Flow Through Worm Bin

Flow Through Vermicomposting Systems

Flow through worm binsare fast becoming a favorite among worm farmers. Sometimes called continuous flow bins or worm reactors the flow through systems was designed to overcome the disadvantages of traditional worm bins. Vermicomposters often move on to a flow through system after starting out with traditional worm bins or commercially produced stackable bin systems.

Traditional worm bins often end up with a water logged muck of castings and bedding at the bottom making harvesting and clean up a mess. Flow through systems have a distinct advantage when it comes to harvesting worm castings and when used properly are extremely easy to maintain. These systems are so effective that commercial worm farms frequently use them.  

Continuous flow bins take advantage of the composting worm’s natural instincts to live within the first few inches of decomposing matter in the topsoil. In a flow through bin system food is added to the top of the bin where the worms live and feed and their castings are harvested from the opening in the bottom.

Flow through worm bins can be constructed from any number of containers or handmade enclosures. Large buckets, garbage cans, old water heaters, and wooden boxes can all be converted into a flow through worm bin. Other flow through systems are constructed commercially or by worm farmers themselves. 

Other flow through worm bin systems are simply made from canvas or heavy duty fabric hung upon a frame. The top is left open and the bottom is tied off. Food and bedding are added from the top and castings are harvested from the bottom.

Pictured here is the Worm Inn flow through worm bin system. This is a simple and effective flow through system ideal for the home worm farming looking for an easy to use flow through system. 

How Flow Through Bins Work 

No matter how a flow through worm system is constructed they all operate on the same basic principal. The bottom of the bin is open with a grid system installed horizontally just above the bottom opening. The grid is designed to hold in bedding. The grid may be constructed from a variety of materials including wire, PVC tubing, metal pipe tubing. Before adding the intitial bedding and food sheets of paper or cardboard are placed on top of the grids to prevent bedding and castings from falling through.  

Composting worms are added from the top. As the worms convert the bedding and food into casting the castings settle and compact at the bottom of the bin. As the compacted vermicompost settles deeper into the bin more food and bedding is added from the top as needed and the process continues.  

When the compacted castings and compost begin to build up and dry out it is harvested from the opening at the bottom of the bin. By this time the paper or cardboard that was placed atop the grids have nearly decomposed and easily fall apart when harvesting begins. From this point on the dry compacted vermicompost at the bottom of the bin is held in place by the grid and harvested as needed.

Harvesting is accomplished by simply loosening and removing the dry casting from the bottom of the bin and allowing it to fall through the grid for easy collection. In a basic frow through systems a small shovel or rake loosens the castings from the grid. In a more complex system the grid system is constructed from tubing which can be turned and loosens the castings.

Larger and commercial flow through worm bin systems have a breaker bar or blade installed just below the grid. The blade is as wide as the bottom of the bin and is drawn across the drying castings and "shave" them off for collection.

 Other Types of Flow Through Worm Bins

Another type of flow through system is the horizontal flow through worm bin. In these systems bedding is added to a long worm bin. Food and worms are added to one end of the bin. As worms convert the food into castings more food is added along side the converted castings. The worms move horizontally toward the food to eat it leaving more vermicompost and castings behind. Over time more food is added and eventually the worms migrate across the bin following the food. Eventually the entire bin is filled with castings or compost. At this point worms, castings, vermicompost, and cocoons are harvested and the process is repeated.  

Outdoor windrows or "vermitrenches" called walking windrows utilize this same concept. However; this system is housed in the ground instead of a bin. So we categorize this system as an windrow not a flow through system and will cover it in more detail in our ourdoor bin pages. 

Sometimes people call stacking worm bins a flow through system. However we don't classify them as a true flow through system; we consider stacked systems a category all their own. While it is true that stacking bins allow worms to migrate up to a higher bin as food is eaten; each bin must be still be removed from the stack for harvesting. For more information on stacking bin worm farms see our stacking bin page.

Flow through worm bins may be a bit more complex to set up. But in the long run their ease of operation and simple harveting system make them a perfect set up for both beginners and more advanced worm farmers.

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