Many gardeners like to use compost in their gardens, and forgood reason. Compost is a great way toprovide nutrients to plants while also recycling yard waste and kitchen scraps.
You can have a compost pile out in the open, or you can usea bin to keep things neat. If you optfor a compost bin, you may be wondering what size it should be.
So, how big should your compost bin be? Acompost bin should have twice the volume of the finished compost that you want. For example, if you want 100 cubic feet ofcompost, then your bin should hold a volume of 200 cubic feet. This allows extra space for material thatwill break down as it is composted.
Of course, the exact size of your compost bin will depend onthe size of your garden and the depth of compost you want to apply. Some gardeners also choose to use 2 or 3 binsso that they can have different compost piles in various stages, so there isalways a “new” pile and always a “finished” pile.
Let’s take a closer look at how to figure out how big yourcompost bin should be.
How Big Should My Compost Bin Be?
The size of your compost bin will depend on two things:
- the size of your garden (dimensions are lengthand width for a rectangular plot)
- the depth of compost you want per square foot(how thick the layer of compost will be)
If you multiply these two numbers together, you’ll have thevolume of compost you will need for your garden.
If you then double that number, you’ll know how much spaceyou need in your compost bin. Thisdoubling accounts for the breakdown of the compost, which will lose about halfits volume as it decomposes.
How do we know that we need to double the volume? Well, according to the University of Wisconsin-Madison, the volume of a compost pile can reduce by 55% to 73% depending on the method used.
The table below will help you to calculate the approximatesize of compost bin that you will need, based on the compost bin volume. The compost bin volume that you will need iscalculated as follows:
(compost bin volume) = 2*(area of garden)*(depth of compost)
(compost bin volume) = 2*(length of garden)*(width ofgarden)*(depth of compost)
When taking your measurements, be sure to use consistent units! Don’t mix up inches and centimeters or use inches for one dimension and feet for another.
|Compost Bin Volume (cubic feet)||Compost Bin Dimensions (feet)||Compost Bin Volume (cubic meters)||Compost Bin Dimensions (meters)|
|Up to 50||5x5x2||Up to 1.4||1.5×1.5×0.6|
|50 to 100||10x10x2|
|1.4 to 2.8||3x3x0.6|
|100 to 150||15x5x2|
|2.8 to 4.3||4.6×1.5×0.6|
|150 to 200||10x10x2|
|4.3 to 5.7||3x3x0.6|
|200 to 300||15x10x2|
|5.7 to 8.5||4.6x3x0.6|
|300 to 400||20x10x2|
|8.5 to 11.3||6x3x0.6|
|400 to 500||25x10x2|
|11.3 to 14.1||7.6x3x0.6|
Let’s take an example to see how this would work inpractice.
Let’s say that you have a garden that is 30 feet long by 20feet wide. We’ll also assume that youwant a layer of compost that is 2 inches (1/6 feet) deep throughout the entiregarden.
Then according to the equation from above, the volume of thecompost bin would have to be:
(compost bin volume) = 2*(length of garden)*(width ofgarden)*(depth of compost)
= 200 cubic feet
Based on the table above, we could use a compost bin withdimensions of 10 feet long by 10 feet wide by 2 feet tall. This would make it easy to dig compost out ofthe bin, due to the short height.
We could also opt for a bin with dimensions of 7 feet longby 7 feet wide by 4 feet tall. Thiswould be a good option if you need to save space (this bin would have half thearea of the previous one).
In fact, we could even opt for a cube-shaped bin that is 6feet on each side and 6 feet tall (6*6*6 = 216 cubic feet).
If you are handy, you could build any of these compost binsout of wood. If you are not, or if youare pressed for time, you could buy an existing bin with the right dimensions.
If you cannot build or find a compost bin with the properdimensions, don’t worry. You cancalculate the dimensions of any bin if you multiply the length, width, andheight together. This will tell you ifit will hold enough compost for your garden.
