Abstract
This study investigated the use of effective microorganisms (EM) to enhance cost-effective biogas purification at household-level application. It involved experimental setups for biogas purification in two different runs: 4 L activated EM and 1 L dormant EM by bubbling biogas through EM purification units. Biogas composition was analyzed using an industry-standard biogas analyzer. The results indicated that EM has the potential for biogas purification through a biological process, to remove H2S and CO2 by involving photosynthetic bacteria (Rhodopseudomonas palustris) in the presence of light. The raw biogas average composition was 62.2% CH4, 37.4% CO2 and 1359.3 ppm H2S. The 4L activated EM batch solution purified the raw biogas to 80.2% CH4, 19.5% CO2 and 786.1 ppm H2S. The corresponding purification efficiencies are 60% for CO2 and 49% for H2S. Purified biogas could be used by the household to cook for 1.82 h (85%) while raw biogas could cover only 55%. The designed biogas purification system can cost only Tshs 91,010/= and purify about 15,000 L of biogas at EM cost of Tshs 9,100/month. Key words: Biogas composition, photosynthetic bacteria, anaerobic digestion, biochemical processes, Rhodopseudomonas palustris, biological desulphurization.
Highlights
Biogas is among the fuels from biomass which has great importance and can effectively replace fossil fuels for obtaining electricity and heat, in the field of transport (Zăbavă et al, 2019)
That might be due to the fact that from day 1 to day 3, the microorganisms were acclimatizing to the environmental conditions created by the introduction of biogas; as times went by, they got acclimatized and started acting on CO2 as a source of energy resulting into more of them being reproduced
During purification of biogas using effective microorganisms, hydrogen sulphide may have been converted into elemental Sulphur or sulphate depending on the mode of metabolisms in which Rps. palustris is switched on
Summary
Biogas is among the fuels from biomass which has great importance and can effectively replace fossil fuels for obtaining electricity and heat, in the field of transport (Zăbavă et al, 2019). There has been an increasing desire for use of biogas because it is a renewable source of energy, which is less expensive, reduce environmental pollution, reducing problems of power energy, environmental vandalism, loss of resources, climate change and promote better public health (Ilyas, 2006). Many communities especially those who live in rural areas meet 90% of their energy needs with biomass, by wood fuel and this dependency on fuelwood has led to a rapid deterioration of Tanzania’s ecosystems (Felix and Gheewala, 2011).
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