NH₃, NH₄, NO₃, SO₃… There is only so much chemistry that we can remember from school, however the chemistry that is becoming more important to understand is Ammonia (NH₃), the effects, and ways in which it can be reduced. The Clean Air Strategy has been produced by DEFRA in order for the government to regulate all sources of pollution to improve the ‘air we breathe, protect the environment and boost the economy’. For one thing, it doesn’t (entirely) blame the agricultural industry for pollution levels, as there are multiple industries that release a number of toxic gases into the atmosphere… According to Defra, agriculture is responsible for 88% of all UK ammonia emissions accounting for £138m of Nitrogen loses per year. Therefore, the government aims to reduce ammonia emissions by 8% in 2020 and 16% by 2030, which would mean a saving of £1.7 billion per year, increasing year on year.
Now, for a bit of chemistry:
What is Ammonia?
Ammonia (NH₃) is a toxic gas that is created when food containing protein is broken down in the body releasing excess Nitrogen (converted from protein) mainly through urine. Ammonia is emitted when urea (Nitrogen) in urine reacts with the urease enzyme in faeces. A cow with 100% N intake, will naturally lose 5-8% in body losses, 20-45% in urine, 25-40% in faeces and 15-30% through milk (around 1kg protein per day).
The reaction urine has with faeces increases the levels of ammonia emitted and is therefore part of major research studies being performed in the Netherlands on how to keep the two waste products separate. Other research is being undertaken as to the effects of reducing protein intakes without having a detrimental effect on yield. However, this is something for your Nutritionist to determine!
NH₃ (ammonia) and NH₄ (ammonium) at an equal level survives at certain levels of pH and temperature. When these change, the fraction of the two elements change. For example, when pH increases, NH₄ is converted into NH₃, leading to a point when NH₄ cannot exist and all ammonium (NH₄) becomes NH₃. The average pH of slurry is 7-8.5, and should high protein diets be fed, this would increase the level of ammonia and pH.
Acidification is a process used introducing small amounts of sulphuric acid to reduce the pH, so that the non-toxic liquid fraction that is Ammonium NH₄ increases within the slurry making it a more environmentally friendly and usable product. Ammonia emissions are reduced by up to 64% for pigs (50% for cattle). Due to the reduction of ammonia into the atmosphere, the Nitrogen losses are also reduced. From 100kg N produced (after losses in the shed, storage and application) non-acidified slurry contains 68kg N whereas acidified slurry contains 88kg/N (cattle) and 91kgN (pigs).
There are multiple different ways in which ammonia is released into the atmosphere, with 25% coming from manure applications, 23% fertiliser applications, 27% through livestock housing and 9% manure storage. The more the ammonia is disturbed, the more is lost. There is a huge amount of research following new regulations in Denmark and the Netherlands. Dutch farmers are having to use techniques such as rapidly incorporating manure into soils [within 12 hours] by using dribble bars and injectors. This will no doubt be one method that will be required by farmers in the UK. With 80% of N potentially lost when using a splash plate method, whereas shallow injection can reduce ammonia emissions by up to 70%. These direct methods of spreading manure will be very beneficial to the environment.
Acidification is very much a new technique in the UK, given how ammonia emissions have not been at such a forefront of new regulatory changes. Alongside that, it can be expensive having to retrofit equipment into an existing system. However, with regulations in Denmark stating that all new dairy housing must meet emission standards of 8.6kg NH₃/cow place/year, it would be feasible to expect similar regulations to make its way across the pond. According to the Clean Air Strategy, plans are to regulate ammonia emissions by requiring low emission techniques to be adopted, introduce land management systems to protect the natural habitats, and to regulate pollution from fertiliser usage. The time is clearly here to start assessing your system and what methods you can adopt to start reducing ammonia emissions.
If you would like to know more about ammonia emissions, the Clean Air Strategy or acidification, please contact Prue at firstname.lastname@example.org or your local FCG office.