Sludge ticks the green box

FARMERS HAVE been urged not to turn their backs on the “considerable benefits” biosolids could bring soils.

The call follows a recent FWi survey which revealed 73% of respondents would not consider making applications of treated sewage sludge.

But there is a considerable wealth of research that shows they can build structure and organic matter and provide a sustainable source of nutrients, pointed out Tim Evans from the Sustainable Organic Resources Partnership.

“There have been 50,000 scientific papers on biosolids – it‘s recognised as the most researched agricultural input,” said Dr Evans.

Although most of these have addressed safety concerns, such as heavy metal content, work carried out by ADAS Gleadthorpe, for example, shows they improve soil structure.

“Applications of treated sludge increase the available water capacity of soils,” said Dr Evans.

“That will become increasingly important as we get a greater frequency of droughty summers.

“There is also evidence to show it acts as a good gradual release nitrate and phosphate source, which is also important as farmers come under fire for nutrient leaching.”

He said there was “no technical reason” why distillers or any other grain end user should have concerns over the use of biosolids in agriculture.

“People who put up arguments against biosolids on the basis that there may be a food scare are working against the fundamentals of sustainable development.

“Distillers produce their own waste that is recycled back into agriculture, after all.”

Treated sewage sludge may suffer from an image problem that relates to its use 30-40 years ago when regulations were not as tight as they are now, he suggested.

“Those farmers who wouldn‘t consider using it may be unaware of the huge improvements in treatment processes that have made fantastic changes in its chemical quality.”

Exhaustive EU-funded research has concluded treated sludge poses no risk of harmful build-up of heavy metals, such as Cadmium, he added.

But recent research has also shown that the Cadmium phosphate ratio in standard compound fertiliser is similar to that found in biosolids.

“It‘s critical we encourage as many people as possible to buy into sustainable development, especially as concern grows over the degradation of the UK‘s soils,” said Dr Evans.