AD As Part Of The 25% By 2030 Solution

As part of its climate plan, the Irish Government has set a target of producing 5.7 terawatt-hours of biomethane by 2030, which is the equivalent of 10% of Ireland’s current demand for natural gas.

Farmers, farm organisations, and agricultural co-ops have been advised to take a key role in developing anaerobic digestion (AD) in Ireland.

“We can sit on our hands and do nothing, and let someone else come in and build these plants, or farmers can get active”, said Dr Maurice Deasy, researcher on Teagasc’s FLEET evaluation of the potential of AD for farmers.

In a recent episode of the Signpost Series podcasts, he said if AD plants are built and operated by farmers, they will benefit farmers.

As part of its climate plan, the Irish Government has set a target of producing 5.7 terawatt-hours of biomethane by 2030, which is the equivalent of 10% of Ireland’s current demand for natural gas. There is an interim target of 1 TWh by 2025.

Biogas from AD plants can be upgraded to biomethane, which can then be used as a direct replacement for natural gas. Biomethane can also be used as CNG fuel for trucks. The carbon dioxide by-product can be used in the food and beverage industry.

The government is due to announce a National Biomethane Strategy for the agriculture sector to deliver on its sectoral emissions reduction target, for businesses to decarbonise, and Ireland to meet its EU renewable heat targets.

Biomethane can help farmers on the double to reach their obligation to reduce emissions 25% by 2030 (relative to 2018).

“Our slurry tanks and slatted sheds contribute to our emissions of methane. If we were taking that slurry out of agriculture and digesting it, capturing that methane, that would help reduce our emissions”, said Dr Deasy.

“Typically in Germany, a lot of maize is used, in the UK you’ve got beet and wholecrop, but also grass. In an Irish context, we’re talking a lot more about grass, because 90% of the agricultural area is grassland and equally, we think we can produce grass without chemical nitrogen which is important in terms of sustainability”, explained the FLEET researcher (Farm Level Economic, Environmental and Transport Modelling of AD).

Teagasc is investigating the use of red-clover silage and multispecies swards for AD plants. Ireland is unique across Europe in producing high yields from grass silage, and the use of legumes such as clover would reduce or eliminate the requirement for nitrogen fertiliser. Some of the current issues with clover swards around rotational grazing, longer rest periods, higher residuals, or fear of bloating, do not arise if the clover sward is being produced as an AD feedstock.

If contrast, if chemical nitrogen is used to grow silage for an AD plant, it reduces the environmental sustainability of the biomethane. “Chemical nitrogen has a huge emission that needs to be accounted for in RED 2”, Dr Deasy explained. RED 2 is the Renewable Energy Directive which requires all EU Member State fuel suppliers to supply at least 14% renewable transport fuels by 2030.

Under this Directive, animal slurries are given a manure credit for the capture of methane that would otherwise be lost to the atmosphere.

Biogas from AD plants is usually converted to heat and power. The electricity can be sold to the grid, and the heat can be used, for instance, to heat a poultry unit, or a cheese processor. In Germany, AD plants often supply district heating systems. “An AD plant is running 24 hours a day, the bugs are always making gas. That creates a power that you can actually store and use when you want it, which is a big difference from solar and wind”, said Dr Deasy. Hence, AD power could be sold at a premium, when demand is highest. However, there are no schemes as yet set up in the Republic of Ireland to sell AD power to the grid.

And how willing might Irish farmers be to supply silage to an AD plant? Finding the answers to that question was part of the FLEET research.

“Most farmers, nearly 65%, were saying ‘no, I wouldn’t supply silage to an AD plant” said Dr Deasy. “I think a lot of that is down to awareness. If you don’t know what AD is, and you’re asked would you supply an AD plant, you’d say, well, ‘no, because I don’t know what an AD plant is’”.

On the other hand, 15% of farmers indicated that they would consider it, if the market price was right. “That’s actually probably enough farmers to supply 5.7 TWh, and 10% of the gas grid. We don’t need every farmer to do this in terms of supplying grass. We need a small amount of farmers to supply grass”.

There was general readiness among farmers to receive the digestate organic fertiliser by-product from AD plants.

But slurry would be needed from many more than 15% of farmers. Usually, AD plants use a a 50/50 blend on a fresh weight basis of silage and slurry. 

“Eighty percent of the power would be coming from the silage, 20% coming from the slurry, or even less” said Dr Deasy. If RED 2 targets are to be met, silage cannot be used 100% in a AD plant, because of the associated emissions, such as from diesel for harvesting. Using the slurry offsets those emissions, because of the extra bonus of capturing the slurry methane otherwise lost to the atmosphere. An AD plant will not want watery slurry, advised Dr Deasy. 

