Dredge Sediment as an Opportunity: A Comprehensive and Updated Review of Beneficial Uses in Marine, River, and Lagoon Eco-Systems

Abstract

Dredging is essential for the maintenance of ports, waterways, lakes, and lagoons to ensure their operability and economic value. Over the last few decades, scientists have focused on the significant environmental challenges associated with dredging, including habitat destruction, loss of biodiversity, sediment suspension, and contamination with heavy metals and organic pollutants. The huge loss of sediment in coastal areas and the associated erosion processes are now forcing stakeholders to look ahead and turn potential problems into an opportunity to develop new sediment management strategies, beyond environmental protection, toward ecosystem restoration and coastal resilience. Moreover, the European and Italian strategies, such as the European Green Deal (EGD) and the Italian Ecological Transition Plan (PTE), highlight the need to reuse dredge sediment in circular economy strategies, transforming them into valuable resources for construction, agriculture, and environmental restoration projects. European legislation on dredging is fundamental to the issue of management and priorities of dredged materials, but the implementation rules are deferred to individual member states. In Italy, the Ministerial Decree 173/2016 covers the main aspects of dredge activities and dredge sediment management. Moreover, it encourages the remediation and reuse of the dredge sediment. This study starts with a comprehensive analysis of the innovative remediation techniques that minimize impacts and promote sustainable, beneficial sediment management. Different remediation methods, such as electrochemical treatments, chemical stabilization, emerging nanotechnologies, bioremediation, and phytoremediation, will be evaluated for their effectiveness in reducing pollution. Finally, we highlight new perspectives, integrated strategies, and multidisciplinary approaches that combine various technological innovations, including artificial intelligence, to enhance sediment reuse with the aim of promoting economic growth and environmental protection.

1. Introduction

Dredging is the removal of sediment from the bottom of water bodies; it is a necessary practice to ensure navigation in harbors and waterways and to manage coastal areas. The results of this practice are dredged sediment. Sediment is made up of sand, silt, clay, and other materials eroded from rock and soil and plays a vital role in aquatic ecosystems: providing habitats and food sources for various organisms [1]. While dredging is crucial for human activities, sediment removal can have environmental impacts. It can disrupt benthic habitats, exacerbate coastal erosion, and increase water turbidity, affecting water quality and light penetration. Furthermore, it can lead to the loss of biodiversity by altering the sediment composition and habitat availability [2]. However, the appropriate management of the dredging project can reduce these consequences or even reverse some of these trends. Dredging can be an effective tool in environmental restoration projects, such as remediating contaminated sites and mitigating the effects of eutrophication [3,4]. In addition, the cleaned dredge sediment can be used for ecosystem restoration and coastal resilience (e.g., nourishment or development of coastal wetlands) [5]. Sediment can naturally contain trace contaminants due to their geological origins or anthropogenic activities, including industrial, agricultural, and domestic sources. Common pollutants include heavy metals (e.g., lead, mercury, cadmium, arsenic), organic pollutants (e.g., polycyclic aromatic hydrocarbons, polychlorinated biphenyls, persistent organic pollutants), and plastic materials (including microplastics) [6]. Contaminated sediment poses significant challenges to its management and reuse. Traditionally, these sediments are disposed of in landfills, and this represents an unacceptable waste of resources. Nowadays, globally, there has been a growing emphasis on sustainable sediment management practices, aligned with the principles of the circular economy [7]. In this respect, in Europe, the European Green Deal (EGD), and in Italy, the Ecological Transition Plan (PTE) emphasize the need for sustainable sediment management, promoting resource efficiency and minimizing environmental impacts [8,9]. A number of multiple directives have an indirect influence on dredging practices, such as the Water Framework Directive (2000/60/EC) and the Waste Framework Directive (75/442/EEC) [10,11]. These regulations also encourage practices like sediment recycling, recovery, and reuse, aiming to improve sustainability and reduce waste generation. Furthermore, the singular member states adopt laws to ensure the correct management of dredging practices. In Italy, Ministerial Decree 173/2016 states on dredge sediment management, basing the process on the level of contamination of the sediments. The characterized sediments can be used for various proposals (e.g., marine landfill and depositing site disposal). To promote sustainable reuse of dredge sediment, the decree promotes the changing of sediment class using remediation technologies [12]. Promising remediation techniques, such as electrochemical methods, chemical treatments, and biological remediation, offer ways to neutralize contaminants and restore sediment safety [13]; these strategies are discussed in detail in the following paragraphs. Sediment reuse presents a variety of possibilities, including applications in construction (e.g., as aggregates, road base materials, or landfill covers) and the development of green infrastructure such as wetlands or coastal restoration projects [14]. These solutions open new avenues for circular economy principles in sediment management and are also discussed.

