With the increasing industrialization of agriculture and the trend towards ”clusters” of animal production in many countries, the animal density and the need to recycle nutrients in the slurry, has become a problem to the surrounding environment in many areas. Since 1980, a number of regulations in different countries have reduced the use of commercial fertilizer and focus has been on a more efficient way of utilizing the fertilizer value in slurry
However, none of these regulations has addressed the problem with airborne ammonia emission and its consequences to nitrogen sensitive nature areas as well as deposits into the waterways and following growth of algae.In Denmark, the latest legislation regulation in 2010 on the use of fertilizer, has for the first time introduced regulation on ammonia emissions from slurry. The legislation makes injection of slurry into grasslands and black soil mandatory from 2011 as well as ammonia emission in nitrogen sensitive areas (34% of agricultural area) must be reduced with 30%.
As the injection technique has a number of serious drawbacks, BioCover A/S set out to develop a system to reduce the emissions from slurry without the need to inject the slurry. The SyreN system uses a known technique – lowering the pH of the slurry, known as acidification – to stop the emission. The SyreN system uses concentrated sulphuric acid to lower the pH of the slurry during application. In addition, different additives can be added to the slurry. Especially iron sulfate is used to reduce the odor from slurry. In addition, the slurry can be “boosted” with the use of N 32, or micro nutrients such as manganese, boron or selenium can be added where needed. The background of the system is thus environmental concerns, but the trial results from lots of test has revealed that the amount of nitrogen from the ammonia to be captured, in combination with a unique way of applying needed sulphur as a fertilizer, is very profitable and because of this, a system that will find its use with application of all slurry regardless of environmental concerns or not.
SyreN - system
Ammonia (gas) and ammonium (salt) are in a chemical equilibrium when dissolved in a liquid as slurry. By lowering the pH value, the equilibrium is displaced and a larger part of the ammonia is to be found as ammonium that cannot evaporate from the slurry. The SyreN system automatically defines and lowers the pH
of the slurry. It uses sulphuric acid to lower the pH, as this is 100% environmentally balanced product and the most concentrated and effective acid to lower the pH. The ammonia is thus transformed to ammonium and readily available to the plants after application, when the slurry penetrates into the soil. Ammonia is the optimal
N fertilizer available to plants and has a minimal loss to the environment as it has a positive charge and does leach out.
Ammonia emission has a very dynamic and variable nature. The amount of ammonia in the slurry will always be variable depending on animals, feeding etc. and the emission depending on the weather conditions on the day of the application, but the reduction in % is depending on the pH of the slurry. A series of emission trails carried out by Aarhus University in 2010, has documented a 50% reduction of ammonia emission in cow slurry, and the SyreN system has been certified by the Danish environmental authorities through an international recognized protocol known as VERA.