Evaluation of Plantain Biomass ( Musa paradisiaca L.), as Feedstock for Bio-Ethanol Production

This study investigated the viability of post-harvested plantain biomass as a promising feedstock for the production of Bioethanol. The properties of the derived bio-ethanol were determined to examine its suitability as a promising and sustainable alternative to petroleum-based ethanol The research revealed that Plantain biomass is made up of Lignocellulosic contents such as extractive, Lignin, cellulose, hemicelluloses, ash and moisture in different propor-tions. The different parts of the biomass such as the flower, stem and leaves were hydrolyzed using H 2 SO 4 . Optimum hydrolysis conditions of 6%w/v acid concentration, 30 min contact time and 80˚C working temperature were established for Plantain stem and flower. However, hydrolysis of Plantain leaves was at the best under the experimental conditions of acid concentration (10% w/v), contact time (120 min) and temperature (120˚C). The highest yield of the bio-ethanol produced was obtained from Plantain stem biomass with a record of 8.04% followed by Plantain flower with a yield of 7.73% and 757% from Plantain leaves The hydrolyzate was fermented using Baker’s yeast (Saccharomyces cerevisiae) at a room temperature of 25˚C and pH of 4.5 for 4 D. The structural determination of the derived bioethanol was conducted using FT-IR analysis and the fuel properties were found to be consistent with those of the conventional ethanol. The SEM analysis conducted on the post hydrolysed biomass confirmed the effectiveness of the hydrolysis scheme adopted as evident on the surface morphology of the biomass. This study confirmed the viability of Plantain biomass as promising feedstock for Bio-ethanol production under the established hydrolysis conditions.


Introduction
Biomass-sourced fuel such as Bioethanol is one of the emerging bioenergy sources presently being exploited in Nigeria. Nigeria as a nation depends heavily on crude oil as the major energy source, while other energy-potential resources are minimally focused.
Yearly, 94% of the energy consumed in Nigeria is sourced from fossil fuel, notably, petroleum [1]. The continuous utilization of this resource over years has adversely contributed to the numerous environmental pollution challenges encountered in the nation. Presently, research attention is being focused on harnessing other energy sources to circumvent the unpleasant consequences of pollution associated with petroleum exploitation. Hence, one of the major areas of research interest is biomass conversion technology. Biomass is generally considered as a dependable alternative resource due to its inherent advantages such as sustainability, renewability, availability, affordability and environmental friendliness [2].
Biomass is an organic material that contains radiant energy stored from the sun. The energy can be harnessed for both domestic and industrial purposes if effective biomass conversion technology is put in place [3] [4].
Plantain is one of the most important crops of the tropical plants. It belongs to the family Musaceae and the genus Musa. It is known as, "Ogede agbagba" in Yoruba, "Ayaba" in Hausa and "Ogadejioke" in Igbo [5]. Plantain is a common food crop grown in many countries of the world.
Nigeria is one of the largest economies that cultivate plantain. About 2.73 million tonnes of Plantain is being harvested annually and the post harvested biomass remnants dispersed unproductively [6]. Plantain is majorly produced in the South and Central regions of Nigeria [7] [8].
Plantains and other cooking bananas produced throughout the humid tropics constitute major source of carbohydrates and contribute enormously to global food security essentially in Africa, Caribbean, Latin America, Asia and the Pacific. Due to the perishability nature of the crop, the rate of postharvest losses varies from one country to another according to the organisation of market chains and modes of consumption [6]. The lignocellulosic biomass is made up of very complex biopolymers comprised of cellulose, hemicellulose, and lignin and small amount of extractive and mineral acids [9].

Sample Collection and Preparation
Plantain (Musa paradisiaca L.) post harvested biomass was collected from Plantain orchard of the Federal University of Technology, Akure (FUTA), Nigeria.
Samples were separated into three portions, labelled as stem, leaves and flower and washed with water to remove every dirt adhered. The samples were sun-dried for 5 D and ground into fine particle size using milling machine. The milled samples were made to pass through 1 -5 mm size analytical sieve.

Acid Hydrolysis
The hydrolysis experiments were conducted using both the laboratory scale reactor and fabricated percolating hydrolysis reactor.

