Phytoremediation is the technique that uses plants and microorganisms associated with them to eliminate, contain or make less toxic pollutants in water or soil. There are plants capable of accumulating and tolerating in their organs certain substances, such as heavy metals, at concentrations that would normally be harmful to other living organisms, including humans. This technique has undoubted advantages: lower costs, low environmental impact and high social acceptability, because can improve the aesthetic appearance of severely degraded environments and their overall ecological value, promoting for example the increase of biodiversity.
By the phyto-extraction the plant is able to absorb contaminants from the soil and transfer them to the stem and leaves. By collecting them, it is possible to gradually reduce the levels of pollutants,
especially after several cycles of collection repeated over the years.
Another technique is phyto-stabilization. This is a passive method, a containment strategy: the plant produces substances that immobilize (i.e. make insoluble) the pollutant in the soil, thus preventing its dispersion in the surrounding environment.
The phyto-degradation is a technique well suited to contaminants of organic origin, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and other by-products of petrochemical activity contained in the soil, often persistent and difficult to degrade. The plants are capable of directly degrading these compounds into molecules less persistent and dangerous to human health and the environment, thanks to the substances produced by their roots.
Through the process of phyto-volatilization the plant is able to absorb contaminants, transfer them to the aerial parts and eliminate them in the atmosphere through transpiration.
All of these techniques are currently being tested worldwide.
Among the most effective plants for Phytoremediation are hemp and bamboo.
Hemp is planted in March and harvested after about 6 months. A land planted with hemp does not require fertilizers and pesticides, is able to absorb pollutants from the soil and air 3 times more effectively than the same area of forest. In addition, hemp has many uses in practically every economic sector, from civil and industrial textiles to bioplastics, building materials, medicine and food.
Bamboo needs about 5 years to develop roots, but after that it has a very fast growth, becomes a weed and absorbs numerous pollutants from the soil and the air, does not require fertilizers and pesticides. Bamboo can be used as wood for construction, furniture and objects, textiles, food.