Managing slurry storage

Farms producing slurry must have adequate facilities and management in place to collect, store and manage slurry and other products, which have the potential to pollute the environment if mis-managed.  For dairy units, dairy washings and parlour drainage must also be collected and contained within the farm slurry storage system.

Farms must have capacity to store the total quantity of slurry likely to be produced in 22 weeks by housed cattle, or 26 weeks for housed pigs. This capacity must also be sufficient to capture and store any rainwater entering the system, this includes from the farm steading where there is a reasonable expectation of contamination with slurry, from dirty yards, silage pits and from parlour washings.

All storage structures, whether these be below ground storage, slurry tower or lagoon, must;

• Be maintained to ensure they are kept free from any structural defects.
• Be fit for purpose and meet a minimum level of structural integrity such that;
  • The base and walls of any channel, reception pit, the walls of any pipe and the base of any tank are impermeable.
  • The walls of any tank are impermeable unless the base of the tank extends beyond its walls and has channels to collect and transfer any escaped slurry to a slurry storage system.
• Where slurry flows into a channel before discharging into a reception pit and is controlled by a sluice or valve, the reception pit has adequate capacity to contain the maximum slurry that can be released by opening the sluice or valve.
• The capacity of any facility used to temporarily store slurry before transferring to the slurry tank must have the equivalent of at least 1.5% of the minimum farm storage capacity.
• Where the slurry storage tank is fitted with a drainage pipe, there are two valves fitted in series that are to be kept locked shut when not in use.
• Earth bank lined lagoons maintain a minimum freeboard of 750 mm and all other slurry tanks maintain a minimum freeboard of 300 mm.

Further information

• Read our Know the Rules Factsheet 1 - slurry and manure storage.
• Consider ideas to reduce dirty water production around the steading.
• You can review the full list of regulations relating to the storage of slurry in light of protection of the water environment are in GBR 32 (Storage of Slurry) in the CAR Practical Guide.

All farms which produce slurry, must have sufficient storage capacity to contain slurry from a minimum 22 week housed period for cattle or 26 weeks for housed pigs.”

Storage capacity must take account of rainfall entering the system, this could include via middens, dirty yards, silage clamps, any dairy or parlour washings and any slurry brought onto farm for any reason. All farms located outside of an established Nitrate Vulnerable Zone will need to comply with minimum storage requirements by 1^st January 2026.

To calculate minimum storage capacity, the farm should take account of:

• Slurry production directly from housed livestock – standard figures are available in NVZ guidance Section 5 Manure Planning Part 2: Livestock Manure Storage.
• Rainfall entering the system, both direct and via run-off from dirty yards, middens and silage clamps - Scottish Rainfall Data is available via the SEPA website – select the closest location on map and use monthly mean data from line graph.
• Any washings or dairy wash water.
• Any slurry imported or exported from the farm.
• Space required for freeboard - all earthbank lined lagoons must incorporate a 750 mm freeboard and all other tanks must include a 300 mm freeboard.

Further information

• Read our Know the Rules Factsheet 1 – slurry and manure storage.
• Estimate slurry production from housed livestock.
• Consider ideas to minimise dirty water production around the steading.
• Calculate slurry storage space – watch the Farming and Water Scotland webinar.
• Use the slurry storage calculator, available on the Rural Payments website.

There are a number of different options for slurry storage.  Choice will depend on the type and volume of the material to be stored, topography and ground conditions, site/location available, maintenance considerations, access and cost.

If you are planning to install a new slurry storage system or substantially reconstruct or enlarge any existing system you must consult with a suitably qualified engineer, have an engineering plan available for the proposed works and retain the engineers final sign-off certificate for the works for the life of the structure.  It may also be worth checking with your local council in terms of any planning restrictions.

Farmers planning a new slurry store or silage structure on the farm, or significantly altering an existing silage or slurry structure, must notify SEPA 30 days prior to starting any development work. 

All slurry storage options must be sited at least 10 m from a surface water or surface drain.  For those considering constructing a slurry store Table 1.3 lists the different slurry storage types most often considered and outlines some of the pros and cons to be aware of.

Further information

• Review the Know the Rules Factsheet 1 – Slurry and manure storage.
• Know the Rules Factsheet 2 – Maintaining slurry storage systems.
• Notify SEPA of new/substantially enlarged slurry system via this form.
• Watch the ‘Managing slurry for folks in a hurry’ Farming and Water Scotland webinar series.

