Scholarly article on topic 'Wheat as a Promising Substitute of Corn for Bioethanol Production'

Wheat as a Promising Substitute of Corn for Bioethanol Production Academic research paper on "Agriculture, forestry, and fisheries"

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Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Neha Patni, Shibu G. Pillai, Ankur H. Dwivedi

Abstract Excessive consumption of fossil fuels, particularly in large urban areas, has resulted in generation of high levels of pollution during the last few decades. All petroleum-based fuels can be replaced by renewable biomass fuels such as bioethanol, bio-diesel, bio-hydrogen, etc. Bioethanol is an attractive alternative fuel because it is a renewable bio-based resource and it is oxygenated thereby provides the potential to reduce particulate emissions in compression ignition engines .It has a higher octane number, and lower cetane number, broader flammability limits, higher flame speeds and higher heats of vaporization than gasoline. The bioethanol can be produced from lignocellulosic biomass, starchy materials such as corn, wheat, cereals etc and sucrose containing feedstocks. Major portion of the production methods uses corn for the same, but since India being the second largest producer of wheat and there is availability of different varieties of wheat, we have selected wheat as a feedstock. After thorough review of extensive literature we finalized two enz ymes viz; glucoamylase and -amylase followed by fermentation process using bake yeast Saccharomyces Cerivisiae. Experiments were carried out to see the day wise decrease in concentration of glucose and increase in concentration of Ethanol by calculating the absorbance using Ultraviolet-visible spectrophotometer. Results obtained were in agreement with the possibility of wheat to be used as a raw material for maximum yield of bioethanol.

Academic research paper on topic "Wheat as a Promising Substitute of Corn for Bioethanol Production"

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Engineering

Procedía Engineering 51 (2013) 355 - 362 =

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Chemical, Civil and Mechanical Engineering Tracks of 3rd Nirma University International Conference

on Engineering (NUiCONE 2012)

Wheat as a Promising Substitute of Corn for Bioethanol Production

Neha Patni*, Shibu G. Pillai, Ankur H. Dwivedi

Department of Chemical Engineering, Institute of Technology, Nirma University, S. G. Highway, Ahmedabad-382481, Gujarat, INDIA

Abstract

Excessive consumption of fossil fuels, particularly in large urban areas, has resulted in generation of high levels of pollution during the last few decades. All petroleum-based fuels can be replaced by renewable biomass fuels such as bioethanol, bio-diesel, bio-hydrogen, etc. Bioethanol is an attractive alternative fuel because it is a renewable bio-based resource and it is oxygenated thereby provides the potential to reduce particulate emissions in compression-ignition engines .It has a higher octane number, and lower cetane number, broader flammability limits, higher flame speeds and higher heats of vaporization than gasoline. The bioethanol can be produced from lignocellulosic biomass, starchy materials such as corn, wheat, cereals etc and sucrose containing feedstocks. Major portion of the production methods uses corn for the same, but since India being the second largest producer of wheat and there is availability of different varieties of wheat, we have selected wheat as a feedstock. After thorough review of extensive literature we finalized two enz ymes viz; glucoamylase and a-amylase followed by fermentation process using baker' yeast Saccharomyces Cerivisiae. Experiments were carried out to see the day wise decrease in concentration of glucose and increase in concentration of Ethanol by calculating the absorbance using Ultraviolet-visible spectrophotometer. Results obtained were in agreement with the possibility of wheat to be used as a raw material for maximum yield of bioethanol.

© 2013 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of Institute of Technology, Nirma University, Ahmedabad. Keywords: Bioethanol; Wheat; Fermentation; Glucose; Saccharomyce Cerivisiae.

