8 Questions About Sand Separation and Recycled Sand Bedding

February 11, 2021
Recycling sand bedding for reuse in the freestalls saves dairy producers from having to purchase new sand. Mechanical Sand Separation Systems are often used to remove the sand from the manure stream and to wash and dewater it for reuse in the stalls. Here are the answers to some common questions about sand separation and recycling.

1. How large does a dairy need to be in order for sand separation to make sense?

Sand-Manure Separation Systems are available for farms of all sizes, with models that range from the SMS12 for dairies with fewer than 400 cows up to the SMS36 Twin for dairies with 4,000 cows or more. 

Separating and recycling sand bedding not only saves dairy producers from having to purchase new bedding, it also reduces wear on manure handling equipment caused by land application of heavy, abrasive sand-laden manure. Sand-manure separation also has a financial benefit in that it allows for the use of anaerobic digestion or biogas systems on farms where sand is used

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Sand-Manure Separators remove sand from the manure stream, rinse off organic matter from the sand particles and discharge the sand at about 20% moisture. 

Read: McLanahan Sand Separation Systems Provide Cost Savings for Dairies of All Sizes

2. Can sand separation be used with flush systems?

Sand separation can be used with all types of manure handling/removal systems, whether it is large volumes of water associated with flush and flush-flume systems or substantially less water with scrape and vacuum systems. The key is having a reliable method to collect and deliver the manure at a central point. From there, a knowledgeable OEM can recommend the ideal system.

Some flush dairies are successful using sand lanes to separate sand from manure. Although very effective for separating sand, the quality of sand recovered by sand lanes is initially poor and requires considerable conditioning by time and pile turning. 

A solution to this can be a mechanical Sand Lane System. Sand Lane Systems dewater and remove fine organic matter from recovered sand. Because the recycled sand is cleaner and drier, it can be recycled faster and with better results in the stalls.

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Sand Lane Systems reduce storage and conditioning time by removing more than 50% of the water and a large amount of organic material from the sand. 

3. What type of sand is best for separation, and what type is best for recovery?

Concrete sand is the best type for bedding material for several reasons. First, it contains just the right mix of smaller and larger particles, which allows for proper drainage of urine or dripped milk. This helps to keep stalls dry and comfortable because concrete sand doesn’t compact as readily as sand with an abundance of fine silts and clays, so it remains loose and comfortable for the cows to lie on.

Because concrete sand contains minimal fine particles, it is also the best type for high sand recovery when used in sand recycling systems. High sand recovery means less material to fill up holding ponds or spread on fields, and less money that needs to be spent on new sand. 

Also, because concrete sand meets a particular size specification, you always know what you are buying in terms of size. Consistent sand size leads to consistent sand-manure separation performance. This is especially important where sand-manure separation is used with anaerobic digestion systems.  

If you can buy concrete, you can buy concrete sand.

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The best sand bedding for freestalls is concrete sand because it contains minimal fine particles, which can lead to stall compaction and poor sand recovery.

Read: The Best Freestall Bedding Sand For Separation and High Recovery? McLanahan Recommends Concrete Sand

4. Is a Cyclone effective for increasing sand recovery?

Hydrocyclones, known simply as Cyclones, have been used in the aggregate and mining industries for more than a century for fines recovery, dewatering, desliming and classification. Whereas gravity settling removes particles down to a particular size, Cyclones cause sand to settle sideways due to centrifugal force.  

When applied in a Sand-Manure Separation System, Cyclones can be used as a primary means of sand separation in applications where the manure is highly diluted, such as in flush and flush-flume systems. 

They can also be used as a secondary means of separation following conventional Sand-Manure Separation Systems to keep fine particles from damaging pumps, filling up lagoons or settling in anaerobic digestion systems.   

Cyclones, when used in conjunction with traditional sand-manure separation, increase sand recovery by up to 10%, for total sand recovery as high as 95% on some dairies (depending on the sand gradation). As previously mentioned, higher sand recovery rates mean more sand is recycled and less money is spent on buying new sand. 

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Agricultural Hydrocyclones provide additional sand recovery when used in conjunction with mechanical Sand Separation Systems. 

