|Cover materials differ in their ability to
absorb liquid. Moisture management in composting toilets is partly
dependent on the absorbency of the cover material used. This is
particularly true for composting toilets that do not utilize a leachate
drain. (The Barrel Composting Toilet
System and the Bucket-to-Barrel
Composting Toilet System are this type of design). A more
absorbent cover material can be used to help dry out compost that is too
wet. Conversely, a less absorbent material may be appropriate for a
toilet that is too dry (although it is usually easier simply to add more
liquid to the compost).
As a guide to the absorbency of common cover materials, the following testing was done. The test is simple and easily replicable by anyone wanting to compare the absorbency of various cover materials. In the near future we hope to test other commonly used cover materials such as shredded paper, chopped leaves, etc. The results will be posted here.
|Dry samples of 4 different cover materials were tested,
including conifer sawdust, conifer wood shavings, finely chopped straw and
horse manure (sifted through 1/2" hardware cloth).
Each material was tested by putting a 1 cup sample into a 1 quart jar, then adding 1 cup of water. A lid was put on the jar and the jar was shaken for about 30 seconds. The jars were then left to sit undisturbed with lids on. After 24 hours, the contents of each jar was emptied into a fine-mesh kitchen strainer and the volume of water was passed through the strainer for 2 minutes and then measured.
Here are the test results, arranged from most absorbent to least absorbent:
Samples of cover material with water added
24 hours later, water from cover material sample is drained through strainer into measuring cup.