Greenhouse gases are those components of the Earth’s atmosphere which, due to their physicochemical properties, have the ability to retain solar energy within the Earth’s atmosphere. These primarily include water vapour, methane, nitrous oxide, carbon dioxide, ozone, freons and many others.
Some of them are natural constituents of the atmosphere that have been present in it for millions of years, in varying concentrations. Their presence in the Earth’s atmosphere is what created the climatic conditions that allowed life to originate and develop. Recently, the concentration of some of them in the air – thanks to human activity – has been gradually and alarmingly increasing. In addition, gases have appeared that are absent under natural conditions, exhibiting similar properties – Freons – that absorb radiation reaching our planet. At the same time, we are seeing an increase in the average air temperature in the lowest, near-surface layers of the atmosphere. This does not exclude localised, abnormal decreases in air temperature and other extreme cooling.
Successive years of water scarcity or excess make Polish farmers understand the financial consequences of climate change like no one else. Climate change is progressing and the coming major climate change is inevitable – how severe and damaging it will be remains to be seen.
The dominant contributor to the greenhouse effect is water vapour (H2O). Its content in the Earth’s atmosphere varies over time and over different areas of our planet (it ranges from 40% to 95%), which is due to the cycle of water circulation in the environment as a result of the processes of evaporation, condensation, sublimation and resublimation – a process over which our civilisation has no significant influence.
Carbon dioxide (CO2) is the second major greenhouse component of the Earth’s atmosphere, although its contribution to the greenhouse effect is an order of magnitude smaller than that of water vapour, but human activity has a much greater impact on its presence in the atmosphere. Since the beginning of the industrial era, the carbon dioxide content of the air has been steadily increasing and it is predicted that by 2100 there will be twice as much of it in the air as there is today. It is also estimated that its impact is up to 50% of the Earth’s greenhouse effect (excluding water vapour).
The provisions of the EU Directive on the reduction of emissions of certain atmospheric pollutants for which human activities are responsible are in progress. In agricultural production, this includes primarily ammonia, plus nitrogen oxides (NOx), sulphur dioxide (SO2), methane (CH4) and non-methane volatile sulphur compounds (NMLZO), as well as very fine dust (PM 2.5).
Agricultural production globally is the source of about 9% of greenhouse gases (GHGs), including ca: 50% methane, 60% nitrogen peroxide and 2% carbon dioxide, equivalent to approximately 475 million tonnes of carbon dioxide (CO2eq.).
Data from the UN’s Intergovernmental Panel on Climate Change (IPCC) leave no doubt that agriculture, forestry and adverse land use change accounted for 13% of global carbon dioxide emissions, 44% of methane emissions and 82% of nitrogen oxide emissions in 2019. Given that the impact of each tonne of methane and nitrogen oxide emissions is many times greater than the impact of a tonne of carbon dioxide, it is not surprising to see social and regulatory pressures responding to the need to reduce their emissions from agriculture. Regulatory factors and social pressure are not the only reason for action to reduce emissions from agriculture. Every farmer is well aware that nitrogen and carbon bound in the soil bring income and profit, while their escape into the atmosphere, is always a big loss, including financially.
According to the National Centre for Emissions Management (KOBiZE), agriculture in Poland is responsible for 8% of greenhouse gas emissions. The main sources of emissions are agricultural soils (45%), from which nitrous oxide mainly escapes after the application of fertilisers. The second largest source of GHG emissions from agriculture is cattle production – mainly enteric fermentation (39%), from where methane emissions originate. Another third source of emissions from agriculture is the management of animal faeces (13%), mainly as a result of improper storage of manure, or slurry, in open tanks.
It should always be borne in mind that nitrous oxide, whose emissions are derived from the inappropriate use of mineral fertilisers, has 298 times the atmospheric warming power of carbon dioxide, and has an atmospheric lifetime of about 120 years. Therefore, the rationalisation of fertiliser use, the correct feeding of ruminants and the correct storage of manure and slurry are very important for climate policy.
The average CO2-equivalent emission in the European Union is 2.5 tonnes per hectare, with noticeable differences between countries, e.g. in Romania it is 1t/ha, in Poland 2.2t/ha, in Belgium 7t/ha and in the Netherlands even 10t/ha.
According to the 4/1000 Initiative proposed by the French Ministry of Agriculture at the Paris Climate Summit in 2015, agricultural soils currently store 1,500 billion tonnes of carbon dioxide in the form of organic carbon, and increasing the amount of carbon in the soil by 0.4 per cent per year could be a very important measure to remove some of the so-called carbon debt from the atmosphere, i.e. the excess greenhouse gases in the atmosphere that have been emitted since the Industrial Revolution. In the last two hundred years, the concentration of CO2 in the atmosphere has increased 1.5 times (from 280 to 411 parts per million). Appropriate management of agricultural land has the potential to capture and store a considerable amount of carbon from the atmosphere in the soil, because it is in every farmer’s interest to increase the humus content in the soil of his fields, as this is what determines soil fertility. According to a report by the European Conservation Agriculture Association (ECAF), switching to reduced tillage could retain up to 200 million tonnes of carbon dioxide per year in European soils.