Can harnessing cow manure lower Ireland’s greenhouse gas emissions?
Caoimhe Bermingham
Staff Writer

In this article, we will discuss how processing cow manure through anaerobic digestion can help Ireland meet its climate change goals and produce energy to light up and heat our homes.

In the EU Green Deal, biomethane, a renewable gas made from cattle and other animal waste, as well as food waste, was highlighted as being a vital tool for decarbonising the European agricultural and energy systems. 

Seeing that Ireland currently has 2 million more cattle than people - 7.4 million to be exact - our nation has access to a lot of cow manure. So our potential to harness biomethane from this waste is substantial. 

That is why it comes as no surprise that the European Commission highlighted Ireland as having the highest potential per capita to produce this carbon-neutral gas. 

Before we explore the possibilities and benefits of cow waste, let’s take a look at the impact the agricultural industry has on climate change in Ireland. 

The Irish agricultural sector and climate change  

In Q2 of 2022, Ireland had the highest greenhouse gas (GHG) emissions per capita in the EU, almost doubling the EU average of 2.02 tonnes. According to the Environmental Protection Agency (EPA), the agricultural sector is the biggest source of these emissions in Ireland.

In order to curb this problem, the Government has ordered the farming industry to lower its emissions from 37.5% to 25% by 2030 so that Ireland can meet its goal of hitting net zero emissions by 2050. 

So how can Ireland’s growing agricultural sector achieve this? Well, this is where the processing of cow manure to produce biomethane comes into play. 

Methane and cattle 

According to the EPA, 75.2% of the emissions from the farming sector come from methane that orientates from the enteric fermentation (flatulating and burping) of livestock, fuel combustion and manure management. 

Methane, which is a colourless and highly flammable gas, is more than 25 times as potent at trapping heat in the atmosphere as carbon dioxide. Shockingly, cows are responsible for around 40% of methane emissions globally. 

As a result, scientists at home and abroad have been looking at ways to lower the amount of methane being released from cows’ digestive systems and from the storing of their manure in slurry tanks. 

The avenues being explored include:
Changing cattle’s diets: Feeding them methane-reducing food and dietary supplements to ensure less methane is produced during the digestive process. 

Altering how cattle are bred: By improving the genetic matching of bulls and cows, beef cows will mature faster and will be ready for slaughter at a younger age, thus reducing the amount of emissions they’re releasing. 

Better manure management: By storing slurry in anaerobic digesters, farmers can capture biomethane gas from manure, rather than having this methane released into the atmosphere. This biomethane can then be used to generate electricity and heat our homes.

How does methane from cow waste impact the environment?

As cattle waste is high in nutrients, farmers use it as fertiliser for their land. Before this natural fertiliser is spread, it must become slurry which is a mixture of manure and water. 

This slurry is stored in slurry tanks on farms until it can be used during the summer. However, while the slurry sits in storage it produces and releases methane into the atmosphere. In fact, 16% of EU agricultural GHG emissions come from the storage of manure/slurry. 

Through anaerobic digestion (AD), we can reduce methane emissions from stored slurries which will allow us to produce and capture biomethane for our use, without having to lower the nutritional quality of the slurry.

What is the anaerobic digestion process?

This is a process which involves the breakdown of manure to produce the renewable gas, biomethane. 

During this process, manure is inserted into a large sealed airless container, known as a digester. In this oxygen-free environment, the manure is broken down into biomethane and carbon dioxide, along with a fertiliser known as ‘digestate’.  

These gases are then piped out of the digester for the farmer’s personal use or for public consumption.

These anaerobic digester systems can range from small farm-based digesters to large centralised anaerobic digesters (CAD) which are supplied with feedstocks from several sources. 

What are the benefits of putting cow manure through the anaerobic digestion process? 

There are several benefits that come from managing and treating cow waste this way, such as:

The production of biomethane: In 2020, 86% of all energy used in Ireland came from fossil fuels. As climate change worsens and natural resources continue to dwindle, this unsustainable reliance on fossil fuels is no longer an option for Ireland.
This is especially true, seeing the Government aims for 80% of electricity in Ireland to come from renewable sources such as AD by 2030. The creation of this renewable gas from manure will help Ireland achieve this goal.

