Fresh start chance for state-of-the-art system
Fresh start chance for state-of-the-art system
It is rare to have the chance to start with a clean sheet of paper when
designing a waste handling and storage system. But that was the
opportunity that presented itself on one Leicestershire farm.
Mervyn Bailey kicks off this Muck Special
DEVISING a new cattle housing and slurring handling complex on a greenfield site avoids the restrictions and pitfalls that come with trying to adapt an existing system. John and Yvonne Liggins, and their daughter Sally, had such an opportunity when, rather than adapt a long serving cubicle system at Fosse Farm, Croft in Leicestershire, they decided to start afresh.
"The existing yard needed an extensive revamp and although we never had a problem, we were finding it more difficult to get insurance for pollution risk," explains Mr Liggins. "So we thought it best to start from scratch and build a new yard on a more suitable site."
The plan called for new housing and milking facilities for the 100 head Woodway Jersey herd, plus facilities for dealing with waste. Loose housing with generous straw bedding was chosen and Peter Russell of Midland Slurry Systems based at Shipston-on-Stour, Warwickshire recommended a lagoon with weeping wall and settlement tanks to deal with parlour washings and slurry scraped from the feeding area and collecting yard.
Liquid storage capacity is based on 23 litres/cow a day (5gal/cow a day), and there is sufficient solids storage capacity for soiled bedding to be removed from the cattle yards once a month. This is spread to the land, along with the settlement tank deposits once a year.
"Our land is free draining, so we can use the dirty water irrigator throughout the winter months," explains Sally. "And we liked the weeping wall idea because it is simpler than an above ground store that would need a chopper unit to deal with straw."
The six bay cattle shed has a central feed passage with a 6m wide feed area either side that can be scraped using a tractor. However, a wooden strip has been set in the floor so that automatic scrapers can be put in at a later date.
A dividing wall separates the 6m wide, 36m long loose straw-bedded area from the feed area to minimise straw waste – it is only at the entrance that straw is dragged into the feed area.
"We wanted loose straw bedding for animal welfare reasons," notes Sally. "We did have some concerns about mastitis but this has not been a problem."
Slurry scraped from the feeding area is pushed into a slatted channel where it drops into a muck mover, an oscillating conveyor that pushes the waste into the lagoon. The idea of scraping up a ramp was discarded due to safety concerns. Besides, it would not be compatible with an automatic scraper system.
"The muck mover really is a brilliant feature and works well as long as the material is not too runny," explains Mr Liggins. "If it is, we simply add some straw and tends to cure any problems."
The weeping wall is constructed of slotted concrete sections measuring 4m high by 1m wide. These have 25mm wide slots to allow liquid to seep into a collection channel. This feeds the settlement tanks, which comprise three 125cu m sections that progressively reduce the level of solids, and a 700cu m holding tank in which the resulting dirty water is stored before disposal. This is then pumped using a JPS pump to an in-field NC Engineering pulse jetter.
"It is essential to keep the lagoon free flowing so no water pockets build up," notes Sally. "Last winter, we did have a build up and when it burst, the settlement tanks were unable to cope with the volume of material."
As a result, a lot of solids have ended up in the main holding tank, which will be sucked up by a slurry tanker – a task that is done each year anyway.
Herd diet can be a factor in the consistency of the slurry in the lagoon, explains Mr Russell.
"If the cows are fed a high gluten diet, the bacteria that normally break down straw and other fibres are less efficient and you can end up with a high proportion of glutinous material in the system that can block the slots," he points out. "This has only come to light as maize has been used more and it should to be taken into account when designing a waste handling and storage system."
A contractor is used to empty the weeping wall once a year with the muck spread on the maize ground. Soiled bedding is cleaned out on average once a month and stored over winter, while roof rain water is kept out of the system by diverting it to a pond.
"The system does what we want it to do and the muck mover really is a good idea," explains Mr Liggins. "We have had a few problems with the lagoon, but then isnt hind sight wonderful!" *