How to Make a Straw-Bale Compost Bin
Straw bales can be stacked to create a simple and inexpensive compost bin. As an organic material, straw breaks down and decomposes over time, and you can eventually incorporate it into your compost pile as a carbon ingredient. Straw is a convenient choice if you're just getting into composting and aren't sure what type of bin you want. You'll gain experience without paying for a bin or materials that may not suit your situation.
How many bales to use depends on the size of individual bales available in your area, how high you plan to stack them, and how much square footage you want for composting. Bales stacked in two or three layers provide sufficient area for composting, although you could get away with just one layer if lifting the bales is a challenge.
If you want to turn compost regularly, stack straw bales to form three sides of a square or rectangular shape, leaving the fourth side open for access. You can also form an enclosed square, filling it full of materials to decompose on their own time schedule without turning. If you get the urge to turn, you can always pull out a couple bales to create access.
A straw bale bin is quick to build. It's easy to expand (or shrink) your bin's size and add adjacent bins. Bales provide good insulation to maintain moisture and heat within the compost.
However, bales can be heavy to transport and lift. If you can't comfortably tote 50 to 80 pounds, straw bales aren't the best option! As straw breaks down, it loses its tidy appearance. Stacks may lose their stability, sag, and look unkempt.
To create a straw bale composting bin, the only materials you need are five or six two-string straw bales. This simple structure uses five two-string bales to form three sides of a single-layer, open-sided bin. Its rectangular interior composting area is about 3 feet wide x 4 1/2 feet long x 14 inches high
Place two bales end to end to form one side wall that measures 6 feet (1.8 meters) long.
Place one bale perpendicular to the first wall as the back wall.
Place the remaining two bales end to end to form the third wall.
One more bale completes the rectangle if you prefer to keep your compost contained in an enclosed bin. Set it against the outer edges of the side walls, making it easier to swing outward if you want to open the enclosure.
Another option for this bin is to stack another five bales for a second layer, increasing the height to 28 inches and providing you with more composting space. This design helps your heap self-insulate and retain more heat and moisture.
Use straw bales to create temporary composting sites. Surround the area where you want to add a garden in a year or two with straw bales and compost within them to improve the soil beneath. As the straw decomposes, work it into your compost, and as the compost decomposes, work it into the soil. By the time you're ready to plant, you'll be plunging your shovel into rich, dark soil and your "bin" will have disappeared, leaving you with nothing to move or store.