Publication - Consultation paper

River basin management plans - silage, slurry and anaerobic digestate – improving storage and application: consultation

Published: 20 Jan 2021
Directorate:
Environment and Forestry Directorate
Part of:
Environment and climate change
ISBN:
9781800045422

Good water quality is important to us all and it is important that we continue to protect this key natural resource in Scotland. This consultation invites stakeholders to respond to a range of proposed updates to The Water Environment (Controlled Activities) (Scotland) Regulations 2011 (“CAR”).

River basin management plans - silage, slurry and anaerobic digestate – improving storage and application: consultation
Part 1 – Storage and application of organic materials.

Part 1 – Storage and application of organic materials.

3. Policy Context.

Good water quality is important to us all. We rely upon it for almost every aspect of our lives: drinking water, the food we produce, industry, tourism and the survival of our ecosystems are all dependent upon clean water. Water also makes a significant contribution to our health, wellbeing, and recreational pursuits.

Silage, slurry, and farm yard manures (FYM) are a valuable resource to farmers, but along with increasing amounts of liquid or fibrous anaerobic digestate, can cause significant emissions and present a risk of pollution of our water environment. In many cases, this is due to inadequate storage capacity, or storage of poor quality.

Agricultural activities associated with these products also contributes to the release of ammonia and greenhouse gases into the atmosphere, and, in the light of the current climate emergency, reducing such emissions is now a matter of primary importance.

Taking steps to ensure better management of the storage and application of organic materials is now a key priority for Scottish Government.

Sufficient suitable storage enables farmers to better manage valuable organic fertilisers by:

  • minimising environmental impact,
  • allowing application at times which maximise benefit, and
  • reducing the use of costly manufactured chemical fertilisers.

These substances can also present a potential risk to water quality when applied to land. This can be a result of:

  • applying too close to watercourses,
  • over application,
  • leaching due to no crop uptake, or
  • applying in inappropriate weather and ground conditions.

The amount of organic material collected in Scotland continues to rise, with increasing numbers of livestock being housed. The total quantity of slurry produced in Scotland is estimated at 6.35 million tons (1.67 billion gallons) per annum[1].

The increase in recent years of anaerobic digestion to provide energy has also seen large volumes of organic crops grown as feedstock. Anaerobic digestion results in large volumes of the processed feedstock available as residue, in the form of liquid or fibrous digestate, which then has to be stored and applied to land efficiently.

The proposals in this consultation will serve the dual purpose of protecting water quality and reducing agricultural emissions of ammonia and nitrogenous gases.

4. Regulatory framework.

The (Control of Pollution) (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003 (“the SSAFO Regulations”) set standards for the storage of silage and slurries, with the aim of minimising the risk of pollution of the water environment.

The SSAFO Regulations were initially introduced in 1991 and consolidated in 2003. These were the first regulations designed specifically to address water pollution resulting from agricultural activities, and they continue to play an important role today in delivering protection for Scotland’s surface and ground waters.

Since the introduction of the SSAFO regulations two other key pieces of European legislation have been introduced, both with the aim of protecting the water environment from potential pollution from agricultural sources.

  • The Water Framework Directive (“WFD”) requires protection and improvement of the water environment, and was given effect with the introduction of the Water Environment (Controlled Activities) (Scotland) Regulations 2005 (“CAR”) These regulations introduced controls over a number of activities which had potential to impact on the water environment; and following updating in 2011, these now include a suite of general binding rules for mitigating diffuse pollution.
  • The Nitrates Directive is a key instrument for protecting ground and surface waters from agricultural pressures. The Nitrates Directive required Nitrate Vulnerable Zones (“NVZ”) to be established for the protection of water from nitrate pollution, and certain actions to be taken in those areas. The Nitrates Action Programme (Scotland) Regulations 2008 (“the NVZ Action Programme”) place controls on the use of nitrogen fertilisers in designated NVZ areas.

Along with the SSAFO Regulations, these regulations play a key role in setting a baseline for the protection of Scotland’s water environment.

In 2006, agricultural fuel oil storage controls were removed from the SSAFO regulations and became the Water Environment (Oil Storage)(Scotland) Regulations 2006, which placed controls on oil storage installations to minimise impact on the water environment. These were subsequently incorporated into CAR as a general binding rule in 2018.

This means that the remaining SSAFO Regulations now only contain provisions regarding the storage of silage (for livestock feed) and slurry.

The proposal in this document to move these provisions into general binding rules within CAR reflects our established approach of consolidating water environment protection provisions into a single set of regulations, where possible to do so, in the interests of efficiency and transparency.

5. Proposals overview.

In carrying out the proposed consolidation exercise, this consultation also proposes some revisions to the existing provisions for silage and slurry storage, and the inclusion of storage of anaerobic digestion feedstock and liquid digestate, to ensure adequate protection of our water environment in the light of ongoing developments in farming practice. The proposed revisions aim to:

  • ensure legislative provisions continue to reflect current good practices in the management of slurry and silage storage;
  • ensure storage facilities cover all organic materials stored as livestock feed and energy production feedstock;
  • ensure proper storage of liquid residues in connection with energy production;
  • ensure storage quantities are consistent with achieving the most efficient use of fertilisers.

In outline, updated provisions relating to the storage and application of slurry and digestate are proposed by means of 8 new general binding rules, in respect of the following topics:

Silage storage (section 6).

Silage and other forage crops have traditionally been stored as winter feed for livestock. These are now also increasingly being stored as an energy crop for use in anaerobic digestion plants. It is proposed that the revised regulations will now extend controls over the storage of these as feedstock for energy production. General binding rules are proposed for:

  • The making and storage of silage in wrapped bales or bulk bags
  • Storage of silage in a silo
  • The drainage of silage effluent to a constructed farm wetland

Slurry storage (section 7).

The amount of storage required on farm for slurry has slightly differing provisions in the NVZ Action Programme and SSAFO. It is proposed that the provisions are consolidated to ensure that all slurry storage requirements, in relation to minimum storage quantities, are the same across Scotland. General binding rules are proposed for:

  • Construction standards for slurry storage.
  • Quantity of slurry storage required.
  • Treatment of certain types of slurry by discharge through a constructed farm wetland

Liquid digestate storage (section 8).

