pages, 3303 KiB

Open AccessArticle

Techno-Eco-Efficiency Assessment of Using Recycled Steel Fibre in Concrete

by Wahidul K. Biswas, Xihong Zhang, Corey Matters and Mitra Maboud

Sustainability 2024, 16(9), 3717; https://doi.org/10.3390/su16093717 - 29 Apr 2024

Cited by 3 | Viewed by 1879

Abstract

The steel industry is one the three biggest producers of carbon dioxide and it is experiencing technical challenges due to the gradual decrease in the quality of iron ore. Steel is extensively used in the construction industry for structural applications like steel components, [...] Read more.

The steel industry is one the three biggest producers of carbon dioxide and it is experiencing technical challenges due to the gradual decrease in the quality of iron ore. Steel is extensively used in the construction industry for structural applications like steel components, while steel fibres are intensively used as additives to concrete in order to improve its performance. It is thus important to consider the use of recycled steel as a replacement for virgin steel in order to address the aforementioned environmental consequences. This paper applies the eco-efficiency framework to determine the economic and environmental implications of the use of recycled fibre in concrete as a replacement for virgin steel. A number of concrete mixes were considered that used virgin, recycled, and treated recycled rebar in concrete. The eco-efficiency framework, which uses a life-cycle assessment approach to calculate the environmental and economic values of concrete mixes in order to determine the portfolio positions of these concrete mixes, was used for comparison purposes and to establish the eco-efficient option(s). Whilst the recovery and recycling process is energy-intensive, the use of recycled steel fibre in reinforced concrete has been found to be eco-efficient and deliver the same level of mechanical performance compared to that obtained using virgin steel fibre. Treating steel fibre could improve its technical performance, but it was found to increase both costs and environmental impacts and was therefore identified as not being eco-efficient. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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14 pages, 2456 KiB

Open AccessArticle

Eco-Efficiency Performance for Multi-Objective Optimal Design of Carbon/Glass/Flax Fibre-Reinforced Hybrid Composites

by Wahidul Biswas and Chensong Dong

Sustainability 2024, 16(7), 2928; https://doi.org/10.3390/su16072928 - 1 Apr 2024

Cited by 1 | Viewed by 1395

Abstract

An eco-efficiency optimisation study on unidirectional carbon/glass fibre-reinforced hybrid composites with natural fibre (i.e., flax) and without flax is presented in this paper. The mechanical performance was assessed by determining the flexural properties obtained via finite element analysis (FEA)-based simulation. Given the required [...] Read more.

An eco-efficiency optimisation study on unidirectional carbon/glass fibre-reinforced hybrid composites with natural fibre (i.e., flax) and without flax is presented in this paper. The mechanical performance was assessed by determining the flexural properties obtained via finite element analysis (FEA)-based simulation. Given the required flexural strength, optimal candidate designs were found using a set of design rules and regression analysis, with minimising the cost and weight being the objectives. An eco-efficiency framework was applied to determine the eco-efficient hybrid composites. Life cycle assessment was an indispensable component of the framework as it helped determine the life cycle environmental impacts and costs of the hybrid composite materials. The environmental impacts and cost values were converted to the eco-efficiency portfolios of these composites for both comparison and selection purposes. The hybrid composites using bio-based flax fibre have been found to be eco-efficient in most of the cases due to the avoidance of energy-intensive and expensive reinforcing materials. The environmental impacts of the hybrid composites using flaxes are 12 to 13% less than the ones using no flaxes and the former are 7 to 13% cheaper than the latter, making the flax-based hybrid composites eco-efficient. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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20 pages, 9664 KiB

Open AccessArticle

The Sustainability of Using DuraCrete as Cement Additive to Estuarine Soft Soil Stabilization

by Ali N. Al-Gemeel, Noor Al-Hayo, Dominic E. L. Ong and Yan Zhuge

Sustainability 2024, 16(1), 231; https://doi.org/10.3390/su16010231 - 26 Dec 2023

Viewed by 1499

Abstract

Large areas of estuarine deposits exist on the coastal plains of the southeast Queensland coast with a countered depth of up to 30 m. These deposits are categorized as sediments that originated during the Holocene Age. The sediments have not been consolidated or [...] Read more.

