Dear Biogas List, I have been thinking about the biggest hurdles to producing more gas from small scale biogas systems (4 cubic meters to 12 cubic meters) and by far the biggest barrier is heat. From the literature I have read it seems that if you increase the temperature of the digester from about 18C (the temperature of our digesters) to 37C you can nearly double the gas yield per unit of input and nearly halve the retention time which would reduce the capital costs.
Does anyone know of tests that have been done or ideas that have been put forth to heat small scale digesters in a controlled manner? (For the moment assume that such a process could be managed on many disparate, small scale biogas systems. That is the next challenge.) The processes I was thinking of were 1.) to heat the biogas system with biogas from the system itself or 2.) to bubble a very slight amount of air through the digester so that there was a slight anaerobic reaction that would produce heat and warm the digester. Or 3.) you could use sunlight to warm the digester if you can warm the digester and not the gas holder as warming the gas holder will only cause the gas to expand and no heat will be transferred to the slurry. These methods are probably most applicable to fixed dome and floating drum. Have either of these ideas been tried? Are there other ideas out there? Cheers, Kyle
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