Anaerobic Digestion on Farms
The introduction of anaerobic digestion has been described as relatively slow in terms of Irish uptake.
Anaerobic digestion (AD), a natural process, is the conversion of feedstock (any organic non-woody material) by micro-organisms in the absence of oxygen into biogas and digestate.
Digesters can be installed for various reasons on farms, such as to eliminate on-farm waste, reduce odours and provide a source of revenue.
The produced biogas can generate heat, electricity, or both. Combined heat and power (CHP) is the most common generated product from anaerobic digestion.
Furthermore, the electricity that is generated through the gas engine can either be supplied to the electricity grid or used for your own consumption.
AD can be applied at a range of scales, and the production capacity is dependent on the system and the amount of available biomass. In turn, systems can range from small, on-farm-based digesters, to large systems with feedstocks being supplied by a range of sources.
Support Scheme for Renewable Heat
The primary objective of the Support Scheme for Renewable Heat is to increase the level of renewable energy in the heat sector.
The aim of this scheme is to contribute to meeting Ireland’s 2030 renewable energy ambition, with the bonus of combating greenhouse gas emissions.
The scheme has the incentive to develop and supply the renewable heat industry. In addition to this, the support scheme aims to bridge the gap between renewable heating systems and conventional fossil fuel alternatives.
Fortunately, the EPA has generated an anaerobic digestion screening tool, which can be used to assist you in assessing the potential feasibility of an AD project on your farm.
Eligibility for support
According to SEAI, they have been appointed by the Department of Communications, Climate Action and the Environment as the administrator for the support scheme.
Furthermore, to meet the eligibility criteria, applicants should:
- Employ designers and installation engineers who are competent to carry out the necessary works;
- Demonstrate heat generating technologies and project installations, which also comply with the Building and Construction Product Regulations, EN Standards, efficiency, technology standards and air quality standards in relation to emissions;
- Applicants should be in receipt of payments which meet the tax clearance requirements;
- Applicants should declare that the proposed heat use is eligible for the scheme and adhere to the verified energy efficiency criteria.
The support scheme offers an installation grant of up to 30% of eligible costs. This funding is available to successful applicants who adopt air source, ground source and water source heat pumps.
Ongoing support, which is paid for up to 15 years, for new installations or those converting to using biomass heating systems or anaerobic digestion heating systems.
The maximum tariffs paid will be 5.6 cents per kilowatt hour of energy produced from biomass heating systems.
The amount paid in terms of tariffs will reduce with increasing output, reflecting the economy of scale associated with larger systems.
Is your livestock farm suitable for anaerobic digestion?
Moreover, if your farm produces manure from cattle, hogs or poultry, anaerobic digesters are an option for you.
Ideally, the screening process as described by the EPA, analysis the size of your farm, whereby livestock numbers are accounted for.
This includes a minimum of 500 head of cattle, 2,000 hogs with anaerobic lagoons or liquid slurry manure management systems, or 5,000 hogs with deep pit manure management systems.
A minimum of 90% of the manure should be collected regularly. Despite these figures, smaller confined facilities could also support successful recovery projects, given site and market conditions.
Farms with different ways of animal housing and manure management systems can adopt anaerobic digestion. However, pre-treatments or modifications may be required.
AD feedstocks and benefits
The biogas industry in Ireland is focused on the injection of biomethane into the national grid. However, prior to injection to the grid, biogas should undergo further upgrading to eliminate CO2 and other gases. This is done through a process of creating biomethane, which resembles the properties of natural gas.
Anaerobic digestion is fuelled by feedstocks, which include farm waste such as slurries (cattle/poultry/pigs), food processing waste, crops grown for AD (maize/wholecrop), silage or grass, in addition to domestic food waste.
Anaerobic digesters can utilise single or multiple feedstocks. Those that codigest slurry with other feedstocks, i.e. waste from other sources, can increase their production of biogas.
The benefit of adopting such a system on your farm includes the generation of additional revenue. This is percolated through the use or sale of biogas energy. The value of the energy produced from the gas should offset the cost of collection and processing.
Electricity generated by way of biogas can be utilised to operate equipment on-farm. For example, dairies operate chillers, fans, vacuum pumps and feed mixers. Alternatively, this electricity can be sold to local grids.
Other options include fuelling boilers or heaters, such as that required for hot wash cleaning and other operations.
In turn, the by-product produced as a result of the anaerobic digestion process is digestate. Digestate is a nutrient-rich fertiliser source, which can be used to eliminate the requirement for chemical fertilisers on-farm.
Supporting the Climate Action Plan
Our target of reducing emissions by 2030 is challenging but is recognised across many sectors as an opportunity to transform economies and contribute to reducing greenhouse gas emissions.
A major focus of Ireland’s Climate Action Plan is to generate significant renewable energy production from sources such as anaerobic digestion.
The availability of renewable energy sources present in Ireland creates an area for potential to export renewable energy produced to the international market.
Furthermore, Ireland is committed to making a difference in the handling of the climate crisis by way of an ambitious target for decarbonisation of the electricity system by 2030.
Moreover, to efficiently manage your anaerobic digestion system, operators and owners should pay regular attention to operation systems, provide necessary repair and maintenance and have the desire to see the system succeed.
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