Production of Bioethanol from Waste Dates in South Algeria: Study and Application

 

Insaf Mehani1, Bachir Bouchekima1, Laouini Salah Eddine2*, Mouna Mehani3

1LENREZA Laboratory, Kasdi Merbah University, B.P 511, Ouargla 30000, Algeria.

2Department of Process Engineering and Petrochemical, Faculty of Technology, Echahid Hamma Lakhdar University, B.P 789, El Oued 39000, Algeria

3Laboratoire de genie des procédés, Université Kasdi Merbah Ouargla, B.P 511, Ouargla 30000, Algérie

*Corresponding Author E-mail: salah_laouini@yahoo.fr

 

ABSTRACT:

One of the main issues that the world is facing is population growth. One of the critical issues would be providing accessible, safe and reliable energy for the current population and the next generation. To provide for the growing population’s needs under the umbrella of sustainable development, one of the vital factors is energy supply. Providing safe, clean and affordable energy for the current population and the next generation is one of the highest priorities. The need for everyone to have access to affordable energy sources, a great dependence on fossil fuels, the depletion of finite resources, as well as the critiques of the negative impact of fossil fuels on the environment are the most notable barriers that incite states to search for new options. In this context, Biofuel is among those renewable energies that can be a substitute for fossil fuels. The bioethanol is the most consumed worldwide biofuel; it can be produced from several other substrates rich in fermentable sugars, namely cellulosic biomass, energy crops and organic waste. This study provides an analysis of the production of bioethanol made from common dates of low commercial value. These represent an excellent material for the production of bioethanol since it is rich in sugar, economic, abundant, and there is no competition with food crops.

 

KEYWORDS: Bioenergy, dates, bioethanol, valorization, South Algeria

 

 


INTRODUCTION:

The need to meet the ever-increasing demand for energy is probably the greatest challenge that society has to grapple with in this new millennium. Virtually every aspect of life on planet Earth requires energy input in one form or another. Although man has in the past used wood for heating and grass for fuel. The energy needs there to be met principally by the use of fossil fuels resources and the world has been almost completely dependent on it1.

 

However, it has been recognized that global crude oil reserves are finite, and their depletion is occurring much faster than previously predicted2. In addition, short-term price volatility has heightened apprehension about the future of global energy security3.

 

In 2008, before the global economic recession began, crude oil sold for over USD 135 per barrel in the market. However, conventional petroleum is essentially non-renewable and intertwined with this practical impediment is an apparent moral dilemma of environmental pollution arising from its very usage4. The combustion of these hydrocarbons makes significant contributions to greenhouse gases (GHG) in the atmosphere and inevitably contributes significantly to global warming5.

 

The transport sector alone accounts for 60% of global oil consumption (International Energy Agency (IEA), 2008), 19% of carbon dioxide and 70% of carbon monoxide emissions6. With the world human population projected by the United Nations to hit 9 billion and the number of cars 2 billion (World Business Council for Sustainable Development by 20507, it is no longer sustainable to continue to combust fossil fuel without regard for the environment. Consequently, the need for environmentally sustainable and renewable energy sources cannot be overemphasized, given the rapid rate of global industrial development8.

 

In addition, the burning of fossil fuels contributes to the emissions of greenhouse gases as well as global warming that causes climate change, the rise in sea level, loss of biodiversity and urban pollution9,10. Energy security and environmental safety are two major issues in the current world that have boosted the demand for an alternative and eco-friendly energy source11. In the face of such a predicament, alternate sources of energy have to be explored to satisfy world energy demand. An increasingly popular idea is the production and use of renewable energies that are self-sustaining and do not contribute much to environmental pollution. New alternative and renewable energy sources, such as solar, wind, geothermal, hydrogen and biomass, are the new sources of supply energy demand for the whole world. Among these different types of renewable energies, bioenergy is particularly interesting since biofuels can directly substitute liquid fuels used in transportation and many other machineries12. The Bioenergy can be defined as energy obtained from biomass, which is the biodegradable fraction of products, waste and residues from agriculture like vegetables and animal origin, forestry and related industries and also, from the biodegradable fraction of industrial and municipal waste13.

