Abstract
Soil contamination is one of the most significant environmental challenges of the present century, with undeniable direct impacts on food security, human health, and ecosystem sustainability. The accumulation of heavy metals, organic pollutants, and industrial and agricultural wastes reduces soil fertility and increases the risk of contaminant transfer to groundwater and the food chain. Therefore, the development and implementation of effective soil remediation and restoration methods are essential. This article provides a comprehensive review of the main soil remediation approaches, including physical, chemical, and biological methods, with particular emphasis on sustainable and environmentally friendly strategies. The findings indicate that bio-based approaches, especially phytoremediation and the use of carbon-based soil amendments such as biochar, can offer cost-effective, scalable, and efficient solutions for the rehabilitation of contaminated soils.
Introduction
Soil, as one of the most fundamental natural resources, plays a central role in food production, regulation of biogeochemical cycles, and environmental sustainability. However, industrial and mining activities, improper waste disposal, excessive use of fertilizers and chemical pesticides, and contaminant leakage from landfills have led to widespread soil pollution in many regions of the world. Pollutants such as heavy metals, persistent organic compounds, and hydrocarbons pose serious threats to human health and ecosystems due to their high persistence, bioaccumulation potential, and toxicity.
Traditional soil remediation methods, including soil excavation and replacement, chemical washing, and thermal treatments, can be effective in reducing contaminant concentrations, but they are often costly, energy-intensive, and destructive to soil biological structure. As a result, recent research has increasingly focused on sustainable, low-cost, and environmentally compatible remediation strategies. This article aims to present a structured review of the major soil remediation methods and to analyze the advantages, limitations, and applications of each approach.
Major Soil Remediation and Restoration Methods
1. Physical Methods
Physical soil remediation methods primarily focus on the separation or direct removal of contaminants. Soil washing is one of the most commonly used techniques, in which contaminated soil is washed with water or chemical solutions to separate heavy metals or organic compounds from the soil matrix. This method can significantly reduce contaminant concentrations; however, the generation of contaminated wastewater and the high cost of its treatment represent major challenges. Mechanical excavation and replacement of contaminated soil with clean soil is also applied in certain cases, but this approach is generally considered a temporary and expensive solution that causes severe disturbance to soil structure.
2. Chemical Methods
Chemical remediation methods involve the use of chemical agents to stabilize, neutralize, or transform contaminants into less mobile or less toxic forms. The addition of materials such as lime, phosphates, or cement-based compounds can reduce the mobility of heavy metals and prevent their migration into groundwater. Although these methods are fast and relatively easy to implement, they do not completely remove contaminants, and their long-term effectiveness depends on environmental conditions. In some cases, chemically induced changes may negatively affect soil biological activity and microbial communities.
3. Biological and Bio-Based Methods
Biological soil remediation methods rely on living organisms, particularly plants and microorganisms, to reduce soil contamination. Microbial bioremediation utilizes the metabolic capacity of bacteria and fungi to degrade organic pollutants such as hydrocarbons. This approach is environmentally safe but relatively slow and highly dependent on specific environmental conditions, including temperature, moisture, and nutrient availability.
Phytoremediation is one of the most important and widely applied biological soil remediation techniques. In this approach, plants reduce soil contamination by absorbing, stabilizing, or degrading pollutants. Certain plant species have a high capacity to uptake heavy metals and accumulate them in their tissues. Due to its low cost, environmental compatibility, and suitability for large-scale applications, phytoremediation has attracted considerable attention. However, it is a time-consuming process and requires proper management of contaminated plant biomass to prevent the re-release of pollutants into the environment.
4. Soil Amendment with Carbon-Based Materials and Biochar
In recent years, the use of biochar as an effective soil amendment has gained increasing attention. Biochar is a carbon-rich material produced through the pyrolysis of biomass under low-oxygen conditions. Owing to its high porosity, large surface area, and chemical stability, biochar has a strong capacity to adsorb heavy metals and organic pollutants. The application of biochar can regulate soil pH, enhance water and nutrient retention, and improve microbial activity. In addition, biochar plays an important role in long-term carbon sequestration and contributes to the reduction of greenhouse gas emissions. These properties make biochar one of the most promising tools for the restoration of degraded and contaminated soils.
Discussion
A comparison of different soil remediation methods demonstrates that no single approach is universally suitable for all types of contamination and soil conditions. Physical and chemical methods, while rapid and effective, are often costly and environmentally disruptive. In contrast, biological and bio-based approaches offer greater sustainability and preserve soil structure, allowing the gradual recovery of ecological functions. The integration of multiple remediation strategies, particularly the combination of phytoremediation and biochar application, can create a synergistic approach that facilitates contaminant uptake while simultaneously improving the long-term physical and chemical quality of soils.
Conclusion
The remediation and restoration of contaminated soils represent a fundamental pillar of sustainable development and natural resource management. The evaluation of various remediation methods indicates that sustainable, bio-based approaches—especially phytoremediation and biochar application—have significant potential to rehabilitate contaminated soils at lower cost and with reduced environmental impact. The future of soil management is moving toward integrated, nature-based solutions that not only reduce pollution but also restore soil ecological functions. The adoption of such approaches can play a crucial role in ensuring food security, protecting the environment, and sustaining soil resources.
Resources
Walid Chmingui, Imene Dridi, Hanen Zaier, Thomas Z Lerch, Claude Hammecker, Mohamed Hachicha, Vacuum pyrolysis of olive pomace for biochar production: Enhancing carbon stability and soil nutrient supply, Results in Engineering, 2025, 108662, ISSN 2590-1230, https://doi.org/10.1016/j.rineng.2025.108662. (https://www.sciencedirect.com/science/article/pii/S2590123025047061) Abstract: Olive pomace (OP), a significant agro-industrial byproduct in Mediterranean countries, poses considerable disposal challenges and offers potential as a feedstock for engineered biochar production. Conventional pyrolysis of OP has been widely studied and often yields biochar with limited aromaticity and variable nutrient content. However, no prior work has explored the potential of vacuum pyrolysis for this residue. Addressing this research gap, this study investigates the use of vacuum pyrolysis (500°C, 15–20 kPa, 2 h) to transform OP into a stable and nutrient-rich biochar. The process yielded 30.9 wt.% biochar with 68.7% fixed carbon, representing an improvement of 20% in carbon retention compared with atmospheric pyrolysis. Elemental ratios (H/C = 0.03 and O/C = 0.18) confirmed high aromaticity and long-term stability, while mineral enrichment underscored high agronomic value. The biochar displayed a cation exchange capacity of 56.2 cmolc/kg and 79% porosity, properties favorable for nutrient cycling, and soil remediation. The carbon sequestration potential was estimated at 2.6 tCO₂eq per ton of biochar applied and heavy metals were below international thresholds, ensuring environmental safety. Beyond material characterization, the work highlights engineering advantages, including reduced inert gas requirements and a reusable syngas fraction (64.6 wt.%) that can offset energy costs. However, as the study was conducted at a single pressure level, the specific contribution of vacuum conditions requires further confirmation through multi-pressure trials. Such results position vacuum pyrolysis as a promising technology for waste valorization, carbon management, and climate-smart agriculture, while future research should address field validation, contaminant screening, and life-cycle performance. Keywords: Olive pomace; Vacuum pyrolysis; Biochar engineering; Carbon sequestration; Nutrient enrichment
Phytoremediation-derived sunflower oil for bio-based polyurethane foams Elzbieta ˙ Malewska a,b,* , Jacek Antonkiewicz c , Maria Kuranska ´ a,b , Piotr Rybarczyk d , Andrzej Rogala d
