An Taisce submitted a damning critique of the Government’s Draft National Biomethane Strategy in response to the consultation which closed on 5th March.

The Draft Strategy lays out a framework for significantly scaling up the production of biomethane via anaerobic digestion (AD) plants using grass silage and slurry as feedstocks. This biomethane will primarily be for injection into the existing national gas grid, displacing around 10% of fossil gas in the gas supply. However, the Draft Strategy failed to fully analyse the potential negative climate and environmental impacts.

In December, An Taisce sent a letter to the government ministers and departments responsible for preparing the National Biomethane Strategy, warning that the lack of input from non-industry stakeholders in its preparation gave the strong appearance of regulatory capture by vested interests.

The Strategy as drafted is undermined by major due diligence failures by government and agencies. Biassed stakeholder consultations favoured the powerful interests most likely to financially benefit from misdirected policy supports, questionable “green gas” credits, and substantial public monies.

While Industry experts, developers, gas users, and State bodies were consulted in the formulation of the Draft Strategy, the key environmental NGO groupings – the Environmental Pillar, Stop Climate Chaos and the Sustainable Water Network (SWAN) – were not. Indeed, crucial expert testimony and multiple peer-reviewed academic findings (see Notes below) highlighting the potential climate and environmental pitfalls of biomethane production have not been incorporated in the Draft Strategy. 

Critically, issues with the leakage of methane, a very potent greenhouse gas, from AD plants have largely been ignored. In many cases, these methane losses from AD biomethane production are likely to be unsustainable, even to the point of being worse for the climate than fossil gas usage. 

Similarly, the Draft Strategy has failed to fully assess the adverse impacts to climate and water quality as a result of the fertiliser input needed to grow the silage that is proposed as a feedstock for the AD plants. Increased ammonia pollution from using digestate, the output from the AD process, as fertiliser is also a known risk that goes unevaluated in the Draft Strategy.

Therefore, the Draft Strategy requires major reconsideration of these findings, strong regulatory requirements and independent oversight to ensure that serious known problems with biomethane production are actually addressed.

Overall, the failure by government and agencies to achieve a wide evidence and stakeholder basis for the National Biomethane Strategy means there is a very large risk of public money being wasted for minimal climate benefit, and a likelihood of failing to reduce nitrogen pollution – ammonia to air, and nitrates to water. 

An Taisce now strongly urges the Government to significantly revise the Draft Strategy and include input from environmental NGO stakeholders and peer-reviewed academic findings. Proceeding with the Strategy as-is seriously risks exacerbating the climate and environmental issues it claims to address.

See An Taisce's full submission on the Draft Strategy here.

Notes to the Editor

1.   Aims of the new Strategy and An Taisce’s concerns

The new Strategy supports a plan to produce substantial amounts of biomethane (displacing around 10% of fossil methane in gas supply) from 150 to 200 anaerobic digestion (AD) plants for injection into the existing natural gas grid. This will require substantial heavy transport to move slurry and silage from farms to large AD plants, and also to carry pressurised methane gas to gas grid injection points and digestate fertiliser back to farms

However, costly public investment in AD biomethane is liable to distract from the urgent need to transition away from fossil gas use and away from intensive dairy farming - this Strategy has been specifically premised on the continuation of business-as-usual activities from these sectors.

An Taisce argues that we do not have time for poorly justified distractions from meaningful climate action like this Strategy. To chart a clear course toward a climate-resilient and fairer future, for most farmers and society as a whole, we require Government and agencies to face up to powerful sectoral interests, instead of preferencing them.

2. Methane losses cancel climate benefits

Expert testimony to the Joint Oireachtas Committee on Environment and Climate Action highlighted the need to address this, stating that “As methane loss may be the largest contributor to the carbon footprint of biogas production it would be important that biogas plants in Ireland monitor, report and address methane losses”.

