Pepa;
Nice four legged feed stock you have there:--))
I have read about as much as I can about the stuff that Al Rutan did, he seems to be the defacto expert on this, and boy do I wish he was still alive.
There's tons of his stuff on the journey to forever website, including drawings.
How do you plan on pressurizing the fuel for heating, cooking?
From reading about the guy who did the chicken poop car fuel, I think your slurry level may be too high.
I think that with the current tank you can do a whole lot with it, which will be perfect for getting all the tank inlets and outlets just right before going the fiberglass route for long term.
I agree, if you have a large enough feed stock two tanks with a week startup offset would be good to cover the gas peeks from loading the slurry and the need to clean the tanks.
Some of the later ones have/had bottom pipes to empty the waste without the need to open the tanks to the air.
Bruce S