Blog Risk Of Sludge 1
08 May 2024 Type: Blog

Understanding the Risks of Sludge in Agricultural Applications

Sludge has found its way into agricultural practices as a fertiliser and soil amendment, and while this may seem like a sustainable solution for waste management, the reality is far more complex. The use of sludge in agriculture poses significant risks to both human health and the environment, raising important questions about the long-term sustainability of such practices.

What is sludge?

Sludge is a byproduct of wastewater treatment processes, composed of organic and inorganic materials, as well as pathogens, microplastics, forever chemicals, and other toxins. While treated sludge, also known as biosolids, may undergo processing to remove some of these contaminants, it still carries a substantial environmental burden.

The risks to human health

One of the primary concerns surrounding the use of sludge in agriculture is its potential impact on human health. Despite treatment efforts, sludge can still contain harmful pathogens such as bacteria, viruses, and parasites. When applied to agricultural land, these pathogens can contaminate crops, water sources, and even the air, posing a risk of infection to farmworkers, nearby residents, and consumers.

Moreover, sludge may contain heavy metals and persistent organic pollutants, which can accumulate in soil and crops over time. Prolonged exposure to these contaminants through consumption of contaminated food or water can lead to serious health problems, including neurological disorders, cancer, and reproductive issues.

Environmental concerns

In addition to the threats to human health, the use of sludge in agriculture can have detrimental effects on the environment. Microplastics, heavy metals and other contaminants present in sludge can leach into groundwater, contaminating drinking water supplies and ecosystems. Excessive application of sludge to soil can also lead to nutrient imbalances, soil degradation, and decreased biodiversity. 

Restrictions on the use of sludge in agricultural applications

Many countries have already started restricting the use of sludge in agricultural applications due to the risk of chemical and plastic contamination in the food chain. 

  • Switzerland: The Swiss Federal Office for Agriculture (FOAG) prohibits the use of sewage sludge on agricultural land used for the production of food.

  • Sweden: The Swedish Environmental Protection Agency (EPA) has set stringent standards for the application of sewage sludge on farmland to minimise risks to human health and the environment.

  • Germany: The German Fertilizer Ordinance (DüMV) sets limits on the levels of heavy metals and other contaminants allowed in sewage sludge used as fertiliser.

  • Denmark: The Danish Environmental Protection Agency (EPA) sets limits on the levels of contaminants allowed in sewage sludge and monitors compliance with these standards.

  • Austria: The Austrian Ministry for Climate Action, Environment, Energy, Mobility, Innovation, and Technology (BMK) oversees regulations related to sewage sludge management.

  • Norway: Norway has banned the use of sewage sludge in agriculture since 1989 due to concerns about heavy metals and other pollutants.

  • Finland: Finland has strict regulations on the use of sewage sludge in agriculture, with limitations on contaminants and application rates.

The need for sustainable alternatives

Given the numerous risks associated with the use of sludge in agriculture, there is a pressing need for sustainable alternatives. Onunda’s sustainable wastewater management solution eradicates land waste, removing microplastics and hazardous chemicals from wastewater, and transforming it into a sustainable source of clean energy and nutrient-rich fertiliser. Hydrothermal carbonization uses waste heat and high pressure and temperature to convert sewage and other organic wastes into their constituent elements: carbon-rich hydrochar and nutrient-rich liquor. Onunda’s nutrient-rich by-products can then be used as an agricultural fertiliser in place of sludge as well in other industrial applications such as cement and brick production.