Farmers may hike intensity to supply silage to AD plants, EPA warns

Demand for fuel for anaerobic digestion plants could tempt some farmers to increase fertiliser use – and damage water quality, agency says

Farmers could be tempted to intensify their farming practices to meet the demands of supplying multiple cuts of silage to Anaerobic Digestion (AD) plants, the EPA has said.

Its submission on the Strategy, seen by the Farming Independent, highlighted a number of risks associated with the government’s target to scale up indigenously produced biomethane to produce around 10pc of Ireland’s current overall gas demand.

While the EPA said it supports the government’s strategy as a crucial step in decarbonising the nation’s economy, it stresses the importance of ensuring that the establishment and operation of new biomethane production capacity adhere to existing legal and regulatory standards aimed at safeguarding the environment.

It highlighted particular risks around managing feedstocks prudently, complying with licensing and regulatory mandates, accurately reporting greenhouse gas emissions, and preserving water quality.

The EPA said the potential risk of environmental impacts from mismanagement of anaerobic digestion plants is high.

It said issues related to appropriate feedstock acceptance and handling (liquid and solid materials), feedstock storage, odour, operations and production, risk of activity losses (production gases, leachates), digestate storage and management etc occur regularly.

“AD plants must operate in compliance with EPA licence conditions to protect the local environment. To achieve general acceptance by the public, the operators of AD plants must ensure they are ‘good neighbours’,” it said.

The EPA said that while it supports the objective that biomethane will play a significant role in the decarbonisation of the agriculture sector, the emissions savings will need to be more accurately estimated.

The EPA also highlighted significant risks relating to water quality of increasing biomethane production.

It said the development of AD plants at scale should not lead to the increased application of nutrients to land areas where existing issues of high nutrients exist.

While the EPA said it welcomes the opportunity to reduce inorganic fertiliser use on land, it said replacement nutrient sources should not lead to an increase in nutrient loss to surface or ground water.

“It is also noted under the Nitrates Directive that biofertilisers are included as part of the allocation of organic nutrients on farms,” it said.

In addition, the EPA said the movement and control of use of organic fertilisers and biosolids is an issue relating to both environmental protection and human health, and should be adequately addressed by the Strategy going forward.

It further said the Strategy includes an estimate that a land area of c120,000ha will be needed to produce silage as an AD plant feedstock.

“Securing a reliable feedstock supply is fundamental to the viability of an AD project and obtaining a longterm supply contract from feedstock producers is critical,” it said.

“However, it is vital that activities associated with producing feedstocks don’t themselves lead to an increase in farm intensification such as the increased use of chemical fertiliser, which can ultimately impact on water quality.

“The use of cattle slurry (20pc of all winter cattle slurry), which is currently an essential part of nutrient management planning, could possibly also inadvertently result in an increased use of chemical fertiliser.

“There is also the risk of low-intensity farmed land being converted to higher-intensity grassland to supply several cuts of silage.

“There is a risk that there will not be enough land banks available in the vicinity of the AD plant where digestate could be applied safely without negatively affecting water quality.”

The EPA also said careful export of digestate from areas high in nutrients to areas that require additional nutrients would be critical to minimise the potential impact on water quality.

“Managing the digestate must be done in accordance with the GAP regulations (similar to chemical fertilisers) and all imports of slurry and exports of digestate to farmers must be readily available electronically to regulators such as local authorities and the Department of Agriculture,” it said.

The EPA also said it is vital that the biomethane strategy is more strongly integrated with water, nature, biomass and land use policies, plans and regulations.

“In particular, it is critical that the full life cycle of the organic feedstock and digestates, from farm, to plant, and back to farm, are central to the mission statement, and any future regulatory processes that may be developed following the strategy,” it said.

“There is the risk of low-intensity farmed land being converted to higherintensity grassland to supply several cuts of silage”