The Scottish government has announced that a £5m Agriculture Transformation Fund will be available this year for farmers and contractors to invest in improving slurry management.

This will be managed by the Sustainable Agriculture Capital Grant Scheme (SACGS) 2022 and can be used to buy items such as covers that will help reduce emissions and improve water quality. The scheme opened this month, with applications due towards the end of May, so all those looking to improve their slurry provision are being encouraged to apply now.

Covering slurry can be costly because of the size, shape and location of the tank, or lagoon. Creating new storage may require planning permission and a greater capital outlay.

As herd sizes increase so too does the need for slurry storage, however simply digging a new lagoon is unlikely to meet forthcoming environmental legislation changes.

It is expected that all slurry storage will have to be covered by 2027 to reduce harmful ammonia emissions and there are a variety of options available to help achieve this.

As with all solutions, slurry storage and covers have been developed to fit a number of price points. All have benefits and drawbacks for different farming systems so here John Tydeman, from slurry equipment specialists, Tramspread, explains some of the options available:

Bag tanks

Bag tanks are not new. Dutch company Albers Alligator have been manufacturing a wide variety for more than 35 years. They are a cost effective and flexible solution to contain slurry in small and large volumes.

They range in size from 200m3 to 7500m3 and can be located on any soil type as only a shallow foundation is needed. Each has integral hydraulic, or electric stirrers, fill/empty pipes and are self-venting, so relatively little management or farmer involvement is needed.

Bag tanks are manufactured in a UV-esistant grey coloured material and when installed, are low to the ground and have minimal impact on the surrounding landscape.

Many farmers have installed bag tanks without requiring planning permission. However, those looking to install a bag tank are advised to seek guidance from their local authority as the location of an installation may require approval.

In addition to the large static bag tanks are smaller portable tanks called Winbags. These range from 100m3 to 350m3 and are typically used as ‘nurse’ tanks, or overflow storage but can be used as a temporary and portable solution requiring only a level, smooth site.

A reeling device called Winsystem rolls the whole bag on to a trailer and will unreel it in another location. The ability to take these bags anywhere on the farm, unreel and fill offers a solution to farmers with difficult to reach fields or fluctuating herd sizes.

The bags are watertight so can be remotely situated, tanker filled or pumped to and emptied when the slurry is needed.

Steel tanks

These may require planning permission and are a higher cost solution.

A stainless-steel tank is created in a segment-like design from profile-reinforced stainless steel shell plates on a concrete base plate. The stainless steel will not suffer corrosion as quickly as other metal alternatives and represents a practical long-term investment.

Almost any size of tank can be created, and most manufacturers also offer hundreds of stock sizes to choose from.

Another steel option is vitreous enamel coated sheet steel which claims a lifespan of up to 45 years. These combine the benefits of steel and glass to form one single material which is more resistant to corrosion.

All steel tanks will require a cover once constructed. Canvas covers will keep out unwanted rainwater but are more expensive than floating covers.

Floating covers

For farmers seeking a quick and easy low-cost solution, floating covers offer an effective way to cover an existing lagoon or tank.

Hexa-Cover, is an innovative and adaptable product that can cover any slurry tank or lagoon and prevents 95% of harmful emissions being released. Made of recycled polypropylene, the hexagonal pieces float on top of any liquid, fit together to fill the space, block light out and gas in.

They are heat, frost and wind proof, with a life expectancy of 25 years. Crucially for busy farms, they require no maintenance and can be installed in two to three hours.

For farms with an existing steel tank, canvas covers can be expensive, up to £40,000 for a 20m diameter tank, whereas a floating solution for the same area would cost approximately £8000.

Concrete stores and concrete lined lagoons

Concrete stores can be constructed both above and below ground. Size is almost infinite.

In all stores, agitation is a major consideration because if the correct management is not applied, then solids can form and over time considerably reduce the available storage volume.

To reach all parts of the lagoon, it is advised that the width does not exceed 30m to enable a mixer to reach the middle of the lagoon. Both pto and electrical mixers are available, with the most common option offered by Tramspread being the Stallkamp submersible electric propeller mixers which can be specified with various fixing and motor options.

Concrete has a lifespan of approximately 50 years. However, concrete is produced in a variety of qualities and finishes so farmers should seek the best available to achieve the longest lifespan for a store.

A below ground slurry lagoon, will require the retaining walls to support the external ground as well as the slurry inside the store. Above ground slurry storage offers more retaining wall options and can potentially allow for taller structures to be constructed.

Sealing the joints between the precast units is necessary to ensure that the liquid is contained inside the slurry store and no cracking appears.

Whilst concrete has been a popular option the environmental effects of slurry lagoons and stores that have failed are significant, especially if the store is large.

Detrimental effects to soil and ground water should be considered and above ground tanks offer a much better opportunity to monitor and maintain the integrity of a tank to prevent any leaks.


Sharing slurry storage to reduce costs

John Akrigg farms 350 acres near Skipton and entered into a reciprocal arrangement with a local dairy farmer to take slurry to fill his two 3000m3 Albers Alligator bag tanks.

The tanks offered a welcome overspill for the next door dairy farm and gave Mr Akrigg a constant supply of slurry for his 200 acres of silage and 50 acres of wheat. “I have 150 breeding ewes of my own and I contract rear sheep and cattle for other farms. The aim is to be N, P and K self sufficient,” he explained.

He benefitted from a government grant of 40% towards the cost of the bags. “I researched grants and found that the Rural Development Programme England was offering 40% for developments as part of the Countryside Productivity Scheme.

"The bag tanks are a really cost-effective investment and give me a future-proof storage facility that should last for at least 25 years,” he added.

“The bag tanks were an easy sell to the local planning authority because they were odour free, had minimal visual impact and therefore would not impact on close by properties. They do exactly what both I need for a fraction of the cost of a concrete store, and should be good for at least 25 years,” concluded Mr Akrigg.