A 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.
Will Hunt from Lydney, Gloucestershire, has a 22,000m3 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 more than 1.5m deep in some areas,” he says.
“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,” says Mr Hunt.
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 which would be very expensive and could potentially cause damage to the lining of the lagoon.
Mr Hunt’s lagoon contains digestate from the family’s 1.5-megawatt biogas plant, fed with manure from the farm’s 1500-head finishing unit, 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 inoculant, SlurryBugs 2024.
The new version of the product, launched at DairyTech in February after two years of extensive research, contains specialised strains of bacteria and fungi that have been found to reduce crust formation by 29%.
Mr Hunt worked with the company to calculate 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.
“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 within three weeks. 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.
Dr David Townsend of EnviroSystems says: “The five strains of bacteria and fungi contained within product 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.
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