Production of bioethanol from vegetable waste using a small scale reactor as an environment management system
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Date
2013
Journal Title
Journal ISSN
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
It is very much evident that the combustion of the fossil fuels at the current rate would
contribute to the environmental crisis globally (Chandel et al., 2007). Studies have revealed
that there are attempts to develop alternative source of energy so as to conserve the
dwindling reserves of crude oil and fossil fuels (Akpan et al., 2005;Taherzadeh and Karimi,
2008; Hossain and Fazliny, 2010).Bioethanol is considered as one of the best alternative
energy sources since it is an environmental friendly and lower pollutant energy source which
can be produced from the lignocelluloses out of the waste vegetables.
Ethanol can be produced by fermentation of any organic materials rich in carbohydrate
through microbial activity. Yeast is one of the most important microorganisms in the
production of ethanol through the fermentation. Previous study has proven that the use of
Saccharomyces cerevisiaes train could optimize the fermentation performance using waste
materials containing sugar and starch (Arumugam and Manikandan, 2011).The utilization of
the waste feedstock for biofuel production does not disturb the food chain as it is a waste-to-
energy concept based. The massive amount of agricultural waste (fruit and vegetables)
generation necessitates the need of technology development to derive economic benefit by
turning this waste into a useful product. For instance, one third of the agricultural products
(vegetables and fruits) in Sri Lankan market system end in waste due to poor handling and
storage practices. (Weerahewa et al., 2004).
Therefore, this study was mainly focused on the production of bioethanol from the rotten
vegetables removed from the Sri Lankan market as an alternative energy source. Further, the
fabrication of a low cost stirring batch type bioreactor system was highlighted to improve
the efficiency of bioethanol production based on the requirement of environmental waste
management system.
Methodology
In order to facilitate the bioethanol production from rotten vegetables, a portable small scale
low cost bioreactor system was fabricated. The overall implementation and scaling up of the
system was based on the waste materials mostly in order to eliminate the unnecessary costs.
Further, a low cost solar dryer was fabricated to minimize the electrical energy consumption
and to maximize drying process.
Approximately 40-45kgof agriculture waste materials which were not suitable for human
consumption, were collected from the local vegetable markets. The selected vegetable waste
were washed and cut into small pieces where they were subjected to sun dry for seven days
under hot sun using the fabricated solar dryer. Dried waste materials were subjected for acid
pre-treatment using Conc.H2SO4 (aq) 60 minutes of boiling at 120°C followed by adding
distilled water and Saccharomyces cerevisiaeaccording to a pre-determined ratio.
Different shaking hour combinations and different fermentation days were evaluated in
order to obtain the optimum requirements. The pretreated mixtures with different shaking
hours were filtered in to different schott bottles separately and measured pH and Total
Soluble Solids (TSS). Bioethanol concentration was estimated according to the method
proposed by Williams and Darwin (1950). Then the statistically significant shaking hour and
number of fermentation dayscombination was employed in to the fabricated bio reactor
modal. Bioethanol concentration, pH and TSS values of the fermented mixture in the bio
reactor was measured while maintaining the all other parameters constant as the laboratory
experiment procedure.Chromic acid oxidation test,Ritter test and Lucas tests were carried
out with respect to narrow down the justification of ethanol been produced (Pasto et al,
1992).AAS (Atomic Absorption Spectrometer) analysis was carried out for further
identification of the elements in the produced raw bioethanol. The statistical analysis was
carried out according to two factor factorial in Complete Randomized Design (CRD)
experimental design using MINITAB 15.0 statistical package.
Description
Keywords
Science and Technology, Technology, Environmental Science, Environment Management System, Bioethanol