Read: McLanahan Agricultural Hydrocyclones an Effective Solution for Sand Recovery

5. How does the Debris Drum work, and is it effective in removing debris?

Dairy manure can contain a variety of debris, which may include ear tags, neck chains, transponders, and hoof blocks, to name a few. Debris Drums remove debris larger than the size of a penny. It is debris of this size that wreaks havoc by causing blockages in Pumps, Cyclones and other process equipment.

A Debris Drum consists of a rotating perforated drum. It precedes the Pump and Cyclone in a Sand-Manure Separation System. As the overflow from the Sand-Manure Separator passes through the drum, fine sand, liquid and manure fibers exit through the holes in the screen, and debris materials discharge at the end of the drum. The liquid, free of large debris, is then pumped to the Cyclones or other process equipment.

With the addition of a Debris Drum ahead of Pumps and Cyclones in a Sand-Manure Separation System, dairy producers have seen a reduction in downtime caused by blockages or clogs. 

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A Debris Drum in a Sand-Manure Separation System removes debris larger than the size of a penny ahead of the Pump and Cyclone.

Read: McLanahan Debris Drum Reduces Downtime by Removing Debris Ahead of Ultra System

6. What is the ideal moisture content in recycled sand ready for reuse?

The ideal moisture content for sand bedding is zero percent; however, this is not always possible or practical. The ideal moisture content, therefore, is “as dry as possible”. 

So what is possible? Newly purchased bedding sand typically has a moisture content between 5% and 10%. Recycled sand discharges from a primary Sand Separation System with as high as 20% moisture. Agricultural Dewatering Screens are used to remove excess water as well as fine organic solids. The ultimate result is a drip-free sand pile that can be reused in freestalls quicker than if the sand was required to gravity drain.

Agricultural Dewatering Screens save producers money by enhancing sand quality, which leads to better cow comfort.

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Agricultural Sand Dewatering Screens provide a drip-free sand bedding, allowing for quicker reuse in the stalls. 

Read: McLanahan Agricultural Dewatering Screens Reduce Moisture Content in Recycled Sand Bedding

7. How much moisture is removed by a Dewatering Screen?

Conditioning is the process of enhancing the quality of recycled bedding sand. It is typically achieved by piling, scraping and spreading sand on a concrete pad. Conditioning requires labor and causes wear and tear on equipment. The person performing this operation must be skilled in the art of conditioning. Still, the end result may be unsatisfactory.

An Agricultural Sand Dewatering Screen installed after a Sand-Manure Separator will remove 40% more moisture, taking the sand’s moisture content from 20% to as low as 12% moisture content. Drier sand means less time is needed for conditioning the sand, less time is needed for handling the sand and less money is spent on purchasing new sand to make up inventory while the recycled sand is drying.

In addition to removing excess moisture, Agricultural Sand Dewatering Screens remove 80% of the organic material from the recycled separated sand. This results in a cleaner, drier sand to put back under the cows. Organic content of recycled sand can be less than 1%.

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Agricultural Sand Dewatering Screens installed after Sand-Manure Separators remove up to 40% of the moisture and 80% of the organic matter from recycled separated sand. 

Read: McLanahan Agricultural Sand Dewatering Screens Remove 40% of Moisture from Recycled Sand Bedding

8. How dry is the sand once it goes through the Sand Bedding Dryer?

If a drier sand product is desired or required, a Sand Bedding Dryer can reduce the moisture content in recycled sand bedding. Sand processed through a Sand Bedding Dryer discharges at approximately 1-2% moisture. The process also eliminates bacteria and organic content, meaning less clinical infections in the herd, lower somatic cell count and improved milk quality.

Once the sand is discharged from the Sand Bedding Dryer, it can and should be reused in the freestalls immediately. 

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Sand Bedding Dryers provide a dry material that can be reused in the freestalls immediately.

Read: McLanahan Sand Bedding Dryers Remove More Than 98% of Moisture from Recycled Sand Bedding

Tags: Bedding Management, Dairy, Agriculture, Manure Management