Hemp and Phytodepuration: a topic for discussion
Phytoremediation uses plants to absorb contaminants, including heavy metals – a study from Poznań University shows that hemp can reclaim degraded mining soil by increasing the amount of humus
Understanding natural depuration processes – What is Phytoremediation?
Phytoremediation is the process of cleaning up contaminated environments by using plants that can absorb contaminants–heavy metals such as Cadmium and Nickel, explosives, pesticides, solvents, and crude oil. The process occurs during the water and nutrient absorption phase carried out by the roots.
The uses hemp – employing hemp in Phytoremediation
The Phytoremediation ability of the Hemp plant is a topic of discussion and confrontation: under scrutiny regarding a potential hemp ability to absorb excess heavy metals in soil and other contaminants by accumulating them in roots and leaves. In doubt is the permanence of the elements within the stem.
Hemp has roots ranging in length from forty-five to ninety centimeters. Hemp is a high biomass-producing plant that can be used through a pyrolysis process: this way, some of the metals absorbed could be recoverable.
Hemp: Phytoremediation cases in Chernobyl, in Apulia for the Ilva disaster
The phytoremediation capacity of hemp has not yet been scientifically proven – but studies such as ‘Potential of Industrial Hemp for Phytoremediation of Heavy Metals’ report how hemp was planted near the site of the Chernobyl nuclear disaster to extract radioactive elements such as chromium, lead, copper and nickel from the soil.
In the Puglia region of Italy, industrial hemp is being used to decontaminate some of the most polluted soils in Europe (BIO SPHERE project – Bio-integrated spirulina hemp remediation). The Ilva steel plant is responsible for the contamination and has been polluting the local soil for decades, poisoning local inhabitants, flora and fauna.
The role of hemp in mining land reclamation – results from a 2021 Polish study
In Poland, lignite, often referred to as brown coal, is used as an energy source and exported. For minerals such as coal, opencast mining is the most common extraction technique. This method impacts the local environment, landscape, and soil, which might need the implementation of land reclamation actions to achieve geological and hydrological stability.
For a 2021 paper by researchers from the Poznań University of Life Sciences (Uniwersytet Przyrodniczy w Poznaniu) and the Institute of Natural Fibers and Medicinal Plants (Intytut Włókien Naturalnych i Roślin Zielarskich), field experiments were conducted on seven-point-five acres in the former lignite mining area of Kazimierz Biskupin, Poland, between 2014 and 2018.
The goal of this study was to examine the feasibility and outcomes of the use of hemp in a former mining area as a tool for reclaiming soil affected by open-pit mining of lignite. The study’s results suggest that Cannabis sativa L. can be beneficial for the large-scale reclamation of industrially degraded soils, as the amount of humus and certain macro elements increases over time in the examined soil. In 2019, wheat was planted and harvested on the reclaimed land. This demonstrates that through the use of hemp in phytoremediation, it’s possible to restore damaged lands for agricultural use in a short amount of time.
Biochar and hemp – Can hemp be coupled with other amendments in phytoremediation?
A study conducted by a team of researchers from the University of Arkansas, in the United Sates, evaluated the use of industrial hemp cultivars and biochar rates for remediating the presence of cadmium (Cd), lead (Pb), and zinc (Zn) in the former lead and zinc mining area of Tar Creek Superfund Site in Oklahoma, an example of environmental heavy metal contamination and part of the Environmental Protection Agency’s (EPA) National Priorities List (Sward et al., 2025).
As a remediation technique for contaminated soils, phytoremediation exhibits a series of limitations. There is a threshold of toxicity beyond which plants are unable to grow and prosper. In addition, the extent of the pollutant uptake into plant tissues remains somewhat modest, necessitating further intervention following the stabilization and removal processes. To mitigate limitations in plant growth and enhance the effectiveness of phytoremediation initiatives, people have been applying soil amendments, such as biochar, to these contaminated soils.
Biochar is a charcoal-like black carbon produced from biomass sources, including animal wastes and plant residues. This material is manufactured via pyrolysis, a process where an organic matter is heated in the absence of oxygen.
Biochar is used to improve the conditions of degraded soils, as the carbonaceous product enhances the soil’s biological, chemical, and physical characteristics, favoring plant growth (Yamato et al., 2006).
A series of studies have analyzed the results of using biochar to alter the availability of heavy metals in contaminated soils. The scientists behind this recent study have explored the possibility of combining phytoremediation with industrial hemp and biochar as a cost-effective strategy to remediate the heavy-metal-contaminated soil of the Tar Creek Superfund site. In this area, applying traditional remediation procedures would cost an estimated $167 million.
Harnessing the full potential of hemp in phytoremediation through the addition of biochar
For this study, published this March in the open access scientific journal ‘Soil Systems’, the researchers collected buckets of heavy-metal-contaminated soil from the Tar Creek Superfund Site. They conducted a heavy metal concentration exam on the soil, which they then classified based on the results. Next, the same soil was sieved, air-dried, and homogenized. The researchers then measured the soil pH, electrical conductivity, and the levels of soil organic matter (SOM) and heavy metals.
The study was meant to analyze the effects of four biochar rates and two hemp cultivars on three levels of soil contamination. For 90 days, the hemp plants were grown in the contaminated soil. After this period, the scientists collected the plants’ aboveground and belowground tissues as well as root samples.
The study’s results showed that higher concentrations and uptakes of these heavy metals were observed in medium and high-contaminated soils compared to low-contaminated soils. These findings confirmed the initial hypothesis regarding the impact of contamination levels on heavy metal absorption.
The two cultivars, ‘Carmagnola’ and ‘Jinma’, showed no significant differences in their absorption abilities. Further analysis showed that although the total plant Zn uptake varied with different biochar rates in high-contaminated soils, the Cd and Pb uptakes remained unchanged by the biochar amendments or hemp cultivar. These results suggest that biochar enhances Zn uptake in severely contaminated soils but does not influence Cd or Pb uptake in less contaminated environments. The research demonstrates the potential of employing industrial hemp and other plant species in phytoremediation.
University of Arkansas
The University of Arkansas is a public American university in located in Fayetteville, United States. Founded in 1871, it’s the first public university in its state.
Roberta Fabbrocino