Scientific assessments of AD biomethane repeatedly stress the importance of fugitive methane losses in leakage from AD plants and from digestate spreading that can cancel out much of the claimed climate benefits. Recent field measurements of multiple operational AD plants – in the UK, by the Danish Energy Agency, in addition to another study focusing  on Denmark and Belgium, confirm that unsustainable levels of AD and digestate methane losses are common. 

The observed average and upper rates are well above the base rate of 0.6% and the maximum of 2% indicated by the Teagasc MACC (p. 120). Teagasc states that ‘an increase in fugitive methane from 0.6% to 2% would halve the mitigation potential’, therefore field measurements indicating substantially higher average and high rates would likely wipe out much or all climate benefits of AD biomethane.

Regarding “Renewable Natural Gas” (RNG) – a common American industry term for AD biomethane – a journal article by Grubert states that:

"RNG is not inherently climate friendly. Based on consideration of both the source of methane used to produce RNG and the likely alternative fate of that methane, and using reasonable assumptions about likely system methane leakage, it is unlikely that an RNG system could deliver GHG-negative, or even zero GHG, energy at scale. …

Under some system leakage rates that have been observed for biogas systems (Liebetrau et al 2017, Scheutz and Fredenslund 2019), RNG might not even meet the less stringent threshold of outperforming Fossil Natural Gas from a GHG perspective. …

This work shows that RNG needs to be carefully evaluated in the context of expected long-run system conditions before it is adopted as a component of a zero GHG energy system, particularly given its potential for methane leakage-related climate pollution."

It is not at all evident that assessments underpinning the National Biomethane Strategy have carried out any such careful evaluation of the national system level fugitive methane or pollution swapping impacts of deploying large scale AD biomethane. This means that there is no strong evidence that supportive policies will achieve much if any climate benefit despite large public monies being invested.

3.   Planned high silage AD feedstock has high environmental risks

A peer-reviewed academic study of slurry to silage ratios in the feedstock for potential Irish AD plants finds that feedstocks using a 50/50 mix, with equal masses of slurry and silage, is liable to increase global warming relative to using fossil (natural) gas, due to AD methane losses. Additionally, it is also liable to increase ammonia emissions, due to spreading the resulting AD digestate fertiliser, thereby maintaining or even increasing pollution impacts on local air and waterways. 

A warming analysis of this study’s methane loss data (see Section 4.3.7) combined with field-recorded AD loss rates shows that the actual warming up to the year 2050 is even worse than indicated using standard emission accounting. However, contrary to the peer-reviewed study of feedstock ratios, the SEAI Sustainable Bioenergy for Heat Study (p. 3) insists that a 50/50 slurry/silage AD feedstock mix is sustainable.

4.   Ireland’s pasture grazed system likely not suitable for AD biomethane

A highly relevant peer-reviewed journal paper by Scott et al. on The Role of Anaerobic Digestion in Reducing Dairy Farm Greenhouse Gas Emissions uses standard climate accounting to assess AD biomethane from different dairy farm system options in Northern Ireland. Crucially, the study finds that small fugitive methane loss rates ‘can wipe out any advantage’ of AD biomethane production. 

Also, particularly relevant to Ireland, Scott et al. find that ‘the effect of pollution swapping is clearly visible when comparing the nitrous oxide emissions that are highest for the Pasture Grazed system’. 

Pollution swapping is a common negative outcome of claimed climate solutions, whereby “savings” are claimed without clarifying negative trade-offs that reduce or cancel out any benefits, or even worsen the overall outcome. Since pasture grazed systems are the primary form of Irish dairy and beef agriculture, this study strongly suggests that large scale AD biomethane production is of limited potential at best for Irish climate action.

Assessing  grass silage feedstock from permanent grassland (as envisaged by the Strategy in Ireland), an AD biomethane assessment by the NGO FeedbackEU referencing European Commission assessment states that:

‘From a climate perspective, biomethane from grass feedstock does not measure up to other uses of this land. Compared with grass-biomethane transport fuel, solar electricity generation can avoid 16 times more fossil energy and afforestation can mitigate 6 times more GHG per hectare of land occupied’.