 

The valuation biomass by biotechnological processes is the solution of choice since it contributes to the production of bioenergy and high-value substances. Among the latter may be drawn from this development, we can quote ethyl alcohol, Strategic Energy substance. Bioethanol is one of the most promising alternatives to fossil fuels, which can be produced from various renewable sources rich in carbohydrates. Many countries, such as USA, Brazil, China, Canada and several EU member states have already proclaimed commitments to bioethanol programs as attempts to reduce the dependence on fossil fuels, where the former two countries have shown the largest commitments thus far. The United States produces the highest amount of ethanol, which has been estimated to be more than half of the total global ethanol produced in 201514. Total ethanol production in the USA has increased dramatically from 175 million gallons in 1980 to 14810 million gallons in 2015 [14]. Ethanol (C2H5OH) has been earmarked as a promising energy source for gasoline (C7H17) due to having several advantageous properties. Even though one liter of ethanol affords 66% of the energy provided by the same amount of gasoline, the former has a higher octane number (106–110) than the latter (91–96), which enhances the performance of gasoline when blended with ethanol15. The higher octane level of ethanol also allows it to be burnt at a higher compression ratio with shorter burning time resulting in a lower engine knock. In addition, ethanol has a higher evaporation enthalpy (1177 kJ/kg at60 °C) than gasoline (348 kJ/kg at 60 °C) and a higher laminar flame speed (around 33 and 39 cm/s at 100 kPa and 325 K for gasoline and ethanol, respectively)16,17. The higher heat of vaporization of ethanol (840 kJ/kg) than that of gasoline (305 kJ/kg) ensures that the volumetric efficiency of ethanol blend is higher than the efficiency of pure gasoline, thereby improving power output18. Bioethanol is an eco-friendly oxygenated fuel as it contains 34.7% oxygen, whereas, oxygen is absent in gasoline. This results in about 15% higher combustion efficiency of ethanol than that of gasoline19, thereby keeping down the emission of particulate and nitrogen oxides. Compared to gasoline, ethanol contains a negligible amount of sulfur, and mixing of these two fuels helps to decrease sulfur content in the fuel as well as emission of sulfur oxide, which is a carcinogen and can contribute to acid rain20. Bioethanol is also a safer substitute to methyl tertiary butyl ether (MTBE) which is commonly used as an octane enhancer for gasoline and is added to the latter for its clean combustion so that production of carbon monoxide (CO) and carbon dioxide (CO2) can be reduced21. MTBE has been reported to make its way into groundwater that contaminates drinking water causing a severely detrimental effect on health22. The US Energy Policy Act released an ANPR (Advance Notice of Proposed Rulemaking) in 2000 under the TSCA (Toxic Substance Control Act) to limit the use of MTBE as a gasoline extender23. However, the development of biofuel production from wheat or corn or other raw materials for human food or animal involved in some way by specialists famine in some countries. On the other hand, bioethanol can be produced from several other substrates rich in fermentable sugars, namely cellulosic biomass, energy crops and organic waste. Indeed, agricultural and agro-industrial produce large quantities of waste that are a nuisance to some environment. Numerous studies have shown that these wastes rich in organic matter were noble products and new materials for many industries. It should be noted that waste dates can be a recoverable raw material to be a source of energy and industrial interest molecules. Waste dates crystallize up to 65% of fermentable sugars and therefore represent a preferred substrate for the production of many substances. Among other ethyl alcohol, the latter from a biotechnological process of anaerobic fermentation is an undeniable economic importance because it is used in various and vital sectors24. The Phoenix culture is the central axis of the Saharian agriculture in Algeria where the date palm predominates with about 22 % of the total area of plantations. The number of date palm reaches 18 millions of which 11 million are productive about 492.000 tons of dates25. A quantity of 200.000 to 250.000 tones is not appreciated and of low value, could be recovered and put on the domestic market a new generation of highly prized and often imported26.