For example, a bin that is 8 feet long by 8 feet wide and 4feet deep would have a volume of 8*8*4 = 256 cubic feet, which would be largeenough (with extra space) for the garden in our example.
However, a bin that is 6 feet long by 6 feet wide and 3 feetdeep would have a volume of 6*6*3 = 108 cubic feet, which would not be largeenough for the garden in our example.(Two such bins would work though!)
Can You Use a Normal Bin for Compost?
Yes, you can use any ordinary container (trash barrel, bin,or container) for compost. However, youmight need to make some modifications so that it is better suited to its newpurpose as a compost bin.
Before putting any yard waste in your compost bin, drillsome holes into the sides. This allowsfor fresh air (with oxygen) to move into the compost, and it also allows excesswater to drain out.
You might also want to build a hatch into the side of thebin to make it easier to shovel finished compost out of the bin.
If you build your own compost bin out of wood, be sure toavoid pressure-treated wood.Pressure-treated wood contains chemicals that you probably do not wantin your garden soil.
You may also want to avoid using plastic containers thatheld chemicals that you do not want in your garden.
What is the Best Compost Bin Design?
The best compost bin design has two or three separatechambers. This design takes into accountthe fact that composting happens in different stages.
For example, you can have one bin to store “finished”compost that is completely decomposed, cool, and ready to add to thegarden. You can have another bin for “unfinished”compost, which has partially decomposed but is still hot.
A third bin could be used to move “unfinished” compost backand forth to turn it. Turning yourcompost helps to aerate it, and also ensures that the materials are evenlymixed. Both air and even mixing willhelp compost to break down faster.
Instead of using compost bins, you can opt to use a composttumbler. A compost tumbler is a containermounted on a stand, with handles that allow it to be turned without a pitchforkor shovel.
You can use two different tumblers side-by-side to keep “finished”and “unfinished” compost separate, as mentioned above.
Whether you have a bin or a tumbler, it helps to have anopening to remove compost when it is finished.This is often achieved by a hatch on the side of a compost tumbler, or ahatch on the side (near the bottom) of a compost bin.
That way, you can open the hatch and let the compost fall(with minimal shoveling) right into your wheelbarrow for easy transport to thegarden.
How Often Should You Turn Compost?
You should turn your compost pile one or two times per week. Continue doing this for as long as the pile continues to steam when it is turned.
This steaming happens due to the heat generated by bacteria in the compost pile. Believe it or not, temperatures in a compost pile can get up to 140 degrees Fahrenheit (60 degrees Celsius).
If the pile does not seem to be breaking down, despiteturning it frequently, then it is probably too dry. In that case, you may need to add some waterby spraying the pile with a hose.
If the compost pile develops a foul odor, it may be too wet,in which case you should add some dry material (such as sawdust or fallen leaves)to soak up some of the excess moisture.Foul odors may also occur early on if you add manure to your pile, butthese odors should disappear over time.
For more information, check out this article on composting from the University of Missouri Extension.
How Long Does it Take for Compost to be Ready to Use?
On average, a compost pile will probably take 6 to 8 monthsbefore it is completely decomposed and ready for use in your garden. However, a well-managed compost pile willdecompose more quickly.
This requires regular turning to mix the materials andprovide aeration. It also requires agood mixture of green (nitrogen-rich) and brown (carbon-rich) materials in thecompost pile.
For more information on green and brown materials, check out my article on how to make compost.
In addition, you will need to maintain proper moisturelevels in your compost pile. This means addingwater if the pile is too dry or adding dry material if the pile is too wet.
Finally, make sure not to put things in your compost pilethat will not break down quickly, or things that will attract pests.
For more information, check out my article on things you should not put in your compost pile.
Now you have a good idea of how big your compost bin should be, based on the size of your garden and the amount of compost you need.
I hope you found this article helpful – if so, please share it with someone who can use the information.
No-dig gardening is a great way to improve soil health that focuses on compost – you can learn more here.
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