Sheet composting is the technique of composting in layers in a low bed, rather than a bin situation. It can contribute to soil enhancement, as well as a weed free planting bed.
It can be very useful in areas where you want to kill off the weeds in preparation for planting desirable plants, and is a similar method to lasagna gardening.
I’ve used sheet composting in areas that I want to kill off weeds and make a new garden, but then eventually moved the resulting compost to other beds.
Some climates are better for using sheet composting methods, as it dries out quickly in hot dry areas. In these conditions, you may want to cover the working compost with tarps or plastic sheets to reduce evaporation.
Try not to cut off all oxygen to the composting material as this will cause anaerobic conditions; if you smell the telltale rotten egg odor, this is what’s happening.
Sheet composting is best used where there is a continuous supply of materials to compost, as well as a large area to work in.
The waste material is placed in flat windrows usually on top of a layer of cardboard or several sheets of damp newspaper, and sawdust, old hay, leaves or straw is added in layers. It will rot down quickly if it’s shredded first. More waste is added, and the layers start to heat up with the microbe activity.
This system is also used in the German Hill method or hugelkulture, where a ditch or hole is dug, filled with kitchen or other waste and the hill built in layers on top. Then potatoes or other crops such as squash can be grown with great results.
Sometimes this method is used in commercial enterprises to make huge amounts of compost from municipal collection, raked leaves and grass clippings. This is usually done on a concrete pad making it easier to turn the compost. The advantage to using a concrete pad is that any leachate can be collected and not allowed to pollute waterways.
In the home garden, this won’t be a problem, but you may decide to plant a mulch bed to utilize the leachate in your situation.
So, use sheet composting if you have a large open area and lots of material to compost, and you’ll be king or queen of the compost in your neighborhood. You can end up with considerable quantities of top quality compost with this technique – but don’t worry, you can never have too much compost!