There are currently no regulations which cover the storage of liquid digestate, a by-product of the anaerobic digestion process. The increased use of anaerobic digestion to produce energy has resulted in large volumes of liquid digestate being produced. It is proposed that the storage of these will also now fall within the revised regulations. The storage of fibrous digestate is already covered by the existing general binding rule 18 of CAR. General binding rules are proposed for:

  • Construction standards for storage of liquid digestate.
  • Storage capacity.

Targeted and efficient application of organic materials (section 9).

In order to ensure the most efficient use and application of organic materials, an addition to the existing General Binding Rule 18 of CAR is proposed to include:

  • The preparation and use of Risk Assessment for Manure and Slurry (RAMS) maps.
  • The use of precision spreading equipment.

6. Silage storage.

6.1 Control of silage effluent.

Other than for use as livestock feed, silage is increasingly being used as feedstock for anaerobic digestion plants. We propose that the current regulations, which apply to the storage of forage crops for livestock fodder, are extended to include forage crops used as feedstock for an anaerobic digestion plant.

Silage effluent is potentially the most potent source of pollution on the farm. Even when a small amount enters a watercourse, it can have a rapid and devastating effect on fish and plant life for a long distance downstream. Great care is needed in the making of silage, and the monitoring and maintenance of silage storage facilities. Even in very small quantities, its effects can be highly destructive. This is because:

  • it is at least 200 times stronger than untreated domestic sewage.
  • it kills fish and the tiny organisms they feed on, through starving them of oxygen.
  • it can affect water abstractions.
  • it can pollute groundwater, springs, wells and boreholes, endangering public, and private, water supplies.

The result of effluent reaching a watercourse can therefore be devastating.

The main causes of pollution from silage effluent are:

  • storing grass when it is too wet; the wetter the grass, the greater the problem of excessive effluent.
  • structural failure of silage clamps, tanks and/or pipework.
  • overflow from effluent tanks.

Silage effluent is highly corrosive - so much so that over a period it can dissolve cement. Silage silos and effluent collection facilities can deteriorate rapidly if they are not properly managed and maintained.

The current controls on silage effluent discharge have been re-shaped into GBR format. They remain mostly unchanged, but we propose that they now contain a provision to protect surface water drainage systems.

The rules relating to the storage of silage bales have also been slightly amended. We propose that silage bales, or bulk bags, should not be stored, opened, or unwrapped within 10 metres of any surface water or opening into a surface water drain into which silage effluent could enter if it were to escape.

We also propose to incorporate the existing SSAFO provision, introduced by The Diffuse Pollution (Scotland) Regulations 2008 SSI 2008/54, that allows silage effluent, at those times when it is less contaminating, to be directed to a constructed farm wetland. This has been amended to allow this to take place once the silo has been opened rather than place a calendar restriction.

Draff, a by-product of the brewing and distilling process, is now also commonly used as animal feed and as a feedstock for anaerobic digesters. We propose that its storage is now included within the controls on silage.

6.2 Proposed general binding rule conditions for the control of silage effluent discharge.

The making and storage of silage in bales or bulk bags.

(a) The bales or bulk bags must not be stored, opened, or unwrapped within 10 metres of any:

(i) river, burn ditch or loch as measured from the top of the bank;

(ii) wetland;

(iii) transitional or coastal water as measured from the shoreline; or

(iv) opening into a surface water drain which silage effluent could enter if it were to escape.

(b) the bulk bags must:

(i) have an impermeable membrane;

(ii) be resealed when not in use, to prevent the escape of silage effluent;

(iii) incorporate a facility designed to enable the removal of excess effluent when present without spillage; and

(iv) be situated on a firm level surface.

(c) The bales must be wrapped and sealed into impermeable membranes or enclosed in impermeable bags.

The drainage of silage effluent which consists mainly of rainwater from a silo to a constructed farm wetland

(a) Such drainage may only take place from a silo if

(i) the silo is open for use;

(ii) the drainage of the silage effluent from the silo to the constructed farm wetland is direct and through a separate channel or pipe from the base of the silo; and

(iii) no crop is added to the silo whilst open.

Q1 – Do you agree with the proposed rules for the control of silage in bales or bulk bags?

6.3 Silage storage structures.

The current silage storage requirements focus on silage structures built between 1991 and the present day. These provisions aim to ensure the structure is soundly constructed, properly maintained and at a safe distance from any watercourse. We propose that these provisions remain mostly unchanged.

The key proposed change is that silage stores constructed prior to 1 September 1991, which were exempted from SSAFO at that time and which still remain so under the current version of SSAFO, will no longer have exempt status. Routine inspections have identified that some older stores pose an environmental risk mainly due to lack of maintenance and there is risk of structural failure due to the corrosive nature of silage effluent.

These stores are now a minimum of 29 years old and, although many of them may be compliant with legislation, it is important to ensure that older stores do not pose a risk to the water environment. For stores built prior to 1 September 1991 it is therefore proposed that they will be brought within the scope of the revised provisions.

A 4 year transitional period from the coming into force date of the regulations will allow operators a period to ensure their stores achieve the minimum standard required.

Stores built after 1 September 1991 should already be compliant with the existing rules, but a 2 year transitional period will be allowed for operators to make any upgrades to ensure full compliance with the revised rules.

For any stores with planning permission but not constructed before the coming into force date of regulations the 2 year transitional period will also apply.

In addition, all new silos brought into operation after proposed regulations come into force must display the maximum loadings for the structure calculated in accordance with paragraphs 15.6.1 to 15.6.3 of the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution and numbered BS 5502-22:2003+A1:2013.

All silage effluent collection systems must have a device fitted, with a dedicated power supply, which triggers an alarm when there is a risk of overflowing.

Currently, SEPA must be notified at least 28 days before any new, reconstructed, or substantially enlarged silo comes into operation. However, at such a late stage, if the design of the store is not compliant, any alterations may be costly. It is proposed to introduce a requirement to notify SEPA before construction commences. This will give SEPA an opportunity to assess an application for compliance and advise on any potential issues.

