The potentials of production of biogas from constructed wetland macrophytes

This study investigated the potential of biogas production from three (3) constructed wetland macrophytes: Water hyacinth (WH), cattail (CT) and Cyperus papyrus (CP). The digesters used had capacity of 0.22 cm3 each. They were operated under anaerobic conditions with organic loading rate (ORL) of 0.2 kg VS/m3.day and hydraulic retention time (HRT) of 5 days. Observations were made for a period of 128 days. The results show that the three macrophytes produced methane (CH4) and carbon dioxide (CO2) in reasonable quantities. The other gases such as H2S and CO were present in minute quantities only. The results show mean biogas production flows of 38.52±13.05, 75.63±14.34 and 38.52±13.05 mL/kg VS for WH, CT and CP respectively. The mean percentage CH4 production for WH, CT and CP were 54.45±6.86, 42.02±11.10 and 38.52±13.05%, respectively. The corresponding mean percentage CO2 productions were 42.71±3.0, 39.73±4.48 and 43.24±2.96%. The energy potentials in terms of calorific value were 9.22, 7.02 and 6.13 W/kg of biomass for WH, CT and CP respectively. It was concluded that from water hyacinth alone, a conservative off-grid renewable energy of about 11,825 MW/year is possible as addition to reduce the Nigerian energy demand gap. Key words: Renewable energy, biogas, macrophytes, constructed wetland, Nigeria.