2. Methodology

This review is divided into the following sections: (1) an introduction section focuses on the impacts of dredging, sediment remediation techniques, and a brief overview of the current regulatory framework for management in Italy; (2) the description of the methodology followed in this manuscript; (3) bibliometric analyses; (4) summary of principal remediation techniques for dredge sediment applied to freshwater and marine sediment and case studies; (5) summary of potential uses of dredge sediment and case studies; (6) the use of artificial intelligence toward the dredge sediment reclamation; and (7) the conclusions. To develop this study, a deep search on the Scopus, Google Scholar database, and Google search engine was carried out to identify relevant studies related to the environmental impacts of dredging, dredge sediment impact, and remediation or reuse strategies. The search queries on both databases included combinations of the following keywords: “dredging impact”, “dredge sediment impact”, “dredge sediment remediation”, “beneficial use of dredge sediment”, “dredging management”, “dredge sediment regulatory framework”, and “artificial intelligence and dredging”. The retrieved articles were manually reviewed and organized into a conceptual framework according to dredge sediment remediation technique or beneficial reuse, both divided by type of aquatic environment (marine, freshwater, lagoon). Publications were selected based on the following inclusion criteria: relevance to the main research themes and availability of sufficient methodological and thematic information. Exclusion criteria included duplicate entries, articles not directly related to dredging or sediment management, and publications lacking methodological transparency. The selected studies were compiled into a worksheet, including author, title, abstract, and relevant information, which provided the basis for this manuscript. To explore research trends and keyword patterns in the selected literature, a bibliometric analysis was performed using the Bibliometrix package in R (‘bibliometrix’ version 4.3.5). This analysis enabled the visualization of thematic networks and the identification of emerging research directions within the field. The combined use of Scopus, Google Scholar, and Google database allowed for a more comprehensive literature search by leveraging the strengths of each platform. Anyhow, we are aware of potential biases associated with the literature review process, such as algorithmic and quality variability bias and geographical bias due to the use of these databases.

3. Bibliometric Analysis

To understand the worldwide impact of dredging, we conducted a bibliometric analysis using data from the scientific search engine Scopus (Elselvier, Amsterdam, The Netherlands). The search was performed by entering the search string (“dredg*” AND “impact*”) in the search document menu with a filter applied to select only scientific articles in English, and no temporal restrictions were imposed. Data were exported in bibText format and were analyzed using Bibliometrix, an open-source software package developed in R for bibliometric analysis and data visualization [15]. The search yielded 2482 documents from 766 different sources, covering a time span from 1971 to 2025. This dataset reflects a wide range of scientific output, with publications from multiple disciplines that have investigated various environmental, economic, and technological aspects of dredging. The annual growth rate was 5.01%, indicating a consistent increase in research activity related to dredging, especially in the last decade. The overall trend in scientific production from 1971 to 2024 is shown in Figure 1, indicating an increasing trend of published scientific articles relating to the impact of dredging over time.

The analysis of scientific production by country showed that the United States (frequency score 1125) is the most influential nation in terms of scientific production on dredging, followed by China (622), the United Kingdom (394), Australia (375), Brazil (285), France (276), Italy (258), Nether-lands (249), Canada (156), and Spain (137). A graphic visualization of the contribution of the major countries is shown in Figure 2.

To highlight keywords related to the impact of dredging, an analysis of the most frequently occurring terms was carried out. The central theme according to the occurrence was “dredging”, followed by “environmental impact”, “environmental monitoring”, “sediment”, “water quality”, and “United States”. As expected, “dredging” and “sediment” were among the most frequently recurring terms because they were the terms used for the search. The terms “environmental impact” and “environmental monitoring” reflect sensitivity towards environmental issues. The term “United States” confirms the centrality of the country with regard to the issue of dredging. The term “pollutant” comes up several times, referring to contamination of water or sediment. Also, some types of contaminants were highlighted, such as “heavy metal”. The analyses underlined the terms “rivers”, “estuary”, and “marine” referring to these ecosystems. Notably, the term “biodiversity” emerges from research, emphasizing the term centrality. This refers to the variety and variability of life on Earth, encompassing the diversity within species, between species, and across ecosystems. In recent decades, biodiversity has become a central theme in global environmental discourse, not only for dredged activities but also in reference to species loss, habitat degradation, and the impacts of climate change. Preserving habitats and, consequently, biodiversity is essential to address future challenges. The search output is shown in Figure 3.

4. Towards the Reuse of Dredge Sediment

4.1. Remediation Techniques on Dredge Sediment

Dredge sediment remediation techniques are increasingly recognized as effective solutions for managing the disposal of sediment, turning it from waste into valuable resources. These methods help reduce environmental risks by removing contaminants and making sediment suitable for reuse in construction, land reclamation, or habitat restoration. As the volume of dredge sediment continues to grow, implementing sustainable and efficient remediation strategies is essential for minimizing negative environmental impacts and supporting circular economic principles. The technologies reviewed offer a variety of approaches for the remediation and reuse of contaminated and non-contaminated dredge sediment. For further details on the technologies, see the technical appendix attached to this review (Supplementary Materials S1).

