Introducing My Homemade Automatic Compost Sifter

Dateline: 20 June 2007

"It is not absolutely necessary to sift finished compost, but there is nothing so pleasing to the sensibilities of an organic gardener as a soft, homogenous mix of well-rotted vegetation. Sometimes referred to as humus, it is the glorious crowning achievement of all who compost."

That quotation is from my book, The Complete Guide to Making Great Garlic Powder, which was published back in 2003. With sifted compost in mind, I further wrote:

"I have sifted compost manually by shaking a screen-bottomed box over my wheelbarrow. In fact, I’ve probably sifted many tons of compost this way. I can tell you it’s a healthful exercise, particularly for the arms, shoulders and chest muscles. But if your garden gets very big, and your compost piles get to be the size of Volkswagen Beetles, and you need to get the job done fast, you’re going to need some help. Don’t even think about trying to convince your wife and kids that they will benefit from the exercise. It doesn’t work.

The Herculean task of hand-sifting massive quantities of compost inspired me to develop my own mechanical (motorized!) compost-screening machine. It is a continuous-feed barrel design. You shovel the compost in one end, sifted matter falls out the bottom, and all the unsiftables (rocks, sticks, missing spoons from the kitchen, and whatnot) exit the other end. This device is easy to build and fairly inexpensive. I plan to publish the plans one day soon."

Well, I never did publish those plans. But I may yet. The sifter sure does work exceptionally well. I just have to spend some time streamlining the design.

Since 2003 I have continued to use my cobbled-together prototype sifter. In this blog entry I’m going to provide you with some photos of the prototype and an explanation of how it works.

The above photo was taken by me while standing atop this year’s compost pile (which will decompose down and be sifted next spring). You can clearly see the sifter and my son, Robert, shoveling sifted compost into my homemade Whizbang Garden Cart.

The sifter consists of a modified 55-gallon metal drum. The ends are cut out of the drum and sections of the sides have been removed. 1/4" hardware cloth has been fastened to the inside perimeter of the drum. The sifting drum rests on a stand. What you can’t see in the picture is that the drum is resting on four inline skate wheels. To make the drum spin, there is an electric motor underneath. A long V-belt runs from a pulley on the motor up over the top of the drum. The weight of the motor keeps tension on the belt. So when I turn the motor on, the barrel spins.

The motor spins at 1725 rpm, which is way too fast for the barrel to spin. I know this because I tried it. So the speed is reduced with a jackshaft and pulley arrangement. It now spins at 40rpm, which seems to be just right. If I ever refine this design into a Whizbang Compost Sifter, I willleave out the jackshaft and pulleys and just utilize a 40rpm gearmotor. It will make everything so much easier.

To use the sifter, it is turned on and shovels full of “raw” compost are tossed into one end of the barrel, as shown in this next picture:

Note the compost pile in the background. It has rotted down very nicely and weeds are growing on the top. The weeds are no problem. The sifter separates them, as you can see in this next photo:

The sifter barrel is slightly angled so the unsiftables migrate out the opposite end. Weeds, stones, sticks, pieces of plastic, paring knives, little army men; it’s amazing what finds its way into our compost pile, and out the end of the compost sifter.

Sifted compost falls down under the screened drum onto an angled piece of plywood. I place a tarp on the ground and the compost flows down onto the tarp. It’s a joy to behold.

The beautiful sifted compost is shoveled into my large-capacity, easy-to-wheel, incredibly useful, homemade Whizbang Garden Cart. From there I use the rich organic fertilizer to grow food for my family. I also use the compost when I plant my yearly crop of stiffneck garlic.

I hope you have been inspired by my homemade compost sifter. You now have the general idea and if you’re handy, you can go ahead and make your own nifty sifter. Otherwise, you’ll have to wait until I get the plans together.