Burton Sparks wrote:A couple additions to the last post:
The 99% risk reduction resulting in safe agricultural use if people are protected would assume a 90% pathogen kill before discharge for a total of 99.9% total risk reduction. Keep in mind though that the passive aeration pipes might inadvertently allow leachate to bypass effective cleaning by the compost. I'd be curious to know if the top of the pile gets the same kind of impermeable "lense" at the top like Dean describes for vermifilters here, making it even more probable that leachate would bypass treatment from compost within the bin. Composting worms naturally occur in manure piles, and adding them may help reduce the risk of bypass (but likely not eliminate the risk given how narrow the bin is) and improve pathogen kill in the compost and any leachate that does trickle down through it.
I suspect that the use of the chute makes it harder to ensure you've fully covered your deposits to prevent smell and effectively prevent bugs from bringing pathogens out. This suggests ensuring you have a seal not just around the bottom of the chute and bin lid, but the top of the chute and toilet seat lid. If you seal everything air tight you could also consider adding a dedicated vent with a bug screen to allow the passive aeration pipes to function while in use and curing.
In summary of the 2 posts, some ways to help ensure the safety of the Geoff Lawton composting toilet method include 1) starting with some finished compost instead of sawdust; 2) adding worms when there is enough moisture to sustain them; 3) ensure the effluent discharge is subsurface; 4) use closed cell foam self-adhesive weather stripping to ensure a good bug seal around the bin lid, chute, and toilet seat; 5) add a vent with bug screen for in use and curing; 6) and either manually aerate at least once every other week while in use and curing or cure for 1-2 years.