Chapter 11: Problem 13

Describe the process of bioethanol production from a high-sugar crop like corn.

Short Answer

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Bioethanol production from corn involves the following steps: 1) Feedstock preparation, where corn kernels are cleaned and milled to increase surface area. 2) Enzymatic hydrolysis, in which enzymes like alpha-amylase and glucoamylase convert starch into glucose. 3) Fermentation, where yeast cells consume glucose, producing ethanol and carbon dioxide. 4) Distillation and dehydration, separating ethanol from other components and removing water to obtain anhydrous bioethanol. 5) Quality control and storage, testing the resulting ethanol for purity and storing until use. This process turns high-sugar crops into eco-friendly, renewable fuel, reducing greenhouse gas emissions and diversifying energy resources.

Step by step solution

Feedstock Preparation

The first step in bioethanol production from corn is to prepare the feedstock. This involves cleaning and milling the corn to break down the kernels into smaller particles, increasing the surface area for enzymes and microorganisms to act upon.

Enzymatic Hydrolysis

The milled corn is now mixed with enzymes such as alpha-amylase and glucoamylase. These enzymes help to break down the starch present in the corn into simple sugar molecules like glucose. The process, called enzymatic hydrolysis, takes place in a vessel called a liquefaction tank, where the mixture is heated and agitated to promote enzyme action.

Fermentation

Once the starch has been converted into glucose, the mixture is allowed to cool, and yeast is added to initiate the fermentation process. During fermentation, the yeast cells consume glucose and convert it into ethanol and carbon dioxide. This step can occur in the same vessel as the enzymatic hydrolysis or a separate tank called a fermenter. The fermentation process takes several days to complete, depending on the desired ethanol concentration.

Distillation and Dehydration

After fermentation, the mixture contains ethanol, water, and other by-products. To separate ethanol from the mixture and increase its concentration, the mixture is heated in a distillation column. As ethanol has a lower boiling point than water (78.4°C), it evaporates first and is collected in a series of trays in the distillation column. The collected ethanol vapor is then cooled and condensed into liquid ethanol. The remaining water and by-products are further processed to extract valuable compounds or used as animal feed. The ethanol obtained from the distillation still contains a small percentage of water, so it undergoes dehydration to remove the remaining water and obtain anhydrous bioethanol.

Quality Control and Storage

Finally, the bioethanol produced is subjected to quality control tests to ensure that it meets the required specifications for use as a fuel. Once it passes the quality tests, the bioethanol is stored in storage tanks until it is transported to fuel blending facilities or sold as a pure fuel. This process efficiently turns high-sugar crops such as corn into bioethanol, an eco-friendly, renewable fuel source, contributing to reduced greenhouse gas emissions and the diversification of energy resources.

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Describe the process of bioethanol production from a high-sugar crop like corn.

Short Answer

Step by step solution

Feedstock Preparation

Enzymatic Hydrolysis

Fermentation

Distillation and Dehydration

Quality Control and Storage

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