Slurry and waste management

Slurry removal

Slurry needs to be removed from a housing system either by manual tractor scraping or by some form of automatic system. The automatic systems either involve scrapers or, alternatively, a flush wash system.

Automatic scrapers

Automatic scrapers tend to be hydraulic, where the scraper blade sits on a saddle which moves around 1m every time the track is pushed forward by the ram. This system requires a track to be mounted on the scrape passage which can be problematic if manual scraping is required. The hydraulic scrapers also require the track to be kept clean in the summer to prevent a build-up of slurry. The slurry layer on the track will cause the saddle to disengage from the track. The track is also not particularly kind to cow's feet.

Other scraper designs rely on chains, ropes or plastic-coated wires. While these systems are kinder to cow's feet, particularly if the chain or rope is recessed into the floor, they require maintenance. Chains and ropes can stretch and break over time.

Slatted areas are particularly important where runs are longer than 25m.

Type and shape of slats have an important bearing on cow comfort, cleanliness and foot health. Slats must have solid, smooth edges and they must be close enough to allow the cow to walk comfortably and easily over them while, at the same time, have a large enough gap to allow slurry to fall through into the store below.

DairyCo Healthy Feet programme recommends the slat width to be 140-160mm with a spacing of 35-40mm.

It is important to keep cross-passages and areas around water troughs scraped regularly in order to avoid a build-up of slurry and pathogens.

Flood washing

The uptake of flood washing in GB has been limited. There has been an interest in this system with large collection yards, due to the difficulties of tractor scraping and the time and cost of manual hosing down.

The quoted benefits for flood washing include:

  • Labour saving compared to tractor scraping
  • More frequent cleaning of passages compared to tractor scraping, often using an automatic timer to flush every 2 hours
  • Passageways keep cleaner with improved foot health

The success of the system depends on creating a wave of water around 20m in length, 75mm in depth moving at a velocity of 2m/sec. This will generally allow the water to be in contact with the slurry for 10 seconds.

The slope of the scraper passage is critical to maintain the momentum of the floodwater. A slope of 2-4% will maintain the momentum with a minimum volume of water.

Slurry storage

When choosing a slurry storage system, it is imperative the bedding material is taken into account.  For example, if cows are housed on sand cubicles then systems such as a slurry bag and steel tower may not be suitable.

Irrespective of the storage system chosen, it is essential that the dangers of storing slurry are fully understood. Underground slurry stores can be particularly dangerous as the mixing of the slurry associated with agitation prior to emptying can lead to the production of hydrogen sulphide gas. Hydrogen sulphide is colourless although it has a pungent, rotten egg odour and can quickly lead to suffocation in poorly ventilated areas.

It is important to make sure that all inputs to a slurry system are fully taken into account when working out the required size of the system. For example, parlour washings, yard run-off and roof water must be taken into account if they enter the slurry store. There are resources available to calculate individual farm requirements.

Environmental Stewardship Schemes

The Environmental Stewardship Schemes promote improved environmental practice by providing financial incentives for a range of environmental measures including buffer strips in both grass and arable land. More information is available from Natural England, Welsh and Scottish Governments.

NVZs are part of cross compliance and are also law in their own right.  Therefore, they apply to farmers within the zones whether or not they claim single farm payment.