Table 1.3 Slurry store options

Drainage from yard middens should be collected and added to the slurry collection system.  Alternatively, rainfall driven lightly contaminated runoff from middens can be put to a constructed farm wetland for treatment.

Where practical, if the yard midden can be roofed it will reduce rainfall running through the midden and cut down on both dirty water production and nutrient losses.

Temporary field middens must not be sited on waterlogged or shallow soils or within 10 m of any ditch, burn, river, loch, wetland or coastal water.  On sloping ground, a wider buffer zone may be required to prevent runoff getting into a watercourse. Water that could be used for domestic supply also needs protecting; for this reason field heaps must not be sited within 50 m of any spring that supplies water for human consumption or any uncapped well or borehole.

In NVZ’s, temporary field heap middens must not be stored for any longer than 12 months in one place and must not be created on a site of a previously cleared heap within 24 months.

When siting middens, consider if there is a risk of public nuisance caused by odours or a potential risk to public health from harmful organisms.  A ‘good neighbour’ policy should be adopted at all times. Note slurry or semi-solid manure should not be stored in middens.

Further information

• Read the Know the Rules Factsheet 5 – Constructed Farm wetlands.

• Learn more about the impact of ammonia from slurry and manures at NetRegs.

Recent updates to regulations mean that if you are planning to install a new slurry storage system or substantially reconstruct or enlarge any existing system, you must seek guidance from a suitably qualified engineer who can put together an engineering plan for the proposed works.

Slurry systems can generate lethal gas, notably hydrogen sulphide, which has been responsible for a number of deaths on farms.  Even for those experienced in working with slurry, please review health and safety guidance in the links below.  

Steps must be taken to avoid unnecessarily collecting clean water within the slurry storage facilities, as demonstrated via the steading drainage plan and storage capacity must meet the minimum 22 weeks for cattle or 26 weeks for housed pigs. All slurry lagoons must be lined with a proprietary liner, which meets the requirements of The Water Environment (Controlled Activities) (Scotland) Amendment Regulations 2021 and lagoons must be fenced to prevent access by people and livestock.

You must notify SEPA that you intend to install a new slurry store and you will have to provide the engineering plan.  This should be done at least 30 days before any work starts.   Once completed, keep the engineers final sign-off certificate for the works, as this may be required during the lifetime of the structure and must be available for submission to SEPA upon request.

For any slurry storage system constructed or substantially reconstructed or enlarged after 1 January 2022, it must have a life expectancy of at least 20 years with proper maintenance.  If the walls are made of earth, these must be lined with an impermeable sheet material, again with a design life of 20 years with proper maintenance.

For all structures containing livestock slurry, they must be situated at least 10 metres from any surface water or surface water drain (including field drains).  You may also want to consider access and proximity of stores to neighbours.

Further information

• The SEPA CAR Practical Guide lists GBR 32 and GBR 34, both rules relating to storage of slurry and liquid digestate.
• To notify SEPA of new or substantially enlarged slurry system 30 days prior to work starting – use this form.
• Visit NetRegs for rules around storing slurry.
• Read the Know the Rules Factsheet 1 Slurry and manure storage and Factsheet 2 Maintaining slurry storage systems.
• See the FAS steading drainage management options

Slurry store covers are one of the ways to reduce the direct loss of slurry gases such as ammonia and reduce the amount of rainwater falling into the tank, which will add to the slurry volume.  Covering the slurry store can, therefore, cut down on the loss of harmful gases driving climate change and leading to air pollution, reduce odour and the possibility of public nuisance and preserve more of the nutrient content within the slurry.

Slurry store covers can be impermeable or permeable, fixed (rigid) or floating. Table 1.4 outlines some of the different types of covers and their pros and cons.  For those considering a new store, it is often more cost effective to install a cover at initial building stage rather than to retrofit.

Further information

• Listen to SAC Consulting’s Seamus Donnelly discussing various different slurry cover options.
• Use this form to notify SEPA of new or substantially enlarged slurry system.
• Review the NetRegs information on Rules for Storing Slurry.
• Read the Know the Rules Factsheet 1 Slurry and manure storage  and  Factsheet 2 Maintaining slurry storage systems.

