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Renewable Gas and Anaerobic Digestion

Anaerobic digestion is the natural process of decomposition of organic matter in an oxygen starved environment. It occurs naturally in nature and releases methane gases into the atmosphere. When organic matter (such as slurry or grass silage) is put into anaerobic digester tanks it is possible to capture the methane gases produced and apply it to useful purposes such as meeting heating and energy needs. The remaining organic matter is called digestate and this can be used as an organic alternative to chemical fertiliser.

Biogas, is the “raw” gas produced through the anaerobic digestion process.

Biogas consists of around 50% to 60% methane with majority of the remaining gas being carbon dioxide.

Biomethane is biogas which has undergone post processing to clean the gas of impurities so that it is identical in terms of cleanliness and quality to natural gas used in Ireland today meaning it can be used directly in all applications where natural gas is currently the fuel of choice.

Renewable gas covers all gases of renewable and sustainable origin which can be injected into the gas network to replace natural gas. Biomethane is the most well established and matured of these but other potential sources do exist such as hydrogen and syngas. On this website renewable gas refers to biomethane.

How is renewable gas different from natural gas?

Natural gas is a finite resource of fossil fuel extracted from the ground.

Renewable gas is produced using a naturally occurring biological process and materials that can be regrown and replaced over a short time. It is sustainable, as greenhouse gas emissions which are created as the fuel is burned are offset by emissions which are avoided throughout the production of the gas. This makes biomethane low or zero carbon over its entire lifecycle.

From an end user’s perspective, no noticeable difference would exist in terms of application.

What is digestate?

Digestate is a by-product from anaerobic digestion. It is an excellent bio-fertiliser and organic soil improver that replaces carbon back into the soil. This helps to reduce the greenhouse gas, CO2, in the atmosphere, while regenerating the soil of grass or tillage lands. Digestate is more environmentally friendly than artificial fertilisers as it slowly releases nitrates and other nutrients into the soil, avoiding their run-off or leaching into water courses.

Renewable Gas Industry

Renewable gas is good for the environment and has socio-economic benefits. It helps farmers to reduce green house gas (GHG) emissions, by recycling agricultural organic materials, producing organic soil improvers and capturing carbon in soil (sequestration). Agriculture currently accounts for 35% of Ireland’s GHG emissions, mainly from current farm practices and land management.

A sustainable Irish renewable gas industry can digest 4.8 million tonnes of slurry and 5Mt of agricultural organic by-products and residues annually. It can produce organic soil improvers with the potential for soil carbon sequestration to save 14Mt of CO2 and an additional 2.6m tonnes of CO2 emissions in energy consumption per year. This reduction in GHG emissions in turn will protect our international renown as an exporter of high-quality food and drink.

Bio-fertiliser, or organic soil improvers, return essential nutrients and carbon to the soil (carbon sequestration), further reducing CO2 in the atmosphere. They also reduce the chance of nitrates leaching into water courses by replacing artificial fertilisers. Organic soil improvers release nutrients slowly, with easy up-take by soil and plants.

Food and drink production processes contribute a further 13% to national GHG emissions and these industries are largely dependent on gas as their primary energy source. Many of the leading agri-food businesses are fully behind the RGFI initiatives and proposals to reduce their carbon footprint and align with EU Green Deal Farm to Fork.

The transport sector is one of the most challenging to decarbonise. Between 1990 and 2017, its GHG emissions increased by 133.2% in Ireland, more than any other sector.

Ireland will not achieve its target of 10% of final energy use in the transport sector from renewables by 2020. Biomethane is particularly well suited for use in heavy goods and commercial vehicles and can reduce carbon emissions by over a fifth compared to traditional fuels, while also reducing other emissions significantly. Heavy goods vehicles and buses are a key target for biomethane. While only accounting for 4% of vehicles on Irish roads, they account for 30% of all emissions in the road transport sector. Gas-powered lorries are now on Irish roads, with demand growing for sustainable alternatives to decarbonise transport.

How is Renewable Gas Sustainable?

