Recent advances in machine/deep learning frameworks for biochar application in soil amendment and remediation

Heavy metal (HM) contamination poses a major threat to environmental health, agriculture and human well-being, requiring effective and sustainable remediation strategies. Phytoremediation, an eco-friendly and cost-effective approach, is widely used for the remediation of HM-contaminated soils. Although phytoremediation holds considerable potential in the extraction, stabilisation and degradation of HMs, its effectiveness is often constrained by limited metal bioavailability, plant stress under toxic conditions and slow metal uptake rates. To address these limitations, this review examines the integration of various soil amendments—the application of biochar, compost, plant exudates, microbial agents and chelating agents—to enhance phytoremediation efficiency. This review critically evaluates empirical evidence on the effectiveness, scalability, economic feasibility and environmental impact of these amendments. By synthesising recent studies, this review advances the understanding of amendment-assisted phytoremediation as a viable solution for treating HM-contaminated soils. In addition, this review identifies practical applications, discusses limitations and explores the potential synergies of these amendments to optimise phytoremediation strategies, ultimately contributing to more effective and sustainable environmental cleanup efforts.

High anthropogenic activities are constantly causing increased soil degradation and thus soil health and safety are becoming an important issue. The soil quality is deteriorating at an alarming rate in the neighborhood of smelters as a result of heavy metal deposition. Organic biowastes, also produced through anthropogenic activities, provide some solutions for remediation and management of degraded soils through their use as a substrate. Biowastes, due to their high content of organic compounds, have the potential to improve soil quality, plant productivity, and microbial activity contributing to higher humus production. Biowaste use also leads to the immobilization and stabilization of heavy metals, carbon sequestration, and release of macro and micronutrients. Increased carbon sequestration through biowaste use helps us in mitigating climate change and global warming. Soil amendment by biowaste increases soil activity and plant productivity caused by stimulation in shoot and root length, biomass production, grain yield, chlorophyll content, and decrease in oxidative stress. However, biowaste application to soils is a debatable issue due to their possible negative effect of high heavy metal concentration and risks of their accumulation in soils. Therefore, regulations for the use of biowastes as fertilizer or soil amendment must be improved and strictly employed to avoid environmental risks and the entry of potentially toxic elements into the food chain. In this review, we summarize the current knowledge on the effects of biowastes on soil remediation, plant productivity, and soil organic carbon sequestration.

Coordination of bacterial biomarkers with the dominant microbes enhances triclosan biodegradation in soil amended with food waste compost and cow dung compost

Insights into the biodegradation of diesel oil and changes in bacterial communities in diesel-contaminated soil as a consequence of various soil amendments

Biochar for soil remediation: A comprehensive review of current research on pollutant removal

This study evaluates the impact of soil amendment applications on improving farmers' income in the production of corn, beans, cotton, soybeans, kale, and mustard greens in the United States. By examining various soil amendment practices, this research aims to identify the most effective methods for enhancing soil fertility, crop yields, and overall profitability for farmers. This study used a descriptive research design and secondary data sources. The dataset was retrieved from the archives of the USDA National Agricultural Statistics Service (NASS), USDA Economic Research Service (ERS), and relevant scientific studies. The dataset period ranges from 2000 to 2022. As part of the findings, this study found that the application of compost and biochar significantly improved corn yields. On average, corn fields treated with compost saw a 15% increase in yields, while biochar treatments resulted in a 20% yield improvement. The study further reveals that the increased yields from soil amendments led to higher incomes for corn farmers, whereby on average, corn farmers experienced a $150 per acre increase in profit due to the yield improvements from soil amendments. Again, the study found that organic amendments such as manure and compost improved bean yields by 12% and 18%, respectively, while lime application in acidic soils resulted in a 10% increase in yields. Also, the study found that soil amendments such as gypsum and biochar increased cotton yields by 10% and 15%, respectively, which in effect aid cotton farmers to experience an average income increase of $200 per acre due to the improved yields from soil amendments. In summary, the application of soil amendments presents a viable solution to the challenges of soil degradation, low crop productivity, and economic pressure on farmers in the United States. Through the enhancement of soil health, soil amendments have proven to significantly improve yields for essential crops such as corn, beans, cotton, soybeans, kale, and mustard greens. Improved crop yields directly translate to higher farmer incomes, contributing to the economic sustainability of the agricultural sector. Keywords: Soil, Amendments, Crops, Income, Farmers, Agriculture, Economic Growth, Corn, Kale, Beans, Cotton, Soybeans, Mustard green, and Production DOI : 10.7176/JEES/14-4-04 Publication date : June 30th 2024

