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SUN-MAR 400 Autoflow Composter

100 gallon capacity SUN-MAR 400
Sun-Mar, with it's double drum auto-flow technology is the first line of self-dispensing composters. The finished compost discharges automatically through the end door as the drum rotates. Sun-Mar is the Mercedes Benz of composters. Composting doesn't get any easier than this. Just fill it, rotate it, and haul compost away to the garden. Voila!

Our Price: $536.99
List Price: $559.99
Includes:Spare Parts: (2) spare vent plugs and (1) spare drum cap
Stock #SM-400

Capacity: 100 GALLON (11 Bushel)
Dimensions: Height: 36", Overall Lenght: 42", Depth: 28"
Includes: The Sun-Mar 400, Optional Rollers, (1) Sample of Compost Swift activator, and "Home composting made easy"

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Our "Down in the Dirt" review
The marvels of modern man show up again. It really doesn't get any easier than this. Even putting it together is a breeze, it just snaps together! As for composting, you put the stuff inside until it’s full, keep twirling it around, and when you think it’s getting a full belly, just open up the end and let the finished compost pour out!

Double drum design, a revolution in composting methods in the new SUN-MAR 400 Autoflow Composter!

With the Autoflow technology your finished compost discharges automatically through the side door as the drum rotates. You can keep putting your kitchen scraps and garden & lawn waste in the top loading door.  The Sun-Mar 400 does the mixing for you.  The Sun-Mar is a gardener’s dream.  It makes composting fun and effortless, and you have the satisfaction of knowing you are doing the right thing by recycling your kitchen and yard waste.

 The Patented double drum design works to move compost along the main outer drum as it rotates, and back through the inner drum before dropping from the output port. The Autoflow provides optimum composting conditions, mixing, oxygenating and distributing moisture throughout.

Features & Specifications:

  • The 200 and 400 units consist of an outer main drum, with an inner drum inside it. It sits in a cradle for support. As the drum rotates the materials move the length of the drum and are picked up by the inner drum and pushed along to the output port, where you harvest your finished product. Materials can be added continually for a constant working and supply of compost, making it easy to be the best recycler in your neighborhood.
  • The difference between the 200 and the 400 models is the length of the unit. The longer unit will take longer to move the materials down the length of the drum.
  • Because there are so few pieces to assemble, it takes only a few minutes to put it together. The 200 model takes only 2 minutes, and the 400 model only 5 minutes to assemble.
  • No waiting for batches to finish
  • Pest resistant
  • Easy to load and turn
  • Compost discharges automatically when you open the output port.


  • The Sun-Mar 400
  • Optional Rollers
  • (1) Sample of Compost Swift activator
  • Spare Parts: (2) spare vent plugs and (1) spare drum

 Benefits of Composting Your Kitchen and Yard Waste Include:

  • Healthier plants, because of the improved soil structure and additional nutrients in the compost
  • Reduced waste disposal costs
  • FREE source of fertilizer
  • Reduced water bills, because soil mixed with compost retains water better than regular soil 

Four Reasons You'll Enjoy Using Our Composters

  • You'll be creating first class compost material
  • You'll spend less waste to the dump
  • You'll have easy to use, top-of-the-line equipment
  • Less likely to be bothered by pests

Composting the SUN-MAR way

Keep the compost moist and oxygenated.  This means rotating the drum regularly to add oxygen, and adding water when the compost gets dry.

Keep the compost warm.

This is not usually a concern because the compost ion the drum and the drum's insulating properties keep heat in.

Aim for the right carbon/nitrogen ratio.

Adding a misture of kitchen and regular yard waste is effective, but for better, faster results, add carbon-rich material(browns) like sawdust, straw, dry leaves, or wood chips. These balance the nitrogen-rich green material and kitchen waste. Chop up the waste if possible: the smaller it is, the faster the breakdowns process. If you use only kitchen waste, you may need  to add bulking material or pre-composted material to help with oxygen penetration as the drum rotates.

You can learn more about what you can use for compost, tips on how to make compost, and a more detail of the steps to make compost in our Compost Guide and our Blog & Forum!


SUN-MAR it has been one of the leaders in Composting Technology for 30 Years. As the acknowledged leader in the field of composting toilets, at SUN-MAR they know the best way to compost is to use a rotating drum. They have used a rotating Bio-drum in their toilets for over 25 years. SUN-MAR's new Garden Composters go a step further by incorporating the patented, double drum, Autoflow designs. The Breakthrough. In SUN-MAR's Autoflow designs, material goes in the top and compost exits automatically out the end as the drum rotates.

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