Renewable Gas produced in Ireland will be required to adhere to sustainability criteria, set out in the Renewable Energy Directive recast (REDII). These criteria require a producer to undergo a life cycle analysis (LCA) of their process, accounting for all emissions associated with the production process from cultivation of feedstocks to processing and transportation of the gas. The results of this LCA must show that the total emissions balance of the process (those created less those avoided / abated) must be below a minimum level for the gas to be certified as Renewable and sustainable.

The Irish Green Gas Certification Scheme will facilitate producers to provide evidence that their processes are fully compliant with these sustainability criteria and provide comfort to end users and policy makers that the gas produced is sustainable.

The following elements are critical to achieve compliance under the GHG calculation in RED II:

  • Plant and process design
    • Slurry supplies fresh of GHG mitigated
    • Methane slippage eliminated / minimised
    • Bio-fertiliser spreading and land bank management / optimisation
  • Feedstock mix (co-digestion)
    • eg max 60% grass and min 40% slurry
  • Cultivation – bio-fertiliser use
    • reduce or eliminate use of artificial / chemical fertiliser
    • mitigation of soil nitrous oxide GHG emissions
  • Renewable energy utilisation 25%-100%
    • heating – bio-LPG, biomethane CHP boiler
    • electricity – solar, CHP, reduce reliance on grid electricity
    • tractors and transport fuel – biomethane
    • hydrogen and ammonia
  • Carbon replacement ie displacement of
    • industrial and horticultural CO2

The GHG Life Cycle Assessment of anaerobic digestion with slurry and grass (or other equivalent feedstocks) must achieve the minimum GHG saving target, but can also far exceed this target.

Renewable gas can play an important part in the circular rural economy with a benefit cost ratio of 1.26 according to the KPMG Business Case for Biomethane in Ireland. Most renewable gas will come from re-cycling bio-degradable and agricultural organic materials, by products, giving farmers the opportunity to close the circle in terms of carbon neutrality, and protecting our sustainable food producer credentials.

Biomethane produced from agricultural organic matter and by-products has the potential to save 2.6 Mt of CO2 pa in energy consumption by 2030, which would significantly decarbonise heat demand across the residential, commercial and agricultural sectors, creating over 3,000 rural jobs and provide an additional complimentary additional income for farming families.

Using renewable gas provides the lowest cost solution to decarbonising heat demand, a more economical alternative to other renewable heat technologies and can save money for end users in the future. It is an on demand, reliable, predictable energy source.

Renewable gas as an indigenous industry gives Ireland greater energy security. About 85% of our energy comes from outside the state at a cost of approximately €5.7 billion per annum. This is a worrying issue for our nation when energy security is one of the biggest challenges facing the developed world.

For the energy consumer already using natural gas, there is a simple switch to biomethane, existing technologies and infrastructure can operate as normal.

Like other gases, biomethane can be stored. The gas network is a form of storage and biomethane would be given priority over fossil gas, reducing reliance on imported gas.

Yes. The renewable gas industry is highly regulated and must adhere to all the safety and regulatory requirements associated with natural gas and as a result it is very safe. AD technology is a mature technology, used all over the world to reduce emissions in agriculture and industrial by-products and waste.

Renewable Gas Forum Ireland (RGFI) represents the interests of the renewable gas industry across all parties to form a collaborated and co-ordinated vision to support policy makers in meeting industry’s mandatory decarbonisation targets using renewable gas. It is a forum for information gathering and knowledge transfer amongst members to ensure the industry is developed under suitable market conditions, providing consumer and investor confidence. The renewable gas industry needs to be operated in a safe, sustainable and competitive manner, built on best practice. See About Us, Our Work

RGFI works closely with the following important stakeholders across the industry;