Shifts in microbial community and water-extractable organic matter composition with biochar amendment in a temperate forest soil

Treatment of the saline-alkali soil with acidic corn stalk biochar and its effect on the sorghum yield in western Songnen Plain

This work aims to study the effect of contaminated soil remediation on some soil properties. Also a remediation experiment was conducted to show the useful effect of two remedies named Triton x-100 and potassium oleate in decreasing the hydrocarbons (aliphatic and aromatic) and heavy metals contents in crude oil contaminated soil samples. Two soils (sandy and calcareous) were contaminated by 1 , 2 and 3 % V/W of crude oil, then each contamination level was treated by 0 (untreated) , 1 and 3 % of the two used remedies. Pots were seeded with barley seeds, barley plant samples were collected at the end of the experiment. The total concentrations of nitrogen, phosphorus and potassium in plant samples and soil under study were estimated. Also, the concentration of hydrocarbons and heavy metals were measured. It can be deduced from the data obtained from this study that the total contents of nitrogen, phosphorus and potassium were significantly affected by contamination by crude oil. Application of Triton x-100 and potassium oleate decreased to high extents the concentrations of aliphatic and aromatic hydrocarbons as well as the heavy metals. For example, the use of Triton x-100 reduced the concentration of aliphatic hydrocarbons by percents reached to 54 % as compared to the non-remedied samples. On the other hand, the concentration of heavy metals as Nickel also decreased by about 55 %, which confirms the efficiency of the used remedies. Also, application of these remedies had increased the total contents of organic carbon, nitrogen, phosphorus and potassium in the treated samples than those in untreated ones. The application of organic remediation of contaminated soils led to limited increase on EC and pH values this result confirms the importance of these organic remedies to reduce the harmful effects on the properties of remedied soil.

Microbial electrochemical technologies (MET) are increasingly being considered for environmental remediation applications, mainly for their unique capability to enhance microbial degradation processes in an environmentally sustainable manner (e.g., without requiring addition of chemicals and with little or even no energy consumption). To date, however, the application of MET for the remediation of saturated and unsaturated soils contaminated by petroleum hydrocarbons (PH) remains challenged by a number of environmental and operational factors which have, so far, hampered a more rapid deployment of the technology. In this context, this critical review has comprehensively analyzed the recent scientific literature dealing with electrobioremediation of PH-contaminated soils, in order to disentangle the impact of key process parameters (e.g., type of electrodes, system configurations, design criteria) and environmental conditions (e.g., soil characteristics and strategies to manipulate thereof, type of contaminants, composition of PH-degrading communities) on the overall remediation performance. Interestingly, the analysis revealed that MET-based soil electrobioremediation has been successfully applied to remove a variety of PH (from alkanes to polycyclic aromatic hydrocarbons and mixtures thereof) from soils displaying a broad range of electric conductivities (0.2–6 mS/cm), using different system configurations (from simple graphite rod buried within soils to more complex tubular electrode assemblies). To date, the limited radius-of-influence of electrodes buried in contaminated soils, which is typically lower than 50 cm, appears to be a main limiting factor which requires specific strategies (e.g., amendment of soil with conductive materials/minerals and/or surfactants) to be properly addressed. Finally, the study highlights the urgent need for pilot-scale testing to confirm the promising results obtained at the laboratory-scale under more controlled, yet often far-less representative, conditions as well as to catalyze the commercial and societal interest towards this novel technology.

The use of available resources for the benefit of both environment and human beings comes under sustainable agriculture. Application of chemical fertilizers and pesticides is against the sustainable management of agricultural resources. Biochar acts as alternative to chemical pesticides and fertilizers by promoting the disease suppression and enhancing plant growth. Current study examines the effect of different biochar concentrations on growth enhancement of tomato plants and availability of essential nutrients like potassium and phosphorus both in the absence and presence of Alternaria solani infection. Soil was amended with green and wood waste biochar (GWB). Both biochar concentrations (3 and 6%) effectively minimized disease progress while enhancing plant growth. However, 6% GWB performed better. Both root and shoot length increased in soil amended with 6% GWB. Both disease incidence and severity reduced drastically in soil amended with 6% biochar. Nitrogen contents increased by 13.07% under stress conditions. The disease incidence was 100% in un-amended soil while it was reduced to just 20% in soil amended with 6% GWB. There was significant drop (6%) in disease severity in 6% GWB amended soil. In short, soil amendment with biochar proved effect strategy for mitigation of early blight in to tomato by stimulating plant growth parameters and minimizing disease incidence. Biochar application is crucial for sustainable agriculture.

