Tom OHern wrote:I saw that you also posted in the Humanure toilet vs biogas digester? thread. Did you read all of that before posting this question? There are a lot of good thoughts there. One of the reasons I don't think it isn't done more often is that in order to produce enough cooking fuel for 1 or 2 people, it takes almost 1000lbs of human waste and an adult produces about 1lbs per day so that is a lot of input for very little output. It just isn't a cost effective system for biogas production. Now, if you already have a biodigester set up, it can handle any human waste that you add up to its capacity, but if you just have human waste, you are probably better off composting it via the Humanure method.
With that said, if you do want to go ahead with a human waste system, here is a site with some considerations: http://www.appropedia.org/Biogas_from_human_waste
There are large scale system that have been done, but they are not cheap nor simple. They involve heat treatments systems for the inputs and UV sterilizations for the effluent output. When you say a "large number" how many are you saying?