Joshua Myrvaagnes wrote:On the down side, ethanol fermentation does release CO2, meaning some of the energy in the manure has been used up just in the transfer process.
Maybe that's a level of energy release that can be recaptured in a no-human-entry greenhouse (ie one where a person can't get in it, even a small child, and accidentally suffocate, but plants can fit inside, and is used only for energy re-capture rather than for growing the largest plants or growing foods, just for growing biomass).
While I commend you for thinking outside the box, or actually inside a box in this case; what you're advocating here is a terrarium with an external CO2 input. It's probably not going to work as you imagine, as the additional CO2 will only aid the plant growth so long as there's no other resource limitation creating a limit on the biomass (such as phosphorus, available sunlight or simply soil volume). Considering that it's a terrarium, some kind of limitation is inevitable. It's entirely reasonable to pipe your CO2 into the greenhouse, but limiting venting to the point that it's hazardous to mammalian life is probably not the best course of action.
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.
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?
Hi Tom OHern,
Thank you for your prompt reply. We have 500 people working in a industry 24/6 and 365 days. We want to use this biogas into the burner of a 100 Kg/hr Boiler.