Notification should be supported by a declaration signed by the construction company confirming that the installation design complies with the regulatory requirements. This reduces the risk of potentially costly post implementation alterations.

SEPA will work closely with farmers during the transition period to help them achieve compliance.

6.4 Proposed general binding rule conditions for the storage of silage.

Storage of silage in a silo

(a) The silo must:

(i) comply with the provisions of paragraphs (b) to (h), and

(ii) if new (including silos constructed from used materials), substantially reconstructed or enlarged have a life expectancy of at least 20 years, with proper maintenance.

(b) the base of the silo must:

(i) comply with:

  • British Standard EN 1992-3:2006([1]) and British Standard EN-1-1-2004 +A1:2014([2]) (for concrete bases), or
  • British Standard EN 13108-4:2016(for hot-rolled asphalt bases)([3]),

(ii) where the silo has retaining walls made other than of earth, extend beyond those walls,

(iii) be constructed with channels to collect silage effluent from the silo, and with channels and/or pipes which must drain any such silage effluent to an effluent tank.

(c) the capacity of the effluent tank must be at least:

(i) for a silo with a capacity of less than 1500m3, 20 litres for every 1m3 of silo capacity, or

(ii) for a silo with a capacity of 1500m3 or greater, 30,000 litres plus 6.7 litres for very 1m3 of silo capacity over 1500m3.

(d) where the effluent collection method associated with the silo incorporates a system of pumps and sumps, it must be fitted with an automatic overfill prevention device with a dedicated electrical supply and an alarm.

(e) the base of the silo, the base and walls of its effluent tank and channels, and the walls of any pipes must be impermeable.

(f) the base and any walls of the silo, its effluent tank and channels, and the walls of any pipes must, so far as reasonably practicable, be resistant to attack by silage effluent and, where the walls are made of earth, they must be lined with an impermeable membrane of 1000 gauge polyethylene or a material of at least equivalent impermeability and durability.

(g) no part of the silo, its effluent tank, channels or any associated pipes may be situated within 10 metres of any surface water or opening into a surface water drain which silage effluent could enter if it were to escape.

(h) if the silo has retaining walls:

(i) the retaining walls must be capable of withstanding minimum wall loadings calculated in accordance with paragraphs 15.6.1 to 15.6.3 of the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution and numbered BS 5502-22:2003+A1:2013,

(ii) the silo must not be loaded to a depth exceeding the maximum depth consistent with the design assumption made in respect of the loadings of the retaining walls, and

(iii) the maximum loadings of any silo constructed (including from used materials), substantially reconstructed or enlarged on or after [coming into force date] must be visibly displayed on the silo.

(i) the silo, its effluent tank, channels, and any pipes must be operationally maintained to be free of any structural defects during its lifecycle.

(j) where any part of an effluent tank is installed below ground level, it must be designed and constructed in accordance with BS 5502 as referred to in paragraph h(i) and must be operationally maintained to be free of any structural defects during its lifecycle.

(k) the silo must not be filled beyond the drainage channels.

(l) where a silo or effluent tank is to be constructed or to be substantially rebuilt or enlarged:

i) the operator must notify SEPA prior to

commencing the works,

ii) the notification under paragraph (i) must be accompanied by an engineering plan for the works to be carried out, and

iii) the operator must retain, for inspection by

SEPA on request, the engineer’s final sign off certificate.

Q 2. Do you agree with the proposed rules on the storage of silage?

Q 3. Do you agree with the proposal to remove exemptions for silage stores built prior to 1 September 1991?

7. Slurry storage.

7.1 On-farm storage of slurry.

Manure management is a key element of farming.

Slurry can be a major pollutant that strips oxygen from water and introduces harmful bacteria into freshwater river systems. Slurry escapes have the potential to kill most river life in its path and contaminate Scotland’s bathing and shellfish waters.

Having sufficient and well-maintained on-farm slurry storage enables farmers to schedule spreading at the optimal time to meet crop requirements and avoid being forced into spreading unnecessarily because of storage capacity limitations.

Spreading at the optimal time increases nitrogen uptake by crops. This reduces the risk of nitrates leaching into the water environment, and makes best use of the nutrients in slurry. As a result, the need for chemical fertiliser is reduced, which has the added benefit of reducing the farm fertiliser costs.

There is also a much greater risk of pollution of the water environment if fertilisers are spread during poor weather conditions.

Pollution by organic manures continues to be a risk to Scotland’s bathing waters and can cause shellfish waters to fail to meet bacterial water quality standards.

The majority of pollution events related to slurry management, or requests to spread in unsuitable conditions are, in the vast majority of cases, related to farms with significant storage deficits, rather than on farms with appropriate storage requirements.

Having sufficient storage capacity gives farmers more resilience to cope with wet or freezing weather, when the risk of slurry runoff, soil structural damage, and subsequent soil wash/runoff can be very high.

It is important that farmers recognise the benefits of adequate slurry storage. Farmers should ensure that proper emphasis is given to the regular maintenance of structures and associated infrastructure. They have an obligation to ensure that storage facilities, including the network of pipes and valves associated with slurry storage, are properly maintained. A number of pollution incidents in recent years have been the result of infrastructure not being properly maintained.

7.2 Current slurry storage capacity requirements in Scotland

The methods for calculating slurry storage capacity under the SSAFO 2003 regulations and NVZ Action Programme produce very similar results. In the interests of consistency, we think it makes sense, moving forward, for the same rules regarding slurry storage capacity to apply across the whole of Scotland.

7.2.1 Current SSAFO requirements.

Under the SSAFO Regulations, there is a requirement to store the likely quantity of slurry produced in a 6 month period unless evidence can be provided to substantiate a reduction in storage capacity. The current SSAFO regulations require that:

“All installations producing slurry shall provide a storage system capable of storing the maximum quantity of slurry which is likely to be produced in any continuous six month period, including allowance for rainwater which may fall or drain into the slurry storage system, unless a shorter period can be justified in a Farm Waste Management Plan.