The effect of a municipal solid waste compost (MSWC), added at 1 and 2% rates, on the mobility, phytotoxicity, and bioavailability of antimony (Sb) was investigated in two soils (SA: acidic soil; SB: alkaline soil), spiked with two Sb concentrations (100 and 1000 mg kg−1). The impact of MSWC on microbial activity and biochemical functioning within the Sb-polluted soils was also considered. MSWC addition reduced water-soluble Sb and favored an increase in residual Sb (e.g., by 1.45- and 1.14-fold in SA-100 and SA-1000 treated with 2% MSWC, respectively). Significant increases in dehydrogenase activity were recorded in both the amended soils, as well as a clear positive effect of MSWC on the metabolic activity and catabolic diversity of respective microbial communities. MSWC alleviated Sb phytotoxicity in triticale plants and decreased Sb uptake by roots. However, increased Sb translocation from roots to shoots was recorded in the amended soils, according to the compost rate. Overall, the results obtained indicated that MSWC, particularly at a 2% rate, can be used for the recovery of Sb-polluted soils. It also emerged that using MSWC in combination with triticale plants can be an option for the remediation of Sb-polluted soils, by means of assisted phytoextraction.

This study conducts a scientometric analysis to explore research trends, intellectual structures, and emerging themes in biochar applications for soil remediation in mining-affected environments from 2014 to 2024. Using bibliometric data retrieved from Scopus and Web of Science Core Collection, a dataset of 6093 unique peer-reviewed articles was analyzed. Descriptive bibliometric indicators, co-authorship and co-citation networks, and keyword co-occurrence patterns were visualized using the Bibliometrix R package and CiteSpace. The findings reveal significant growth in biochar research post-2018, driven by its increasing application in stabilizing heavy metals and improving soil quality. Co-citation cluster analysis identifies key thematic areas, including "mine soil," "cadmium-contaminated soil," and "dynamic redox conditions," reflecting biochar's role in addressing complex contamination challenges. High citation and sigma values emphasize seminal contributions, particularly on biochar's physicochemical properties and its interactions with heavy metals and microbial communities. Emerging trends highlight growing interest in ecological restoration, microbial dynamics, and innovative approaches such as nanobiochar and machine learning applications. This study provides critical insights into the evolution and interdisciplinary scope of biochar research, offering a roadmap for advancing its application in soil remediation and sustainable land management. Future directions include optimizing biochar formulations for diverse contaminants, integrating computational tools, and exploring its long-term ecological impacts to enhance its transformative potential for environmental sustainability.

The application of machine learning methods for prediction of metal immobilization remediation by biochar amendment in soil

Selenium concentrations in the soil environment are directly linked to its transfer in the food chain, eventually causing either deficiency or toxicity associated with several physiological dysfunctions in animals and humans. Selenium bioavailability depends on its speciation in the soil environment, which is mainly influenced by the prevailing pH, redox potential, and organic matter content of the soil. The selenium cycle in the environment is primarily mediated through chemical and biological selenium transformations. Interactions of selenium with microorganisms and plants in the soil environment have been studied in order to understand the underlying interplay of selenium conversions and to develop environmental technologies for efficient bioremediation of seleniferous soils. In situ approaches such as phytoremediation, soil amendment with organic matter and biovolatilization are promising for remediation of seleniferous soils. Ex situ remediation of contaminated soils by soil washing with benign leaching agents is widely considered for removing heavy metal pollutants. However, it has not been applied until now for remediation of seleniferous soils. Washing of seleniferous soils with benign leaching agents and further treatment of Se-bearing leachates in bioreactors through microbial reduction will be advantageous as it is aimed at removal as well as recovery of selenium for potential re-use for agricultural and industrial applications. This review summarizes the impact of selenium deficiency and toxicity on ecosystems in selenium deficient and seleniferous regions across the globe, and recent research in the field of bioremediation of seleniferous soils.