Fuel Efficiency of Biogas and Biogas Plant Construction
The fuel efficiency of cattle dung is 11% and that of Biogas from same dung is 60%, Biogas technology holds promise of revolutionizing energy scene-conserving forests, preventing soil erosion and providing energy security in rural areas.
Normally a 3 cubic meter capacity Biogas plant is considered sufficient to meet the heating and lighting needs of a rural family of 6 to 9 persons.
Biogas Plant Construction
Currently in Nigeria, the Environmental Health Officers Registration Council of Nigeria is championing the course of widening the horizon of knowledge of the public that the biogas plant can be constructed a hundred percent using local materials.
Two types of the plant are being advocated by EHORECON for domestic biogas plant the flexible type and the dome type.
The flexible type is made of rectangular sewn air tight tarpaulins material with provisions for charging the plant and removal of the gas and spent slurry respectively.
Read Also : Other Methods/Technologies for Solid Waste Treatment
A flexible tank of 2.5 cubic meters submerged about one (1) meter on the surface of the ground will be sufficient for a family of 4 – 10 persons.
Fig. (a) & (b): Construction of Flexible Tank Biogas Plant and the Plant with Full Gas Yield. Photo taken at Federal University of Technology Owerri).
Also, the dome type has been successfully constructed in Nigeria using local available materials as shown below. The tank is a modification of PVC water tanks making provision for stirring, charging, and gas harvest and slurry removal
House hold Level
Kitchen waste, cattle dung, garden waste, leaves of trees can be digested and digested product reused at household level.
Community bio degradable waste such as cattle dung of stray cattle and from abattoirs, garden waste, leaves of roadside trees, human excreta from individual/community toilet etc., can be digested in community biogas plant and end products can be reused.
Commercial bio degradable waste generated from hotels, parks and gardens, and leaves of roadside trees etc. can be digested in commercial biogas plant and the end products can be fruitfully utilized commercially such as gas engine, liquefied natural gas productions, lifting water for irrigation purposes etc.
The gas production varies from 0.29 cubic metres per kg of volatile solids added per day to 0.19 cubic metre 0.16 cubic metres per kg added per day in different seasons. The volatile solids destruction ranges from 40 to 55%. The sludge has good manurial value of Nitrogen, phosphorous, and potassium (NPK ratio is 1.6: 0.85: 0.93). The process gives a good performance at a retention time of 30 to 55 days varies as per season.
Read Also : Traditional Solid Waste Disposal Methods
In conclusion, amongst the sundry technologies for the management of solid waste described in this chapter, it is obvious that pyrolysis/gasification and pulverization/shredding require advanced technological development though pyrolysis may be applied to a wide range of solid waste materials.
It is only the biogas technology that is within the technological reach of the third world and less developed countries like ours. Besides this, the biogas technology holds a great promise as a source of manure for farmers aside from its energy recovery characteristics.
The technology can serve individual households, communities and small to medium scale industries as energy source.
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