Using a Tub Grinder
After weeks of hard work cleaning the woodland, transporting the organic debris - bark, stumps, logs, and brush - to the compost yard, and then seeing it all go through the tub grinder, we now have a massive pile of usable mulch - the biggest we've ever had here at my farm.
Every couple of years, I call in the hardworking team from Material Processors, Inc., located in Warwick, New York. Their large machinery grinds all the material into small chips. Then it is all passed through a second time to make it even finer and mixed with leaf mold, aged horse manure, and chicken droppings. What's left is nutrient-rich "black gold" for all my gardens.
Here are the photos, enjoy.
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- Here is a drone shot of logs being dropped into the tub grinder. It’s amazing what these machines can do. All of these logs are ground in just a couple of minutes. (Photo by Brett Albright)
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- Here at my farm, we have a very systematic process for preparing material for the tub grinder. For several weeks before the tub grinder arrives, and during its visit, large piles of organic debris are collected along the carriage roads.
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- Hundreds of these felled trees are diseased ash trees – infested and killed by the emerald ash borer. The borer larvae kill ash trees by tunneling under the bark and feeding on the part of the tree that moves water and sugars up and down its trunk.
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- All of the cut trees and brush is brought to the compost yard in a back field.
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- Once a good amount is collected, I call in the team from Material Processors, Inc. – a company that focuses on recycling green waste, and clearing and preparing land spaces for development. I’ve been using them for years – so efficient and wonderful to work with every time.
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- Tub grinders are extremely large and heavy, so the team delivers the tub grinder and excavator to the farm the day before to set it up and prepare it for work. Most tub grinders are powered by diesel engines.
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- Tub grinders are named for the distinctive in-feed hopper – the large round tub, normally 10 to 14-feet in diameter and roughly six-feet deep. Before any equipment is used, all the controls are checked to make sure everything is in good working order.
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- These machines have a variety of screens for the output. The screen selection for each job is usually based on the type of material being processed and the desired end-product.
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- Here is the excavator, which is used to pick up the material using its large “jaws grab” bucket attachment and drop it into the tub grinder.
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- The jaws can pick up, move and sort several large logs or pieces of debris at a time.
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- Here’s a drone view of the machinery at work. I drive up to see the progress as often as possible. It is always sad to see the trees go, but I am glad they can be repurposed into usable rich materials for the gardens. (Photo by Brett Albright)
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- Tub grinders rely primarily on gravity to feed the material into the hammermill at the bottom of the tub. As the tub revolves, the hammermill below, shatters the wood into smaller fragments.
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- As the tub spins, friction actually causes some of the wood to smoke.
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- A conveyor belt located below the screens transports the finished product away from the mill to this discharge conveyor which then carries the material away from the machine.
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- The continuous discharge conveyor deposits the material onto a separate mound.
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- Every day more and more debris is brought to the compost yard and piled near the tub grinder. I shared some photos at the beginning of this process. The tub grinder is usually at the farm for three weeks.
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- There is also a pile of horse and chicken waste that gets mixed with the fine wood chips. Do you know the difference between compost and mulch? Compost and mulch are often used synonymously; however, there is a big difference between the two. Compost is biologically active material that breaks down from organic matter. Mulch, on the other hand, is any material, organic or inorganic, that covers a given soil surface.
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- The machines do this over and over, one load at a time. There is a lot of dust and occasional debris flying around – it is very important to stay several feet away whenever visiting an excavator and tub grinder at work. The team prefers to work on rainy days, which helps to cut down on all the dust.
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- Here is the output after two weeks. A tractor and bucket help to condense the pile as much as possible.
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- The entire grinding process is actually quite mesmerizing to watch. It is also extremely loud – the tub grinder can be heard all the way on the other side of the farm.
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- Here, the process is almost done. The pile is now put through the grinder a second time. The second pass makes it even finer.
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- And here is the pile at the end of the job – our biggest pile yet. It took a lot of hard work and manpower, but now we have all the material we need to dress all the gardens here at the farm.
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