Large areas of estuarine deposits exist on the coastal plains of the southeast Queensland coast with a countered depth of up to 30 m. These deposits are categorized as sediments that originated during the Holocene Age. The sediments have not been consolidated or subjected to considerable pressure since the end of the Ice Age. The structure of these deposits consists of large ratios of porosity, causing high soil compressibility, which lowers the bearing capacity of the soils. Therefore, the soils of the region cannot maintain sufficient support for construction loads, and consequent malfunctions could occur in short-term and long-term periods. The objective of this paper is to investigate the suitability of new soil stabilization additives in the southeast Queensland region and the optimum additive content of cementitious materials and an advanced mixing modifier branded as DuraCrete. A combination of Portland cement and DuraCrete was used as a soil additive. Three DuraCrete-to-cement ratios were used: 2%, 3%, and 4% by weight. Soil collected from the Port of Brisbane region was treated by adding the additives as a percentage of its weight; four percentages were considered: 10%, 20%, 25%, and 30% for each combination of additives. The performance of the treated soils was examined under unconfined compression after 28 days of curing. The results revealed that increases in the unconfined compressive strength were detected as DuraCrete was added to the mixtures. For 30% additives, increases of about 15%, 34%, and 17% were detected when DuraCrete was added as 2%, 3%, and 4%, respectively. The results also revealed that 3% DuraCrete content provided significant stabilization compared to 2% and 4% for 25% and 30% additive-treated soils; such behavior was also observed for the specimens of 25% content of additives. Additionally, DuraCrete can be considered a promising material that can be combined with cement to obtain the desired stabilization of soft soils. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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Review

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29 pages, 4937 KiB

Open AccessReview

Thermodynamic Models of Solid Oxide Fuel Cells (SOFCs): A Review

by Vera Marcantonio and Lucrezia Scopel

Sustainability 2024, 16(23), 10773; https://doi.org/10.3390/su162310773 - 9 Dec 2024

Viewed by 2254

Abstract

In the delicate context of climate change and global warming, new technologies are being investigated in order to reduce pollution. The SOFC stands out as one of the most promising fuel cell technologies for directly converting chemical energy into electrical energy, with the [...] Read more.

In the delicate context of climate change and global warming, new technologies are being investigated in order to reduce pollution. The SOFC stands out as one of the most promising fuel cell technologies for directly converting chemical energy into electrical energy, with the added benefit of potential integration into co-generation systems due to its high-temperature waste heat. They also offer multi-fuel flexibility, being able to operate on hydrogen, carbon monoxide, methane, and more. Additionally, they could contribute to carbon sequestration efforts and, when paired with a GT, achieve the highest efficiency in electricity generation for power plants. However, their development is still challenged by issues related to high-temperature materials, the design of cost-effective materials and manufacturing processes, and the optimization of efficient plant designs. To better understand SOFC operation, numerous mathematical models have been developed to solve transport equations coupled with electrochemical processes for three primary configurations: tubular, planar, and monolithic. These models capture reaction kinetics, including internal reforming chemistry. Recent advancements in modeling have significantly improved the design and performance of SOFCs, leading to a sharp rise in research contributions. This paper aims to provide a comprehensive review of the current state of SOFC modeling, highlighting key challenges that remain unresolved for further investigation by researchers. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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25 pages, 1223 KiB

Open AccessReview

Integrating Lean Management and Circular Economy for Sustainable Dentistry

by Maria Antoniadou

Sustainability 2024, 16(22), 10047; https://doi.org/10.3390/su162210047 - 18 Nov 2024

Cited by 2 | Viewed by 2490

Abstract

The increasing focus on environmental sustainability has prompted the healthcare sector, including dentistry, to reconsider waste management practices. Dental offices generate various waste streams from outdated technologies, including single-use plastics, hazardous materials, and digital waste. This scoping review explores how integrating circular economy [...] Read more.