  • Gas Networks Ireland (GNI) owns, operates, builds and maintains the natural gas network in Ireland. They are responsible for ensuring that gaseous fuels are transported from production to end use in an efficient and safe manner.
    GNI are primarily responsible for:
    – Providing connections to the gas network for biomethane injection.
    – Operating the Irish Green Gas Certification scheme to certify the injection of biomethane onto the network.
    – Developing off grid solutions to ensure gas can be transported from source of production to end user in an efficient manner as possible.Gas Networks Ireland have an ambition to have 20% of the gas flowing through their network as renewable gas by 2030 and have been a key promotor and enabler of the renewable gas opportunity in Ireland to date.
  • Gas Shippers and Suppliers oversee the entry and sale of renewable and natural gas in Ireland.
  • Commission for Regulation of Utilities oversees the regulation of the gas, energy and water sector and will be a key decision maker in relation to polices relating to access and standards associated with the gas grid.
  • Department of Agriculture, Food and the Marine (DAFM) oversees the application of animal by-product regulations for the use of agricultural feedstocks for biomethane production. They are also now responsible for the delivery of many of the climate action targets associated with agriculture specifically.
  • Department of Communications, Climate Action and the Environment is primarily responsible for the delivery of national and European policy relating to energy, decarbonisation and the environment.
  • Teagasc is the national organisation tasked with research and advising national policy in relation to the future of agriculture, on matters such as sustainability and viability.
  • The Farming Community is at the core of renewable gas production. RGFI works closely with representatives of the farming community such as the regional co-operatives the Irish Farmers Association , the Irish Cattle and Sheep Farmers Association, and others, to ensure a coordinated approach which represents the best interests of the farming community is taken.
  • The Waste Sector. Although the overall resource potential of this sector is smaller than that of agriculture, it still could decarbonise ~3% of Ireland’s natural gas demand.
  • End Consumers who will purchase the renewable gas to offset their own energy needs.

Realising the Vision

The European Commission released a report in 2017 that showed Ireland has a higher potential for biomethane production per capita than any other EU member state. This is due to its grass-based rural economy.

RGFI commissioned KPMG to produce a Business Case for Biomethane in Ireland and a Cost Benefit Analysis including the wider economic benefits of biomethane. The KPMG report presents a realistic and sustainable approach to developing a thriving, renewable gas industry focussed on agriculture and the use of biomethane to meet heat demand in residential, commercial and industrial use. The report shows a benefit cost ratio of 1.26 to 2050 i.e. there is a good long-term return on the investment.

Anaerobic digestion is a mature technology, tried and tested across the world. More than 17,500 AD plants are already operating in Europe and France currently builds a new AD biomethane plant every 4 days.

Major agri-food, drinks and biopharma companies are committed to developing an indigenous, renewable gas industry as a means of reducing their carbon footprint, in line with mandatory requirements and compliance with new regulations from 2021.

Gas Networks Ireland (GNI) has committed to fully decarbonising its gas network by 2050. Ireland already has a national network of gas pipes and related infrastructure in place.

Capital investment is required to develop a scalable, renewable gas industry, which would then be self-sustaining.

In line with EU sustainability criteria, certain feedstocks will be significantly prohibited for use in the production of biomethane going forward, such as the use of energy crops. This means that Ireland’s renewable gas industry will predominantly rely on feedstocks which are considered to be wastes, such as food waste, and manures, or residues (produced as a by-product or in addition to a main process), such as sequential crops, excess grass silage produced from increased soil productivity and portions of feed or food production not suitable for human consumption. Ireland is exceptionally well positioned in this regard due to the scale of our grass-based agriculture.

Current gas demand which could be met theoretically with biomethane feedstocks:

  • Up to 3% of natural gas demand could be met from the food processing sector.
  • 70-80% could be met using a mixture of grass silage (available in excess of livestock requirements) and manures.

Other potentially large resources to increase biomethane production include sequential and rotation cropping, and in time the biological methanation of renewable hydrogen at scale.

All this combined with expected future technology efficiencies means Ireland could in theory achieve 100% biomethane as a direct replacement to natural gas consumption.

However, just because a feedstock is theoretically available does not always mean it will be useable in reality. Constraints such as the cost of feedstock, location and willingness of parties to supply the feedstock as well as other competing uses means that what is more likely to be achieved is somewhat less than this. In respect of what experts believe is actually achievable in Ireland:

  • The European Commission suggest a target of 13 TWh (~23% of gas demand) would be achievable by 2030.
  • SEAI suggest up to 28% of current gas demand could be produced as biomethane.