4.1.1. Electrochemical Remediation Technologies

Electrokinetic (EK) remediation is a promising electrochemical approach widely explored for the treatment of sediment contaminated with heavy metals. This technique involves the application of a direct electric field across the sediment matrix, promoting the mobilization of contaminants. Although EK remediation has been extensively studied under controlled conditions, its application has remained largely limited to laboratory-scale experiments. A growing body of research has examined the use of EK remediation in various types of sediments (marine, estuarine, lagoon, and lake sediments), each characterized by different physical and chemical properties. In a study conducted in the Darsena Pescherecci area of the Port of Piombino (Italy), a hexagonal EK configuration was employed to treat approximately 60 kg of marine sediment. The system demonstrated the effective removal of heavy metals under optimized conditions, offering a glimpse of the potential scalability of the approach [16]. Further investigations have explored EK treatment in both artificial and naturally contaminated marine sediment. For example, ref. [17] applied graphite electrodes directly to the sediment matrix and observed a significant removal of PAH, although the technique showed limited effectiveness for mercury (Hg) and arsenic (As). Other studies have focused on improving the efficiency of treatment by optimizing operational parameters, for example, in [18], where marine sediment co-contaminated with heavy metals and PAHs was dragged using a combination of periodic voltage gradients, citric acid (CA), and surfactants such as Tween 20 (TW20). This approach significantly enhanced contaminant desorption and mobility, resulting in improved remediation outcomes. The role of electrolyte composition has also been investigated in detail. In the case of lagoon sediment from the Camorim Lagoon in Rio de Janeiro, Brazil, ref. [19] demonstrated that the addition of complexing agents like ethylenediaminetetraacetic acid (EDTA) and humic substances markedly improved metal mobilization and removal. Similarly, ref. [20] examined the EK treatment of sediment stored for over 13 years in the Tancarville repository in the upper Seine estuary, France. A periodic EK regime (8 h ON, 16 h OFF) was applied over 21 days using 40 V (1 V/cm), with citric acid (0.1 M, pH 2.36) at the cathode and ultrapure water at the anode. The process effectively reduced contaminant levels in 64 L of estuarine sediment to meet criteria suitable for land reclamation. In a related study, ref. [21] investigated the use of EK remediation to mitigate ecological risks associated with metal-contaminated lake sediment. The treatment combined EK with chemical agents such as EDTA, nitric acid, and acetic acid. Despite being applied to relatively small sediment volumes (e.g., 0.54 L per 100 g), the treatment showed strong potential in reducing contaminant concentrations and associated risks.

4.1.2. Chemical Remediation

Chemical remediation, or sediment washing, is a technique that involves treating contaminated sediment with chemical solutions to desorb and transfer pollutants from the solid phase into a liquid washing medium. The efficiency of this process largely depends on the selection of chemical additives, which can include acids (e.g., nitric, hydrochloric, sulfuric), bases (e.g., sodium hydroxide), surfactants, and chelating agents (e.g., EDTA, EDDS). At the end of the process, these additives must be completely removed from the treated sediment to prevent secondary recontamination. Coarse-grained sediment typically responds better to chemical flushing, while fine-grained sediment presents greater challenges due to higher surface area and stronger binding of contaminants. For this reason, careful preliminary extraction tests are required to optimize key parameters such as chemical type and dosage, contact time, temperature, agitation, and the number of washing cycles necessary to meet environmental standards. Recent studies have demonstrated the versatility and effectiveness of chemical remediation in different types of sediments. For example, ref. [22] investigated a multi-stage washing process to treat two distinct contaminated sediments in Italy: mercury- and arsenic-rich sediment from the Bay of Augusta (Sicily) and the area of Bagnoli in the Gulf of Pozzuoli. The treatment protocol consisted of the following: (1) alkaline washing with NaOH to remove metals bound to humic substances; (2) a Fenton-like reaction using α-cyclodextrin (aCD) to stabilize Fe(II) and oxidize As(III) and Hg(0/I); (3) complexation of metals with aCD; and (4) a final reaction with sodium sulfide (Na₂S) to convert mercury into soluble polysulfide complexes. This sequence achieved removal efficiencies ranging from 56–72% for arsenic and 76–95% for mercury, demonstrating the potential of integrated washing-oxidation-complexation strategies. A different approach was taken by [23], who conducted batch extraction experiments to assess the effectiveness of chelating agents (EDTA and EDDS) in removing arsenic, lead, zinc, copper, nickel, and chromium from sediment collected in Malmfjärden Bay (Sweden). The study analyzed the impact of chelating agent type, concentration (0.01 M and 0.05 M), and pH on extraction performance. Results indicated that EDTA, being more cost-effective than EDDS, was particularly efficient at leaching cationic metals bound to the reducible fraction of the sediment. Additionally, acidic conditions enhanced arsenic extraction, while higher chelating agent concentrations favored the removal of copper, nickel, and chromium. Similarly, ref. [24] conducted two sediment-washing campaigns to evaluate the efficacy of various chelating agents (EDTA, EDDS, citric acid, and acetic acid) in removing heavy metals (Ni, Cu, Zn, Cr, Pb, Hg) and total petroleum hydrocarbons (TPH) from marine sediments collected in Augusta Bay (Italy). The batch extraction tests considered the influence of pH (4 and 9), contact time (0.5 to 24 h), and chelating agent concentration (0.05 M to 1 M) using a 1:10 solid-liquid weight ratio. Results indicated that citric acid, due to its high biodegradability and cost-effectiveness, achieved superior removal efficiencies for both inorganic and organic pollutants, especially at acidic pH and prolonged contact time. EDTA was found to be effective mainly for inorganic contaminants, particularly under alkaline conditions, while EDDS showed good performance for the removal of Pb. The study concluded by proposing a conceptual layout for a large-scale sediment-washing plant, highlighting the technical and economic feasibility of citric acid as the primary extractant.

