What is the solution for domestic sewage?

Don't flush your toilet every time you have a wee, the energy to pump and clean the water to flush the toilet causes a lot of C02 Emissions Wee outside when possible don't get caught though in public you can face a criminal charge for exposure just tell the cops you were helping save the environment if they ask you questions. There will be no charge if no one was around to see you.

As for the other sewerage put it in a bucket and use it on your garden and don't tell the neighbours what it is mix it well with your soil. Or collect it in mass amounts and sell it for energy production. Methane and fertiliser for farmers.