Trench compost is a simple composting method that buries food waste and green plant materials in a hole or trench. It is a great way to increase soil fertility and deal with organic waste without much work.
For a quick introduction, watch the video Trench Composting in 60 Seconds.
- Dig a hold or trench 12-18" deep in your garden, at least 6" away from the nearest plants. You can dig a large hole or trench and fill it slowly over time, or dig a new small hole each time you have organic waste to bury.
- Put green materials* (kitchen waste, green plants, or grass clippings) into the hole or trench. Leave space at the top to cover it.
- Cover the material with at 6-8" of soil.
- Cover the open trench with a stout board to avoid accidents or dig a new hole for each batch of kitchen scraps
- No maintenance necessary.
Nearby plants will benefit from the nutrients, moisture, and beneficial microbial activity as the materials break down in the soil. You can plant directly into the trench area after 3-6 months. In annual gardens, consider alternating the placement of the compost trench and plants back and forth each year.
*Green materials are nitrogen-rich, fresh stuff such as green plants, grass clippings, and kitchen waste. Kitchen waste here includes vegetables and fruits, tea bags, coffee grounds and filters, egg shells, and grain-based products but excludes meat, bones, dairy, and grease.
What composting style does it fit?
Trench compost is one of the lowest-maintenance system available and so works well for both hands-off and hands-on composters. It adds fertility to garden soil, but does not make finished compost that can easily be moved.
What space does it need?
Trench composting requires garden space. Holes can be dug 6" or further from most plants, depending on root spread. Compost-sensitive plants may require slightly more room.
How does it work?
Trench compost relies directly on the decomposition microbes and bugs present in the soil to break down organic waste. The material receives moisture and oxygen directly from the surrounding soil. The soil particles also hang on to the nitrogen from the decomposing materials and keep it from off-gassing as methane and bad smells.
Can you use it all year?
Trench compost can be used in the spring, summer, and fall. It is difficult to trench compost in winter, as new holes cannot be dug and loose dirt for covering waste will freeze solid.
There are two main options to continue diverting organic waste during the winter months. The first option is to place kitchen waste into a large container outside to store frozen outside until spring, when it can be added into a trench. Alternatively, consider adopting an indoor composting method during the winter such as bokashi buckets, vermicomposting, or compost tubs.