ELSEVIER

1. Introduction

Global demand for energy continues to grow due to rapidly expanding human population and increase of the industrial prosperity in developing countries. The major energy demand is still supplied from conventional fossil fuels such as oil, coal and natural gas. Utilization of fossil fuels over the last century and following years has drastically increased the level o f greenhouse gasses in the earths atmosphere [1]. These facts along with inevitable depletion of the worlds energy supply, and unstable oil market have renewed the interest of society in renewable sources that might serve as an alternative. All petroleum-based fuels can be replaced by renewable biomass fuels such as bioethanol, bio-diesel, and bio-hydrogen. Ethanol has long been considered as a suitable alternative to fossil fuels either as a sole fuel in cars with dedicated engines or as an additive in fuel blends with no engine modification requirement when mixed up to 30%. Today, bioethanol is one of the most dominant biofuel and its global production showed an increase over the last 26 years with a sharp increase from 2001. Worldwide production capacity in 2005 and 2006 were about 45 and 49 billion liters per year, respectively and total output in 2015 is forecast to reach over 115 billion liters [2].

♦Corresponding author. Tel.: +91-2717-241911; Fax: +91-2717-241917 E-mail address: neha.patni@nirmauni.ac.in

1877-7058 © 2013 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of Institute of Technology, Nirma University, Ahmedabad. doi:10.1016/j.proeng.2013.01.049

Bioethanol (ethyl alcohol, grain alcohol, CH3-CH2-OH or EtOH) is a liquid biofuel which can be produced from several different biomass feedstock and conversion technologies. It is an attractive alternative fuel because it is a renewable bio- based resource and it is oxygenated thereby provides the potential to reduce particulate emissions in compression-ignition engines [3] Its properties allow for a higher compression ratio, shorter burn time and leaner burn engine, which lead to theoretical efficiency advantages over gasoline in an internal combustion engine [4, 5]. The major portion of ethanol worldwide is produced generally by the fermentation of sugar obtained from molasses, cereals, and fruits. It can also be produced from lignocellulosic biomass, starchy materials [6, 7] such as corn, wheat, cereals etc. and sucrose containing feedstocks. Cereals contain phytic acid. Phytic acid readily forms complexes with many metals (zinc, iron, calcium, copper, etc.). These complexes show high stability over a wide range of pH values. Besides, the tendency to bind metal ions, phytic acid also shows binding properties towards macromolecules such as proteins and starch [8, 9].

It was found that phytic acid-starch complex is resistant to degradation by a-amylase thus being unavailable during the preparation step of ethanol [10] and also since India produces wheat in appreciable amount, we can check the possibility of using it as a feedstock. Wheat is a very good raw material for bioethanol production. To complete gelatinization of wheat starch, a temperature of about 65°C is required [11]. Despite extensive technological advances in ethanol production from various feedstocks over last few decades the price of the second generation ethanol is still high [12]. So use of wheat i.e., wastes or unusable wheat would prove to be a cost effective and better option for ethanol production.

2. Feedstock for Bioethanol Production

Biological feedstocks that contain enough amounts of sugar or the materials that can be converted into sugar, such as starch or cellulose can be fermented to produce bioethanol to be used in gasoline engines [13]. Bioethanol feedstocks can be conveniently classified into three types: (i) sucrose-containing feedstocks (e.g. sugar beet, sweet sorghum and sugarcane), (ii) starchy materials (e.g. wheat, corn, and barley), and (iii) lignocellulosic biomass (e.g. wood, straw, and grasses). Different feedstocks that can be utilized for bioethanol production and their comparative production potential are given in table 1[14]

Table 1. Different feedstock for bioethanol production and their comparative production potential

Feedstock Bioethanol production potential

Sugar cane 70

Sugar beet 110

Sweet potato 125

Potato 110

Cassava 180

Maize 360

Rice 430

Barley 250

Wheat 340

Sweet sorghum 60 Bagasse and other cellulose biomass 280

One major problem with bioethanol production is the availability of raw materials for the production. The availability of feedstock for bioethanol depends on geographic locations and also varies significantly from season to season. The price of the raw materials is also highly volatile, which can highly affect the production costs of bioethanol[15] .Because feedstocks typically account for greater than one-third of the production costs, maximizing bioethanol yield is imperative[16].

