Republic of Yemen

Hodeidah University
Faculty of Engineerin
Chemical Engineering Branch

BIOETHANOL PRODUCTION

Perprated By

Mohammed Derhim Mohammed Saif Al-athwari

Mohammed Yahya Mahmud Amoh
Hafeth Saeeed Qaid
Yassin Waseem Mohammed Hussein Mahwiti
Mohammed Hassan Ahmed Galm
Amjad Mohammed Abdelraqib
Abdullah Ali Salem Bashanfar
Mohammed Ebrahim Naser Shaaban
Tawfiq Abdulgalil Hazem Alalwani

Supervision By
D/ Awad Hussein

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Introduction
Bioethanol is a type of renewable fuel produced from organic materials that can be
fermented, such as plants or agricultural residues. Bioethanol is primarily used as an
alternative to gasoline in car engines and can be mixed with gasoline to improve fuel
efficiency and reduce greenhouse gas emissions. This technology is part of the global
shift toward renewable energy, offering a sustainable solution to reduce dependency on
fossil fuels and mitigate environmental pollution.

Bioethanol is produced from materials containing sugars or starches, such as corn,

sugarcane, cassava, or even spoiled fruits and vegetables. During the production process,
these materials are converted into fermentable sugars using enzymes, and then yeast is
added to convert the sugars into ethanol through the fermentation process.

Bioethanol has several advantages that make it an attractive option for sustainable
energy:

 Renewable nature: It can be produced sustainably using agricultural materials that can
be grown annually.

 Emission reduction: When used as an alternative fuel to gasoline, bioethanol can

reduce carbon dioxide emissions that contribute to global warming.

 Support for the local economy: Local biofuel production can stimulate the
agricultural and processing industries.

 Energy security: Bioethanol helps reduce reliance on imported fossil fuel sources.

With increasing attention to environmental sustainability and natural resource

management, bioethanol is expected to continue playing a key role in the future as an
alternative, environmentally friendly fuel

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The basic prinnciple of bioethanol production.

The basic principle in the production process of bioethanol is the conversion of organic
materials such as sugars, starch, or cellulose into ethanol through fermentation. This
process can be summarized in the following steps:

1- Preparation of raw material: Raw materials rich in carbohydrates such as corn,

sugarcane, or other plant materials are selected. In the case of non-sugar materials
like cellulose, the materials are processed using enzymes or acids to convert them into
simple sugars.

2- Fermentation: Yeast (typically Saccharomyces cerevisiae) is added to the hydrolyzed

sugars, where it converts them into ethanol and carbon dioxide through fermentation.

3- Distillation: After fermentation, ethanol is separated from other components through

distillation to increase its concentration.

4- Dehydration: In some cases, ethanol is dehydrated to remove water, making

bioethanol ready for use as fuel.

Production of Bioethanol from starch

The production of bioethanol from starch is a biological process that involves converting
the carbohydrates in starch into ethanol through hydrolysis and fermentation. Below is a
brief description of the main stages of this process:

1. Raw Material

Raw Materials: Sources rich in starch such as corn, potatoes, rice, or cassava are used.
Then it’s cleaned and ground into a powder or dough to facilitate processing.

2. Starch Hydrolysis

To convert starch (a complex carbohydrate) into simple sugars like glucose by:

1- Enzymatic Hydrolysis:
Amylase and Glucoamylase enzymes are added to break down the starch molecules into
glucose.

2- Thermal Treatment:
In some cases, starch is heated to facilitate its breakdown.

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3. Fermentation
The fermentation process is the basic stage in bioethanol production process, and it
carried out though the following stages:

- Yeast adding: The most commonly used yeast for this process is Saccharomyces
cerevisiae.

- Anaerobic Fermentation

Converting Glucose to Ethanol: In the absence of oxygen, yeast begins to convert glucose
into ethanol and carbon dioxide through the fermentation process.

- Growth Phase: Yeast starts to grow and multiply rapidly, consuming glucose.

- Fermentation Phase: Once most of the oxygen is used up, yeast shifts to anaerobic
fermentation, converting sugar into ethanol and carbon dioxide.

4. Product Separation

Distillation: After fermentation is complete, ethanol is separated from the solution using
distillation. Ethanol is vaporized due to its lower boiling point compared to water, and
then condensed to separate the pure ethanol.

5. By-products

Carbon Dioxide: Carbon dioxide is produced as a by-product of fermentation. It can be

collected and used in other industries like carbonated beverages or agriculture.

Remaining Yeast: The remaining yeast after fermentation can be used in animal feed or
as a protein-rich food product.

6. Control of Conditions

- Temperature: Excessive heat can damage the yeast and halt fermentation. It is important
to maintain the appropriate temperature.

- PH: The PH should be kept suitable for yeast, as Saccharomyces cerevisiae prefers a pH
between 4.5 and 5.5 .

- Aeration: Oxygen levels can affect yeast activity. Fermentation is an anaerobic process,
so oxygen should be minimized once fermentation begins.