The increasing focus on environmental sustainability has prompted the healthcare sector, including dentistry, to reconsider waste management practices. Dental offices generate various waste streams from outdated technologies, including single-use plastics, hazardous materials, and digital waste. This scoping review explores how integrating circular economy principles with lean management practices can enhance sustainability and operational efficiency in dental clinics. Using the PRISMA methodology, the review identifies 30 articles that passed the Cochrane Risk of Bias Tool and the Critical Appraisal Skills Program (CASP) checklist from 2000. Circular economy principles focus on reducing waste and maximizing resource reuse, while lean management seeks to improve efficiency and minimize process waste. Together, these approaches can significantly reduce resource consumption and enhance recycling efforts in dental practices. Despite barriers such as high technology costs, regulatory constraints, and limited recycling infrastructure, case studies highlight successful implementation in healthcare settings, demonstrating improved environmental and operational outcomes. Collaboration between dental professionals, policymakers, and industry leaders is essential for promoting the adoption of these sustainable practices. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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27 pages, 6457 KiB

Open AccessReview

Phytocapping for Municipal Solid Waste Landfills: A Sustainable Approach

by Arifuzzaman, Md Mizanur Rahman, Md Rajibul Karim, Guna Alankarage Hewa, Robyn Rawlings and Asif Iqbal

Sustainability 2024, 16(18), 8230; https://doi.org/10.3390/su16188230 - 21 Sep 2024

Viewed by 1805

Abstract

This paper reviews the historical developments in landfill technology and its drawbacks. It introduces phytocapping, in light of previous research, as a promising, eco-friendly and sustainable technology for municipal solid waste (MSW) landfill covers in order to reduce landfill gas and leachate generation. [...] Read more.

This paper reviews the historical developments in landfill technology and its drawbacks. It introduces phytocapping, in light of previous research, as a promising, eco-friendly and sustainable technology for municipal solid waste (MSW) landfill covers in order to reduce landfill gas and leachate generation. This paper highlights the challenges to successful phytocapping, such as selection criteria for appropriate plants and growth media, and the importance of new research into overcoming these challenges. It also presents a database of plants used in landfill phytocapping studies worldwide. In addition, the performance, economics, and sustainability of phytocapping technology are evaluated in comparison to ordinary MSW landfill methods. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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20 pages, 2648 KiB

Open AccessReview

Recycling Clay Waste from Excavation, Demolition, and Construction: Trends and Challenges

by Liliana Carolina Hernández García, Sergio Neves Monteiro and Henry A. Colorado Lopera

Sustainability 2024, 16(14), 6265; https://doi.org/10.3390/su16146265 - 22 Jul 2024

Cited by 3 | Viewed by 3628

Abstract

The recycling of clay waste from construction debris highly depends on the chemical and mineralogical composition of the waste. Clays and clay minerals are known to be among marginal construction waste, representing an interesting opportunity and platform to produce other low-cost and low-carbon [...] Read more.

The recycling of clay waste from construction debris highly depends on the chemical and mineralogical composition of the waste. Clays and clay minerals are known to be among marginal construction waste, representing an interesting opportunity and platform to produce other low-cost and low-carbon materials due to their possibilities for functional material design, such as adsorbents, drug delivery, catalysts and photocatalysts, and nanocomposites. The present review analyzes a wide variety of mechanisms for encapsulating organic and inorganic species between the layers of clay minerals. Through the compilation of advances in acid activation, exchange of inorganic cations, intercalation, and pillarization, new applications for clay materials are generated, paving the way to a nanometric world with functional, magnetic, adsorption, and catalytic capabilities. New trends are consolidated in the reuse of recycled clays in infrastructure projects, such as hydraulic concrete, water purification, soil fertility, pigments and paints, food packaging and storage, and ceramic appliances. It is concluded that clay waste is suitable to reuse in many industrial products and construction materials, enabling a reduction in the consumption of raw materials. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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27 pages, 5868 KiB

