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A beef farmer battling crust issues on his digestate lagoon since covering it two years ago is pleased with the early results of a new slurry inoculant.

The farmer from Lydney, Gloucestershire, has a 22,000 m3 lined lagoon, which was installed in 2016 without a cover and, at the time of installation, was agitated using mechanical propellors.

However, due to the clean air strategy and a drive for farmers to cover their lagoons, he installed a gas membrane over the top in 2022, swapping the mechanical mixers for liquid mixing due to the cover.

“The liquid mixers suck the liquid out of the lagoon on one end and pump it back into the other end to try and agitate it. However, it hasn’t worked, and now we have a crust over 1.5m deep in some areas,” he says.

Covering a lagoon makes it impossible for farmers to know what is going on underneath the cover. It was only by luck that he had to cut the cover when installing a new piece of apparatus that he became aware of the actual extent of the crusting problem.

“We couldn’t believe that the crust was that thick in places, and that got us looking at options to get on top of the issue,” he says.

Not only does a crust eat up valuable space in the lagoon, but if it is not removed, it can result in a very costly exercise for a farmer by cutting the cover fully open and employing a digger to extract the crust. “This would be very expensive and could potentially cause damage to the lining of the lagoon. It was something we were keen to avoid,” he says.

The lagoon contains digestate from the family’s 1.5 megawatt biogas plant, fed with manure from the farm’s 1,500-head beef finishing herd, crops, and some poultry manure from neighbouring farms. The dry matter of the digestate is slightly higher than that of pure slurry, up at about 7%.

Keen to get on top of the problem and with a fear his whole lagoon, which at the time was 75% full, could end up turning to crust, he approached Liz Russell at EnviroSystems after hearing about their new slurry inoculant, SlurryBugs 2024. The new version SlurryBugs was launched at DairyTech this year (2024) after two years of extensive research. It contains specialised strains of bacteria and fungi that have been found to reduce crust formation by 29%.

 EnviroSystems calculated the amount of product that was needed. The lagoon was treated for its full capacity with 44 x 1.5 kilo bags. The SlurryBugs were mixed evenly into 5 x 100 litre containers of warm water to form a solution and left for about 30 minutes for the bugs to ‘come alive’. Once bubbles started appearing, the product was added to the lagoon through the hole in the cover and mixed in using the liquid pumping system to get an even spread.

After only three weeks, there was already some evidence the SlurryBugs were working, with bubbles appearing on the surface of the lagoon and the crust breaking down.

“Where we did have the visual assessment through the temporary cut in the cover, we could see activity with bubbles appearing on the surface and the crust cracking. We have now repaired the cut in the cover, but we are hopeful that after only a month since using the product, the bugs are working their magic under the cover and breaking down the crust,” he says.

Explaining how the product works, Dr David Townsend at EnviroSystems says: “The five strains of bacteria and fungi contained within SlurryBugs are unique to our product and have been found to work most effectively on maximising the complex lignocellulosic biochemical pathways within slurry stores.

“The bacteria secrete enzymes which break up the undigested fibre (cellulose and other plant matter), releasing the soluble nutrients and making them available for spreading onto land, producing a more homogenous liquid slurry.

“Our research has also found increases in each of the following nutrients in the treated slurry- Ammonium N +21%, Phosphorus +48%, Potassium +17%, Sulphur +31%. This is because organic materials are released into the slurry when the crust is broken down.

“Not only does our product make slurry handling easier, but it also reduces the need for bought-in fertiliser,” he adds.

Envirosystems urges anyone with a slurry cover to make sure they are considering options such as SlurryBugs to manage crust levels.

“It can also save farmers time as I’d hope that by reducing the separation of solids from the liquid and having a more homogenous digestate, it will save me time having to agitate it,” he adds.

More information on this product can be found here: SlurryBugs

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