A green technology is poisoning Welsh rivers despite being hailed as an environmentally friendly way of dealing with waste, campaigners have warned.
Anaerobic digesters are widely regarded as a safe and clean way to process food and farming waste, and even small quantities of sewage.
They have also been proposed as a way to reduce existing river pollution by consuming some of the vast amounts of manure produced by intensive farming, with at least one farming company making use of them in their pollution reduction plans.
However, the use of the residue the process leaves behind as a fertilizer for crops is now being blamed for poisoning many of Wales’s rivers.
Digesters have been linked to substantial river pollution because after the residue, called digestate, has been spread on fields it can be washed downhill and into rivers. The digestate contains nutrients which are good for crops but when in rivers can kill fish and other creatures, and cause algal blooms.
In 2019, digestate spread onto fields washed into the River Mole in North Devon, killing 9,000 fish.
Gail Davies-Walsh, chief executive of Afonydd Cymru (the Welsh Rivers Trust) told i: “The end product is a really, highly super-concentrated digestate and we need to understand what we should be doing with that much better.
“Right now it’s spread on the land, and many of our rivers haven’t got capacity for any more nutrients to be added to them.”
Only 45 per cent of Wales’s rivers are considered to be in good ecological status, while 60 per cent of rivers classified as Special Areas of Conservation have excess levels of phosphorus which can lead to algal blooms and deoxygenation of the water which kills plant and animal life.
While digesters should reduce the overall amount of muck spreading because they can be used to process slurry, campaigners fear that they are being used to justify the expansion of intensive agriculture resulting in, at best, continued high levels of pollution.
Afonydd Cymru and Fish Legal, a group which helps fishers to seek legal redress on pollution, have written to the Welsh ministers for climate change and for rural affairs calling for an urgent review into the regulation of digesters.
Read More: Green tech intended to fix Welsh rivers is actually poisoning them
