Many gardeners and composting enthusiasts know that compost provides an ideal soil amendment, but few are aware that it can be used as a main ingredient in growing soil. Store-bought potting soil provides a prime growing medium for seeds and seedlings, but it's often quite expensive, especially when you need to purchase multiple bags. Although it takes a bit of time, inexpensive homemade compost can be converted into a prime growing medium for your young plants, including seeds and seedlings.
Break down the organic matter in your compost. Pick up a handful of the organic material and smell it; finished compost possesses an earthy scent and does not have any lingering odors from any of the food scraps or other waste that you put in your compost heap. Let the compost sift through your fingers and note the texture; it should have a dark brown appearance and a crumbly texture.
Scoop finished compost into a five-gallon bucket with a hand trowel. Pack the compost loosely in the bucket, letting it fill the bucket completely. Fill a second five-gallon bucket with plain topsoil. Break up clods of dirt with your trowel as you add the soil so it's loose and powdery. Carry the buckets to your kitchen, putting the container of soil in a safe place that is out of reach of children.
Preheat your oven to 180 degrees Fahrenheit. Sprinkle the finished compost into roasting or baking pans with sides that are minimally 2 inches tall, filling each baking container with approximately 1 1/2 inches of compost. Spray water on the compost with a spray bottle to dampen it slightly. Carefully put the compost-filled pans in your oven and cook them for 30 to 35 minutes to kill off any pests and weed seeds that may have survived the composting process.
Remove the pans of compost from the oven and let them cool completely. Wash the five-gallon bucket with hot water and soap; dry the bucket. Dump the pasteurized compost back into the empty bucket. Measure out 1 cup of pasteurized compost; pour it into the third five-gallon bucket. Measure out 1 cup of plain topsoil; pour the topsoil on top of the cup of compost. Mix the two ingredients together with a trowel. Repeat this entire mixing process until you've created the amount of growing soil that you need for your seeds or seedlings.