Hemp as a water filter – a sustainable solution for clean water

Clean water is one of the most important resources of our time – and at the same time, it is increasingly under threat worldwide. Heavy metals such as copper, lead and zinc find their way into our rivers and groundwater through industry, agriculture and sewage.

The consequences are not only ecological damage, but also health risks for humans and animals. Efficient, cost-effective and environmentally friendly methods are needed to reduce these pollutants. One exciting approach is hemp.

Hemp as a biosorbent

Scientists have investigated how hemp can be used in water treatment. The key lies in what is known as biosorption: certain functional groups in hemp fibre – such as hydroxyl, carboxyl or phenol groups – bind heavy metals and organic pollutants directly to the surface. Hemp thus acts like a natural sponge, drawing metals out of the water.

Laboratory experiments have shown that hemp biosorbents extracted from the stems can absorb copper ions with a capacity of up to around 87–90 mg per gram of material. These values are within the same range as conventional filter materials, but are significantly cheaper and more resource-efficient to produce.

Forms and applications

Hemp can be used in various forms: as powder, granules, fibres or even felt. Each variant has its strengths. Fibres and felts, for example, are flexible and can be easily integrated into filter systems. Granules, on the other hand, have a particularly large surface area, which enables a high absorption capacity.

Research groups in Europe have also shown that hemp felts are capable of binding not only copper, but also a whole range of other metals such as lead, cadmium and zinc. Hemp often achieves a similarly high or even better performance than conventional materials such as activated carbon – at lower cost and with significantly less environmental impact.

Advantages over conventional methods

Many methods used today to remove heavy metals – such as ion exchange resins, membrane filtration or chemical precipitation – are expensive, energy-intensive and generate secondary waste. Hemp, on the other hand, grows quickly, requires hardly any pesticides, binds CO₂ during its growth and can be easily disposed of or even incinerated after use in the filter to recover the bound metals.

It is also particularly interesting that parts of the hemp plant are by-products of fibre or seed production. Those parts such as shives or dust, which have been of little use until now, could play an important role in water treatment in the future – and thus open up an additional source of income for farmers.

Outlook

The use of hemp as a water filter is still mainly at the laboratory and pilot stage. However, the results are promising. In future, hemp could help to purify wastewater from industrial plants, remove pollutants from rivers and lakes, or even be used in smaller, decentralised filter systems – for example, in rural communities.

Hemp is thus proving once again that it is much more than just a plant for textiles or food. It is a true all-rounder that can play an important role not only in agriculture and industry, but also in environmental protection.