“Fibre doesn’t make biogas either, so those big, high yields of lignocellulose silage which is very good for feeding a suckler cow, very good for the rumen health, that’s not what an AD plant wants”, he added.

The FLEET researchers assessed the profitability of selling silage for €30 to €40 per tonne. Dairy would always be more profitable. But at €40 a tonne, one could possibly make more from AD silage than from tillage. “On average, it’s not very likely that a tillage farmer would go towards growing grass for AD”, Dr Deasy said.

“For your sheep and cattle enterprises, once the price of the AD silage gets to €40 a tonne, then it does look to be more economically viable to sell grass for AD compared to your existing system. There has to be increased profitability, to make a farmer shift over from one system to another, otherwise why change, why take the risk?” he said.

“I think AD has a role in achieving some of our greenhouse gas emission savings, particularly from our slurry from ruminants”, Dr Deasy said. “If a farmer has too many cows, here’s an opportunity. You could sell your artic load of slurry, you can get your certificate. Now you’ve reduced your organic loading”. 

On a dairy farm, about 10% of emissions would typically be associated with the slurry tank, which is emitting methane.

“The advantage of AD is that if you are taking that slurry out of the farm, exporting it to an AD plant, capturing that methane, now we can use that as an energy source”.

The slurry would be collected as fresh as possible.

Dr Deasy favours a system which would incentivise farmers to produce both food and energy. If farmers can grow more grass than they can feed to cows, the excess could be used to supply AD plants, diversifying farm income. AD also will create considerable rural employment, since it involves three or four cuts of silage, managing slurry, distributing digestate, etc.

The digestate fertiliser from AD plants is typically 6-8% dry matter, like livestock slurry. However, the fertiliser value is increased, particularly the plant-available nitrogen. And digestate has a verified nutrient content. 

”You have more nitrogen and it’s more available, so you get a much better crop response,” Dr Deasy said.

If a farmer supplying feedstock doesn’t need the digestate back, they can receive a credit instead, and someone else will use the digestate. Arable farms, in particular, will greatly value this fertiliser.

Northern Ireland and the UK already have many AD plants. Pig slurry, food waste, industrial waste, are all very good feedstocks, but they are limited resources. “The big potential in terms of reaching the big numbers is in cattle slurry and grass silage,” said Dr Deasy.

Teagasc Grange is the site of a pilot AD plant. Per day, it will need about 10 tonnes of grass silage at 25% dry matter and nearly 15 tonnes of slurry. It will need silage from about 70ha, and the winter slurry from 1,000 cattle.

The plant will produce about 3.2 Gigawatt hours of energy per year. However, much larger (20 to 30 GWh) plants, fed primarily on agricultural materials, are expected. Such a plant would need about 100 tonnes of silage a day, and 150 tonnes of slurry.

(Source – Irish Examiner – Farming – Stephen Cadogan – 03/02/2024)

Biomethane Can Help Greatly To Decarbonise Irish Agriculture

Officials are wrestling with cost, location and regulation.

A major role is envisaged for Irish farmers to own, operate, and supply feedstock to plants producing biomethane. But the challenges of high investment costs, regulatory and permitting requirements, and technical expertise, are emphasised in the draft National Biomethane Strategy published last week.

The cost of producing biomethane depends on factors such as the scale of the plant, feedstock supply, the proximity of anaerobic digestion plants to the gas grid, and financing. 

Larger, grid-connected plants can produce biomethane significantly more cheaply. But smaller plants might get better buy-in from farmers, the rural community, and the agribusiness sector. 

According to the draft strategy, 140 larger plants producing biomethane in Ireland align closely with the successful biomethane industries developed in Denmark and the UK. 

They can produce biomethane significantly more cheaply than smaller plants utilising truck and trailer transport of gas and are seen as the best chance of meeting Ireland’s 2030 biomethane production target (5.7 TWh) but with a smaller involvement for the farming community.

Draft Strategy

The draft strategy, however, suggests co-ops could allow for greater farmer involvement and/or ownership in larger plants.

Smaller plants processing material from farms and consuming the energy on-site (using the “raw” biogas product for heat and power) will not contribute substantially to national biomethane targets but can be important to decarbonise agriculture. 

They can also play a strong role in the ‘social acceptance’ of the anaerobic digestion process to produce biomethane. There are 43 of these plants already in Ireland, processing materials such as landfill waste, municipal solid waste, sewage waste, and animal slurries, to produce biogas for electricity generation.

