Biogas methane concentration

For anaerobic systems, methane gas is an important product. Depending on the type and nature of the biological components, different yields can be obtained for different biodegradable wastes. For pure cellulose, for example, the biogas product is 50% methane and 50% carbon dioxide. Mixed waste feedstocks yield biogas with methane concentrations of 40-60% (by volume). Fats and oils can yield biogas with 70% methane content. 

Twice BTU yield as Biogas (methane) vs dry/dir. combust. Relatively few large concentrations of animals. 

Potential of biogas/methane generation of waste could be also determined experimentally in batch tests, semi-continuous-flow or continuous-flow reactors. Batch tests are based on measurement of the amount of biogas (and the concentration of CH in biogas) isolated during the fermentation of the portion of material placed in a closed vessel. Parameters determined in the batch test are called biogas potential or Biochemical Methane Potential (BMP). A detailed review of conditions in which these tests are conducted is presented in the work made by Angehdaki et al. (2009). 

If more feed was added, the amplification was again evident. After 20-30 days, the added metal seemed still able to affect the CH4 C02 ratio. It is important to note that during such a period the concentration of the metal in the liquid phase in the reactor was always higher than that in the control. The increase in the CH4 C02 ratio is produced by a more effective conversion of CO2 to methane Ni(II) increases the ratio to 4.5 compared with 3 found in the biogas in the control (Figure 8.4). 

Determination of the dissolved part of CO2 in the aqueous phase is necessary for a complete determination of the biogas production. Compared to methane (solubility= 18.35 mg/1 at p=l,013 mbar and T=35 C) the maximum solubility of carbon dioxide in aqueous media is 1,141 mg/1. In preliminary tests, dissolved CO2 was determined at the end of the test in the test setup by means of different detection methods. In the one case, the dissolved CO2 quantity was determined by the acidification with HCl, in the other case, CO2 determination was carried out by means of a DIC concentration analysis in the test setup. A comparison of both determination methods via HCl addition and DIC determination leads to similar results. Piichner also ascertained similar results via DIC determination compared with HCl addition in her investigations. In this tests the determination of DIC was carried out by the HCl addition method. 

Porpatham, E., Ramesh, A., Nagahngam, B. 2008. Investigation on the effect of concentration of methane in biogas when used as a fuel for a spark ignition engine. Fuel 87(8-9) 1651-1659. 

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