These SSAFO requirements are expressed in very general terms, and have left it open to differing methods in calculating the required level of storage. To avoid inconsistencies, a more structured approach to calculating storage levels is required.

General binding rule 18 of CAR, initially introduced in 2008 via the Water Environment (Diffuse Pollution)(Scotland) Regulations 2008, placed controls on the application of organic manures during poor weather conditions or when there is no crop nutrient need. As a result, this requirement, which ensures more beneficial use of manures and slurries, makes it is difficult to justify a lesser amount of storage capacity in a Farm Slurry and Manure Management Plan, (formerly referred to as a Farm Waste Management Plan).

Making best use of nutrients on the farm – A Farm Slurry and Manure Management Plan.

Manures and slurries contain valuable plant nutrients. Key to making best use of these nutrients is having sufficient storage capacity on farm to be able to apply them at the most appropriate time, by taking into account soil and weather conditions and when the crop can make best use of the available nutrients.

Producing a Farm Slurry and Manure Management Plan (FSMMP), previously referred to as a Farm Waste Management Plan (FWMP), can be used to calculate the volume of storage capacity needed to allow you to make best use of the nutrients in slurry and manures and also highlight where improvements could be made to make better use of current storage capacity. All farms which produce slurry must have sufficient storage capacity to allow them to store slurry produced over the winter housed period to avoid the need to apply slurry over the winter months when the soil conditions may not be suitable or where there is insufficient crop need.

More information on how to produce a FSMMP is contained in the 4 Point Plan which can be found on the Farming and Water Scotland website (www.farmingandwaterscotland.org/). If in doubt, guidance on how to move towards an FSMMP should be sought via a suitably accredited agricultural consultant.

Having sufficient storage capacity allows slurry to be used more efficiently and reduces the need to apply additional, bought in, chemical fertilisers. GBR 18 was introduced in 2008 to control the applications of organic fertilisers. Measures include controls to prevent the applications of organic manures, such as slurry, during times when there is no crop need, or on waterlogged or frozen land.

Sufficient slurry storage capacity will also contribute to Scotland’s commitment to reduce GHG emissions by ensuring slurry is applied when there is maximum uptake by crops.

The requirements of GBR 18 are:

18 (g) no organic fertiliser may be applied to land that—

(iv) is frozen (except where the fertiliser is farm yard manure), waterlogged, or covered with snow;

18 (i) fertilisers must not be applied to land:

(i) in such amounts that the crop requirement for nitrogen is exceeded;

(ii) in excess of the amount required to maintain the soil phosphorus status at acceptable agronomic levels; or

(iii) during heavy rainfall or where heavy rainfall is forecast within 24 hours;

Compliance with GBR 18 requires farmers to be more resilient in their approach to slurry storage and not be placed in the position of spreading slurry as a means to take pressure off slurry storage and risking adverse environmental impact.

7.2.2 Current Action Programme for Nitrate Vulnerable Zones slurry storage requirements.

Those farming in Nitrate Vulnerable Zones are required to comply with the rules set out in The Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008. The Action Programme requires that farms within Nitrate Vulnerable Zones have sufficient storage to contain:

  • the amount of slurry produced by housed cattle in a 22 week period: or
  • the amount of slurry produced by housed pigs in a 26 week period:

with the calculation based on set values on livestock excreta.

In calculating the capacity of storage facilities figures must be included for:

  • the quantity of any rainfall that is likely to enter storage facilities (directly or indirectly) during collection or storage;
  • the quantity of any cleaning water that is likely to enter storage facilities.

This gives farmers the capability to comply with the requirement on not spreading slurry, which is a high nitrogen content fertiliser, during the closed period when there is the greatest risk of leaching to the water environment.

7.3 Proposed slurry storage capacity requirements.

Slurry is a valuable resource for farmers and should be applied when it can achieve most benefit. Application at times when there is no crop uptake, or soil benefit, is a waste of this valuable resource.

Changing weather patterns of recent years have shown an increased risk of wetter periods throughout the year when spreading slurry is not beneficial to the crop or the environment. Adequate storage will help farmers better manage these situations and comply with the requirements of GBR18.

As noted in 7.2.1, the method for calculating slurry storage requirements in SSAFO, if carried out correctly, should produce very similar results to the method for calculating slurry storage requirements for those farming in Nitrate Vulnerable Zones.

In the interests of consistency, we propose that the slurry calculation as currently used in the Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008 is adopted as the standard calculation for slurry storage capacity requirement across Scotland.

The proposed standard to apply across Scotland, from housed livestock, will be storage capacity for the amount of cattle slurry produced in 22 weeks, and in the case of pig slurry 26 weeks. The storage capacity is to be calculated using the set values and calculation method already set out in The Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008.

Those farms currently compliant with SSAFO and which have 6 months storage should be compliant with the proposed rules and require no action. Those that have less than the 6 months storage will now be required to make arrangements for a minimum of 22 weeks storage for housed cattle and 26 weeks for housed pigs.

In future, when planning new storage facilities, the figure used to predict expected rainfall should be based on M5 rainfall data rather than average rainfall. M5 is the predicted quantity of rainfall that will occur once in every five years over a four month period (known as the M5 120 day rainfall). This will usually occur during the months October to January inclusive, and, given changing weather patterns, will provide a more realistic figure.

When planning new slurry storage serious consideration should be given to roofing the store to prevent the ingress of rainwater and reduce emissions.

Reducing the volume of rainwater will give farmers additional slurry storage and reduce the pressure to spread slurry in unsuitable conditions.

Where slurry storage needs to be increased to meet storage capacity requirements (22 weeks cattle/26 weeks pigs) it is proposed that farmers can have various options to increase storage capacity by: extending existing storage, building a lagoon, or the use of slurry bags. The requirements for each of these is set out in the rules.

Operators will also continue to have the opportunity to have an arrangement for additional compliant storage capacity offsite, but they must be able to provide evidence confirming that this is a permanent arrangement.

The standards, and calculation method, for the volume of excreta produced by pigs and cattle are set out in the 4 Point Plan, available on the Farming and Water Scotland website. It is also planned to make available an online spreadsheet to facilitate calculation of storage requirements.

