Greenhouse Gas & Gaseous Emissions Mitigation

Sustainability and maintaining our green image is crucial for Irish agriculture as we export 80 – 90 % of the products we produce here. Irish agriculture currently contributes 37% of total greenhouse gas (GHG) emissions in Ireland.

GHG emissions on Irish farms come primarily from carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Methane and nitrous oxide are the main contributors for agriculture contributing 65% and 30% of GHG respectively. Farmers are expected to reduce total emissions by 22-30% by 2030 under the climate action plan.

Actions to Reduce Greenhouse & Gaseous Emissions on Farm:

Grazing Management

The management of the grazing swards throughout the year is critical to the reduction of GHG’s. Every extra week that the grazing season is extended by will reduce GHG emissions by 1%. The extended grazing will also directly impact on farm profitability as every extra tonne of grass dry matter grown per hectare and utilised is worth roughly €173 to the farmer. The extended grazing will also have a direct knock on effect of reducing emissions deriving from slurry storage as animals are housed for a shorter period of time. The grazing of better quality swards throughout the grazing season was shown to reduce emissions by up to 15% daily e.g. by reducing pre grazing covers from 2,000kg/dm/ha to 1,400kg/dm/ha. When the eight week peak growth period is managed appropriately it can result in reductions of 1-2% in GHG emissions as animals will be grazing and utilizing top quality swards. These reductions can be achieved by walking and measuring grass on your farm weekly using tools like pasture base to aid in the process. Good grazing infrastructure to avoid poaching is also vital.

Fertiliser Use

A change in fertiliser use from CAN to protected urea has the potential to reduce GHG emissions by 7-8% on dairy farms with protected urea having 71% lower nitrous oxide emissions than CAN. By switching from urea to protected urea it will also reduce ammonia loses to the atmosphere by up to 79% as found by Teagasc, while not a GHG it is a potent air pollutant. The imminent reduction in nitrogen use going forward will directly reduce nitrogen emissions and nitrogen losses to water. A reduction in fertiliser by 25% will reduce overall emissions by up to 5%. It is vital that farmers have their soil fertility at optimum levels so as not to allow the reductions in nitrogen use reduce farm profitability. A nutrient management plan based off recent soil samples will identify where nutrients will be best utilised. Improving nitrogen use efficiency is another area where GHG emission reductions can be achieved by utilising more nitrogen that is applied leaving less to be lost to the environment

Energy Efficiency

Through the adoption of energy efficient technologies and renewable energy sources it is possible to increase farm energy efficiency. Reducing energy use by 20% will reduce GHG emissions by 1%.

EBI

Recent research from Teagasc has shown that for every €10 increase in EBI there was a reduction of 1% in GHG emissions per kg of milk solids while also improving profit/cow by €20. These increases in profitability and reduction in GHG emission by improving EBI are possible through:

1. Improving Milk Production through increased yield and composition from grass thus directly decreasing emissions per kg of milk solids.
2. Improving Fertility in turn will reduce calving interval and replacement rate, compact calving will allow an extended grazing season where cows will graze and utilise more grass reducing methane.
3. Improved Health resulting in animals having less disease and lasting longer in the herd leading to higher production and lower replacement rates.
4. Improve age at first calving will have heifers calving down at the optimum age of between 22-26 months increasing lifetime production efficiencies and idle time.

LESS

LESS minimises the surface area to which slurry is applied and places the slurry close to the ground which in turn reduces the surface area of the slurry exposed to the air therefore reducing emissions lost to the atmosphere. Ammonia is the primary gas lost at slurry spreading through volatilisation, although ammonia is not a GHG it can indirectly contribute to GHG emissions. Research by Teagasc has shown that a reduction of up to 70% in ammonia emissions can be achieved by adopting LESS technology which can be seen in the figure 1. The application of slurry in the spring time with LESS technology will lead to a 50% increase in the availability of nitrogen compared to splash plate and a 50 % increase in availability of nitrogen compared to summer application also. This roughly supplies an extra 3 units/N/1,000 gallons of slurry and up to 5units/N/ 1,000 gallons using injection technology. The increased placement and utilisation of nutrients will allow chemical fertiliser applications to be reduced directly reducing nitrous oxide.

Clover

Incorporating clover into the grass sward can reap huge benefits in terms of nitrogen reduction whilst also increasing production. White clover has rhizobia bacteria in its roots that fix nitrogen from the air and it can supply between 50-200kg N/ha per year. White clover can increase sward production by up to 1.5 tons/DM/ha/yr. It was shown that milk solids production increased by 20-48 kg/cow on these swards with a farm profit increase of €108-€305/ha. Research conducted in Moorepark found that clover has the potential to reduce nitrous oxide emissions by 40% on swards with 20-25% clover present, as a result of the reduced levels of chemical nitrogen required.

Glanbia Ireland through the recently launched sustainability action payment has committed to assisting its dairy suppliers to enhance the environmental and economic sustainability of their family farms through the adoption of a series of measures and technologies.

First Published 14 June 2022