Environment, Development and Sustainability

, Volume 13, Issue 3, pp 519–533 | Cite as

Energy analysis for onsite and offsite suburban wastewater

  • Peter A. Omojaro


The environmental consequence of meeting the planet’s energy requirements has shown that biological degradation of organic constituent from wastewater does not only produces biogas. It also produces flammable methane that has 21 times more global warming potential or greenhouse effect than carbon dioxide. This becomes a loss of potential renewable energy when it is flared. This study investigates recoverable energy from cassava wastewater and effect of unrecovered onsite (not from treatment plant) wastewater energy. Sludge from both onsite untreated and offsite treated wastewater from a cassava processing station in a sub urban community of Nigeria was analyzed. The result shows that the offsite treatment has a methane potential of 27.428 m3/day compared to the onsite methane emission potential with 17.807 m3/day. The onsite 17.807 m3/day of methane is equivalent to 0.126 kgCH4/year of emitted methane base on industrial procedure standards by the IPCC (2006) guidelines for national greenhouse gas inventories. An additional 54.03% of methane will be recovered if the onsite emissions were to be captured . At an emission efficiency of 0.025 kgCH4/kg COD, the untreated wastewater indicates a potential contribution to the greenhouse effect. A mathematical model analysis was presented for ease in determining the amount of methane emitted from the untreated wastewater. This study support suggested methodologies and previous work comparing anaerobic offsite methane potential and untreated wastewater methane emission potentials along with its greenhouse effects.


Energy recovery Wastewater UASB Methane Greenhouse gas Emission factor 

List of symbols


Maximum CH4-producing capacity (kg CH4/kg COD)


Biological oxygen demand (g/m3)


Theoretical conversion factor for methane in anaerobic treatments


Methane emissions in inventory year, (kg CH4/year)


Chemical oxygen demand (g/m3)

\( V_{{{\text{CH}}_{4} }} \)

Volume of methane produced at standard condition (m3/day)


Emission factor for industry i, (kg CH4/kg COD)


Emission factor for each treatment/discharge pathway or system, (kg CH4/kg COD)


Greenhouse gas


Greenhouse warming potential


Tank height (m)


Hydraulic retention time (h)


Industrial sector


Each treatment/discharge pathway or system


Endogenous coefficient per day


Methane correction factor


Organic loading (kg/m3/day)


Net mass of cell tissue produce per day (kg/day)


Flow rate (m3/day)


Fraction of COD removed (%)


Amount of CH4 recovered in inventory year (kg CH4/year)


Organic component removed as sludge in inventory year (kg COD/year)


Solid retention time (d)


Total organically degradable material in wastewater from industry I in inventory year, (kg COD/year)


Total solid retention (g/m3)


The up-flow velocity (m/h)


Tank volume (m3)


Yield coefficient, gvss/gbCOD


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringEastern Mediterranean UniversityFamagusta, via Mersin-10Turkey

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