It is proposed that to achieve compliance with the 22/26 week minimum storage requirement a transitional period of 4 years from the date of regulations will apply for all those farming outwith a Nitrate Vulnerable Zone

Q 4. Do you agree with the proposed revisions to consolidate the storage requirements for slurry across Scotland at 22 weeks for housed cattle and 26 weeks for housed pigs?

7.4 Slurry storage in a slurry tank, lagoon, or slurry bag.

As with silage storage, the current slurry storage requirements focus on structures built between 1991 and the present day. These provisions aim to ensure the structure is soundly constructed, properly maintained and at a safe distance from any watercourse. We propose that these provisions remain mostly unchanged.

However, as with silage storage, the key proposed change is that structures constructed prior to 1 September 1991, and which are still exempt, will no longer have exempt status.

Any such stores are now a minimum of 29 years old and although those which have been extended, enlarged, or modified since 1991, should be compliant with existing legislation, it is important to ensure that older stores do not present a risk to the water environment. Routine inspections have identified that some older stores propose a risk due to their age or lack of maintenance and failure has potential to cause a significant pollution event.

A 4 year transitional period is proposed from the coming into force date of the regulations for any stores built prior to 1 September 1991. This will allow operators a period to ensure their stores achieve compliance with the standard required.

Stores built after 1 September 1991 should already be compliant with the existing rules, but a 2 year transitional period will be allowed for operators to make any upgrades to ensure full compliance with the revised rules.

For any stores with planning permission but not constructed before the coming into force date of regulations the 2 year transitional period will also apply.

Where slurry storage needs to be increased to meet storage capacity requirements (22 weeks cattle/26 weeks pigs) farmers may opt to increase storage capacity by building a lagoon. Lagoons are a popular method to increase storage capacity and it is already best practice to line lagoons to avoid leaching to groundwater. The proposed rule will make it a legal requirement that lagoons are lined with an impermeable liner to protect groundwater.

We also propose that the storage of slurry in slurry bags is brought within the scope of the legislation. To minimise risk, slurry bags must be in bunded containment which has an impermeable liner and a means of removing rainwater from the bund.

Where slurry is stored in slurry bags there is the advantage that rainfall does not need to be taken into consideration in calculating storage quantity.

It is also proposed that the current restriction of slurry tankers not having a capacity exceeding 18,000 litres, which applies when slurry is stored temporarily while being transported, will be removed.

7.5 Proposed general binding rule conditions for the storage of slurry.

Storage of slurry from housed livestock on a farm in a slurry storage system or a slurry bag

(a) The minimum capacity of the on farm storage facilities for slurry must be sufficient to store a quantity of slurry likely to be produced in;

(i) 26 weeks by housed pigs, or

(ii) 22 weeks by housed cattle

plus any additional inputs to, or exports from, storage as set out in rule (c).

(b) the total quantity of slurry referred to in paragraph (a) is to be calculated by adding up the total figures produced for each type of livestock, as applicable, in accordance with the formula for housed pigs or housed cattle, contained in regulation 7(2) of the Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008.

(c) in calculating the minimum capacity of the slurry storage system and/or slurry bags necessary to comply with paragraph (a), the following figures must be included:

(i) the quantity of any rainfall (including any fall of snow, hail or sleet) that is likely to enter storage facilities (directly or indirectly) including from dungsteads, silage pits or dirty yards;

(ii) the quantity of any cleaning water that is likely to enter the storage sytem or slurry bag;

(iii) the likely quantity of any imported slurries and liquid digestate added to the storage facility; and

(iv) the quantity of any slurry exported off farm.

(d) the slurry storage system must:

(i) comply with the provisions of paragraphs (e) to (n); and

(ii) if new (including constructions with used materials), substantially reconstructed, or enlarged have a life expectancy of at least 20 years with proper maintenance.

(e) subject to paragraph (k) the base and walls of any slurry storage tank, any channels, reception pit, and the walls of any pipes shall be impermeable.

(f) the base and walls of any slurry storage tank, channels and reception pit, valves, and the walls of any pipes must be protected against corrosion in accordance with paragraph 7.2 of the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution and numbered BS 5502-50:1993+A2:2010.

(g) the base and walls of any slurry storage tank and any reception pit must be capable of withstanding characteristic loads calculated on the assumptions and in the manner as set out in paragraph 5 of the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution BS 5502-50:1993+A2:2010.

(h). The capacity of any facility used for the temporary storage of slurry, before it is transferred to a slurry storage tank, must be the equivalent of at least 1.5% of the minimum on farm storage capacity required by para (a).

(i) where slurry flows into a channel, before discharging into a reception pit, and the flow of that slurry is controlled by means of a sluice or valve, the capacity of the reception pit must be sufficient to store the maximum quantity of slurry which can be released by opening the sluice/valve.

(j) no part of any slurry storage tank, channels, pipes or reception pit may be situated within 10 metres of any surface water or opening into a surface water drain which slurry could enter if it were to escape.

(k) the slurry storage tank, channels, pipes, valves, and reception pit must be operationally maintained to be free of any structural defects during their lifecycle.

(l) where the walls of the slurry storage tank are not impermeable:

(i) the base of the tank must extend beyond its walls and be provided with channels designed and constructed so as to collect any slurry which may escape from the tank; and

(ii) It must have adequate provision to collect, drain and store slurry from these channels to a slurry storage system.

(m) where the slurry storage tank or reception pit is fitted with a drainage pipe:

(i) there must be two valves in series on the pipe and each valve must be capable of stopping the flow of slurry through the pipe and must be kept shut and locked in that position when not in use.

(ii) Sub-paragraph (i) does not apply in relation to a slurry storage tank which drains through the pipe into another slurry storage tank of equal or greater capacity or where the tops of the tanks are at the same level.

(n) where a slurry storage system has walls which are made of earth, the system must not be filled to a level which allows less than 750 millimetres of freeboard, and in all other cases the slurry storage tank must not be filled to a level which allows less than 300 millimetres of freeboard.

(o) where a slurry storage system has walls which are made of earth, it must be lined with an impermeable sheet material of a type approved by SEPA.