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Production of Bioethanol from Molasses

The production of bioethanol from molasses is a biological process in which the sugars
present in molasses are converted into ethanol through fermentation using
microorganisms such as yeast. The main steps involved in this process:

1- Preparation of Molasses

Molasses is a by-product of the sugar industry, consisting primarily of unreacted sugars

such as sucrose, along with some minerals and organic materials. For this process:

- Purification of Molasses: Molasses contains impurities such as ash, dirt, and other
organic matter. It is typically purified by filtration to remove these materials. In some
cases, processes like filtration or straining are used to remove suspended particles.

- Conversion of Complex Sugars to Simple Sugars: Sometimes, molasses contains

complex sugars or sugars that are not fully fermentable (such as sucrose), so these sugars
are converted into simpler sugars like glucose and fructose by adding enzymes such as
amylase or invertase. This process is called hydrolysis.

2- Preparation of the Nutrient Medium

- Adding Nutrients: To support the fermentation process, molasses is mixed with a

medium containing essential nutrients for yeast growth. These nutrients include
mineral salts like phosphorus, nitrogen, and sulfur. Adding these elements is
necessary to ensure optimal yeast growth.

- Adjusting PH: The PH of the medium is adjusted to an optimal range for yeast
growth, typically between 4.5 and 5.5.

3- Fermentation Process

- Adding Yeast: Yeast of the species Saccharomyces cerevisiae (the yeast commonly
used in food and beverage industries) is added to the prepared molasses. This yeast is
responsible for converting sugars into ethanol.

- Fermentation: The yeast begins to consume the sugars, converting them into ethanol
and carbon dioxide through the fermentation reaction.

- Fermentation Duration: The fermentation process can take anywhere from several
hours to several days, depending on the temperature, molasses concentration, and
yeast concentration.

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4- Removal of Yeast and By-products

Once fermentation is complete, the yeast and organic by-products are separated through
methods such as filtration or centrifugation. The remaining yeast can be used in other
industries or for animal feed.

5- Distillation

- Primary Distillation: After fermentation, the liquid contains ethanol at a concentration

of about 10-15%. To increase the ethanol concentration, the liquid is passed through a
distillation unit. In this step, ethanol is separated from water and other components
based on their boiling points. Ethanol boils at 78.37°‫آ‬C, while water boils at 100°‫آ‬C.

- Secondary Distillation: In some cases, additional distillation may be performed to

improve the purity of the ethanol, producing ethanol with a concentration of 95-96%.

- Water Removal: To obtain anhydrous ethanol (ethanol without water), techniques like
absorption using materials such as silica gel or aluminum oxide or vacuum distillation
are used.

6- Purification of Ethanol

The produced ethanol may contain impurities or by-products from the fermentation
process, such as organic acids. Therefore, it is purified through:

Filtration: To remove large impurities.

Continuous Distillation: To improve ethanol purity.

Chemical Analysis: To determine the purity of ethanol and ensure it meets required
standards for use.

7- By-products

- Fermentation By-products: After fermentation, some by-products such as residual

yeast and unreacted compounds remain. These by-products can be reused in animal
feed or for wastewater treatment.

- Distillation By-products: The by-products from the distillation process can also be
used as chemicals in other industries or as biofuels.

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Bioethanol production from cellulose
Ethanol production from cellulose (lignocellulosic conversion) is an advanced process
and considered a promising option for sustainable production. Cellulose is a polymer
made of glucose molecules and is the main component of plant cell walls. Ethanol can be
produced from cellulose through several steps:

1- Pre-treatment (Mechanical or Chemical Breakdown:)

- Raw Materials: Materials rich in cellulose, such as wood, rice straw, wheat straw,
agricultural residues, or any fibrous plant material containing cellulose, are used.

- Process: Cellulose has a complex structure, so the raw materials need to be treated to
break down the cellulose molecules into smaller parts. This is done using mechanical
methods (like grinding) or chemical treatment (such as using acids or bases) to break
the bonds between cellulose molecules.

2- Hydrolysis or Enzymatic Conversion to Simple Sugars:

- Enzymes: After breaking down the cellulose, enzymes like cellulase are used to
convert the cellulose into simple sugars (like glucose). Cellulase breaks the molecular
bonds between glucose units in cellulose, making them fermentable.

- Chemical Hydrolysis: Chemical catalysts may also be used to speed up the

conversion process to fermentable sugars.

3- Fermentation:

- Once simple sugars like glucose are obtained from cellulose, they are fermented using
yeast or genetically modified microorganisms to convert them into ethanol.

- Genetically Modified Microorganisms: Sometimes, yeast or bacteria strains are

genetically modified to enable them to ferment the sugars derived from cellulose or
even other sugars like hemicellulose.

4- Distillation:

After fermentation, distillation is used to separate the ethanol from other components.
Distillation helps to concentrate the ethanol and separate water and other compounds.

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