Hemp is environmentally friendly in a number of well-known ways. It’s a regenerative food source. It can be used to make more sustainable fabrics, paper and building materials. Some industrious engineers are even using hemp to create “hempcrete” blocks to replace concrete. But for some time, scientists have also been investigating hemp’s powerful ability to clean up contaminated soil and make it healthy again.
It’s been common practice for centuries throughout the world for farmers to rotate their crops from field to field to allow the soil to replenish the nutrients needed to sustain future crops. But as industrial farming took over, farmers began planting the same crops in the same fields, over and over, until the soil would eventually become infertile. Now farmers everywhere are looking for ways to revitalize their soil, and hemp can play a big part.
Hemp can help refresh depleted soil by restoring stability and nutrients to the area. Hemp’s roots grow deep very quickly, holding soil together and protecting the area from erosion. When the plant is harvested, it also leaves behind large amounts of biomass that can be left to decompose and enrich the soil once again.
But what’s even more incredible is its purported ability to absorb heavy metals left over from environmental disasters—occurrences that are supposed to leave soil barren and useless.
Cannabis and hemp advocates have long told anecdotes about the plant being used to help mitigate the damage left in the wake of the devastating Chernobyl nuclear disaster. It turns out that the stories were true. In the 1990s a team of Russian scientists led by Ilya Raskin planted hemp in the contaminated fields near the Chernobyl site. The team wanted to test hemp’s ability to draw heavy metals out of the ground in a process that Raskin called “phytoremediation.” The team was reportedly successful and found that the hemp plants were able to clean the contaminated soil.
Traditional methods for soil remediation include physical and chemical methods that are expensive and harmful to the environment. But for the most part, scientists have been unable to form biological answers for the problem that can scale to the necessary degree.
In 2001 German scientists reproduced the experiment, planting hemp on a plot of land that had been contaminated by sewage. According to the team, they were able to remove lead, cadmium and nickel from the ground.
Research Backed Up
Until recently the federal ban on cannabis prevented researchers from studying phytoremediation through hemp. But ever since the 2018 Farm Bill was signed in to law, interest has once again been piqued. The U.S. Environmental Protection Agency has estimated that the cost of using phytoremediation to remove hazardous heavy metals from soil ranges from 20 to 50 percent of the cost of technologies currently in use.
We recently spoke to Doug Fine, New Mexico hemp farmer and author of Hemp Bound, about the possibility that hemp cultivation could regenerate soil. “I can vouch that hemp has phytoremediative—soil-building—qualities for a personal reason,” said Fine. “I’m very excited that my own hemp variety has been used successfully in an early phase university study.”
As Fine chronicles on his website: “I received word that researcher Hanah Rheay at New Mexico State University (under the guidance of Professors April Ulery and Catherine Brewer) is reporting in her American Society For Horticultural Science conference presentation on August 10  that she is seeing initial success in uranium uptake from contaminated mining soil planted with a hemp variety that I’ve been developing for five seasons.”
According to Rheay’s presentation, Fine’s hemp was able to transfer uranium and radium from tainted soil into the plant. “As a phytoremediator, hemp is capable of translocating numerous heavy metals and even radionuclides into plant tissues from the soil,” said Rheay.
Now a landmark study in South Africa is putting the theory to the test by planting hemp in areas of the country that have been devastated by unethical mining practices. According to Hemp Today, Tiago Campbell, a master’s degree candidate in environmental science at the University of the Witwatersrand, is attempting to remediate polluted lands within the Witwatersrand Basin, one of the world’s largest gold deposits. According to South Africa’s Federation for a Sustainable Environment, there are at least 380 abandoned mines in the area containing “elevated levels of toxic and radioactive metals” including arsenic, cadmium, cobalt, copper, zinc and uranium.
Campbell has been comparing the phytoremediation abilities of hemp to other plants and says hemp is a “heavy metal hyper-accumulator” compared to Indian mustard, water hyacinth, alfalfa and sunflower. Hemp’s ability to grow in contaminated soil with little to no negative effects on the plant is also being tested by Campbell. He reports that nearly 1,000 cannabis plants appeared to grow normally in lab tests using the polluted soil.
Campbell told reporters that he believes that hemp could simultaneously repair damage to the soil, make the area inhabitable for humans again and bring economic gains for local residents.
The hemp that Campbell is harvesting from the experiment will not be safe for use in foods or other health products meant for human use, but it should be safe for construction uses.
The current studies swirling around the topic are revealing absolutely fascinating results, and they could hold the key to revitalizing farmland ravaged by decades of pollution. There are still some downsides to consider—like the drain on certain nutrients that hemp is responsible for or the large amounts of water needed to produce the plant—but compared to the upsides, they might be worth the opportunity cost.