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Choose a composting toilet

Composting toilets treat faeces with a carbon bulking material and air instead of water. They cut water use, but only work well if sized and managed properly.

How

1. Understand the types: self-contained units with a small built-in chamber, and central (remote) systems with a large chamber below the floor. Batch systems use two or more chambers so one can rest while the other fills.
2. Size for storage: the Eawag Compendium design figure is about 300 L of material per person per year, and nobody should need to handle material in its first year.
3. Check approval. In the United States, NSF/ANSI 41 (Non-liquid Saturated Treatment Systems) is a common product standard, but it does not cover how you manage the end product. Ask your authority which standards it accepts.
4. Plan ventilation: a vent pipe and often a small fan keep odours and flies down. Add the fan to your power budget.
5. Plan your bulking material supply (sawdust, wood chips, ash or paper) and storage space for it.
6. Remember greywater still needs a separate treatment route.

Sources

1. Composting Chamber (adapted from the Eawag Compendium of Sanitation Systems and Technologies). Akvopedia, accessed 2026-11
2. NSF/ANSI 41-2018: Non-liquid Saturated Treatment Systems. ANSI Webstore (NSF International standard), accessed 2026-11
3. Compendium of Sanitation Systems and Technologies (1st edition). Eawag-Sandec, accessed 2026-11

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