Dear Richard
Without answering your questions at all, I offer the following: is there a good reason why biogas is not operated in a pressurised vessel so that it can be tapped directly into a container at pressure? Is it simply too expensive to build a pressurised tank with pressure locks to get the material in and out? It is a bit obvious that there would be no compression needed it was operated in a sealed steel vessel. The bacteria would pressurise it themselves. Do they stop growing under pressure? A digester composed of long PVC tubes would take 9 bars easily. That could provide 5 bar tank filling ‘on tap’. Possible? Crispin +++++++ Not to be facetious about the bag lady in the prior post, but there has to be some practical alternative. Biogas is said to be too expensive to compress. The comparison was made to LPG for transportation. Like most one line conclusions it may or may not be though, ... In different circumstances. What amount of energy per unit atmosphere of compression is expended? Is it a linear increase with increasing pressure ? Lets have that plot then talk about practicality of transport per various volumetric requirements of the rest of the 99%, like the lady carrying the bag so, perhaps she is not left doing so, so to speak. I have heard about an intrepid country inventor, Harold somebody, who used his refrigerator compressor to generate about 200 psi (12+ atmospheres) off from his chicken manure, to run his car around his town. What is a practical minimum compression for transport and say week long domestic use? Would an extended tank -in-tank biogas digestor, properly ballasted and suspended by ropes on a basic windlass, generating up to say 15 psi, sufficient to contain the required volume in an inner tube? (Where is Boyle when we need him! ) . Even the simple wrapping of sealed plastic bags filled with biogas, with ubiquitous inner tube tire rubber strips can generate substantial compressive forces... . It all comes down to time and effort versus cost and time of alternatives---assuming of course that the so called beneficiary wants it and can function as a community member pursuing it. Having lived on a tank in well system for four years in Tanzania, am all for a practical solution. Richard Stanley
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