Ireland’s first purpose-built central gas injection (CGI) facility was developed in 2019 in Cush, Co Kildare, where locally produced biomethane is being successfully injected into Ireland’s gas network as a demonstration facility – the first its kind in Ireland.

Gas Networks Ireland’s Green Renewable Agricultural Zero Emissions (GRAZE) project received €8.5m from the first round of the government’s Climate Action Fund. It will support the installation of the first connected central grid injection (CGI) facility on the transmission grid near Mitchelstown, Co Cork, for biomethane and a grant scheme to support circa 74 compressed natural gas vehicles. When fully operational, this CGI facility will provide enough energy to heat 54,000 homes. Local farmers, working co-operatively, could transport renewable biomethane from their on-farm AD plants to this central injection point.

By mid-April 2020 GNI received over 100 preliminary enquiries for direct grid injection from proposed AD plants into the national gas grid.

Approximately 75% of enquiries related to agricultural organic materials and by products processing through anaerobic digestion.

Gas Networks Ireland (GNI), through their EU funded Causeway project, in collaboration with the National University of Ireland, Galway, are developing a gas transport re-fuelling network for Ireland with 70 compressed fast filling gas stations. They are promoting compressed natural gas and biomethane for trucks, vans and buses.

Compressed natural gas and biomethane for trucks, vans and buses, can offer both commercial savings to the operator and reduced carbon and particulate emissions. These vehicles account for 4% of Ireland’s transport vehicles but produce 30% of all emissions associated with transport. Other technologies such as electric are currently unproven to accommodate large driving ranges and weight requirements. This means that biomethane is currently the only real sustainable option commercially viable today.

Biomethane can also play a role in domestic and light goods vehicles, which is common practice across mainland Europe. However, as government policy for this sector is primarily focused on electrification it is not envisioned that biomethane will play a major role without a change in government strategy.

Another interesting application for biomethane in transport is to support decarbonisation of our tractor fleet.

New Holland’s biomethane powered T6.180 tractor

While there have been a number of concept machines over the years, New Holland has been a leader in developing biomethane-powered machinery. Its biomethane-powered tractor, the T6.180 scooped the 2020 sustainable tractor of the year award at Agritechnica.

The tractor is fully powered by upgraded biogas (biomethane) produced on farms. According to New Holland, the biomethane-powered T6 has up to 30% lower running costs when compared to diesel. In the field the T6.180 tractor produces 99% less particulate matter in comparison to the equivalent diesel tractor, while CO2 emissions are reduced by a minimum of 10% and overall emissions by 80%. The tractor units are expected to be commercially available in 2021.

Capital costs. Renewable gas has to be produced from organic materials and has high capital and operational costs. To encourage initial growth of the industry, the socialisation of the cost of biomethane production is generally accepted. Other key requirements are a declared policy position from government to support biomethane production, capital grants, EU funding potential, access to low cost funding and private equity investment.

The above measures would facilitate the renewable gas industry to mature and drive competitiveness and efficiency to reduce the cost of producing biomethane within the next 10-15 years.

For AD developers and private investors, the main obstacles are investor certainty and confidence in government support and policy measures, the funding of projects, reliability of the feedstock, and ensuring connection to the grid.

Developing renewable gas projects can take a number of years, so committed, long-term investment is essential.

RGFI is working, in a consultative and constructive manner, with its members, key stakeholders in industry and funding and government to develop the framework to take this forward.

Political support. Renewable gas is a well-established, mature industry across the world and mainland Europe. However, it has not been supported to date by policy in Ireland. Clear and declared policy support and direction for a renewable gas industry in Ireland will be the most important enabler to the future growth of the sector.

Acknowledgement of wider benefits of renewable gas. Renewable gas is a low-cost option to decarbonise when compared against other decarbonisation alternatives, such as electrification of heat and transport for example, but it is more expensive than natural gas (a fossil fuel) which is the comparator to which it is most generally considered. In order to fully understand the overall value of renewable gas as an indigenous industry, and on demand, carbon neutral fuel, better acknowledgement of the wider economic benefits is needed.