Table 1.4 Types of slurry store covers

The type of livestock housing system affects the physical characteristics of the manure or slurry. For instance, solid FYM (Farm Yard Manure) is produced by the addition of straw or use of other bedding materials. Slurry is produced where housing and feeding systems use little or no additional bedding materials, and where excreta is scraped from solid floors or trodden into collection tanks beneath slats.

Some systems such as straw courts use a separate scraped feed area to reduce straw use and these produce a combination of both FYM and slurry.

All liquids produced from where livestock are housed must be drained or scraped to a suitable collection system. These liquids include drainage from passages and aprons used by livestock or where slurry is scraped, contaminated wash water from milking parlours and washdown (dairy, pig and poultry buildings), and drainage from traditional byres.

Straw has traditionally been the bedding material of choice, however, other materials are available.

When considering alternative bedding, the material must keep stock clean and dry, provide a comfortable bed and provide a healthy environment for housed cattle.

Aside from the needs of the livestock, choice of alternative bedding materials will also be dictated by what is available in the local area, suitability and space for on-site delivery and storage, level of management needed and if the material can subsequently be applied to land or if composting is required.

Keeping buildings well ventilated, making sure rainwater from gutters and downpipes doesn’t enter the housing and ensuring drinking troughs are not leaking or over filling will also help keep bedding dry and prolong its life. Removing soiled or damp bedding will also help to reduce bedding losses and maintain a healthier environment for livestock.

Some bedding materials can be used in combination, for example a layer of sand under straw bedding to aid drainage and keep straw drier.Table 1.5 lists a range of different livestock bedding options, alongside some of the known pros and cons.

Table 1.5 Range of different livestock bedding options

Note - bedding using gypsum or waste plasterboard is not acceptable as it may present a serious risk to animal and human life due to the release of hydrogen sulphide gas.   

Further information

• Read the FAS information note on Alternative Bedding Materials and information on bedding for lambing sheds.

Housing types that minimise contact between the slurry and the atmosphere, by rapid removal and covering of slurry, minimise air pollution and losses of nitrogen.

There are a number of slurry management techniques and flooring systems for housed livestock that can not only benefit cow health and productivity through reducing contamination of beds and animals, but also improve slurry management and reduce emissions to air.

• Slatted floors with below ground slurry storage – gaps in the floor allow urine and slurry to fall into the storage pit below, either by gravity or the trampling action of cow traffic. This process can be accelerated with the use of a scraper.
• Automatic passage scrapers – regularly scrape passageways reducing slurry build up.  Note these automated systems need to be well managed.  Large volumes of slurry can be gathered at the head of the scraper, which is then pushed onto cow’s feet.  This could increase dermatitis risk.  These systems don’t fully clean the floor and will leave a slurry residue.
• Robotic scrapers –These mobile units with a front mounted scraper system work best with slatted floors, collecting and scraping slurry from around the shed, forcing it through slats as it navigates its way around the shed. Some systems do have an onboard collection tank, these are best suited to cleaner floors handling smaller slurry volumes.  Again, scrapers don’t fully clean the floor and will leave a slurry residue.
• Flood washing systems – these systems flood cubicle passageways to ‘wash’ slurry from the surface. These systems often use lightly contaminated water or diluted slurry, which will not reduce emissions as a film of slurry is left, allowing ammonia emissions.  A better rinsing option would be clean or collected/recycled rainwater, providing a cleaner rinse and less risk of residues, however, this practice will add to the volume of slurry to be collected, stored, handled and spread.
• Low emission flooring – low emission floors are gently sloped towards a urine channel, which collects livestock urine and reduces mixing time between dung and urine, cutting down ammonia emissions.
• Grooved floors – similar to the principle of slatted floors, the floor contains grooves to allow slurry and urine to fall through, facilitated by a toothed scraper running over the grooves.
• Frequent vacuum removal – vacuum systems can be used for frequent slurry removal (at least twice a week) from underfloor storage. Currently this technique is more common in pig housing systems.

Slurry systems can generate lethal gas, notably hydrogen sulphide, which has been responsible for a number of deaths on farms.  Even for those experienced in working with slurry, please review health and safety guidance in links below

Further information

• Techniques to reduce emissions in pig production are listed in this article here.
• Download the HSE leaflet Managing Slurry on Farms.
• Read the Safety when working with slurry
• Read the FAS article Beware Slurry Gases.