Composting Toilet Chamber Dimentions

[alexgadd]

I am starting to build a compost toilet, and need some advice.

I am building a twin chambered vaulted toilet that is an external build. As a result the toilet area will be raised above the chambers.

I am looking to find out an informed decision on the size of the chambers required. There are two of us, the toilet will be in use approx 10 months a year and (if it makes a difference because of temperature) we are in Spain.

Any help / advice greatly appreciated.

Alex