The SEAI Heat Study Key Insights and Teagasc MACC reports fail to include this essential comparison for renewable heat, that is: comparing the land, energy and emissions efficiency of biomethane and hydrogen use injected into the gas grid relative to that of using solar and wind generated electricity and heat pumps. This appears to be a major assessment failure by these independent agencies.

5.   Regulatory limits on total national nitrogen use are essential

There is also a serious risk that total nitrogen use increases rather than decreasing as required by policy commitments.

Nitrogen pollution from agricultural fertiliser application and cattle excretion is a major environmental issue such that policies in the EU and Ireland target reduction of total nitrogen farm inputs via fertiliser and feed. However, assessments of biomethane potential by Teagasc, SEAI, Gas Networks Ireland, and some energy experts, have repeatedly ignored or downplayed the danger that biomethane production could maintain or increase total nitrogen imports, which have already increased by 20% since 2010.

A primary academic reference for grass production for AD biomethane has been a UCD-Teagasc study that relies on maximising nitrogen fertiliser inputs to land, but expert assessment has shown that this would increase environmental impacts and elementary calculation shows it would greatly decrease national system nitrogen use efficiency.

The more recent SEAI-Teagasc research for the SEAI Heat Study states that red clover mixes requiring no chemical nitrogen input can produce silage for AD. However, this advice will only be credibly applied if it can be shown that AD silage is actually being produced via such low nitrogen-input methods. This would be very difficult to monitor and ensure. 

Therefore, strictly applied limits on total national reactive nitrogen imports, in both fertiliser and feed, are likely required, and with additional regulation by watershed to ensure water quality. Otherwise, it is all too likely that Ireland’s total nitrogen use will not go down as much as required to align with EU Farm to Fork objectives.

6. Speculative gas costs, waste management arguments, and claimed “avoided emissions” are a poor basis for AD biomethane mitigation assessment

As seen over the past three years, fossil (“natural”) gas prices are subject to dramatic fluctuations due to geopolitical events, therefore the gas prices used in most AD biomethane mitigation assessments are speculative or notional at best. Waste management arguments advocating AD to process dairy manure and slaughter waste (possibly including male calves) do not align with mitigation objectives if agricultural emissions do not go down in line with sectoral emissions ceilings. 

Moreover, the basis of “avoided emissions” in mitigation assessments rests on highly questionable assumptions including, the false presumption that bioenergy production from biomass is inherently carbon neutral and that it is wrong to imply that biomethane production is environmentally unproblematic. There is a failure to make clear that emissions can only be meaningfully “avoided” if Ireland’s legally binding carbon budgets and constituent sectoral ceilings are being met, which is not the case.

7. AD biomethane is a high cost energy source

The SEAI Heat Study states that biomethane ‘can be a competitive option if the costs and benefits are shared across all gas grid users’, but the new Strategy fails to spell out how this will be achieved. Instead, a few powerful gas users and biomethane supply chain interests are likely to benefit most and any financial benefits to the public remain unclear, so they urgently require clarification. Until such clarification, by SEAI’s definition, biomethane will not be competitive or beneficial.

Noting the crucial importance of regional and national system analysis, a European Commission biomethane assessment (p. 237) states:

"Biomethane counts among one of the most expensive RES options (also compared to wind, solar etc.). Covering heat demand by heat pumps is in many cases a more cost-efficient solution than using expensive biomethane to generate heat". 

This strongly suggests that Ireland’s emphasis on using biomethane in “renewable” heat production via the existing gas grid and claimed renewable gas credits is misguided, as electrifying heat delivery via heat pumps and the rapidly decarbonising electricity grid is liable to be far less expensive.

8. AD methane can have unintended consequences

Nor have the Government, its departments, or assessing agencies, spelled out the danger of unintended consequences from large scale AD biomethane roll-out. In California, the programme of paying for biomethane renewable gas credits from AD has come under serious expert critique for spurious emissions accounting and US dairy industry observers note that ‘the returns from energy generated by large farms may accelerate the growth of the mega-dairy farms’.