Hydrogen sulphide (H2 S) is a colourless gas that is toxic to living organisms (including humans, livestock and plants). It has a characteristic odour of rotten eggs. On the farm, it can be formed by the anaerobic decomposition of proteins in closed tanks containing manure, slurry, in septic tanks, in compost piles when the composting process takes place without access to adequate air, and in poultry houses, barns or stables. The concentration of hydrogen sulphide in closed containers, such as a septic tank, can be so high that it threatens human life. Hydrogen sulphide is also a by-product of biogas production. In this case, however, it is often disposed of because it can cause adverse corrosion of the equipment in which the biogas is burned.
Ammonia (NH3 ) is a colourless poisonous gas easily recognisable by its pungent odour. As nitrogen is a component of proteins, the breakdown of these chemical compounds leads to the formation of ammonia. Virtually all ammonia emissions come from agriculture. Two main sources of ammonia can be identified on the farm: animal excreta (79%), especially if improperly managed, and improperly managed urea fertilisation (21%), up to 30% of which can be lost in this way. Particularly damaging from both the point of view of nitrogen loss and adverse ammonia emissions is poor storage and leaving fertilisers containing nitrogen in ammonia form, including organic fertilisers, on the soil surface. More on this page.
The primary document for reducing ammonia emissions and improving air quality to a level that does not cause adverse effects or risks to human health and the environment is the Directive of the European Parliament and of the Council of 14 December 2016. Poland’s obligations to reduce ammonia emissions relate to two timeframes: the first covers the period 2020-2029 and adopts a reduction limit of 1% per year, and the second will start in 2030 and assumes a 17% reduction in ammonia emissions per year.
Reducing the release of ammonia in livestock production can be achieved by:
- a change in the animals’ feeding regime (balanced rations, use of high-quality feeds);
- changing the way animals are kept;
- creating conditions that limit chemical reactions during storage of animal manures;
- the use of livestock manure in a manner that reduces nitrogen losses.
By 2030, it is planned to promote the following changes in fertiliser application technology considered as sources of ammonia emissions:
- the subsoil application of urea-based fertilisers;
- spreading slurry by methods other than splashing;
- ploughing in manure within 12 hours of spreading on the field.
Both gases, hydrogen sulphide and ammonia, are poisonous to humans and animals. As both gases are formed, among other things, in premises where animal production is carried out, these buildings must be equipped with an efficient ventilation system including an air purification system. In older buildings, systematic ventilation by opening windows or doors is necessary.
On fruit-focused farms with cold stores or freezers, there can be a significant risk of ammonia poisoning – this gas is used as a refrigerant. A leak in the system can cause a risk to the life and health of both those working on such a farm and neighbours.
Carbon dioxide (CO2 ) is a colourless and odourless gas that is a natural component of the air. The concentration of carbon dioxide in the atmosphere has been increasing significantly in recent decades, and since the late 1990s the concentration of CO2 in the Earth’s atmosphere has increased by almost 25%.
Carbon dioxide is produced during the combustion of both solid and liquid fuels as well as plant, animal and waste residues. It is also a natural product of the respiration of living organisms, bacteria, plants, humans and animals. It is formed during composting as well as in decay processes. In addition, it is secreted by plants when they have no access to light.
Sulphur dioxide (SO2 ) is a colourless gas with a pungent and suffocating odour. In higher concentrations it is a strong irritant and even poisonous. Due to its bactericidal and fungicidal properties, it is used as a food preservative. It is formed, among other things, by the decomposition reaction of non-volatile sulphuric acid salts (sulphites). The negative effects of SO2 in the atmosphere are manifested not so much in the greenhouse effect as in the formation of so-called acid rain. Acid rain is detrimental to both the plants themselves and the soil. On the farm, sulphur dioxide is mainly produced during the combustion of solid fuels – there is a relatively high amount of sulphur in coal, liquid fuels and any waste.
Methane (CH4 ) is a colourless and odourless gas. It is widely used for heating as it is the main component of gaseous fuels, i.e. natural gas and biogas. Methane is a gas whose greenhouse potential is more than 23 times that of carbon dioxide. Hence, despite its lower concentration, its aggregate environmental impact is significant.
In nature, apart from methane extracted as fuel and methane associated with coal seams, it is formed during the anaerobic decomposition of plant remains. In practice, anaerobic conditions are created when the soil is completely flooded with water, which is why methane formation processes can be observed in swampy areas, where so-called “mud gas” is produced. In agricultural activities, methane gas is also generated by fermentation processes in the digestive system of livestock, ruminants (e.g. cattle, goats and sheep).
Nitrous oxide (N2 O) is a colourless gas with a faint sweetish odour. The effects of nitrous oxide in the atmosphere are doubly detrimental. Its greenhouse potential is 298 times greater than that of carbon dioxide, and on top of that the gas damages the ozone layer that protects life on Earth from cosmic radiation. The main source of nitrous oxide is processes in soils, especially those fertilised with nitrogenous fertilisers. In the so-called nitrification and denitrification processes, soil bacteria produce N2 O, which is released into the atmosphere. The second major source of emissions is the combustion of fossil fuels and biomass.
Nitrogen oxides (NOx ) – is the common name for the entire group of nitrogen and oxygen compounds. Their harmful effect on the environment consists mainly in combining with water and, as a consequence, in the formation of so-called acid rain, as in the case of sulphur dioxide. The main sources of nitrogen oxides are the combustion of fossils and biomass. Nitrogen oxides also result from the oxidation in the atmosphere of ammonia, which is mainly formed during human agricultural activities. It is worth considering how the quantities of gases produced on the farm can be determined. Possible direct measurement of emissions only makes sense if the emission source is a point source. Such point sources of emissions are e.g. cookers, livestock buildings or storage places for e.g. compost, manure, slurry, dung etc., but even then measurement may be difficult. For example, the measurement of emitted gases from piggeries, barns, stables or other buildings can be carried out relatively easily as long as all the air leaving the building is concentrated in the designed ventilation outlets. It is much more difficult to measure if the rooms are ventilated, e.g. by opening windows. Measurement from diffuse sources – e.g. from a field – is very difficult, so the emissions of individual gases can be determined on the basis of continuously developed calculators available e.g. on the Internet or based on publications in professional publications. When using such sources, however, it is worth bearing in mind that they are based on certain assumptions and estimates, which allow an order of magnitude to be determined, but not the exact emissions from a specific farm.