Each year, more than 750,000 tonnes of toxic landfill liquid are combined with sewage at treatment plants and spread on farmland across England.
The substance, known as leachate, drains through landfill waste and carries a dangerous mix of chemicals, many of which are hazardous to health and the environment.
Across the country, hundreds of landfills generate around 3.5 million tonnes of leachate annually. Much of this liquid is transported to sewage treatment works where it is mixed with domestic waste and industrial effluent to create sludge, often referred to as biosolids. This sludge is then sold to farmers as fertiliser, while treated liquid is discharged into rivers and seas. However, many harmful chemicals escape treatment and end up polluting waterways or accumulating in soils.
Leachate often contains toxic substances such as PFAS, also known as forever chemicals, alongside PCBs, dioxins, flame retardants, solvents, endocrine disruptors, microplastics and other hazardous pollutants. Many sewage plants are not designed to treat such complex waste, increasing the risk of harmful substances passing straight through the system. Experts warn that these chemicals can disrupt treatment processes, reduce efficiency and eventually contaminate food supplies through crops grown on affected land.
Analysis shows that of the 750,000 tonnes of leachate mixed with sewage, more than half receives only basic biological treatment, which fails to remove most dangerous substances. This not only adds strain to already overburdened treatment works but also contributes to untreated sewage being discharged into rivers and seas.
Campaigners argue that many of the chemicals in landfill leachate were buried to keep them out of the wider environment, yet are now being reintroduced into soils and food production through fertiliser use. The testing regime for sludge remains outdated, focusing only on heavy metals under regulations set in 1989, leaving many modern pollutants unregulated.
The practice is entrenched because sewage plants provide the cheapest disposal option for landfill operators. Water companies profit by charging to accept leachate and then selling the resulting sludge, while farmers use it as a low-cost fertiliser. This cycle has created long-term dependency, with experts warning that abruptly halting the practice would overwhelm the limited number of specialist treatment facilities.
The scale of the issue varies across regions, with landfills in the south-west producing over 1.2 million tonnes of leachate, followed by the north-west at 719,000 tonnes and the south-east at 500,000 tonnes. Major water companies including Severn Trent, United Utilities and Wessex Water handle the largest volumes.
Environmental groups argue that the situation represents a hidden crisis, with toxic liquids leaking from old and active landfill sites and re-entering the ecosystem through agriculture and waterways. They are calling for urgent government action, including stricter regulation, better monitoring, investment in modern treatment technology and a national strategy to tackle forever chemicals and other hazardous pollutants.
Experts also warn that many historic landfill sites continue to generate leachate for decades, with insufficient funds set aside for long-term management. If disposal costs rise, some sites may be abandoned, leaving no responsible party to address future contamination risks.
The issue highlights a major gap in England’s waste management system, where dangerous substances buried in landfills are now re-emerging into rivers, soils and the food chain. Without urgent reforms and stricter controls, the toxic legacy of landfill waste threatens to remain an escalating environmental and public health challenge.