(p) a slurry bag may only be used to store slurry if:

(i) the bag is constructed of impermeable material of sufficient strength and structural integrity, and is unlikely to burst or leak in its ordinary use;

(ii) situated in a bund, of equivalent capacity to the slurry bag, where the bund is lined with an impermeable sheet material, of a type approved by SEPA, and has a means of removing rainwater from the bund.

(q) where a slurry storage system (including a reception pit or channels) is to be constructed or to be substantially rebuilt or enlarged;

i) the operator must notify SEPA prior to

commencing the works,

ii) the notification under paragraph (i) must be accompanied by an engineering plan for the works to be carried out, and

iii) the operator must retain, for inspection by SEPA on request, the engineer’s final sign off certificate for the works.

Q 5. Do you agree with the proposal to remove exemptions for slurry stores built prior to 1 September 1991?

Q 6. Do you agree with the proposed rules for slurry storage?

7.7 The treatment of certain types of slurry through a constructed farm wetland.

The treatment of certain types of contaminated water through a constructed farm wetland is currently regulated by SSAFO. The current conditions will continue to apply but drafted as a general binding rule.

The treatment of slurry by draining through a constructed farm wetland

(a) Slurry may be drained to a constructed farm wetland only if it consists mainly of rainwater and washings which derive from:

(i) a midden, which mainly contains farm yard manure and is situated where its contents can be affected directly by precipitation;

(ii) any uncovered yard, used by livestock to move from one area to another but not including areas covered by paragraph (b),

(iii) a yard used for the gathering or holding of livestock for no more than once a week and which can be directly affected by precipitation.

(b) slurry must not be drained to a constructed farm wetland from areas :

(i) where livestock are gathered or held more regularly than once a week; or

(ii) used for livestock movement or holding prior to, during, or after being:

(a) milked;

(b) housed; or

(c) fed;

(c) slurry which contains pesticide must not be drained to a “constructed farm wetland”.

(d) all reasonable steps must be taken to ensure that the drainage of slurry through a constructed farm wetland has no adverse impact on the water environment.

8. Liquid digestate storage.

8.1 On-farm storage of digestate.

The current move towards alternative energy sources has resulted in a large number of anaerobic digestion plants being constructed.

The anaerobic digestion process produces large volumes of digestate in both liquid and fibrous form. These substances are similar in nutrient content to slurry and farm yard manure.

Therefore, to minimise any risk to the water environment we propose that the storage facilities for the liquid fraction from the anaerobic digestion, and run off from fibrous residue, should be consistent with those for slurry.

We propose that where the storage is for application to land then the storage requirement should be sufficient to avoid spreading when there is no crop need, or when spreading conditions do not meet legislative requirements.

8.2 Liquid digestate storage in a tank, lagoon, or bag.

The proposed rules for the storage of liquid digestate are much in line with those for the storage of slurry.

The rules on construction standards for storage apply to all storage of liquid digestate whether on farm or other commercial sites.

Where liquid digestate stores do not currently meet the requirements within the regulations, a 2 year transitional period from the regulations coming into force will apply.

Storage of liquid digestate in a liquid digestate storage system or slurry bag.

(a) Where liquid digestate is produced on farm, there must be sufficient storage capacity to accommodate the volume of liquid digestate produced during periods when application is not authorised under activity 18 of column 1 of this Schedule, or would not comply with the requirements of the [Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008.

(b) where liquid digestate is imported onto a farm, there must be sufficient storage capacity on the farm to store quantities imported during periods when application is not authorised under activity 18 of column 1 of this Schedule, or would not comply with the requirements of the Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations 2008.

(c) in calculating the minimum capacity of storage facilities the following figures must be included;

(i) the quantity of any rainfall (including any fall of snow, hail or sleet) that is likely to enter storage facilities (directly or indirectly) including from dungsteads, silage pits or dirty yards;

(ii) the quantity of any cleaning water that is likely to enter the storage system or slurry bag;

(iii) the quantity of any slurry from housed livestock;

(iv) the likely quantity of any imported slurries and liquid digestate added to the storage facilities; and

(v) the quantity of any liquid digestate exported off farm.

(d) a liquid digestate storage system must;

(i) comply with the provisions of paragraphs (e) to (k); and,

(ii) if new (including construction with used materials), substantially reconstructed, or enlarged on or after [coming into force date] have a life expectancy of at least 20 years with proper maintenance.

(e) the base and walls of the digestate storage tank, and walls of any feedstock tank, channels and pipes must be impermeable.

(f) the base and walls of the digestate storage tank, any feedstock tank, valves and the walls of any pipes must be protected against corrosion in accordance with paragraph 7.2 of the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution and numbered BS 5502-50:1993+A2:2010.

(g) the base and walls of the digestate storage tank and any reception tank must be capable of withstanding characteristic loads calculated on the assumptions and in the manner as set out in paragraph 5 of the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution and numbered BS 5502-50:1993+A2:2010.

(h) no part of the liquid digestate storage tank, feedstock tank and pipes may be situated within 10 metres of any surface water or opening into a surface water drain which digestate could enter if it were to escape.

(i) the liquid digestate tank, pipes, valves, and feedstock tank must be operationally maintained to be free of any structural defects during their lifecycle.

(j) where the digestate storage tank is fitted with a drainage pipe:

(i) there must be two valves in series on the pipe and each valve must be capable of stopping the flow of digestate through the pipe and shall be kept shut and locked in that position when not in use.

(ii) sub-paragraph (i) does not apply in relation to a liquid digestate storage tank which drains through the pipe into another liquid digestate storage tank of equal or greater capacity or where the tops of the tanks are at the same level.

(k) where a liquid digestate storage system includes a lagoon with walls which are made of earth, the lagoon must not be filled to a level which allows less than 750 millimetres of freeboard, and in all other cases the liquid digestate storage tank must not be filled to a level which allows less than 300 millimetres of freeboard.

(l) where a liquid digestate storage system includes a lagoon with walls which are made of earth, the lagoon must be lined with an impermeable sheet material of a type approved by SEPA.

