Your article (Millions of tonnes of toxic sewage sludge spread on UK farmland every year, 7 July) gives some insight into the environmental impact of the practice and the paucity of regulatory control. The legal case had been made as far back as 2015 that the spreading of sewage sludge – which the water industry prefers to call “biosolids” – should be brought under the potentially much tighter environmental permitting system that applies to the spreading of other industrial wastes applied to land for agricultural benefit. Not surprisingly, the very mention that sewage sludge be treated as a “waste” drew strong resistance from water companies that feared a collapse in the market.
However, this is only part of the story. The ban on dumping at sea, coupled with the move away from landfill, has seen a huge shift from putting waste in one place to smearing it in ever more discrete parcels over farmland and elsewhere, purportedly for ecological improvement. In additional to sewage sludge, there are construction waste soils, waste compost and anaerobic digestate, plus a range of non‑waste soil improvers deposited. Examples such as pig carcasses in compost on farmland testify to what some people will try to get away with if not properly regulated.
While there may well be good examples of using treated waste to improve soil, the cumulative environmental burden of the range of practices is largely unchecked and unknown.
John Galvin
Former policy adviser, Environment Agency and Defra
• There is a £6m research project studying the use of pyrolysis on sewage sludge that should assist in sequestering carbon in the soil and which may reduce pollutants like Pfas – so-called “forever chemicals”. The project undertaken by Thames Water, Ofwat and other collaborators aims to deliver a continuous flow system that could be widely deployed, and the research is due to complete in 2027.
If successful, this technology would allow our sewage sludge to be used as an agricultural input while meeting our wider needs to reduce pollution and climate emissions. However, we will need to further invest in our water-treatment system. Can the privatised water industry meet the challenge?
Andrew Wood
Oxford
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