There has been a row back by the Department of Agriculture regarding the requirement for farmers with uncovered outdoor slurry storage to roof their tanks by the end of next year.

An obligation to roof these topless stores by the end of 2027 appeared as an action in the Department’s Ag Climatise roadmap in 2020, with all new slurry stores built since 2022 having to be roofed as they were constructed.

Senior Department inspector Ted Massey stated that the requirement has since been dropped due to questions around the feasibility of retrofitting covers onto these existing roofless stores.

Massey also suggested that the ammonia emissions reduction that would result from roofing these tanks – which was the reason for the measure’s inclusion in the Department’s climate roadmap – would prove relatively insignificant given that slurry forms a crust.

This puts slurry storage options such as overhead towers and lagoons in to contention for those looking to store large volumes of soiled water or slurry.

However, there are still a large cohort of farmers that have existing concrete tanks that are unroofed and may be querying as to if there is better value to be gotten from roofing over these instead of creating additional storage.

Slatted outdoor tanks were always safe as the slats were seen as a cover over the slurry, slowing down any air movement, but farmers are still curious.

The most likely cases of these are collecting yards, but there are also a portion of farmers that use slatted areas for feeding of cows with roofed or unroofed cubicles attached. Take for example a tank that measures 41.4m (eight bays in length with two 1.5m agitation points) overlaid with a 14ft 6in slat (internal tank width of 4.1m) and a depth of 2.4m. This holds a total capacity of 407.4m³ (89,619 gallons). If it was roofed, 373.42m³ of it would be usable storage, with 200mm of free board having to be accounted for.

But in this case, it’s not roofed, so our freeboard jumps to 300mm and we now have to take average rainfall for the closed period in to account.

Taking Tipperary for an example; Gurteen College records an average rainfall amount of 96mm in October, 96mm in November, 93.6mm in December and 44.3mm for half of January totalling just under 330mm of rainfall across the closed period. Tack on an extra 100mm extra free board and we lose 430mm of our tank depth to rainfall equating to 72.9m³ (16,075 gallons) which is 17.9% of our tank.

The above example is not particularly huge at only eight standard 2,000-gallon tankers, but would it make sense for this farmer to roof over it if they were tight on slurry storage? Let’s do the sums using the TAMS reference costs as a rough guide. They thankfully saw a small jump (10%) in the review of costings last September, but be mindful that actual costs could still be higher.

Currently, bovine slatted areas are costed at €277.72/m², with this including the slats. Where the slats are in situ like they are above, a deduction is made to the tune of €75.12/m² leaving us with a costing of €202.60/m².

When we exclude the agitation points, we have 168.96m² of slatted area to cover, giving us a total cost of €34,231.29 in total. If we are going to the bother of roofing over the slats, we are as well to include an overhang at a cost of €9,048.26 (€98.18 x 92.16m²) bringing our total bill to €43,279.55.

We are now collecting no water while cows and feed are both dry, while a grant amount of €17,311.82 (40% rate) does bring the cost back nicely.

Flipping it over to the other side, and though we wouldn’t build a tank for 72.9m³ of slurry, at a rough costing of €9,500, creating additional slurry storage as opposed to roofing does look a better option, especially if a farmer was to get a 60% grant rate under TAMS.

Some farmers and contractors will argue that with LESS and umbilical systems, watery slurry is more desirable for spreading. Personally, I would be more in favour of roofing the tank and keeping feed and animals dry and adding water if necessary for agitation.

I think the truth can be seen by the number of farmers who are now roofing over topless cubicles.

They placed short stanchions in situ while creating the cubicles and have grafted on to these and roofing over the cubicles. Again, I think it is more from an animal health and welfare point of view rather than a saving on slurry storage.

It’s not all sunshine however with roofing an older tank. Older tanks (pre-2009) will require an engineer’s report to certify that they are leak proof, have a working life of at least 20 years and are capable of supporting the structure to be built. Grant aid will not be given to construct a building over a tank constructed with block walls. In fact, grant aid will not be given for the replacement of slats for block wall tanks, something many farmers are unaware of.

The above structure would also require full planning permission before grant approval due to its size, and the cost of this and the engineers report will have to be factored in to the budget of the build.

The farmer could go and build the shed without a grant and save the cost of an engineer’s report, but at a 60% grant rate in particular there is a decent deduction on the build, while the specification of the shed will also likely be higher.