Open AccessReview

Sustainable Biocomposites: Harnessing the Potential of Waste Seed-Based Fillers in Eco-Friendly Materials

by Cristiano Fragassa, Felipe Vannucchi de Camargo and Carlo Santulli

Sustainability 2024, 16(4), 1526; https://doi.org/10.3390/su16041526 - 10 Feb 2024

Cited by 11 | Viewed by 3731

Abstract

With the growing concerns over environmental degradation and the increasing demand for sustainable materials, eco-friendly composites have gained considerable attention in recent years. This review paper delves into the promising realm of seed-based fillers, reinforcements and polysaccharidic matrices in the production of biocomposites [...] Read more.

With the growing concerns over environmental degradation and the increasing demand for sustainable materials, eco-friendly composites have gained considerable attention in recent years. This review paper delves into the promising realm of seed-based fillers, reinforcements and polysaccharidic matrices in the production of biocomposites that are yet focusing on those seeds, which can be considered industrial process waste. Seeds, with their inherent mechanical properties and biodegradability, which are often the waste of production systems, offer a compelling solution to reduce the environmental impact of composite materials. This paper explores the properties of various seeds considered for composite applications and investigates the processing techniques used to incorporate them into composite matrices. Furthermore, it critically analyzes the influence of seed fillers on the mechanical and physical properties of these eco-friendly composites, comparing their performance with traditional counterparts. The environmental benefits, challenges, and limitations associated with seed-based composites from waste seeds are also discussed, as well as their potential applications in diverse industries. Through an assessment of relevant case studies and research findings, this review provides valuable insights into the outlook of seed-based composites as a sustainable alternative in the composite materials landscape, emphasizing their role in promoting a greener and more responsible approach to materials engineering. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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Other

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16 pages, 2614 KiB

Open AccessSystematic Review

A Systematic Review and Meta-Analysis of the Sustainable Impact of Sewage Sludge Application on Soil Organic Matter and Nutrient Content

by Enzo Antonio Lecciolle Paganini, Rafael Barroca Silva, Ludmila Ribeiro Roder, Iraê Amaral Guerrini, Gian Franco Capra, Eleonora Grilli and Antonio Ganga

Sustainability 2024, 16(22), 9865; https://doi.org/10.3390/su16229865 - 12 Nov 2024

Viewed by 2055

Abstract

The increasing scarcity of natural resources makes the linear production model unsustainable, highlighting the need for more sustainable practices under the umbrella of circular economic principles. Sewage sludge emerges as a promising solution to provide soil organic matter (SOM) and nutrients. This meta-analysis [...] Read more.

The increasing scarcity of natural resources makes the linear production model unsustainable, highlighting the need for more sustainable practices under the umbrella of circular economic principles. Sewage sludge emerges as a promising solution to provide soil organic matter (SOM) and nutrients. This meta-analysis evaluated the impacts of three levels of sludge application (low, medium, and high) on organic matter (OM), nitrogen (N), phosphorus (P), copper (Cu), and zinc (Zn) contents, considering different areas and experimental conditions worldwide. The analysis included 37 studies and 355 comparisons, after screening 7625 records, following the 2020 PRISMA protocol. The effects of sludge concentrations, continents, and types of experiment (field or greenhouse) were evaluated. Sewage sludge application significantly increased OM, N, Cu, and Zn levels, mainly at medium and high rates. The largest effects were observed in greenhouses, suggesting variation by location and environment. Moderators explained a part of the variation in the results, but the residual heterogeneity test revealed that there is still unexplained variability. Full article

(This article belongs to the Special Issue Recycling Materials for the Circular Economy—2nd Edition)

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