January 13, 2014
What You May Not Know About Grinding Up Trees
On Friday's blog, I showed you how my farm crew was spreading compost over the garden beds. As you may know, we make all that compost in an area of the farm called the compost yard. Throughout the year, the crew amasses quite a large pile of organic debris from the farm including stumps, logs, and brush. This year, and sadly so, that pile was enormous because it contained more than 150 stately trees that came down in last year's Hurricane Sandy. All of this material will eventually decay but, in years past, we've brought in an industrial machine called a tub grinder to grind it all up and accelerate the decomposition of this organic matter. The tub grinder does a fine job, but grinding so many large trees would take a very long time. After some research, we decided to have the massive pile of wood first pass through a different machine called a horizontal wood grinder. Yes, I'm sad about losing so many trees, but I'm glad that they are now decomposing into compost for future use around the farm.
1 We had quite a mountain of broken trees, which were dragged out of the woods and hauled off to the compost yard. Desirable logs were set aside in a different pile for Dominic to saw into lumber with his portable sawmill.
2 A year after Hurricane Sandy, the crew was still hauling. This is Chhiring operating the Hi-Lo and bringing more tree trunks to add to the pile for grinding.
3 Because we had so much volume, we hired a company that brought in a horizontal grinder, a powerful machine used in construction and demolition grinding.
4 An excavating machine loaded enormous trees onto the feed hopper.
5 The feed hopper can fit a lot of debris and has a flat chain conveyor.
6 The flat chain conveyor moves the trees towards the grinding chamber.
7 The toothed compression roller feeds the wood into the grinding chamber, where it is reduced to shreds within seconds.
8 After passing through a grate, the shredded wood travels on a continuous conveyor, away from the grinding chamber.
9 This metal plate beneath the conveyor is a magnet, which attracts metal objects, such as nails.
10 The grinder is controlled remotely by the operator, Jim Rogan.
11 The excavator kept feeding the grinder.
12 Chhiring kept hauling more trees from the woods.
13 This grinding process is actually quite mesmerizing to watch and the aroma of saw dust fills the air.
14 When the pile of shredded wood got too large, Jim operated a wheel loader and moved the pile....
15 Bucket by bucket...
16 To make room for more shredded trees.
17 You can see in this photo that the shreds are quite large.
18 As the wood pile got smaller, the shredded pile became enormous.
19 Moving time again!
20 After two days of grinding, this is what remained of all those trees!
21 The next step was to swap the horizontal grinder for a tub grinder. A tub grinder is able to grind logs and stumps, but it takes a longer time than the horizontal grinder does.
22 The wheel loader was used to transfer the shredded pile into the tub grinder.
23 As the tub revolves, a hammer mill below, shatters the wood into smaller fragments.
24 Again, the ground wood travels on a conveyor.
25 The tub grinder produces a much finer end product, but the first machine, the horizontal grinder, sped the whole process up. Now the decomposition into compost can begin!