Like many cities, Dublin has an inglorious past when it comes to its sewage. For decades about 300,000 tonnes of sewage sludge a year was loaded on to a ship and dumped in the sea somewhere beyond the Nose of Howth.
So, when details emerged of a new waste-water treatment plant for the city at Ringsend, there was a sense of relief. A new way had been found to dispose of the sludge coming from the capital's toilets. It was to be heat-treated, converted into organic fertiliser - 12,000 tonnes of it a year - and added to farmland, though forestry was initially envisaged. Dubliners would be breaking down the urban/rural divide every time they flushed the toilet.
Since then much has changed. Various forms of animal feed were implicated in health scares. Last August, as the EU was contending with fallout over dioxins in foods (with animal feed again implicated), the French government admitted untreated sewage, septic tank residues and effluent from animal carcasses were used in producing its animal feed. It later said it was a "temporary malfunction".
Then the Dutch health ministry discovered human sewage was being added to animal feed in the Netherlands. One company had connected its toilets to the feed production system.
Many abattoirs throughout Europe, it also emerged, steamhose waste and animal faeces from killing-room floors, which they later use as feed, with or without treatment. It is not surprising, therefore, that how we use human/animal waste - a valuable source of nitrogen and phosphorus - for agriculture has come close to the top of the EU public health agenda.
The application of by-products of human sludge generated by a "state-of-the-art" plant to land on 200 tillage farms, mainly in south Leinster, is clearly an entirely different process from those questionable feed manufacturing practices. That said, it is just one step removed from the food chain.
The acting assistant Dublin city manager, Mr Matt Twomey, said the conversion of sludge would be so extensive there would be no risk to health or the environment. "It is not going to be used for animal feed. That is where problems arose in the past. There are very strict guidelines compared to the way farmers use slurry. This is going to be far, far superior."
The material would be dried, disinfected and ground into granules. As for moves by some countries to stop disposing of human waste on land, Mr Twomey said much depended on the land used and the "quality of product being applied". In Dublin there would be no end-products of heavy industry or "oral contaminants".
As disposal at sea is now prohibited, General Utilities, a water company with disposal experience, has an interim contract to remove the sludge. A contract for the new plant is about to be agreed with International ABA, a consortium of Ascon Ltd, Black and Veatch (UK) and Anglian Water. They will be responsible for sludge disposal.
A particular difficulty arises under such an arrangement, according to the Dublin MEP, Ms Patricia McKenna, because of a failure to separate domestic and industrial sewage which gives rise to heavy metals. This could lead to problems with disposal on tillage land as heavy metals could eventually end up in the food chain.
An EU directive requires monitoring of heavy metals in such instances, so disposal within the limits would not be so bad, she said. "But given the track record of local authorities, this has to be of concern."
According to the Food Safety Authority of Ireland chief executive, Dr Patrick Wall, human manure can be used as organic fertiliser without risks, if properly treated. Raw sewage disposal on land could be a serious pollution/health risk, but applying treated waste (which is "almost sterile"), underpinned by strict protocols - especially on how and when it was administered - should not be of concern.
Dr Wall, however, believed the most appropriate way of adding such wastes to land was to inject them into the soil, rather than spraying or spreading them on soil or applying them directly to crops. The corporation justifies spreading sewage compost on soil like a standard fertiliser on the basis of the level of treatment. It will undergo "class A" treatment set by US Food and Drug Administration standards, which are not adopted anywhere in Europe, said its project manager, Mr Battie White.
EU worries, he added, had to be put in the context of the UK, Germany and France, for example, spreading 40 per cent of human sludge on agricultural land, in most cases not treated to the extent planned for Dublin.