 

MATERIALS AND METHODS:

Biological Material:

Saccharomyces cerevisiae was used for the production of alcohol. Saccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental in winemaking, baking, and brewing since ancient times. Saccharomyces cerevisiae was used for the production of alcohol. Saccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental in winemaking, baking, and brewing since ancient times. It was originally isolated from the skin of grapes (one can see the yeast as a component of the thin white film on the skins of some dark-color fruits such as plums; it exists among the waxes of the cuticle). It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model bacterium. It is the microorganism behind the most common type of fermentation. S. cerevisiae cells are round to ovoid, 5–10 micrometer in diameter. It reproduces by a division process known as budding.

 

Preparation method:

The production of ethanol from waste dates comprises the following steps:

·      Washing dates,

·      Absorption in hot water (85 ° C extraction),

·      Pitting which separates the rings of the pulp, which is ground and transformed into, must that is sent in turn fermentation.

·      Addition of dilution water, acid and yeast,

·      Distillation of wine dates.

 

 

Fig. 1: Diagram of the various stages of manufacture ethanol

 

Vegetable Material:

The raw materials used in this study are shown in Figure 2. They consist of a dried variety on certain varieties of common dates from the south region of Algeria, which has a low market value. The selection was based on the damaged varieties that can be used neither to human feed or to animal feed.

 

 

Fig. 2: Vegetable material

 

Bioreactor of fermentation

The fermenter used in this study is shown in Figure 3. The reactor cover was provided with several pipes in order to monitor different parameters such as ethanol yield, yeast growth, pH value, temperature and so one. The bleed valve is located at the bottom of the bioreactor. In addition, it includes a stainless steel flange to prevent gas leakage.

 

 

Fig. 3: Bioreactor of fermentation

 

Preparation of dates:

After washing, the imbibition of dates is carried out using a hot water (90 to 95°C) to facilitate coring. Water imbibitions with high sugar will be used as dilution water. Dates were then diluted with 200 g of pulp and 800 ml of water. The pH of the must be adjusted to between 4.3 and 4.7 with sulfuric acid (H2SO4, 1N). This acidic pH detrimental to bacterial growth is conducive to yeast overgrowth. For inhibiting the bacterial growth and favorite overgrowth of the yeast27.

 

Alcoholic Fermentation:

After inoculating the medium with baker's yeast Saccharomyces cerevisiae (1 g/l)28, the bioreactor is immersed in a water bath where the temperature is maintained at 30±2°C. The fermentation is carried out under anaerobic conditions for 72 hours. However, the fermentation is promoted by agitation due to the movement of bubbles of CO2 released.

During the fermentation, we followed:

      pH evolution;

      Total sugars;

      The density.

 

Alcoholic Distillation:

At the end of fermentation, the wine is distilled to extract ethanol. The distillation temperature is about 78°C29

 

Determination of pH:

The pH determination is essential to the control of the must before and during fermentation. Its variation provides information on the metabolic activity of the yeast during the conversion of sugars into alcohol. PH determination is accomplished by a direct reading with a pH meter.

 

Density Determination:

The density was determined using a pycnometer of capacity 10 cm3.

 

Determination of Total Sugars:

The determination of total sugars is performed by the method introduced by Dubois.

 

Determination of Alcohol Degree:

It was determined using a hydrometer (graduated from 0 to 100°).

 

RESULTS AND DISCUSSION:

In what follows, we analyze the results of physicochemical must dates for fermentation time 0h, 24h, 48h and 72h respectively. The variation of total sugars during alcoholic fermentation is given in figure 2.