4.1.3. Solidification/Stabilization Methods

Dredge sediments are typically characterized by poor geotechnical properties, high compressibility, high water content, and low shear strength, which make them unsuitable for direct use in construction without prior treatment. Consequently, they are often treated as waste and disposed of in designated containment areas, which may lead to environmental degradation and loss of potentially reusable material. Stabilization has emerged as an effective approach to enhance the engineering properties of dredge soils, allowing their conversion into functional fill or construction materials. Although this technique does not aim to remove contaminants, it plays a critical role in immobilizing pollutants, thereby reducing their mobility and bioavailability in the treated matrix. Ordinary Portland cement (OPC) remains the most widely used binder in stabilization processes; however, its high production cost and significant environmental footprint have driven increasing interest in alternative or supplementary binders. Several studies have explored the partial replacement of OPC with industrial by-products (IBPs), which not only improve sustainability but also contribute positively to the mechanical performance of the treated sediment. For example, ref. [25] examined the incorporation of fly ash, ground granulated blast furnace slag (GGBFS), red mud, and phosphogypsum (PG) into OPC-based mixtures for marine sediment. These IBPs were shown to enhance hydration reactions by promoting the formation of contentious products such as C-(A)-S-H, CAH, and AFt, which help densify the matrix and improve long-term strength. In particular, the addition of PG and calcium aluminate cement (CAC) significantly boosted compressive strength, allowing for reductions in OPC usage while maintaining or enhancing structural integrity. CAC proved especially effective in improving both early strength development and deformation resistance, supporting the feasibility of using treated dredge sediment as a reliable fill material. A novel approach was proposed by [26], who developed a synergistic solidification/oxidation system (SOS) for stabilizing dredge sediment collected from a freshwater lake. This method combined OPC with sodium persulfate (SP), an oxidizing agent that also contributed to structural improvement. The presence of SP was found to substantially increase the unconfined compressive strength (UCS) of the sediment, particularly in samples with varying fulvic acid content, suggesting its suitability for complex organic-rich matrices. In a pilot-scale experiment, ref. [27] investigated the stabilization/solidification of marine sediment from the Mar Piccolo area of Taranto (Italy), using a combination of lime, organoclay, and activated carbon. The process enabled the transformation of 974 kg out of every 1000 kg of dredge material into a usable product, effectively reducing landfill disposal volumes to just 0.65 m³ per ton of sediment. This study illustrates the real-world applicability of S/S techniques not only for improving the mechanical performance of dredge sediment but also for facilitating large-scale recycling and environmental sustainability.

4.1.4. Adding Sorbent Amendments

Amendments have gained increasing attention in recent years as effective in reducing or eliminating the bioavailability of contaminants bound to soil or dredge sediment and have been used in both in situ and ex situ tests. Among these, activated carbon (AC)—both in granular (GAC) and powdered (PAC) form—and Biochar (BC) have proven to be effective in immobilizing a wide array of pollutants through adsorption processes. For example, ref. [28] used activated carbon (PAC) and granular activated carbon (GAC) for in-situ remediation of PCB-contaminated sediments from Oskarshamn Harbor, Sweden. The thin layer coverage effectively reduced contamination, but negative effects on benthic communities were found. However, sorbent amendments can be magnetized; these offer the opportunity to recover them after usage. Laboratory-scale studies have demonstrated the practical efficacy of these magnetized sorbents in sediment remediation. For instance, ref. [29] developed a new activated carbon (AC) material for in situ remediation of PCB-contaminated sediments. The new material did not have acute toxicity effects on Chironomusriparius and Lumbriculus variegatus, with a significantly higher remediation potential than GAC (up to 89% reductions in PCB bioaccumulation). Ref. [30] evaluated magnetic activated carbon (MAC) derived from AC and BC, for the in-situ remediation of PAH-contaminated sediments. An 8.1% MAC amendment (5% AC content) reduced aqueous PAHs by 98% in three months, matching the performance of 5% pure AC. MAC recovery after three months was 77%; incomplete recovery led to a temporary PAH rebound, followed by a decline after six months. However, 77% recovery was insufficient to fully mitigate MAC-related ecotoxic effects on Lumbriculus variegatus.