Positive externalities exist such as security of supply, dispatchability, rural regeneration and job creation, decarbonisation of energy and agriculture, circular economy principles and better use of waste streams as well as positive air and water quality impacts. When taking consideration of this, Renewable gas offers an extremely cost competitive option.

Scale and setting will always be considered in planning applications. However, the benefits in developing a circular economy to benefit rural Ireland, reducing GHG emission, and soil carbon sequestration, will also be taken into account. A good business and operational plan also strengthens planning applications, demonstrating the alignment with government policies for rural Ireland, Foodwise, Harvest 2025 and the European Green Deal strategy and Farm to Fork initiatives.

Planning applicants will be required to address any potential issues which could arise, such as noise, odour, traffic management, land bank or safety concerns, in line with best practices. An Appropriate Assessment for the proposed AD plant, expanding to ecology, hydrology, archaeology and any other requirements, should be included to support the application.

RGFI can provide advisory support for members in respect of planning application requirements.

AD plants are highly regulated and related planning permission is only given when the planning authority is satisfied that appropriate mitigation measures are in place to reduce noise and odour risks.

Anyone developing an AD plant should facilitate a public consultation with the local community and key stakeholders from the outset to address any concerns, provide information and demonstrate the socio-economic benefits to all concerned.

In the case of an optimum sized 20GWh AD plant, fed on slurry and grass silage, approx. 2% of land within a 10km radius, or c.445 hectares would be required to supply feedstock. This would have little or no impact on the amount of land used for food production. RGFI is promoting anaerobic digestion as a complementary technology to existing farm practices. Even if the renewable gas industry grew to its maximum potential in Ireland it would have no significant negative impact on food production.

Slurry will be one of the main feedstock sources in Irish anaerobic digestion plants, in combination with other organic materials and by products. In exchange for slurry management, farmers will be able to access bio-fertiliser organic soil improvers to fertilise the land. This high-quality fertiliser is free of pathogens and high in available nitrogen, with greater absorption into the soil and which, over time, increases the fertility and productivity of the land. Approximately 16,000 tonnes of slurry would be required per annum for a 20GWh plant.

Other farm wastes or residues which are available on site, or in close proximity to the site, can supplement and reduce the need for slurry and grass.

Farmers must ensure that the biomethane they produce will adhere to the sustainability criteria set out under RED II. As a rule of thumb, this typically means that in the region of 37% or more of the plant’s feedstock must come from manure or similar feedstock to ensure compliance. Other factors that can impact the sustainability criteria are set out in the section on the Green Gas Certification Scheme.

Farmers and Renewable Gas

The opportunity in Ireland is to create a circular, rural economy whereby agri-feedstock of excess grass, rotation and catch crops and residues will be used to produce biomethane for heat, and transport.

The digestate by-product is an excellent bio-fertiliser organic soil improver and will reduce carbon footprint by displacing artificial fertilisers and associated increasing costs of chemical fertilisers.

Farmers may wish to invest in these plants, lease land for them, operate them, and, or, contract to supply feedstock.

Farmers can use the AD plant to improve slurry management, address N, P, K or ammonia issues and reduce the use of chemical fertilisers while also bringing currently unproductive land into profitable use.

The whole process reduces greenhouse gas emissions and captures carbon in the soil.

The AD biomethane technology is being promoted and designed to be a complementary discipline to existing farm operations and land management practices. The majority of individual farmers will not be able to build and supply feedstocks as a sole enterprise. This means an approach whereby farmers pool feedstock and resources to develop a plant in co-operation will be required. Alternatively, some projects can be developer led, where a plant is built and operated by one party with contracts for feedstock provision with farmers in the local area. Typically, an average AD plant will require a number of farmers’ inputs to provide feedstock and land, and to operate the plant.

All different sizes and types of farming enterprises are suitable for AD. The key ingredient is bringing together the right collective mix.