Table 2[17, 18] shows comparison of production cost, yield and conversion rate of different feedstocks.

Table 2.Comparison of production cost and bioethanol yield from different energy crops

Yield (t/ha//year)

Conversion rate to sugar or starch (%)

Conversion rate to bioethanol (l/ ton)

Sugar cane Cassava Sweet sorghum Corn Wheat

70 150 80 410

3. Wheat: A Promising Substitute

3.1 Food vs. Fuel

India being the second larger producer of wheat after China and it can be considered as a promising substitute of corn for bioethanol. Secondly, a huge quantity of wheat is wasted every year due to mismanagement in the warehouses thus this waste wheat can also be utilised for bioethanol production. It is shocking that wheat is ruined in the government godowns due to lack of proper storing facilities. Food items are rotten in the government warehouses not in kilos but in tons which later on not good for any living beings to use. Thirdly, Wheat is not going to add on to food vs. fuel war as wheat can be replaced to some extent by different crops like rice, maize, barley etc. Moreover, different hybrids of wheat can be developed specially for this purpose.

3.2 Global Scenario

Wheat is produced in 120 countries and accounts for about 19 percent of the world's calorie supplies .It is used primarily as flour for making bread, pastry, pasta and noodles etc. It is also used to feed livestock, with the feed used for accounting for about 17 percent of global wheat consumption. In addition the by-products from milling wheat into flour are used as feed. The annual global production of dry wheat is about 529 Tg. Asia (43%) and Europe (32%) are the primary production regions. Like rice, China is the largest producer of wheat with about 18% of global production at an average yield of 3 :4 dry Mg ha_1.The second largest producer is India, where dry wheat production is 71 Tg (12%), and the yield is 2:4 dry Mg/ha[19].

Table 3. Uses of wheat grain [5]

Feed Seed Waste Food Food Other

(%) (%) (%) manufacture (%) uses

(%) (%)

Africa 4.68 2.26 5.71 0.18 85.87 1.30

Asia 4.34 5.46 4.50 0.64 84.31 .74

Europe 38.78 8.13 2.44 1.60 46.7 2.33

North America 28.69 8.07 0.03 0.00 62.78 0.42

Central America 7.95 0.95 8.07 0.00 73.08 9.95

Oceania 42.00 8.29 4.02 3.07 28.19 14.44

South America 4.35 3.73 5.11 0.00 86.80 0.01

World 16.72 6.11 3.72 0.84 71.13 1.48

The composition of wheat flour media is given in the table 4[20].

Table 4. Composition of wheat flour media

Components Wt% whole Wt% pearled Wt% barn- free

wheat flour wheat flour wheat flour

Moisture 12.4 12 10.6

Starch 68.5 70 79.3

TKN 1.9 1.8 2.1

protein 11 10.3 12.3

phosphorus 0.286 0.291 0.174

Magnesium 0.067 0.067 0.019

Potassium 0.572 0.487 0.284

calcium 0.039 0.036 0.021

Thus from the above data it can be concluded that starch percent in wheat is quite higher which can be used to convert this starch into ethanol by fermentation [21].