4.1.5. Thermal Desorption

Thermal remediation methods use heat to desorb, volatilize, or degrade contaminants, often offering advantages over chemical or electrochemical treatments, especially for complex or fine-grained matrices where diffusion limitations hinder other approaches. It has been used for the remediation of numerous types of contaminants and has been applied to dredge sediments. For instance, ref. [31] investigated TD for the treatment of hydrocarbon-contaminated marine sediment, which is often challenging to remediate due to its cohesive and low-permeability nature. Their results demonstrated that heating at 200–280 °C for just 10 min could achieve TPH removal efficiencies ranging from 75% to 85.2%. The lighter hydrocarbon fractions (e.g., C12–C30) were more easily volatilized, while the heavier fractions (C32–C40) remained more persistent, underscoring the need for temperature optimization according to the specific contamination profile. In parallel, microwave heating (MWH) has emerged as a novel and energy-efficient thermal approach for the remediation of contaminated solids. Unlike conventional TD, MWH relies on the dielectric heating properties of the material itself, resulting in volumetric and rapid heating. This allows for faster treatment and reduced energy consumption. Ref. [32] evaluated the application of MWH for the remediation of severe hydrocarbon-contaminated sediment from Augusta Bay, integrating citric acid (CA) as a chelating agent. The study demonstrated that MWH at 650 W could raise the sediment temperature to 305 °C, achieving TPH removal rates of approximately 95.6% after 10 min and 99.6% after 15 min. Notably, the addition of 0.1 M CA improved removal efficiency to 99.7% in just 15 min, and 0.2 M CA reduced the required treatment time to 10 min. Life cycle assessment (LCA) further supported the environmental sustainability of MWH, showing a 75.74% reduction in total environmental damage compared to electrokinetic remediation. Beyond hydrocarbons, MWH has also been applied to heavy metal remediation. Ref. [33] studied a microwave-assisted hydrogen peroxide (MW−H₂O₂) oxidation process for river sediment contaminated with metals such as Cu, Zn, Cd, and Pb. The treatment was particularly effective in acidic conditions (pH 0–4), where metal desorption was enhanced. Increasing the microwave temperature (25–85 °C) and irradiation time (up to 6 min) significantly improved metal release, while maintaining metal stability post-treatment, thus minimizing environmental risk.

4.2. Biological Remediation Techniques

Biological remediation techniques use living organisms to degrade or immobilize contaminants. It offers an environmentally sustainable and cost-effective approach to treating contaminated sediment. Among these, bioremediation, vermiremediation, and phytoremediation have gained significant attention for their potential to address a wide range of contaminants, including heavy metals, organic pollutants, and petroleum hydrocarbons. These techniques rely on the metabolic capabilities of micro- and macro-organisms and plants to remove or neutralize pollutants in sediment.

4.2.1. Bioremediation

Bioremediation involves the use of microorganisms to degrade or transform contaminants into less harmful substances under optimal environmental conditions with the addition of nutrients. This method has proven to be effective for large-scale remediation due to its low energy requirements and cost-effectiveness. Furthermore, it can be applied to a broad spectrum of contaminants, including hydrocarbons, heavy metals, and pesticides. For example, ref. [34] demonstrated that the combination of bioaugmentation (the addition of specific microorganisms) and biostimulation (enhancement of microbial activity through nutrient addition) significantly reduced the half-life of tributyltin (TBT) in contaminated sediment. In this study, biostimulation alone resulted in the degradation of approximately 50% of TBT within 20 weeks, showing the potential for microbial remediation of persistent contaminants. Sulfur-oxidizing bacteria, such as Acidithiobacillus thiooxidans, have been identified as key agents for the oxidation of sulfide minerals in dredge sediment, thereby promoting the release of heavy metals [35]. Fungi have also shown promise in enhancing the mobilization of sediment contaminants. For example, ref. [36] evaluated the effectiveness of different microorganisms for the bioremediation of marine sediments heavily contaminated by heavy metals (HMs) in Portman Bay (Northwestern Mediterranean Sea). At the laboratory scale, autotrophic bacteria, acidophilic heterotrophic bacteria, and marine filamentous fungi (Aspergillus niger and Trichoderma sp.), alone or in combination, were compared for the bioleaching of metals. The results showed that the addition of fungi led to the best removal yields, with arsenic solubilization eight times higher than chemical treatments and twice as high as bacteria.

4.2.2. Vermiremediation

Vermiremediation utilizes earthworms to remediate contaminated soils and sediment. Earthworms not only degrade organic contaminants but also enhance soil structure and nutrient cycling, making them valuable in remediating contaminated environments. While their effectiveness can be limited in highly toxic soils, and their activity is influenced by environmental conditions, studies have shown that Eisenia fetida and other species can significantly reduce heavy metal concentrations in contaminated soils [37]. In another study, the addition of Eudrilus eugeniae earthworms reduced the concentrations of heavy metals like copper, zinc, manganese, chromium, and nickel. In addition, earthworms improved soil enzyme activities, improving soil health and reducing metal toxicity, as confirmed by seed germination assays [38].

