A Tub Grinder at Work

April 2, 2022

It's very busy up at my compost yard - one of the most important areas on my Bedford, New York farm.

Over the last few weeks, my outdoor grounds crew has been gathering all the organic debris - logs, stumps, bark and brush, and transporting it to the compost yard in preparation for the tub grinder. I like to call in the massive machine once a year or once every two years, to reduce the size of our debris pile into much finer, usable wood chips and mulch. The tub grinder from Material Processors Inc. arrived this week and is already making lots of progress.

Here are some photos and videos, enjoy.

: This may be our largest pile of debris yet at the farm! It’s all piled up in my large compost yard ready for the tub grinder.

: For years, I’ve used a team from Material Processors, Inc. – a 30-year old company that focuses on recycling green waste, and clearing and preparing land spaces for development.

: 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.

: 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. It is moved into position close to the wood pile. Before any equipment is used, all the controls are checked to make sure everything is in good working order.

: Most tub grinders are powered by diesel engines. Here is a closer look at the back of the unit, where all the mechanicals are located.

: Tub grinders 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.

: A conveyor belt or augers located below the screens transports the finished product away from the mill to this discharge conveyor which carries the material away from the machine.

: 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.

: The jaws are huge and can pick up, move and sort several large logs or pieces of debris at a time.

: Of course, there is always a fire extinguisher nearby for safety.

: 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.

: The excavator works with a hydraulic system allowing the operator to raise and lower the long boom and bucket. Because the chassis is built on top of the undercarriage, it is also able to rotate 360-degrees. As the big machines are used, one also cuts large logs into smaller pieces nearby.

: Tub grinders are typically loaded from the top. Here, one can see a load as it is delivered to the grinder just before it is dropped.

: Here is the continuous discharge conveyor carrying the material away from the machine and onto a mound. It is always sad to see the trees go, but I am glad they can be repurposed into usable rich materials for the gardens.

: 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. This day was perfect – on and off showers from morning to afternoon.

: This tractor and bucket work to keep the processed mound together and neat. Later, this pile will be put through the grinder a second time. The second pass makes it even finer. The 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.

: In this area, I also have several piles of organic material in different stages of decomposition – mulch, leaf mold, and manure. It will all be ready to use after it is mixed together, turned and then sieved through the grinder.

: This crew has been doing this for many years and works very quickly and efficiently. Everyone at the farm visits the area several times a day to see them at work.

: It’s a huge job to grind all of this debris. The crew will be here for several more days. I can’ wait to see how much is produced after everything is processed. I’ll be sure to share more photos.