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The photo above is courtesy of Brad Ashdown of RLC Park Services Canada. The vermicomposting toilets are located just inland from the sea at Sombrio Beach on the southwest coast of Vancouver Island of Port Renfrew, British Columbia, Canada. The system has 2 pit toilets sitting over the outside chamber. There are 6 chambers, 3 for each of the 2 toilet buildings that sit atop of the constructed pit as shown in the photo. Once the first chamber is full, the toilet is slid over to the second chamber, and so on.

Essentially the wooden constructed area below the pit toilet building is lined with a fine mesh screen, so that urine can escape and insects together with the small animals can’t enter the system. All the human excrement deposits in this area and wood shavings are added periodically to the pile. Each chamber is approximately 12 square feet in size and with initial compost worms or red wigglers density of 4 handfuls or about 2 pounds of worms including bedding per chamber. When the area below the pit toilet is filled with excrement and shavings, the toilet is moved to the adjacent chamber.

As shown in the photo that along the wooden wall there are cross walls creating separate square chambers, each the size of the toilet building. Essentially there becomes the pile of excrement and wood shavings that has plenty of air flow. With the help of the compost worms and beneficial soil microbes, the pile is decomposed to a smaller pile of soil that can be excavated as humus from the chamber; so that the vermicomposting toilet building can eventually be moved back over it again for use.

The effectiveness of vermiculture and vermicomposting in human pathogen reduction for USEPA (United States Environmental Protection Agency) biosolids stabilization has been studied in Orange County, Orlando, Florida by Eastman et al (2001). A field experiment tested the feasibility of vermicomposting as a method for eliminating for four human pathogens indicator (fecal coliform, Salmonella spp., enteric viruses, and helminth ova) obtain USEPA Class A stabilization in domestic wastewater residuals (biosolids). It is an honor for me to be one of the co-authors of the article above.

The conclusion is that compost worms Eisenia fetida have a consumption rate of 1.5 times their biomass every 24 hours proportionally with the percentage of compost worm biomass to biosolids at a 1.7 ratio weekly. Additional biosolids should not be incorporated for a minimum 6 days to maximize pathogens reduction. Compost worms should not be harvested before this time.

Vermiculture – vermicomposting is safe for the environment, however due to compost worm population, sustainability and fluctuation, the stabilization time will need to be proportionally adjusted until a stabilization equilibrium is obtained and maintained as confirmed by sampling analysis.

According to the applied finding above, the baseline guide for quantity of compost worms and amount of biosolids to be stabilized and safe for the human can be described: Kilogram of biosolids divided by 7 = Biosolids per day divided by 1.5 (consumptive rate of compost worms) = Kilogram of earthworms required for stabilization.

-Bintoro Gunadi