4.2.3. Phyto-Remediation

Phytoremediation, the use of plants to decontaminate sediment and soils, offers a highly versatile and visually appealing approach to environmental restoration. This technique is especially effective in removing metals, oils, pesticides, and even plastic pollutants. The major advantage of phytoremediation is its ability to work on large-scale projects, offering a natural and low-cost solution to contamination. Salt-tolerant plant species, such as Phragmites australis (common reed) and Halimione portulacoides, have been successfully employed to remediate sediment contaminated with tributyltin (TBT), a toxic compound commonly found in marine sediment. These plants can accumulate pollutants in their tissues, thus reducing the concentration of contaminants in the surrounding sediment and improving the overall health of the ecosystem [39]. Similarly, other studies have explored the remediation potential of Spartina maritima and Sarcocornia fruticosa in estuarine sediment, with varying degrees of success depending on the plant species and the level of contamination. These plants not only accumulate contaminants but also improve sediment structure and nutrient cycling by oxygenating the soil with their root systems [40]. The use of plants to remediate petroleum-contaminated sediment has also shown great promise. In this context, ref. [41] investigated the performance of Zea mays and Festuca arundinacea in highly contaminated, aged soil. Both species demonstrated strong resilience and contributed to a marked decrease in total petroleum hydrocarbons (TPHs) over time. Notably, tall fescue achieved the highest remediation efficiency, removing up to 96.3% of initial TPHs. The application of peat as a soil amendment further enhanced plant growth and soil quality. The concentration of contaminants can represent a major challenge for effective phyto extraction, as highlighted in [42], which evaluated six months of phytoremediation using Phragmites australis grown on dredged sediments from urban retention tanks. The comparison between uncontaminated (S_uncont) and contaminated (S_cont) seedlings demonstrated that high levels of potentially toxic elements (Zn, Cu, Cd, Ni, Cr, Pb) can inhibit plant growth and function.

5. Turning Dredge Sediment into a Resource: Recently Tested Strategies

5.1. Dredge Sediment Utilization as Inert Materials

The preservation of natural resources and the sustainable utilization of waste materials are key components of sustainable development. Dredged sediment traditionally considered waste, is increasingly being explored as a valuable resource for various applications, such as concrete production, construction materials, and environmental remediation. One promising application is the incorporation of dredge sediment into cement formulations. Research on uncontaminated sediment from Dunkirk Harbor (France) showed that replacing up to 20% of cement with dredge sediment reduced mortar strength but still surpassed the performance of reference mortar. This sediment replacement also achieved a C30/37 strength class in concrete, indicating its potential in construction [43]. Additionally, combining dredge sediment with plastic waste has been explored. One study created lightweight aggregates by combining 70% sediment-based mineral filler with 30% thermoplastic waste. These aggregates met the European Standard for lightweight aggregates and displayed favorable mechanical properties, such as low water absorption compared to natural aggregates [44]. The creation of composite materials using marine dredge sediment, overburden soil, and lime production waste has also been investigated. These composites exhibited good mechanical properties, such as an axial resistance strength of 18.9 MPa, and are suitable for use in tiles, bricks, and road bases [45]. Additionally, marine dredge sediment has been tested for cement production by treating it at high temperatures (650 °C and 850 °C) to eliminate organic compounds and activate clay minerals. Sediment treated at 650 °C showed improved compressive strength and proved to be the most cost-effective treatment [46]. Beyond cement, dredge sediment has been utilized in brick production. One study incorporated incinerated waste and river dredge sediment into lightweight, thermally insulating clay bricks, achieving satisfactory mechanical properties after firing at temperatures between 800 and 1000 °C [47]. Additionally, the potential of combining specific river sediments with hemp shiv and palm oil fiber (POFl) was explored. Bricks made with these mixtures met the minimum tensile strength standard, demonstrating the feasibility of using dredge sediment in sustainable brick production [48]. Dredge sediment also shows promise as an adsorbent for environmental remediation. One study developed a low-cost adsorbent from dredge sediment (DSD) for the removal of crystal violet dye from aqueous solutions. The DSD, primarily composed of clay minerals like illite and kaolinite, exhibited a high surface area and mesoporous structure, which enhanced its adsorption capacity for dyes [49]. Another study combined dredge sediment with zeolite and bentonite to create ceramsite, a lightweight material suitable for water treatment applications. The resulting ceramsite had a high specific surface area (51.68 m²/g) and large porosity (53.93%) and met the standards for macroporous materials [50]. Dredge sediment can also be utilized in road construction. Research has shown that dredge sediment, when used as embankment or subgrade material, can offer environmental and economic benefits. A field test conducted in the Port of Dunkirk, France, demonstrated that dredge sediment used as subbase material met design specifications and posed no significant environmental risks in terms of contaminant leaching, including trace metals and chlorides [51]. Within its uses as an inert material, the dredged material has been used as material for the covering of sanitary landfills. In this context, ref. [52] reused dredge material from ports in Istanbul and Kocaeli (Turkey) as capping material for a sanitary landfill. A comprehensive analysis was conducted to assess the physical, chemical, mineralogical, toxicological, and leaching characteristics of the DM. Both raw and processed forms were tested to evaluate their geotechnical suitability for landfill components such as cover layers, base or cap liners, and fill materials. The study concluded that non-hazardous dredge sediment could be effectively repurposed within different sections of landfills. This approach offers notable environmental and economic advantages over conventional disposal methods, such as marine dumping or upland storage.

