Using a Tub Grinder at the Farm
There's a lot going on in my compost yard - one of the most important areas on my farm.
During the year, my outdoor grounds crew amasses quite a large pile of organic debris - bark, stumps, logs, and brush. All of it is either repurposed as milled lumber, or left to decay and made into garden dressings, such as mulch and compost. To help with the decomposition process, a tub grinder comes to property every couple of years. This large piece of machinery grinds the material into much finer, usable wood chips.
Dan Repola, of Material Processors, located in Warwick, New York, has managed our projects several times. Once all the wood has gone through the tub grinder, Dan passes it through again to make it even finer. Enjoy these photos of this very interesting process.
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- This wood pile has gotten quite large – felled trees, branches, leaves, etc., but none of the material ever goes to waste. It is stored in piles in a large back field.
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- Looking closely, you can see the piles are actually quite organized – brush and sticks are in one pile…
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- And right next to it, miscellaneous logs and stumps.
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- Here is Chhewang in the Hi-Lo dropping off more debris.
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- Once there is a large enough amount, we call in a tub grinder to reduce the wood and green waste material. Tub grinders are named for the distinctive infeed hopper – the large round tub, normally 10 to 14-feet in diameter and roughly six-feet deep.
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- For years, I’ve used a team from Material Processors, located in Warwick, New York.
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- Material Processors also sends an excavator which will load all the material onto the feed hopper of the tub grinder.
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- The excavator is fixed with a large “jaws grab” attachment to pick up all the debris.
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- Here is my new property director, Fred Jacobsen, standing next to the “jaws grab” to show just how large it is.
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- The tub grinder is moved into position in front of the large wood pile. Tub grinders are typically loaded from the top by the excavator.
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- A continuous discharge conveyor carries the material away from the machine and piles it up in a mound.
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- Before any of the large logs go into the tub grinder, Dan saws them into more manageable pieces.
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- Dan has been doing this for many years, and cuts through a lot of the wood in very little time.
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- Before the end of the first day, Dan begins operating the excavator and grabbing large amounts of logs and brush.
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- It is then transferred into the revolving tub of the grinder. There is a lot of dust and occasional debris flying around.
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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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- Here, the grinder is filled with debris, but it quickly disappears into the grinder.
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- Once the debris is reduced, the fragments travel on the long conveyor belt, forming a large mound next to the machine.
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- Fred flew his drone to get a couple more shots from above – here is a better look. The grinding process is actually quite mesmerizing to watch.
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- Dan moves one load after another with the excavator.
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- As the tub spins, friction actually causes some of the wood to smoke. Everyone wears masks and appropriate eye gear for protection near the machinery.
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- Dan continues the process for several hours, but he will be at the farm for about four days to complete all the work.
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- You can see how finely the wood is ground up. Dan will run it through a second time to make it even finer.
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- Here is a view of the ground up wood after a couple of days. It’s amazing this is what remains from all the trees and brush. It will eventually make wonderful compost and mulch for my gardens.
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