No, manure need not smell
The more farm animal, the more manure. The more manure, the more smell. Not necessarily, the Finns have found a way of taking the smell out of the smelly stuff.
The path-breaking innovation by Professor Erkki Aura is a new kind of biological-chemical slurry treatment system. It is being prepared for market launch in a development project run by MTT Agrifood Research Finland. First farm-scale pilot installations are on stream and commercial products are expected to be on the market within a few years.Markku Järvenpää, Programme Director at MTT, says that the volume of slurry generated in cow and pig farming is usually too large for the fields available, and even if there is a sufficient area of fields, the transport costs of and emissions from the slurryquickly become a problem. The nutrient content of the slurry is too high, and the surrounds of large pig farms are not for people with sensitive noses.
“The environmental authorities look very closely at slurry processing when they grant environmental permits. The lack of processing technology has conspicuously hampered investment,” says Järvenpää.
Phosphorus and nitrogen are the main problems on the nutrient front, says Anni Kokkonen, an MTT researcher. Phosphorus content is too high to enable all slurry to be spread on the fields. Also, plants cannot utilize the organic nitrogen in the manure, which then accumulates in the soil and is
released in an uncontrolled manner.
Microbes and enzymes at work
The structure of manure slurry makes it difficult to break it down by traditional methods. The new processing method, which is being currently being patented, turns the trick by means of several consequent processes that can be implemented as separate projects.
The process is based on aerated biological treatment using soil microbes. The microbes and the enzymes they produce eliminate the smell and convert the organic molecules in the manure into such a form that they can be precipitated and separated. After the biological stage, most of the phosphorus in the manure can be chemically separated and used later as fertilizer.
The pH value of the remaining slurry is raised, making the mixture a strong base, after which the nitrogen is extracted. The solids in the slurry are then precipitated chemically, leaving water which complies with the requirements for wastewater. The volume of the humus extracted in the process for spreading into the fields is only a fraction of the original volume of the slurry.
All this adds up to an enormous improvement. The smell is gone, the nutrients are recovered for useful employment, and water is cleaned. A Finnish innovation to note.
By Jussi-Pekka Aukia
Illustration Kalle Talonen
