For decades, sewage sludge has been quietly spread across Britain’s farmland, marketed as a nutrient-rich fertiliser. But insiders and scientists warn that hidden within it is a mix of household and industrial chemicals such as Pfas (“forever chemicals”), pharmaceuticals, pesticides, hormone-damaging chemicals and microplastics, threatening the long-term health of the land.
Every year, 768,000 tonnes of this byproduct of wastewater treatment is spread over 150,000 hectares of agricultural land in England. The practice is banned in some countries, such as Switzerland, but in the UK it continues with little scrutiny and has become a covert route for dumping toxic industrial waste, experts say.
“It’s a Trojan horse,” said a water sector insider. “Pfas, pharmaceuticals, endocrine disruptors and microplastics hidden in sludge threaten the long-term sustainability of humanity’s farmland.” These pollutants are not tested for under current regulations, which only require screening for a handful of heavy metals.
Spreading sludge is incentivised because it is the cheapest disposal method. “It would cost water companies a lot to get rid of it themselves,” said an Environment Agency (EA) officer, who asked to remain anonymous. “So they’re happy to give it to farmers cheaply or for free.”
For farmers, rising fertiliser costs make it appear a win-win. “It’s a closed loop where everyone absolves themselves of costs,” the officer said.
Industries also benefit by sending liquid waste to wastewater plants, which is cheaper than incineration or other methods.
“Some water companies have made big business decisions around taking industrial wastewater and getting paid for it,” said a second EA insider. Both sources are concerned about using sewage works to dispose of hazardous waste – especially landfill leachate, which is often added to systems unequipped to treat it.
“As soon as you let industrial waste into your sewer network, your sewage becomes hazardous waste,” said the first EA officer. “Masking it as sludge and calling it fertiliser is a problem.”
The result is a system that financially benefits water companies, farmers and industry – but not the public or the environment.
“If it’s seen to be given away it could be viewed as a waste, and they absolutely abhor the waste label,” said the second EA source. “The water companies say they can make a profit from it but they are very reluctant to give us any hard data – they claim commercial confidentiality.”
Dr David Tompkins, a soil and waste expert at the consultancy WSP, said: “It’s what’s in it – and what we don’t remove – that’s the problem. We’re dealing with Pfas, microplastics, flame retardants and other hazards.”
Regulations set in 1989 are no longer fit for purpose, the second EA source said. “Metal levels have dropped, so the system says ‘great, we’re fine’ – but everything else is ignored.”
Oversight is weak, they said. “We won’t know when or how much sludge is going to be spread. Records are kept by the water industry, and they like it that way.”
“Digesters are continuous systems and are designed to remove pathogens, not these chemicals,” said a water expert. Even then, “new sludge mixes with old, and some is removed before it’s fully digested”, they said. “A portion of what goes to land is not properly treated.”
Scientists suspect these contaminants are entering the food chain. “We’ve seen Pfas and pharmaceuticals accumulate in crops and livestock,” said the expert. But there is no requirement to test food for these substances and therefore little data on it.
The EA has long known sludge contains pollutants. A 2017 internal report warned of physical contaminants “potentially resulting in soils becoming unsuitable for agriculture”. That information was not shared with farmers.
“Quite the opposite,” said Georgia Elliott-Smith of the campaign group Fighting Dirty. “In 2022, farmers were incentivised by Defra to spread sewage sludge as part of the sustainable farming initiative.” Defra says it encouraged organic matter use generally, without specifying sludge.
“At a time when British farming is on its knees,” Elliott-Smith added, “the government has again prioritised corporate interests. Farmers now face a hopeless choice: cheap but toxic sludge, or costly agrochemicals.”
In Germany, Belgium and the Netherlands, sludge spreading on farmland has been reduced or banned. Switzerland incinerates all its sludge and stores the ash for phosphorus recovery. Tompkins noted: “They know it’s expensive. But they’ve decided it’s necessary.”
In the UK, political will is lacking. “It’s regulation by inertia,” Tompkins added. “The Environment Agency is working within tight budgets that can limit its monitoring capacity.”
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Richard Benwell, the CEO of Wildlife and Countryside Link, said: “Other countries are paying attention, with bans in some US states on Pfas-polluted sludge, as well as in several European countries. It’s time for the UK government to set tough standards to stop this chemical pollutant ending up on farms, along with action to cut down on these harmful chemicals at their source.”
For Tompkins, “we need to price food and water properly. Regulations tend toward the minimum baseline. If we want better, we’ll have to pay for it. Sludge has value but the way we manage it destroys that value.”
Critics also point to the voluntary “safe sludge matrix”, a guide developed by industry and consultants, as a fig leaf. “There is nothing safe about the safe sludge matrix,” said one industry expert.
“It’s a PR exercise,” said the second EA insider. “It was designed to protect [water companies’] access to the land bank. They don’t want retailers or farmers losing confidence in spreading.”
The consultants ADAS were involved in the creation of the matrix. A spokesperson said it was introduced to address food safety and human health risks from microbial pathogens after a year of intensive consultations. The agreement was made between Water UK and the British Retail Consortium, and included inputs from a range of interested parties including the EA, the Ministry of Agriculture, Fisheries and Food, as well as the National Farmers’ Union, Country Land and Business Association, food manufacturers and food processors, it said.
Martin Lines, the CEO of the Nature Friendly Farming Network, said: “Farmers want to protect their soils and grow safe food, but they’re being put in a tough position. Sewage sludge is being spread with little testing or transparency. Contaminants like Pfas and microplastics shouldn’t be anywhere near farmland. Without proper regulation, this isn’t a circular economy – it’s a failure of oversight.”
A long-promised regulatory overhaul through environmental permitting regulations was due in 2023, but the deadline passed with no new date in sight.
Experts say a better system would start upstream, controlling what enters treatment plants. New EU rules will require pharmaceutical and personal care product makers to pay 80% of waste treatment costs, but the UK has no such mechanism.
“We’re not in control of the life cycle of the molecules we create,” said a water expert. “They go out into the biosphere and build up. All these substances are accumulating.”
Some argue the legal tools already exist. According to Tompkins, “there’s a clause that could be interpreted to say ‘anything hazardous’ should be checked. So if we wanted to look for all these other things, we could.”
Ultimately, said the first EA source, “once you let industrial waste into your works, what comes out isn’t sewage sludge. It’s hazardous waste.”
Water UK said spreading bioresources was a longstanding, regulated practice that helps farmers and reduces reliance on chemical fertilisers. While some contain Pfas or microplastics, it said, legal standards and test methods were lacking and had to be set by government. It said water companies were supporting research and trialling uses like biofuels.
The Environment Agency said sludge must not harm soil or water and that it enforced strict rules, with thousands of farm inspections each year. Defra said it wanted sludge to be used safely and sustainably and had launched an independent water commission to review the rules.