The Machines We Use in Industrial Composting
I am a real nerd when it comes to compost. During 8 months working at a research farm in California I spent hundreds of hours between counting microscopic creatures, formulating compost recipes, and turning piles by hand. I developed an awe for the microscopic world: busy, complex, and varied, landscapes hidden in smallness.
Now I work at Soil Dynamics. We do not turn piles by hand. We do not measure our compost ingredients in 5 gallon buckets, but instead in loader buckets - 5 yards each. I am now 300-1000 times more time-efficient when I turn compost. The landscape that captures my awe now is one of magnitude. Massive, powerful, and surprisingly precise: these are the machines that we rely on at Soil Dynamics.
Tractor, Turner, and Water Wagon. This lets us turn about 300 yards of compost in just a few minutes. The water wagon holds 1700 gallons of water that spray from nozzles just above the turner blades so that the compost is evenly moistened when necessary..
In its natural habitat, this shepherd of compost sleeps with the flock. Piles are 12 feet wide by up to 300 feet long. That's as much as 400 yards per "windrow".
Here's one of two loaders that we rely on. To move lots of material, obviously this does the trick. But I was amazed at Alonso's dexterity with this behemoth while we were building a wall out of concrete blocks (like in the background of this image). I hooked chains to the blocks, then Alonso would lift and place them. He could set the block, then nudge the block half an inch into the perfect position. It reminded me of an elephant shelling a peanut.
Meet the tub grinder. At the bottom inside that round tub this machine has a cylinder spiked with "teeth," fist sized hunks of steel that punch apart any thing in the tub. Logs, stumps, root balls, occasional rocks no doubt -- it all gets pounded into bits small enough to fit through whatever size screen is installed under the blade. This machine turns trees into mulch. It's why mulch has that frayed texture compared to wood chips.
The screener, this was featured in our most recent newsletter, so maybe you saw it there. This machine accepts loads of material into a hopper (left in photo) and then pushes it onto a gently sloped rotating screen (right). A conveyor catches screened fines from under the screen, and chunky material that cannot pass through the screen falls onto a different conveyor. Both fractions are carries in opposite directions, off and up forming two large mountains of material. (see next photo)
Many horsepower makes light work, that's the old saying right?
Behold the side-dump. This dump trailer holds 25 yards, the largest unit of material that comes or goes from the compost farm*. It's the way we interact with the world at large, as well as a small fleet of familiar looking garbage trucks that haul yard waste and food waste. A smaller regular looking truck can deliver more modest loads of compost, mulch or topsoil for retail clients.
*with one exception, the "live bottom" looks like a regular big-rig, it holds up to 100 yards, but only fills all the way up with mulch. Anything else would be too heavy.
Last but not least (except in size) the skid-steer. This is a familiar one, it can zip around, carry modest loads, it can hold a fork lift or a bucket, I use it to shave off the edges of windrows if they're too wide. It has the most variety of uses, like a swiss army knife.
We hope you enjoyed a little glimpse behind the scenes. Some of my coworkers have worked with machinery in oilfields, I have mostly worked in educational gardening! Never with machinery until now. We all know that humans have the power to shape the world, but I've never understood it up close. I'm glad that we at Soil Dynamics put all this horsepower to good use.
All we do is recycle. Everything we haul away from clients to the compost farm is unwanted material, and everything we deliver to clients is transformed into a valuable product to beautify our landscapes and improve environmental quality.
-Ben Samuelson