These biogas plants could be upgraded to develop biomethane, which is more efficient. Biogas is now seen as an expensive way to generate renewable electricity, with a shift across Europe to instead generate biomethane for high-temperature heat, gas grids, and the transport sector. 

Ireland has only two biomethane facilities yet, with most of their biomethane coming from the processing of waste, and used in the transport sector.

According to the draft strategy, expecting end users to absorb the full extra cost of biomethane (“the green premium”) is likely to result in sub-optimal use and make achieving the full 5.7 TWh target challenging.

Historically, most European governments subsidised biomethane through financial support, such as a feed-in tariff guaranteeing the biomethane developer revenue for every unit injected into the gas grid.

Economic Incentive

However, at the demand end, Irish companies covered by the EU’s Emissions Trading Scheme would have a substantial economic incentive to switch to biomethane. They normally have to purchase ETS allowances to cover gas consumption (€90 per tonne in 2023), but not for biomethane, because it is a zero-carbon-rated fuel.

Discussions with developers have revealed getting direct access to the national gas network is a key objective, even though the cost of connecting anaerobic digestion plants to the grid in Ireland has been shown by developers to be about two or three times more expensive than in neighbouring countries. 

Using gas pipelines is the most efficient, sustainable, and cost-effective way to get gas to end users. Trucking the gas is more expensive and less sustainable. 

However, due to the location of Ireland’s existing gas network (which does not for example extend to counties such as Kerry, Donegal, Leitrim, Longford, Roscommon, and Sligo), truck transport is expected to have a key role.

The policy for biomethane is that the customer pays 30% of the costs for connection infrastructure. More than 75% of biomethane plants in Europe are grid-connected.

The Departments of Agriculture, and Local Government will develop a standardised code of practice for local authorities assessing anaerobic digestion and biorefinery planning applications. 

Lengthy timelines for planning decisions are frequently highlighted by stakeholders as impeding the speedy development of such facilities. Although Europe has more than 20,000 plants in operation, it is a relatively new and unknown technology in Ireland, which could lead to confusion and inconsistent decisions by local authorities.

The draft strategy envisages biorefineries co-located with anaerobic digestion plants. They would process materials such as grass and other forages to extract valuable compounds such as proteins and fibres, before the anaerobic digestion process. 

With the highest proportion of permanent grassland in Europe, Ireland is well-positioned for biorefineries producing, for example, protein feed for animals, or even food-grade protein. The Government will invest up to €30m in biorefinery piloting and demonstration over the next three years.

Although getting involved in the ownership of the biomethane sector may be daunting for the agri-sector, it is likely to be the biggest supplier of raw material for anaerobic digestion and biorefineries, and the main user of the digestate raw material. 

Climate Targets

And, crucially, without biomethane, Ireland is unlikely to meet its legally binding climate targets, including agriculture’s extremely challenging 25% emission reduction target.

In Europe, 64% of biomethane is produced by agricultural plants. Other important feedstock sources include organic municipal solid waste (11%) and industrial waste (11%).

Research at Teagasc Grange recommended an equal mix of grass silage and slurry (on a fresh weight basis) as a balanced feedstock. For the lowest emissions per unit of energy produced, silage should be produced with minimal chemical fertilisers, so the incorporation of legumes, such as white or red clover into perennial ryegrass, or multi-species pastures, is required.

Teagasc estimates about 120,000 ha (less than 5% of available land) will produce enough silage to feed the ADs. Clover or multi-species swards will reduce the hectares required, but some displacement of livestock is a likely consequence.

Slurry from 1.3 million cattle will be required to meet the 2030 target. This represents about 20% of all winter cattle slurry produced in Ireland. No-emissions all-year-round slurry storage at anaerobic digestion facilities will be crucial.

Other useful agricultural feedstocks include poultry litter (producing an impressive 1.35 MWh of biomethane per tonne, compared to grass silage’s 0.836 MWh).

The digestate left behind after anaerobic digestion has typically been viewed as a waste product burden, with operators commonly paying farmers to take it away. However, transforming it into valuable biobased fertiliser can make it a revenue earner, according to the draft strategy.

Agriculture Minister Charlie McConalogue has said he looks forward to hearing people’s views on the draft biomethane strategy. “This will inform the final strategy, which we will publish at the end of Q1 2024.” The closing date for submissions is February 27.

Environment Minister Eamon Ryan said the Government was firmly behind the development of a sustainable biomethane industry of scale in Ireland, and noted increased availability of an indigenous, renewable gas in Ireland would boost the long-term security of our energy system.

(Source – Irish Examiner – Farming – Stephen Cadogan – 06/02/2024)