Center for Regenerative Agriculture and Resilient Systems

How to Build Your Own Bioreactor

Inside the Johnson-Su Bioreactor

The Johnson-Su Bioreactor method of creating compost is quite different from other composting methods in several respects. The most common commercial windrow composting processes are usually designed and operated for speed and maximum product flow. Unfortunately, this focus does not allow the compost to degrade sufficiently. It can even produce an immature compost that in some cases is detrimental to plant growth. Most home composting methods require building a pile and turning it at regular intervals. Both windrow and static pile approaches can produce undesirable smells, attract flies, and be problematic with neighbors. However—when built and maintained correctly—the Johnson-Su bioreactor never needs turning, never has smells, and does not attract flies. The material is composted aerobically which encourages a complete biological breakdown of compost materials that results in a microbially diverse, fungal-dominant product.

Normal compost is similar to mulch in consistency. The compost from Johnson-Su composting bioreactors has the consistency of clay when mature. You can actually squeeze it like clay through your fingers. When mature this compost can be applied as an extract, used to coat seeds for planting in large farming operations, or be applied directly as a soil amendment. 

It is quite important to follow the instructions to do the process correctly and get the results you need. 

For example, the Bioreactor is constructed specifically for stability, durability, breathability, and moisture content consistency. You don't want the material to fall apart before compost maturity which takes one year. Use woven landscaping cloth to allow enough air infiltration without drying out the composting material and all the microbes and living creatures within. There needs to be sufficient moisture level. See below for more tips!

Required Materials and Tools

To build a Johnson-Su bioreactor, you’ll need some readily available materials and a few tools. Chances are you will be able to find these locally but links are provided if you cannot. Please refer to full instructions (below) to learn more. 

Materials consist of

  • rebar jigOptional: A rebar jig (Figure 1 at right) to hold the drain field pipes in place as you fill the Johnson-Su bioreactor. If you have helpers or if you are willing to adjust the pipes as you fill the bioreactor, you will not need the jig. 

Tools required are

Share the Wealth

Join our Bioreactor Registry(opens in new window) to share the results of your bioreactor project. Or find out who is participating already(opens in new window).