Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
Periodic sludge pump-out
Passive
One of 2 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
A licensed tanker that comes every few years to pump out the sludge that builds up in a septic tank or small treatment plant. The sludge is taken away and treated elsewhere. Every tank needs it, so it is a regular cost and a service you depend on, unlike composting the solids yourself.
Build it
This solution is not buildable as a DIY project.
Cost
Medium
Upkeep
Seasonal
Skill to build
Specialist
Lifespan
Not applicable, a recurring service action (pump-out), not a physical component with its own lifespan
Embodied carbon
None
Space / material use
Low
Output timing
Continuous process
Skill to repair
Specialist
Regulation (FR example)
On-site sanitation (assainissement non collectif): the installation must be declared to and approved by the local SPANC before work starts, and is subject to periodic inspection. Arrete du 7 septembre 2009 modifie.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Periodic sludge pump-out (This page) Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Specialist · Upkeep: Light · Change to daily life: None · Works without the grid: Yes Choose it if you have a septic tank or a small treatment plant and want the sludge taken away by a licensed service.
Managed thermophilic humanure composting Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Regular · Change to daily life: Occasional · Works without the grid: Yes Choose it if you use a dry toilet and want its solids turned into compost on site.
We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.