Sunday, January 11, 2015

Hey Grinderguy, do I need a Windrow Turner?

                If you are new to the composting industry, you are probably wondering what, when and why compost operations use windrow turners. Whether you are composting yard waste, food waste or sludges, a windrow turner is an essential part of composting material but not necessary in every case.
                Composting takes water and oxygen in an open air environment. We can get technical and discuss carbon and nitrogen levels, but regardless of that, you need water and oxygen.      
A windrow turner is used to aerate a compost pile, mix materials, apply liquids and to generally loosen material in a windrow. The more oxygen, the more the materials heat up and start the composting process. Pretty simple. Just like your leaf pile in your back yard.
In general, in a food waste or municipal sludge application, it would be very difficult to convince me of a reason not to use a windrow turner. The mixing action of a turner and the ability to provide oxygen to all the material in the compost pile is something you cannot do efficiently with a wheel loader. Having the ability break up heavier materials like sludges, and break apart food waste particles, is just something you cannot do with a wheel loader.  These heavier, wetter materials tend to block any airflow through the windrow. The more airflow, the more oxygen, the hotter the pile, the more composting of materials.  This means a faster compost process. If you are short on site space, the faster the composting, the more material you can compost. A windrow turner provides adequate air flow into the materials and increases the porosity of the pile by loosening the materials. Without the oxygen, piles will turn anaerobic and create enough odor that neighbors in the next county will be complaining.
When it comes to yard waste composting, the materials are generally loose to begin with, so turning with a loader is generally sufficient. The problem comes when you get to 25,000-30,000 ton per year. With that volume of material, you need to speed up the process and compost faster. With that much material, you can keep a windrow turner busy and do a much better job of aerating the windrows than a wheel loader. This will help speed up the process and produce compost in probably half the time as just bucket turning with a wheel loader. It will also save you a lot of site space because a wheel loader needs to get in between the piles to turn the windrows when a straddle Windrow Turner doesn’t. Piles can run together at the edges with some Windrow Turners.
So do you need a Windrow Turner?
·         What type of materials are you composting?
·         What volume of materials are you composting?
·         What kind of site space do you have?
·         Do you need to apply water or liquids to your windrows?
These questions should answer everything for you.
There are different types of Windrow Turners. Pull behind type which is towed by a tractor for example, and operate alongside the tractor and straddle type that sits atop a windrow. The straddle type Windrow Turners are able to turn larger windrows and turn heavier loads. The pull behind type is fine for small windrows and startup operations.
                So what do you look for in a Windrow Turner?
·         Define your volumes and decide which type will work best.
·         If you are short on site space, look for a unit that can turn windrows that are inches apart. This saves and incredible amount of site space.
·         Look for one that can apply liquids while you are turning. Yard waste compost will compost much more quickly when you are adding water to them.
·         If you are composting sludges and food waste, look for some kind of air filtration system for the operator cab. Ammonias and other chemicals build up in windrows and the air quality inside the operator cab may be contaminated.
·         Match the windrow width and height to the Windrow Turner size
·         Look for a unit that will turn the entire windrow not that just rototills a pile. Lifting and piling will generate the most porosity to the pile.
·         Ask about options like scraper devices, windrow displacement and tracks or tire drive.

While this is just a general outline, it should put you on the right path to your needs.

Questions, Dave Whitelaw

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