 

 

Fig. 4: Evolution of total sugars during the fermentation

The sugar is a major component of a large variety of fruits juices, its presence in the form of sucrose, glucose, fructose, may serve as a regular supply of energy to keep cells alive. Dates are rich in sugar ranging from 73% to 83% a dry weight basis and consisted mostly of the two inverted form, glucose and fructose28, sucrose. The microorganism S. cerevisiae has an optional anaerobic breathing on the alcoholic bioconversion process. In the anaerobic phase, the glucose is transformed into the ethanol by fermentation effect. In the light of these results, we can see that after 72 hours of fermentation of musts, a significant degradation of total sugars is revealed, this transformation was especially active during the first 48 hours. During the first 48h of transformation, the process is active, especially between 24 and 48 h. The total glucose rate is strongly decreased during the time from 13.8% at the beginning of the fermentation process to 3% after 72 h. However, total sugars were not completely consumed by the yeast; due to the cessation of growth of Saccharomyces Cerevisiae caused by the accumulation of toxic substances29. Sasson reported that fatty acids, especially octanoic and decanoic acid formed by the yeast concentration in milligrams per liter, become toxic to yeast29. The evolution of Ph and density obtained respectively for a time fermentation equal at 0h, 24h, 48h and 72 h are given in figure 5 and 6.

 

 

Fig. 5: Evolution of pH during the fermentation

 

 

Fig.6: Evolution of density during the fermentation

As it can be seen from this table, the density decreased significantly during the fermentation process from 1.054 to 0.987 g/cm3, which was caused by the transformation of sugar into bioethanol and the loss of mass under the CO2 form. Also, a significant rapid decline of the pH from 6.3 to 4.109 during the first 24 h. The rapid reduction observed at the beginning can be attributed mainly to the production of carbon dioxide that acidifies the medium, followed by the production of ethanol and a small amount of carboxylic acids with short chains. The alcohol produced in the laboratory has the following characteristics: volatile, flammable, clear, with a pungent odor. The different stage of fermentation is shown in Figure 7.

 

 

 

 

Stoned date Milling dates

 

 

After 72 h of fermentation

Fig. : different stages of fermentation.

 

 

Fig. 8: Ethanol produced in the laboratory

The average values of physicochemical parameters of alcohol produced from the waste of dates are listed in Table 1.

 

Table 1: Physicochemical parameters of Alcohol

Symbol

Signification

Mean values of the parameters

Ph

Potential of hydrogen

5,639

D

Density

0,8752

R

Alcohol (rectification)

88°

 

Infrared Spectrum of the Bioethanol

The vibration sign of the biofuel produced is identified using the Infra-Red Spectra. following wave numbers 2990, 3300 and 2990 cm-1, corresponding to the molecules group C-H, O-H and C-O respectively. Vibrations of the following bands are noted:

     2900cm-1: stretching vibration corresponding to the CH group;

     3300cm-1: OH stretching vibration corresponding to a specific alcohol.

 

 

Fig. 9: Infrared spectrum of the bioethanol

 

 

Fig. 10: Gas chromatography-mass spectrometry analysis

 

Table 2: Cost and gain of the process

Product

Price

1 Kg of date

20 AD

1L of Alcohol(78°)

13100 AD36.

1 Kg of Date (0,4 L)

5240 AD

Load

Electricity

1 DA kW. H

Workforce

20 DA /Kg

Stuff

20 AD

Byproducts

Nucleus Dates

5 AD

Nucleus Dates

1 AD/L

Gain =5225 DA/Kg

 

CONCLUSION:

In the light of these results, we can see that Ethanol produced checked the conditions and global standards. It can be concluded that waste dates lost each year can be a potential source for the production of many products and can benefit from a good portion of its expenditure on imports.

 

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

 

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Received on 16.07.2018          Modified on 17.08.2018

Accepted on 30.08.2018        © RJPT All right reserved

Research J. Pharm. and Tech 2018; 11(12): 5359-5364.

DOI: 10.5958/0974-360X.2018.00976.9