When addressing slurry storage issues, minimising the volume of ’dirty’ liquid is a good place to start. Drainage systems can be modified to collect dirty water, such as yard run-off and parlour washings, which can then be stored separately from slurry and applied during the NVZ closed period when conditions allow.
But to really have an impact on the problems created by slurry, installing a separator is the most positive step to take. With the liquid fraction extracted and pumped to a lagoon, only fibrous material remains to store in bulk.
"Separating allows these different materials to be stored and applied to the land in the most appropriate way – and with minimal smell," emphasises Adrian Tindall of Bauer. "They will also provide more consistent nutrient analyses than slurry, so they can be applied at the appropriate rate to reduce reliance on bagged fertiliser, while conforming to Nitrate Vulnerable Zone restrictions where necessary."
Traditional methods of bulk slurry storage do not make it easy to properly utilise what a growing number of producers now recognise as a valuable commodity rather than mere ’waste’ – especially as mineral fertiliser prices continue to rise.
"Unlike slurry, no pre-application mixing is needed so the liquid fraction is easily applied by dirty water irrigator, or by tanker or field injector," he adds. "Extracted solids with 30% or higher dry matter can be stockpiled in field heaps where nitrogen losses will be lower than from slurry, in readiness for application ahead of ploughing for maize, cereals and other spring crops."
Applied by spreader to fields where its nutrient content and organic matter will do most good, the switch over also eliminates the ’slop factor’ that comes with loading, transporting and spreading slurry.
"That’s got to be a better approach than scraping or pumping whole slurry to an above ground store or lagoon where it settles out and has to be mixed before being spread," Mr Tindall adds. "In fact, the cost of installing mixers in a new slurry store is about the same as a separator, so it makes more sense to go the separation route and reap the additional benefits."
For the majority of livestock producers, the prime attraction of separation is its impact on storage capacity.
"A dairy unit with an existing storage problem or looking to increase herd size will find 20-30% more storage capacity by installing a separator," Adrian Tindall points out. "In that situation, the handling and utilisation benefits are an added bonus."
Two types of separator are available: the large screen type with revolving rollers and brushes, and the screw type, which Bauer has produced for the past 25 years.
"All our separators are built with a cast iron housing that contains a heavy-duty stainless steel screw and stainless steel screens," Mr Tindall points out. "They have few moving parts and components are hard-wearing for a long and low-cost service life."
Screens are available with a choice of four slot sizes to suit different materials and the weighted discharge flaps are adjustable to create sufficient resistance in the raw material for liquid to be extracted efficiently at good throughputs. A notable feature of the Bauer separator design is that it can produce the highest dry matter of any machine of its type.
Bauer’s two established models, the S655 and S855, use a 5.5kW motor, with the former able to tap into single- as well as three-phase electricity supplies. Otherwise, the principle difference between them is the length of the separation chamber, which influences throughout.
The S655 is rated to handle up to 20cu m of slurry an hour, while the S855 is rated at 30cu m/hr – although in both cases, output is greatly influenced by the consistency and make-up of the material.
A new 3kW compact model rated at up to 15cu m/hr is being added to the range. It can also run on single-phase electricity in addition to three-phase and uses the same stainless steel screw and slotted-screen separating technology as the larger units. However, at less than £10,000 it is competitively priced for farms with 80 to 120 dairy cows.