Hydrolysis Using Laboratory Scale Reactor
The laboratory-scale hydrolysis reactor was set up using a pressure pot assembled with a digital thermometer. The first batch of the hydrolysis experiment was conducted using the reactor as follows: One gram (1 g) each of the plantain biomass fractions was hydrolysed under the following experimental conditions of temperature ranging from (80˚C, 100˚C, 120˚C) acid concentration (2%w/v, 4%w/v, 6%w/v, 8%w/v and 10%w/v) and contact time (30 min, 60 min, 90 min, and 120 min).

Hydrolysis Using Fabricated Percolating Reactor
Five hundred (500) grams of stem, leaves and flower of the prepared biomass samples were weighed, transferred into separate plastic buckets, stirred thoroughly and introduced into the fabricated reactor for bulk acid hydrolysis. Optimum hydrolysis conditions of acid concentration (6%w/v H 2 SO 4 ), temperature (80˚C) and contact time (90 min) were adopted for plantain stem and flower biomass. The same procedure was adopted for plantain leaves biomass at the optimum conditions of 10%w/v acid concentration, temperature of 120˚C and contact time of 120 min. At the end of the acid hydrolysis reaction, the mixture was allowed to cool for 1h and filtered. The residue was kept in refrigerator for SEM analysis. The pH of the hydrolyzates was monitored with pH meter and regulated using 6 mL of 2 M NaOH to attain a pH of 4.5 which was conducive for yeast cells.

Preparation of Baker's Yeast (Saccharomyces cerevisiae)
Saccharomyces cerevisiae (120 g) was weighed and added to 100 mL of distilled water at a temperature of 20˚C in a sample bottle and agitated on a shaker at 300 rpm for 30 min to activate the yeast prior to use.

Fermentation of the Hydrolyzed Biomass
The fermentation of the hydrolyzed biomass was carried out as described by Ogunsuyi and Badiru (2016). The prepared Saccharomyces cerevisiae was then added to the hydrolyzed biomass, thoroughly stirred and covered with aluminium foil paper and kept at a temperature of 32˚C in a dark cupboard for 4 -5 D [16]. The mixture was stirred on daily basis and the ethanol level produced was monitored using Alcohol hydrometer method [17].

Distillation of the Fermented Biomass
At the end of the fermentation, the fermented broth was distilled using a simple distillation method. The bio-ethanol distillate was collected at 78˚C method described by (Ogunsuyi and Badiru 2016).

Purification of the Distilled Liquor
The distillate was purified and collected over a temperature range of 78˚C -78.5˚C using synthetic CaO to remove water and other extraneous impurities. Hence, a yield of 40 mL of the pure bio-ethanol was obtained. The bio-ethanol was kept in an airtight bottle in a refrigerator prior to FT-IR analysis to determine various functional groups contained in the liquor. The bio-ethanol yield was calculated and recorded. Table 1 shows the results of the fibre components of the various fractions of the biomass (flower, stem, leaves). The result showed that extractive contents were 26.56%, 22.04% and 33.71% for flower, stem and leaves respectively. Lignin contents were found to be 46.00%, 28.00% and 27.00% for flower, stem and leaves respectively. The results were consistent with the value reported by Bilba et al., (2007) for banana leaves [18] [19] and for pseudo-stem reported by Abdullah et al., (2014). Holocellulose content was noted to be 55.00%, 70.30% and 63.30% for flower, stem and leaves. While the α-cellulose contents were found to be 33.00%, 29.00% and 30.00% for flower, stem and leaves respectively. It was observed that the values were not in agreement with the finding of Kabenge et al., (2018). This discrepancy could be attributed to the varied chemical composition of the agro-waste [20]. Hemicellulose contents were recorded as 22.00%, 41.           than those of other fraction (Plantain flower and leaves) as shown by the fibre analysis reported in Table 1.

Yield of Bio-Ethanol Produced
The Percentage (%) yield of the derived Bio-ethanol was calculated using: where; W is the weight (Yield) of the Bio-ethanol and V is the Volume of the Bio-ethanol Density of ethanol given as 0.789 g/cm 3 and ( ) M is the mass of the biomass used.   [16]. This showed that the derived bio-ethanol have a good ignition ability.

Conclusion
Preliminary fibre composition analysis conducted on the biomass revealed the promising potential of plantain biomass due to its high hemicellulose content.