Development of a household anaerobic digester for rural areas in Sudan

Year 2017, Volume: 4 Issue: 2, 53 - 63, 10.08.2017

Hazir Farouk Mutaz Elobaid Omer Abdelazim Mohammed Salah Khalid Bakheet Andrew Lang

Abstract

This
study is aimed at developing an anaerobic digestion system that can produce biogas
for cooking purposes at the household level. A lab-scale batch digester was designed
and constructed using polypropylene material with a capacity of 20 litres, and with
the biogas captured in a floating-top gas reservoir. This initial small-scale
construction was mainly to study some important parameters of the anaerobic
fermentation process. The parameters studied were: biogas production from
various types of organic material, the levels of acidity and dry matter of the
organic material, the affect of temperature within the container, along with an
evaluation of the time scale and rate of gas production. Four types of organic
material were used, including fresh and dry cow dung with dry matter content of
20% and 90% respectively, dry chicken manure with dry matter content of 90%,
and food waste with dry matter content of 10%. The test conducted with fresh cow
dung was at a time of low ambient temperature in the Sudanese winter, while the
tests for the other three feedstock materials were conducted in the higher
ambient temperature of the Sudanese summer. The results from the lab scale
revealed that the gas production rate was directly proportional to the reactor temperature,
while the dry matter contents in the organic material dictated the required
mixing ratio with water. Using results from the lab-scale reactor, the digester
design was improved and scaled up using a cylindrical water tank with a
capacity of 225 litres. Using feedstock of 84.3 kg of fresh cow dung with dry
matter of 20% dilutd with water to 10% dry matter, the design was tested at a
digestate temperature of 37-38 degrees Celsius. The test covered the calorific
value of gas produced, gas consumption rate using a single burner, and the efficiency
of the burner. The results were that the calorific value of the biogas was
20.52 MJ/m³, the burner had a gas consumption of 342 liters per hour
during a simulation of normal operation for household cooking use, and use of a
standardized process indicated a burner efficiency of 51.7%.

Keywords

anaerobic digestion, biogas, household, rural areas, Sudan

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