4. Ethanol Production from wheat: A Literature Review

Although in France ethanol is mostly produced from beet molasses, it is also produced from wheat by a process similar to that of corn. Some efforts have been done for optimizing fermentation conditions. For example, Wanget al. (1999) [22] have determined the optimal fermentation temperature and specific gravity of the wheat mash. Soniet al. (2003) [19] have optimized the conditions for starch hydrolysis using a-amylase and glucoamylase obtained by solid-state fermentation of wheat bran. To enhance fermentation performance, high gravity fermentations have been proposed, particularly for the case of wheat mashes. To accelerate high gravity fermentations, the controlled addition of small amounts of acetaldehyde during the fermentation has allowed the reduction in cultivation time from 790 h to 585 h without effect on the ethanol yield. It is believed that this positive effect may be caused by the ability of acetaldehyde to replenish the intracellular acetaldehyde pool and restore the cellular redox balance (Barber et al., 2002) [23]. Fermentation of wheat mashes of very high gravity (VHG) has been proposed as well.VHG fermentation technology implies that high ethanol concentrations are obtained from very concentrated sugar solutions. Thomas et al. (1996) [24] emphasize that considerable amounts of water can be saved by applying this technology to ethanol production. Additionally, the implementation of VHG fermentation increases the throughput rate of an ethanol plant without the need of increasing the plant capacity. Bayrock and Ingledew (2001) [25] designed and tested a system that combines the multistage continuous culture fermentation and the VHG cultivation for a feed stream containing 150-320 g/L glucose using S. cerevisiae. The maximum ethanol conversion obtained in the process indicated the feasibility of implementing this technology, particularly in the continuous production of ethanol from wheat starch in the chemical industries [26].

5. Materials

• Wheat: Wheat flour obtained from different varieties of wheat can be used in India such as LOKVAN,

147, MALAVRAJ, POTIA, and SHARBATI.

• Enzymes: Two enzymes are normally used for starch hydrolysis:

1. a-amylase: These are obtained from Aspergillus oryzae, Bacillus amyloliquefaciens, and Bacillus licheniformis. [27]It is used to degrade starch from wheat substrate. The enzyme is stable to heat at 90°C .The optimum temperature for this enzyme is 85- 900C.

2. Glucoamylase: These are usually obtained from Aspergillus niger and Rhizopus species [27]. It degrades dextrin to fermentable sugars. The optimum temperature for this enzyme is 55 - 60 0C.

• Producing microbial strain: As a producing microorganism, baker' yeast Saccharomyces Cerivisiae is

Fermentation can be carried out at 280C. All chemicals, enzymes and yeast were purchased from Piyush chemicals.

6. Experimentation

Bioethanol is prepared by the fermentation of plants containing sugar and starch. Industrially, the production of bioethanol from starch-containing cereals takes place in five steps:

• Milling, i.e. the mechanical crushing of the cereal grains to release the starch components

• Heating and addition of water and enzymes for conversion into fermentable sugar

• Fermentation of the mash using yeast, whereby the sugar is converted into bioethanol and C02

• Distillation and rectification, i.e. concentration and cleaning the ethanol produced by distillation by removing co- products

• Drying (dehydration) of the bioethanol [28]

However, the production process of bioethanol from wheat is different as it incorporates a different energy and co -product concept:

• The wheat was cleaned and grounded in a mill. The bran was separated from the wheat grains and is used to generate primary energy in a biomass plant. The next processing step separates the gluten from the rest of the grain. This grinded wheat is mixed with 250 ml of water and 0.416 gm of a amylase and placed in water bath maintained at 70°C with stirring continuously by mechanical stirrer for 45 min.

• After cooling to 550C, 0.1 ml of glucoamylase was added into the mixture. The mixture was kept at 600C for 30 min. After this, mixture was cooled to 300C. By adding enzymes the starch contained in the wheat is converted into fermentable carbohydrates, which can then be fermented into alcohol.

• The sample was then cooled and transferred quantitatively to the flask and inoculated with 5gm of well stirred aqueous suspension of Saccharomyces cerevisiae (yeast). In the next step, the fermentation process, yeasts convert the carbohydrates into alcohol and CO2. Finally the mixture was left for fermentation for 75 hours approximately. The alcohol-containing mixture that is produced is referred to as "mash".

• The mixture was transferred to round bottom flask connected with fraction distillation column and kept in water bath at around 800C till an appreciable amount of product was obtained for analysis. Distillation separates the alcohol from the other constituents of the mash.

• In the rectification process this alcohol was then cleaned again. The dehydration - also referred to as drying - of the alcohol then removes virtually all the water it contains. The result is bioethanol with an extremely high purity of 99.7 vol%.