(m) a slurry bag must only be used to store liquid digestate if:

(i) the bag is constructed of impermeable material of sufficient strength and structural integrity, and is unlikely to burst or leak in its ordinary use; and

(ii) situated in a bund, of equivalent capacity to the slurry bag, where the bund is lined with an impermeable sheet material, as approved by SEPA, and has a means of removing rainwater from the bund.

(n) where a liquid digestate storage system is to be constructed or to be substantially rebuilt or enlarged:

i) the operator must notify SEPA prior to

commencing the works,

ii) the notification under paragraph (i) must

be accompanied by an engineering plan for

the works to be carried out, and

iii) the operator must retain, for inspection by SEPA on request, the engineer’s final sign off certificate for the works.

Q 7. Do you agree with the proposed rules on the storage of liquid digestate?

Q 8. Do you agree with the proposed revised requirements for the notification of new silage, slurry, or liquid digestate structures?

9. Risk assessment maps and precision application of slurry and digestate.

It is proposed to introduce new rules to GBR 18 of CAR.

9.1 Risk Assessment for Manures and Slurry (RAMS).

Carrying out a simple Risk Assessment for Manure and Slurry (RAMS) is an easy way to plan applications of organic materials whilst following good agricultural practice and reducing pollution risk. The risk assessment only needs to be carried when manures, slurries, and other organic materials (sewage sludge/digestate) are likely to be applied.

A risk assessment must contain a map of the farm, which clearly shows:

  • the delineation of every field;
  • the area of every field in hectares;
  • the location of all surface water, wells and boreholes or similar work sunk into underground strata for the purpose of providing a water supply;
  • any area of land with a slope of 12 degrees or more;
  • the location of any field heaps; and
  • any other area of high risk to the water environment.

A RAMS map can help to plan applications around the farm; it looks at land suitability and takes into account pollution risks. A RAMS map will:

  • Identify no-spread zones and spreading risks, providing a clear guide for contractors and farmworkers spreading manure, slurry or other organic fertilisers.
  • Demonstrate improvements to current good practices. Following good agricultural practice means less likelihood of pollution occurring.

Carrying out a risk assessment is a legal requirement within Nitrate Vulnerable Zones (NVZs). However, the risk of manures and slurries entering watercourses extends across the whole of Scotland and puts the water environment, including sensitive bathing waters and shellfish waters, at risk of contamination from faecal bacteria. Many of these protected waters are in the 89% of Scotland outwith NVZ catchments.

To ensure that due consideration is given to identifying all high risk areas it is proposed that the requirement to carry out a risk assessment for organic manures is extended to the whole of Scotland. It is also proposed to introduce a requirement that the holding operator must issue a copy of a Risk Assessment for Manures and Slurries (RAMS) map to the person carrying out the application of organic manures.

Guidance on completing a RAMS map is available on the Farming and Water Scotland website.

(n) Where organic manures are to be applied to land;

(i) a risk assessment must be carried out in respect of that land, including the preparation of a map of the farm which clearly shows;

(aa) the delineation of every field,

(bb) the area of every field in hectares,

(cc) the location of all surface water, wells and boreholes or similar work sunk into underground strata for the purpose of providing a water supply,

(dd) any area of land with a slope of 12 degrees or more,

(ee) the location of any field

heaps, and

(ff) any other area of high risk

to the water environment,

(ii) the person carrying out the application of organic fertilisers must be provided with a map for the area to which fertiliser is being applied,

(iii) no field heap of organic fertilisers may be located in any area of high risk identified on the map.

Q 9. Do you agree with the proposal that a RAMS map should be prepared, and issued to those carrying out organic fertiliser spreading operations?

9.2 More efficient application of slurry and liquid digestate.

A feasibility study of slurry storage on Scottish farms, carried out on behalf of Scottish Government, and published in January 2018, estimated that 6.35 million tons of slurry is produced annually in Scotland. The majority of this slurry is spread directly to land, or as liquid digestate following processing through anaerobic digestion plants.

There are a number of methods to apply slurry and digestate:

Broadcast application by splash plate, either high or low trajectory, which is an ageing technology, is not an efficient method. There is a lack of control over the application area, which has a potential to be an impact on water quality, along with contributing to poor air quality and indirectly to climate change through volatilisation to ammonia gas. Slurry spreading with a splash-plate can result in very high losses of 80% - 100% of the total ammonia. Many countries are now prohibiting their use.

Low emission slurry spreading systems give more control over application and minimise runoff and emissions. Methods such as dribble bar/band spreader, trailing hose or trailing shoe can, depending on which method used, reduce ammonia emissions by up to 60%. Slurry injection can achieve up to 70% reduction in ammonia emissions through shallow injection, with deep injection methods achieving up to 90% reduction. Injection methods are less suitable on some soil types and topography, and figures can vary depending on a number of factors.

It is estimated that agricultural activities account for around 90% of ammonia emissions. The use of Low Emission Spreading Equipment is a very effective way to reduce ammonia emissions and improve water quality.

It is best practice to apply nutrients to meet crop need taking into account soil analysis and crop type. Manures and chemical fertilisers should be applied in the right amount, at the right time, and in the right place by the most efficient method to prevent losses to both air and water. If too much manure and/or fertiliser is applied to land, applied by an inefficient method, or is applied in unsuitable weather conditions, nitrogen will be lost from the farming system as ammonia or nitrous oxide to air, and nitrate to water.

Many countries now accept that there are significant agronomic, environmental, and financial benefits to be achieved by using precision/low emission application equipment. Using a low emission system can benefit the farmer through:

  • increasing the N value as the result of more effective application.
  • a quicker return to grazing by improving flexibility of application as a result of reduced contamination of grass.
  • reduction of the odours released during and after application.

To minimise the risk from broadcast spreading it is proposed that a ban on the use of

upward, or high, trajectory splash-plates – which may also be referred to as a ‘swan-neck’ or ‘bent-elbow’ attachment – is introduced from 1 year of regulations coming into force.

The use of ‘rain guns’ falls within the category of high trajectory and it is proposed to apply the same conditions as for high trajectory splash plates and ban their use from 1 year of regulations coming into force.

