Dealing with odours generated by industry or wastewater plants is a demanding business. The more troublesome pollutants occur in very small concentrations - parts per million in thousands of litres of air - and their regulation is ever tightening.
That includes volatile organic compounds (VOCs), which readily convert to gas, and are more and more the focus of rigorous environmental legislation.
It might not appear to be glamorous, but according to Mr Ian Phillips, project manager of Bord na Mona Environmental, the odour abatement industry is a high-tech one. Looking at its Monashell technology, it is hard to disagree. Its essence is in the role played by bacteria living on the mussel shell which consume sulphur compounds that cause odour problems. Moreover, the bacteria are capable of dealing with high concentrations of such compounds.
The Monashell process, for which his company holds the worldwide patent, is a combination of "some very clever chemistry, some very basic chemistry, some smart engineering, some advanced biology and seashells". It was developed by Bord na Mona Environmental's Clean Air Business Unit, which has established a global presence in the production of the relatively cheap, biologically-based treatment of air pollutant, as opposed to more costly and complex processes.
The system deals with sulphur compounds, notably hydrogen sulphide and mercaptan (which skunks rely on for their lack of popularity), which are produced during waste-water treatment, some foodprocessing, meat-rendering or production of pharmaceuticals. Living beside such facilities has frequently been a very unpleasant experience.
The air stream to be cleaned passes over millions of microbes immobilised (in effect, stuck) on the shells. They are usually bacteria with an ability to digest sulphur compounds and convert them to sulphuric acid. The acid is deposited in a liquid surrounding them but they do not operate well in acidic conditions.
Dealing with this problem is the basic chemistry bit. The sulphuric acid binds with calcium carbonate in the shells to produce a harmless salt; gypsum, water and carbon dioxide. The most complex part was the creation of a mechanism to immobilise the microbes on the shells, and yet keep them alive during operation and when the system is shut down. Exactly how this is done is clothed in the secrecy of the patent.
The bacteria are usually from colonies that grow happily in volcanic areas, though in some cases they come from a variety of sources, and a cocktail is added to the shells, which are a by-product of mussel farming. The latter approach is now being used for treating VOCs, with which Monashell is showing impressive results.
Mr Phillips said the beauty of the system is that it is "very close to perfect", with at least 97 per cent gas removal. It also entails low maintenance, though the shells have to be changed every two years. The technology has been successfully introduced to some 15 industrial plants and waste-water treatment units in the Republic, and more than 70 facilities in Britain. The European market is growing, too. Municipal authorities in Milan recently installed a system for the city's solid-waste-composting system.
It was while working on a new system in Britain some years ago that the potential of mussel shells emerged. In the past, peat filtration system were deployed, but there were problems with maintaining the right acidity (pH) level. In a hit-or-miss search for a better filter, the shells were tested, in the knowledge that they were a good source of calcium carbonate for counteracting acid.
Monashell's capabilities are such that the technology is now being adapted as a treatment option for treating VOCs, with pilot tests showing impressive results. Such a system is bound to attract the interest of pharmaceutical, chemical and coating industries.
Bord na Mona has diversified a lot over the past 10 years. It continues to successfully convert peat into commercial products, but success in providing environmental solutions, such as that possible through Monashell, has added a new technological edge to its operations.