6.1 Preliminary Test

5ml of 0.25M K2Cr2O7 solution and 1 ml of 0.1M AgNO3 solution and 5ml of 6M H2SO4 is added to the distillate . A blue green colour was obtained due to the formation of chromium (2) sulphate according to the reaction:

2K2Cr2O7 + 8H2SO4 + 3CH3CH2OH -Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O

6.2 Confirmatory Test

After preliminary test, sample is subjected to UV-Vis( Ultraviolet-visible) analysis .The spectrophotometer is set to absorb the blue green(560 nm) colour of the light that is produced in the reaction .In order to determine the precise amount of alcohol present, a calibration curve must be produced . A calibration curve shows the relationship between absorbance of the light and concentration of a chemical in a sample. For this purpose we made six different solution of alcohol of known concentration and obtained their absorbance values from spectrophotometer as shown in table 5. After that curve is plotted with absorbance values on Y axis and concentration value on X axis as shown in figure 1.

Table 5. UV-Vis analysis of pure ethanol

Sr. No Concentration(ml/ml) Absorbance

1 05 0.353

2 1.0 0.361

3 1.5 0.366

4 2.0 0.375

5 2.5 0.381

6 3 0.388

0 12 3 4

Concentration of ethanol (ml/ml)

Fig. 1. Standard graph for Ethanol Estimation

Now the obtained sample was analysed using spectrophotometer and we obtain the peak curve as shown in figure2 .The maximum peak is obtained at 560 nm and its corresponding absorbance value is 0.677 .Using this absorbance value the concentration of our alcohol sample was found to be 25.46 v/v from the calibration curve . Again, from this 25.46 v/v solution four different solution of varying concentration were made and there corresponding absorbance values were obtained as shown in Table 6. And again the curve is plotted between absorbance and concentration as shown in figure 3, which is found to be in agreement with the Lambert- Beer's law.

Standard graphs were drawn to estimate glucose concentration in the broth (Fig. 4). The broth contained 0.274mg/ml of Glucose in the first day. Glucose was estimated in the broth on every day. After 3 days of fermentation the amount of glucose remained was 0.022 mg/ml. The day wise consumption of glucose in the fermentation broth is shown in Figure 5. Similarly day wise confirmation of the ethanol formed is also done by checking for the CO2 gas evolved.

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Fig. 2. UV-Vis Report

CONCENTRATION (ml/ml)

Fig. 3. Graph of Absorbance vs. Concentration of ethanol obtained

Table 6. UV-Vis analysis of ethanol obtained

Sr. No Concentration (ml/ml) Absorbance

1 0.6365 0.0178

2 1.273 0.03623

3 2.546 0.06893

4 5.092 0.1568

Fig. 4. Standard graph of glucose estimation

7. Results and Conclusions

Fig. 5. Day wise estimation of glucose in the fermentation broth

Wheat is very cost effective material because of high yields and suitable composition of the grain. Looking to the percentage of waste wheat all over the world especially in India, the percentage of the starch component which can be converted easily to ethanol, conversion rate to sugar or starch, corresponding rate to bioethanol and significant yield of the bioethanol produced, it can be said the wheat is a promising substitute for producing bioethanol. Methods and different parameters are needed to be investigated. Similarly many varieties of wheat are available in India, we have used flour of sharbati variety of wheat, other varieties can also be used to evaluate for ethanol production. Ethanol yield depends on the area or location from where the wheat samples were taken and also on the temperature conditions maintained during fermentation and enzymatic preparation of flour samples.

For economically feasible bioethanol production, several hindrances are to be overcome. These refer to the four major aspects which are feedstock, conversion technology, hydrolysis process, and fermentation configuration. With regard to feedstock major obstacles are cost, supply, harvesting, and handling in case of fermentation configuration. In conclusion it may be said that to solve the technology problems of the conversion process, science and efficient technology are to be applied, so that bioethanol production from agricultural wastes may be successfully developed and optimized in the near future.

Acknowledgements

The author would like to express their deep sense of gratitude to Institute of Technology, Nirma University to provide the infrastructure and financial assistance to this Project.

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