What can biomethane be used for?
Biomethane can be:

  • Injected into the national gas grid to be used as vehicle fuel or used in portable compressed gas containers.
  • Used in gas boilers to heat our homes, water or high-temperature steam.
  • Used to power gas engines that produce electricity, or electricity and gas, which when combined make combined heat and power (CHP).

    It saves farmers money: Farmers can produce energy for their own personal use by putting their manure through this process, thus lowering their energy bills. 

    They will also have the potential to have an additional income stream if they choose to sell the excess electricity or heat that their biomethane produces. 

    Seeing this process also creates the valuable fertiliser, digestate, farmers can save the money they would normally have had to put towards buying a chemical fertiliser for their farms. 

    It’s more environmentally friendly: By pumping cow waste into anaerobic digesters, it reduces the amount of waste ending up in landfills, the amount of hazardous natural gases being released into the atmosphere and it helps decarbonise the agriculture sector. 

    It’s a dispatchable source of renewable electricity: Unlike solar panels and wind turbines that depend on certain weather conditions to generate energy, AD facilities can produce biomethane to produce electricity constantly. As biomethane can be stored for later use, the AD of cow manure can provide renewable energy during periods of low wind levels or when electricity is in high demand.

    It helps us take part in the circular economy: Harnessing cow waste to create a source of energy prevents the unnecessary extraction and burning of raw materials to generate electricity. It also creates a valuable fertiliser. 

    The process is an example of how the agricultural sector can participate in the circular economy, a model of production the Irish Government is adopting to tackle climate change. 

    Is the biomethane industry compatible for Ireland?

    Yes, it is. 

    According to Gas Networks Ireland, biomethane can seamlessly replace natural gas on the gas network today and is fully compatible with existing appliances, technologies and vehicles. 

    If the correct supports are put in place to create a biomethane industry in Ireland, the Irish Government estimates that 20% of the current natural gas demand could be met by biomethane by 2030. 

    To support this, the Government recently announced that 3 million will be provided in funding each year for the next four years to help kickstart a farm-based AD sector. 

    Are there facilities in place to support the biomethane industry on a larger scale? 

    Yes to an extent. 

    In 2019, Gas Networks Ireland opened the first dedicated renewable gas injection point in Cush, Co. Kildare, which sees domestically produced biomethane from farms being pumped into the national grid.

    The construction of a second gas injection facility is to be built in 2023 in Mitchelstown, Cork, and will receive biomethane from up to 20 local farm-based producers. 

    It is also expected to create 6,500 jobs across the sector. 

    Both injection centres will have the capacity to heat 75,000 homes, while also helping to decarbonise local agriculture. 

    However, to generate the levels of natural gas the Government wants to harness from AD by 2030 and to reduce our GHG emissions, 200 plants will need to be built by 2030.

    Are other countries using anaerobic digestion to harness natural gas?

    Yes, they are.

    Denmark, Germany, France, the UK and the Netherlands are all using AD to produce natural gas and reduce their GHG emissions.

    Denmark in particular has seen a lot of success in its AD sector. Currently, 32% of its total electricity generated from biofuels comes from its AD industry. By 2030, the Danish Government plans for this figure to increase to 72%. 

    Germany, the leading producer of biogas in the world, has increased the amount of cow manure it puts through the AD process to generate its natural gas, rather than mainly relying on crop waste. 

    The future of Ireland is green energy

    The possibilities and advantages that can come from putting cow manure through the AD process are undeniable. 

    With the beef and dairy industries expected to continue to grow and flourish for years to come, it is essential that this process is undertaken and supported by the agriculture sector and the Government as a way to lower the sector’s GHG emissions and energy usage. 

    Seeing that gas and electricity prices are skyrocketing due to a shortage in supply, the importance of having access to biomethane (harnessed from cattle waste) is invaluable as it will ensure we are able to light and heat our homes. 

    It will also help lower energy prices

    Read our other articles about renewable energy

    If you are interested in renewable energy and how Ireland is dealing with climate change, check out some of our other articles on these topics!

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