5.2. Agricultural Applications of Dredge Sediment

Multiple studies have explored its suitability as a growing substrate, soil amendment, or input in soil regeneration processes. Ref. [53] investigated the use of dredge sediment from Malmfjärden Bay (Sweden), combining it with compost to grow lettuce. Although plant growth was achieved, the size of the lettuce was reduced, likely due to the soil’s texture. The study emphasized the need for ecotoxicological assessments to evaluate potential risks to both plant development and human health. It concluded that while untreated sediment may not be appropriate for edible crops, it could be suitable for cultivating ornamental or bio-energy plants. Similarly, Ref. [54] evaluated the use of remediated marine dredge sediment as a substrate for strawberry and pomegranate cultivation. Their findings revealed no significant impact on fruit quality, and even when sediment with relatively high contamination levels was used, the product remained safe for consumption, supporting the feasibility of agricultural use following proper remediation. Further studies reinforced the importance of pre-treatment of dredge sediment. Ref. [55] showed that pre-washing dredge sediment to reduce salinity, followed by pH neutralization, enabled 100% barley germination, suggesting that proper treatment can significantly improve sediment viability as a plant-growing medium. Ref. [56] examined various solidification and stabilization (S/S) techniques, including the use of cement, clay, fly ash, and green-synthesized nanozero valent iron (nZVI) to reduce trace element concentrations in dredge sediment. Although most treatments lowered contaminants, some resulted in plant stress, underlining the importance of aligning the choice of treatment with the target plant species and intended agricultural use. In a pilot-scale experiment, ref. [57] utilized sediment from the Navicelli Canal (Pisa, Italy) mixed with green waste from Florence to cultivate Photinia × fraseri. The co-composted mixture increased microbial diversity (bacteria, fungi, and archaea) compared to untreated sediment, with no significant ecotoxicological effects and excellent plant growth results. However, risks remain, especially with contaminated sources. Ref. [58] assessed microcystin-contaminated sediment from Lake Taihu (China) used as a substrate for lettuce. While plant growth improved due to additional nutrients, lettuce grown in sediment from algal bloom periods contained detectable levels of microcystins, alongside reduced soluble sugar and Vitamin C content. These results highlight the critical need for monitoring and risk evaluation when repurposing contaminated sediment for agriculture. Instead, ref. [59] found positive outcomes in the United States, where sediment from the Illinois River enhanced the physical and chemical quality of sandy soils. Treated soils exhibited improved water-holding capacity, cation exchange capacity, and nutrient content, leading to increased biomass and grain yield in corn and soybeans. Metal concentrations in plant tissue and soils remained within safe limits. Dredge sediment also presents an opportunity for resource recovery, particularly as an alternative source of phosphorus for agricultural use. In this context, ref. [60] evaluated the fertilizing potential of lake dredge sediment, focusing on its phosphorus content and plant availability. The study found that freshly dredge sediment contains a form of phosphorus predominantly bound to amorphous iron (Fe-P), which can be bioavailable under appropriate conditions. This form was identified as a significant contributor to plant nutrition, suggesting that such sediment can act as a slow-release P fertilizer.

