Abstract: | Results from piggery-waste digestion fit those from a continuous culture of acetate utilising methanogenic bacteria showing that the acid to methane step of this digestion can be regarded as an independent continuous culture behaving as predicted by a simple continuous culture model with a wash-out dilution rate of about 0.4 day?1 and a Ks value of about 800–900 mg acetic acid dm?3. However, this was only possible because the waste contained a high concentration of free acid and the application of the results to other digestions is discussed. |