It is also proposed that, from 1 year of regulations coming into force, slurry spread by contractors, or by larger enterprises, can only be spread by low emission precision equipment. Many of these may already be utilising these methods.

Although the aim is for all slurry and liquid digestate in Scotland to be applied by precision methods, it is appreciated that there may be financial implications for smaller enterprises in the short term.

It is therefore proposed that, in support of smaller enterprises, prohibiting the use of all types of splash plates will be phased in, with a total ban from 5 years from date of regulations. In the interim: from 1 year of date of proposed regulations, until 5 years from date of regulations, precision methods for slurry application will only apply to farms with more than:

  • 100 milking cows
  • 200 beef cattle
  • 800 fattening pigs or breeding sows

Beef cattle numbers to be calculated based on livestock over 2 years old being 1 unit, and those under 2 years old 0.5 of a unit.

Many smaller herds may also be on a straw based system and therefore will not be impacted by the requirement to apply slurry by precision methods.

As liquid digestate can be more susceptible to ammonia loss, due to nitrogen being more freely available, all liquid digestate will be required to be spread by low emission spreading equipment from 1 year of regulations coming into force.

  • from [1 year of date of regulations] slurry may not be applied by means of high trajectory raised splash plate or rain guns,
  • from [ 1 year from date of regulations] slurry;

(i) applied by contractors.

(ii) applied on farms with more than 100 milking cows, or 200 beef cattle livestock units, and

(iii) applied on pig units with more 800 fattening pigs or 800 sows.

can only be applied using precision equipment,

  • from [1 year of date of regulations] liquid digestate can only be applied using precision equipment,
  • from ( 5 years of date of regulations) all slurry must be applied by precision equipment.

Q 10. Do you agree with proposals for the application of slurry and liquid digestate by precision equipment?

10. Interaction with Nitrate Vulnerable Zone legislation.

The proposals in this part of the consultation are a further step in consolidating regulations on protection of the water environment into a single piece of legislation. The Silage Slurry and Agricultural Fuel Oil (Scotland) Regulations have remained largely unchanged for 30 years while farming methods, and our approach to protection of the water environment, air quality, and climate change, have changed considerably over that period.

Some of the measures proposed as general binding rules have been in force in the Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations for a number of years, and are best practice methods which we consider should be now carried out by all farmers across Scotland.

The key points are:

  • Farmers across Scotland must comply with all general binding rules.
  • The Action Programme for Nitrate Vulnerable Zones (Scotland) Regulations shall remain in force and will continue to be the key tool in reducing nitrate levels in those areas where the levels are above the required standard.
  • Farmers in Nitrate Vulnerable Zones shall be required to comply with general binding rule measures and, in accordance with Cross Compliance rules, the standards in the Action Programme regulations

Taking forward these measures will not only protect water quality but also contribute to achieving Scotland’s targets on air quality and climate change.

11. Definitions.

The definitions used within The Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) (Scotland) Regulations 2003 need updating to include the changes made in 2008 to allow dirty water to be diverted through a constructed wetland. There are also some additional definitions to reflect the use of energy crops/feedstock.

BS 5502” means the Code of Practice on Buildings and Structures for Agriculture published by the British Standards Institution and numbered BS 5502.

“constructed farm wetland,” means a series of one or more ponds for the treatment of certain types of slurry or silage effluent consisting mainly of rainwater, which have been constructed in such a manner that any discharge from the ponds does not pollute the water environment.

“draff” means the residue of grain after fermentation of the grain in a brewing or distilling process.

“farm” means land occupied as a unit for agricultural purposes.

“farm yard manure” means a mixture of bedding material and animal excreta in solid form arising from the housing of livestock (excepting such arising from the keeping of birds for the production of food), and includes digestate fibrous residue.

“forage crop” means any crop grown as food for livestock or for use in energy production,

“housed” means kept permanently or overwintered, indoors or outside, on a collection based slurry system.

“impermeable sheet materials” means:

(a) synthetic rubbers, EDPM (ethylene propylene diene monomer rubber) and butyl,

(b) plastics, including poly vinyl chloride, low density polyethylene and high density polyethylene, and

(c) reinforced geomembranes.

“livestock” means any animal kept for use or profit as part of a commercial enterprise.

““liquid digestate” means;

(a) the liquid fraction, or

(b) any run-off from the storage of fibrous residue,

resulting from an anaerobic digestion process of a consistency that allows it to be pumped or discharged by gravity at any stage in the handling process,

“liquid digestate storage system” means;

(a) a liquid digestate tank,

(b) any reception pit and any effluent feedstock tank used in connection with the liquid digestate tank, and

(c) any channels and pipes use in connection with the liquid digestate tank, any reception pit or any effluent or feedstock tank.

”liquid digestate tank” includes a lagoon or tower used for the storage of liquid digestate.

“reception pit” means, a pit used for the collection of slurry before it is transferred into a slurry storage tank or for the collection of slurry discharged from such a tank.

“silage” means any forage crop (including draff) which is being, or has been, conserved by fermentation or preservation (including the use of additives), or both, and which is intended for consumption by livestock.

“silage effluent” means;

(a) effluent produced from any forage crop which is being made or has been made, into silage,

(b) a mixture consisting wholly of or containing such effluent, rainwater or groundwater emanating from a silo, silage effluent collection system or drain.

“silo” means any structure used for making or storing silage.

“slurry” includes;

(a) excreta, including any liquid fraction, produced by livestock whilst in a yard or building (including woodchip corrals), or

(b) a mixture consisting wholly of or containing such excreta, bedding, feed residues, rainwater and washings from a building or yard used by livestock, dungsteads or middens, high level slatted buildings and weeping wall structures or any combination of these, provided such excreta is present.

“slurry storage system” means;

(a) a slurry storage tank,

(b) any reception pit and any effluent tank used in connection with the slurry storage tank, and

(c) any channels and pipes use in connection with the slurry storage tank, any reception pit or any effluent tank.

“slurry storage tank” includes a lagoon, pit (other than a reception pit) or tower used for the storage of slurry.


Contact

Email: eqce@gov.scot