SOURCE:

Faculty: Engineering
Department: Agricultural And Bio-resources Engineering

CONTRIBUTORS:

Umeghalu, I. C. E.
Nwuba, E. I. U.

ABSTRACT:

Presently, man relies on fossil fuels as his major source of energy. However, the negative effects of fossil fuels usage have provided the pedigree to consider other alternative energy sources. Bio-fuel offers option as alternative energy source due to its environmental friendliness, its sustainability and it is renewable. Traditional crops used as dedicated energy crops for bio-ethanol production seems to have violated the technical and ecological reliance standard in terms of sustainability, by interfering with food chain. The aims and objectives of this study is to investigate the potentials of wild cocoyam, jackfruit seeds, water yam and yellow yam for bio-fuels production in terms of: (i) Characterization of the crops; (ii) Optimizing the enzymatic hydrolysis for ethanol production; (iii) Produce ethanol from the starches; (iv) Produce biogas from the fermentation brutes; (v) Study the kinematics of the biogas production. The starches of the crops were extracted by wet milling method. Reducing sugar yield was optimized using the Central Composite Design (CCD) and the result analyzed using Design Expert 8.0.7.1 Trial Version where time, enzyme concentration, water quantity and temperature are the variables. Saccharomyces cerevisiae yeast was used for starch fermentation. Distillation of fermentation wort was done using distillation apparatus. The broths were used for biogas production. Optimization of cumulative biogas production was studied using CCD and the optimized result analysis was investigated using Design Expert 8.0.7.1 Trial Version where major variables are time, inoculums concentration, water quantity and substrate concentration. Starch yields from the crops were: wild cocoyam-65.42%, jackfruit -51.65%, water yam-41.65%, and yellow yam26.17%. Optimal reducing sugar yield of 166.15mg/mg, 136.44mg/mg and 122.23mg/mg respectively were obtained for wild cocoyam, water yam, and yellow yam at the temperature of 70oC, 0.3g/g enzyme concentration, 3ml/g water quantity and at 3hrs while yield of 142.58mg/mg was obtained for jackfruit at temperature 70oC, 0.3g/g enzyme concentration, 3ml/g water quantity and at 2hrs. Ethanol yields were: wild cocoyam (79.6%); jackfruit (72.6%); water yam (63.1%), and yellow yam (53.6%). The cumulative biogas yields of 136.44ml, 122.23ml were obtained for wild cocoyam and jackfruit seed wastes respectively. Results from the study showed that wild cocoyam, jackfruit seeds and water yam are very good primary feedstock while yellow yam can be supplementary feedstock for bio-fuels production.