Biogas Questions for Ben Peterson

Would it be feasible for a passive biogas system (like the one above) to be used as a replacement for modern waste treatment plants? The only thing I am thinking that would be kept is a strainer for catching the weird stuff that goes toilets.

I read somewhere that 1 meter cubed per person is about the amount of room needed in a biogas digester for handling household toilet business. Is that number somewhat correct? If not, what do you advise?

Right now where I live it is -40, and often it doesn't get warmer than -4 F for weeks on end.

How do you best deal with long period of cold weather (it's below 32 for about 5 months)? Deeper installation? Larger capacity? Is it even appropriate in this type of climate?

I've been thinking about the spillway / outlet slowly freezing up.

I don't have alot of experience with digester gas. Woodgas is made from heating up wood at high temperatures and phase shifting it from a solid into a gas.

What could be cool is to use the flare gas from a gasifier and the waste heat from an engine to store up heat in water (thermal mass) and then use that water to warm up your digester. Could you place some hot water lines in the base of the digester and let the heat slowly rise?

Those are some pretty cold temperatures for digesters. With gasifier heat you could probably get 9 months of use instead of 5-6.