Currently, any pig farming operation in Ireland would produce enough slurry for a 20 GWh plant.

In many cases, a mixture of dairy beef and tillage farms would be encouraged to collaborate in setting up a cluster of 5 or 6 farms working co-operatively.

Most sucker, beef farmers and beef finishers that keep cattle under roof could provide slurry and could also utilise set-aside grassland to supply grass silage to the AD plant. This industry would provide livestock farmers with an outlet for excess grass, particularly in areas where beef farming is dominant.

Tillage farmers could plant rotation and catch crops of mixed grass swarths including red clover as part of their five-year rotation. They can also grow a second catch crop in the year as the crops do not have to be at full maturity when harvested for anaerobic digestion.

It is recommended that AD plants be within a range of 100km access to a central grid injection facility in order to be economically viable. There may be an option to supply large gas consumers directly who are off grid. Some developments will not meet the requirements for direct gas injection, currently distances of 14 km of low pressure gas pipeline is economically viable for large AD plants.

The best feedstocks are agri-food and drinks by-products, however, grass and slurry will be the most common feedstock in Ireland’s renewable gas industry. Teagasc figures show that the average grass yield could be increased by at least 50%. University College Cork research shows how underutilised land, particularly in the less intensively farmed areas in the west of Ireland and the midlands, could be brought into production.

Start Up Costs / Funding Support

The capital cost of a 20 GWh/yr plant (1MW electrical equivalent) including biomethane upgrading technology, is in the region of €5.5m. Due to economies of scale, a 40GWh plant is about €8m.

Robust commercial and funding structures offering 15-20 year contracts have been pivotal to the development of the renewable gas industry across Europe. Power purchase agreements from large gas consumers in the manufacturing and processing sectors will also assist.

The RGFI / KPMG analysis shows that a total income of around €8.8 c/kWh is required to make a farm-scale 20 GWh/yr biomethane plant viable. At current energy prices, this would mean a socialisation in the cost of producing biomethane of between 5c/kWh and 6c/kWh.

The cost-benefit analysis of supporting an indigenous renewable gas industry found that for every €1 of support provided, €1.26 would be returned due to wider benefits to the economy.

In order to achieve RGFI’s vision of replacing 12% of current natural gas consumption with renewable gas, approximately 227 agri- and industry-led AD plants, along with 15 larger dedicated commercial waste AD plants, will need to be developed by 2030.

This will require a capital investment in the region of €1.5bn, a government capital grant, implementation of Article 23 obligations under the EU RED II policy, and socialising the cost of producing biomethane.

The European Investment Bank (EIB) has approved €700 million of financing for agriculture and the bio-economy. The initiative aims to unlock around €1.6 billion of investment in these sectors by supporting private companies operating throughout the value chains of production and processing of food, bio-based materials and bioenergy.

The government has included biomethane in its plans to reduce carbon emissions by 2050, however RGFI industry members would like to see a more ambitious target of 12% for biomethane in the grid by 2030. (The government target is just 3%).

RGFI is working through its members and with government to develop the framework for policy supports for biomethane.

A range of economic funding options have been presented to government in the KPMG Integrated Business Case for Biomethane in Ireland, using the principles of socialisation of production costs as the most acceptable and preferred solution to support the price differential. These include a gas public service obligation levy, a biomethane obligation scheme and capital grants.

The second round of the government’s Climate Action Fund, primarily funded by a levy on oil companies, will leverage a multiple of the €500m committed to it by the government.

The first round included funding for a GNI project to trial the central grid injection of biomethane.

RGFI is calling for :

  • An all-of-industry, all-of-government approach to implementation strategy and policy support for biomethane – specifically taking into account the needs of agri-food, drinks, biopharma, and the agricultural industries, to comply with new regulations under the European Green Deal strategy and Farm to Fork initiatives.
  • A biomethane target of 12% by 2030 – as the minimum required to realise the vision for this sector.
  • Government to introduce Renewable Energy Directive II, Article 23, in 2021, ahead of its 2026 target, in support of the KPMG / RGFI integrated Business Case for Biomethane in Ireland.
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