Hemp for Soil Remediation and Biochar: Turning a Challenge into Opportunity
When most people think of industrial hemp, they picture sustainable building materials, textiles or bioplastics. Yet one of hemp’s most valuable qualities lies beneath the soil. Hemp is a natural phytoremediator, which means it can draw pollutants such as heavy metals, pesticides and hydrocarbons out of the ground. This ability makes it a powerful tool for restoring contaminated land across the UK, from post-industrial brownfield sites to farmland affected by legacy chemicals.
Once hemp has absorbed these contaminants, a critical question arises: what should we do with the harvested crop?
Not All Hemp is Fit for the Supply Chain
It is important to be clear that hemp grown for soil remediation should never enter the food chain. Research has consistently shown that hemp absorbs pollutants into its stems, leaves and particularly seeds. That makes it unsuitable for food, feed or personal care products.
In short, this type of hemp is not for your table, livestock or bathroom cabinet.
However, that does not mean the plant loses its value.
Biochar: A Sustainable Second Life
One of the most promising pathways for contaminated hemp is biochar.
Biochar is a stable, carbon-rich material created through pyrolysis, a high-heat, low-oxygen process. It is increasingly recognised as a sustainable tool for carbon sequestration, soil improvement and construction.
When hemp biomass is pyrolysed, the contaminants do not simply vanish. However, studies show that heavy metals tend to remain locked within the solid biochar, rather than being released into the atmosphere or other by-products. With proper oversight, this makes hemp-based biochar safe for non-agricultural applications such as:
Additives in concrete, bricks and insulation materials
Road base or landfill cover
Soil amendment for non-food vegetation and erosion control projects
This approach not only prevents contaminants from re-entering the environment but also adds real value to land restoration efforts.
What the Research Shows
Several international studies highlight hemp’s potential in this space:
Ahmad et al. (2021): Found that while hemp leaves and roots accumulate high levels of heavy metals, the stalks (especially bast fibres) showed much lower contamination, suggesting potential industrial uses.
Rees et al. (2023): Reviewed how pyrolysis can stabilise contaminants, concluding that biochar from polluted biomass is viable if leaching is properly managed.
Vithanage et al. (2017): Demonstrated that biochar can immobilise metals and act as a sorbent in soil and water remediation, though it must never be used in food systems.
A UK Opportunity
Here in the UK, large areas of land remain degraded or under-utilised because of industrial pollution and historic chemical use. Hemp could provide a cost-effective, nature-based solution for remediation while creating new circular economy opportunities. By converting contaminated hemp into biochar for construction and environmental projects, we can turn a challenge into a benefit and support the transition to a cleaner and greener future.
