Once they become moist and moldy, old bales are not even suitable bedding. The best way to recycle them is to compost them in a pile. However, keep in mind that the healthiest compost for plants is compost that contains a variety of organic material. Old bales of hay, straw or alfalfa should not make up much more than one quarter of the material in your compost pile. Otherwise, it may not heat up enough to break down its contents. If you have many bales, store them for use in future piles. Or, construct several compost piles and use the old bales all at once.
Cover the bottom of your compost bin with a 4-inch layer of material from the bale. If you chop it up into small pieces first, it will compost much more quickly.
Moisten the hay layer with a few short sprays of water from a hose.
Add 6 to 8 inches of a variety of organic material, all chopped up into the finest pieces possible. The general rule is that if it is organic and vegan (no animal parts or animal byproducts like oils or cheeses), it's okay to go into the compost pile. For the best compost, focus on nitrogen-rich material like vegetable waste from the kitchen, garden or field. Mix up this layer with gloved hands. It should be as moist as a wrung-out sponge. If not, add a few cups of water or more moist material, like fruit pulp.
Add a 1-inch layer of soil. This can be harvested directly from the ground.
Add 3 inches of animal manure. If it is dried out, moisten it with a few sprays from the hose. Dust the layer (whether or not you have moistened it) with lime or wood ash.
Repeat steps 1 to 5 until the material reaches the top of the bin. Then stop adding to the pile.
Mix the ingredients of the compost pile thoroughly with a pitchfork after it has cured for four weeks. Squeeze a handful. If it is not as moist as a wrung-out sponge, add a bit of water to the pile and turn until it is. Continue to turn and check the moisture level once every four weeks until the pile turns to humus (crumbly, brown soil) in a few months.