Living toilet (urine-diverting, larvae-processed)

Passive

One of 5 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.

What your site needs

A room that stays above roughly 20 C, or the larvae go dormant and the bin stops working -- the experiment saw exactly that in October. A separate container for the diverted urine, and somewhere for the finished substrate to go. No plumbing, no drain and no supply, but the bin sets the fixture's footprint rather than the pan does: in the flat it ran, the bin's length decided where the toilet could be, and it ended up next to the kitchen

A urine-diverting dry toilet whose solids are eaten in place by black soldier fly larvae rather than set aside to cure. That is the difference that matters indoors: a composting toilet needs somewhere to compost, which is the one thing a flat does not have, while larvae reduce the solids to a fine, odourless substrate inside the toilet's own bin over days rather than months. Urine, which is the bulk of what a body produces -- roughly ten times the volume of the solids -- leaves separately at the front and dilutes into fertiliser. The larvae are the whole mechanism and also its limit: they slow markedly below 20 C, so a cold room stalls the bin.

Cost

Low

Upkeep

Frequent

Skill to build

Basic

Lifespan

The larvae bin is the wearing part and the rest is joinery. The Boulogne-Billancourt build used a PLA bin that cracked at the folds inside the four months; the report's own recommendation is stainless steel, which would outlast the toilet around it

Embodied carbon

Low

Space / material use

Medium

Output timing

Continuous process

Skill to repair

Basic

Regulation (FR example)

Dry toilets are explicitly permitted (arrete du 7 septembre 2009 modifie) but must be declared to the SPANC, and byproducts must be composted on the property without discharge or nuisance to neighbours. In a flat that last condition is the whole difficulty, and it is what this design answers: the transformation happens inside the bin rather than in a heap outdoors. Where the substrate finally goes is still the household's problem to solve

Inputs

• Human waste

Outputs

• Compost
• Nutrients

How does this solution compare to others for the same need?

Compare building and maintaining complexity, as well as efficiency where possible.

Build skill and upkeep burden are proxies (lower burden = simpler to maintain); the efficiency column is this sub-function’s ranking, 1 = best. “N/A” where an axis isn’t rated here.

Sources

• Low-tech Lab wiki, Sciences Participatives : Toilettes vivantes (Biosphere Experience citizen-science programme, 699 trials Sept-Oct 2024)
• Rapport Biosphere Urbaine (Biosphere Experience), four-month apartment experiment, Boulogne-Billancourt 2024

What this page does not tell you

No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.