5.3. Sustainable Management and Large-Scale Reuse of Dredge Sediment

Large-scale applications include land reclamation, wetland and habitat restoration, beach nourishment, agricultural soil improvement, and use as construction fill for infrastructure such as roads, levees, and dikes. It is an effective strategy to manage dredge sediment, transforming it into a valuable resource. As an example, the Eems–Dollard project in the Netherlands aims to improve water quality and enhance natural habitats by reusing dredge material [61]. This initiative exemplifies the “beneficial use of dredge material” philosophy, contributing to estuarine restoration and climate resilience. Another flagship project is the Fehmarnbelt Tunnel, a submerged connection between Germany and Denmark. This infrastructure endeavor plans to reuse 100% of the dredge sediment generated during excavation for environmentally beneficial purposes, minimizing waste and supporting sustainability goals [62]. In addition to these initiatives, various studies demonstrate the technical feasibility and ecological value of using dredge sediment for habitat creation and coastal defense. In the Mississippi River Delta (United States), sediment deposition over 70 years has led to the formation of more than 800 hectares of new land in West Bay, as confirmed by remote sensing analyses [63]. Similarly, ref. [64] assessed the reuse of New York Harbor sediment for environmental enhancement, identifying viable applications such as artificial reef creation, oyster reef restoration, marsh and mudflat rehabilitation, and upland habitat construction. In the Westerschelde estuary (Netherlands), ref. [65] tested an alternative dredging strategy in which clean sand was placed seaward of an eroding intertidal flat to restore shallow-water habitats. Five years of monitoring revealed that sediment slowly migrated toward the flat, increasing the extent of subtidal and intertidal areas without negative ecological impacts, although no new habitats were formed. Ref. [66] introduced the “Mud Motor” concept to enhance salt marsh development, successfully increasing mud transport based on weather conditions and offering new insights into its feasibility for land reclamation. Moreover, ref. [67] demonstrated that fine-grained dredge sediment can support the recovery of tidal lagoons by increasing elevation, reducing erosion, and boosting system resilience. While nearshore disposal is common for dredging materials from maintenance operations, uncontrolled migration remains a risk. In this regard, ref. [68] developed a predictive tool to model sediment transport and sandbank movement, allowing for more strategic placement. Beach nourishment also represents a practical reuse strategy. Ref. [69] successfully applied sand from nearby port dredging operations to restore coastal areas, achieving outcomes such as dune field expansion, enhanced habitats for nesting shorebirds, and increased recreational space.

6. Artificial Intelligence (AI) and Its Potential Role in Dredge Sediment Remediation

Artificial Intelligence (AI) refers to the ability of machines to process data and make decisions autonomously, adapting their behavior without explicit programming. In recent years, AI has been increasingly applied across various environmental fields due to its capacity to analyze complex systems and optimize decision-making processes. However, to date, there is a lack of documented studies that specifically apply AI to the remediation or treatment of dredge sediment. Despite this, the potential for integrating AI into dredge sediment management is significant. AI could support multiple aspects of the remediation process, including the prediction of contaminant behavior, the optimization of treatment strategies, and the selection of the most sustainable reuse options based on site-specific conditions. For instance, machine learning models could assist in identifying suitable stabilization techniques or in forecasting long-term environmental impacts under different reuse scenarios. The application of AI has already demonstrated its value, particularly in the biodegradation of petroleum hydrocarbons. For example, an artificial neural network (ANN) applied an updated ANN to enhance fluoranthene degradation by Mycobacterium litorale [70]. Additionally, ref. [71] conducted an optimization study of total petroleum hydrocarbon (TPH) degradation in diesel-contaminated soils using Paspalum scrobiculatum, a tropical plant, with the support of ANN modeling. These works highlight how AI can be used to optimize biological remediation processes, guiding microbial or phytoremediation-based strategies more efficiently.

7. Conclusions

Dredging continues to be an essential activity for maintaining the operability of ports, navigable waterways, and lagoon systems. In recent years, there has been a significant shift in perspective from viewing dredge sediment as a waste product to recognizing it as a potential resource. This change aligns with broader efforts to embrace principles of circular economy and sustainable environmental practices. Dredge sediment is now considered a valuable input for environmental recovery, particularly through innovative remediation and reuse strategies. Recent advancements in sediment management have introduced a variety of technologies, such as electrochemical remediation, chemical washing, thermal desorption, biological treatment, and solidification/stabilization. These approaches not only help reduce the concentration of contaminants but also improve the physical and chemical characteristics of the sediment, making it suitable for beneficial applications such as land reclamation, habitat creation, and construction material production [72]. The integration of emerging technologies like artificial intelligence has further opened new avenues for optimizing treatment processes, improving environmental monitoring, and increasing remediation efficiency. This shift reflects a broader move toward sustainable and circular practices that aim not only to mitigate environmental harm but also to promote ecosystem restoration and resource efficiency. However, despite these promising developments, there are significant concerns regarding the economic feasibility and practical implementation of these technologies. High energy costs, complex logistics, and the uncertain scalability of many remediation methods pose major barriers to their widespread adoption [73]. Legislative frameworks also play a crucial role in determining how dredge sediment is managed and whether reuse projects can proceed. Italy’s Ministerial Decree No. 173/2016 promotes sediment reuse, encouraging sediment reuse. But, in the UE complex permitting procedures, lack of harmonized standards, and insufficient public awareness contribute to the regulatory and institutional challenges facing sediment valorization efforts [74]. Despite that, one particularly promising area is the beneficial reuse of sediment, especially in high-volume dredging contexts where traditional disposal is no longer viable. Reuse options such as land reclamation, coastal defense, and wetland restoration offer tangible environmental and economic benefits and have already been successfully implemented in countries like the Netherlands. There, sediment has been repurposed to create green spaces and public parks, demonstrating its potential for both ecological enhancement and human use [75]. Dredging can be a useful tool in environmental restoration projects [76], for example, in cases of contamination, by removing contaminated sediment, and in cases of eutrophication. Nonetheless, care must be taken when intervening in restoration projects. The human impact on restoration projects is still unclear, and for this reason, these measures must be applied with care, planning, and execution of specific ecosystem restoration projects [77].