Anaerobic digestion of grass-cuttings under mesophilic and regulated digester pressure
by Ishmael M. Ramatsa; Esther T. Akinlabi; Robert Huberts
International Journal of Renewable Energy Technology (IJRET), Vol. 9, No. 1/2, 2018

Abstract: The successful functioning and stability of an anaerobic digester depends on the interplay of several factors, each of which is very important to the success of the system as a whole. pH is central to the whole system as it dictates the survival for the bacteria. In this study the effect of digester pressure was investigated at a fixed temperature of 36°C. The digester pressure was manipulated using back pressure regulator. Grass cuttings were used as feed material to the digester. Three pressures of 2bar, 4bar and 6bar were investigated for a period of ten days. The characteristics and methane yield achieved when digesting grass cuttings under constant digester pressure (gauge pressure) suggested that it is possible to produce biogas that has minimal amount of CO2. The highest methane compositions at 0bar, 2bar, 4bar and 6bar were 55.77, 62.2, 65.8 and 71.2% and carbon dioxide compositions were 58.85, 35.2, 32.5 and 26.2%. The amount of CO2 decreased significantly with increased pressure and the pH values dropped to 7.01, 6.96 and 6.78 respectively with increase in pressure.

Online publication date: Wed, 28-Feb-2018

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