Bioethanol
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Lecture 1
Energetic Biotechnology
Bioethanol is the most commonly used biofuel, which is an alternative to fossil fuel and is produced by the fermentation of sugars of different lignocellulosic sources.
The biodegradability and reduced toxicity of bioethanol, for which biomass is used as a primary substrate as well, are its main advantages over fossil fuels.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7867074/
Advantages:
Applications:
Bioethanol
https://biologyreader.com/production-of-bioethanol.html
History of Bioethanol Production
Ancient Beginnings
Bioethanol production has its roots in the ancient world, where fermentation was used to create alcoholic beverages. The process of fermenting sugars into alcohol by yeast was well-known in many ancient civilizations, including Mesopotamia, Egypt, and China. These early applications were focused on producing beverages rather than fuel, but the technology laid the groundwork for future innovations.
19th Century: Early Industrial Uses
The industrial potential of ethanol was first recognized in the early 19th century. In 1826, American inventor Samuel Morey experimented with ethanol in an internal combustion engine, demonstrating its potential as a fuel. Ethanol gained further traction during the mid-19th century, when it was used as a lamp fuel. However, this use was diminished by the rise of kerosene, which was cheaper and more readily available.
By the late 1800s, ethanol’s potential as a fuel became more prominent, especially with the growing popularity of automobiles. Henry Ford, one of the most influential figures in the development of the modern car, designed his early Model T engine in the 1900s to run on ethanol as well as gasoline.
https://www.energyresourcefulness.org/Fuels/ethanol_fuels/history_of_ethanol.html
History of Bioethanol Production
Early 20th Century: Ethanol and Gasoline
As cars became more common, gasoline took center stage due to its abundance and low cost, but ethanol remained in the background as a fuel alternative. During the First World War (1914–1918), ethanol was used as a fuel in Europe due to oil shortages. Similarly, during Prohibition in the U.S. (1920–1933), ethanol use was restricted due to its association with alcoholic beverages, further limiting its fuel applications.
1970s: Oil Crisis and the Resurgence of Ethanol
The modern resurgence of bioethanol as a fuel began during the oil crises of the 1970s. When global oil prices surged due to geopolitical tensions, many countries sought alternatives to reduce their reliance on imported petroleum. Brazil, in particular, emerged as a leader in bioethanol production. The Brazilian government launched the Proálcool Program in 1975, mandating the widespread use of ethanol made from sugarcane as a transportation fuel. In the U.S., corn, a widely grown crop in the U.S., became the primary feedstock for ethanol production. By the 1980s, ethanol was blended with gasoline to produce gasohol, a fuel mix containing 10% ethanol and 90% gasoline, which helped reduce emissions and improve air quality.
1990s and 2000s: Growth and Policy Support
The 1990s saw further expansion in bioethanol production, driven by environmental concerns, particularly related to air pollution and climate change. Ethanol was recognized for its ability to reduce greenhouse gas emissions compared to fossil fuels. Governments in the U.S., Europe, and other regions began to promote ethanol as part of broader efforts to reduce carbon footprints.
https://www.energyresourcefulness.org/Fuels/ethanol_fuels/history_of_ethanol.html
Bioethanol is classified as a liquid biofuel that can be produced from carbohydrate sources through the feedstock fermentation process, using different conversion technologies.
These feedstocks may be classified in four groups:
https://www.sciencedirect.com/science/article/abs/pii/S2589014X23002141
First-generation bioethanol, 1G - uses edible biomass (corn, sugar cane);
Second-generation bioethanol, 2G – uses lignocellulosic biomass which comes from abundant and renewable crops that are nonedible feedstocks;
Third-generation bioethanol, 3G – uses algae biomass.
First-generation bioethanol: production process requires more land area for the cultivation of crops, due to which the capital cost in the first generation is quite higher. The bioethanol produced from such feedstocks contains a high sugar concentration comparative to the other feedstocks.
First-generation bioethanol is made of the next plants:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10063169/#:~:text=Bioethanol%20production%20of%20the%20first,%2C%20and%20South%20America%2C%20respectively.
Second-generation bioethanol: makes the use of lignocellulosic biomass like wood, straw, grass and wastes etc.
The production process does not require much capital cost for the maintenance and operation of sophisticated equipment. The feedstock necessary for its production can be grown in poor quality marginal land, which produces low greenhouse gas emissions.
Third generation bioethanol: It makes the use of algal biomass whose cultivation is easy (can be cultivated on marginal land). Bioethanol derived through the cultivation of algal biomass has high energy density and conversion energy.
Lignocellulosic biomass
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7867074/
https://www.eubia.org/cms/wiki-biomass/biofuels/bioethanol/
Video ( 5 min):
https://www.youtube.com/watch?v=4OT9ekEF9cg
Video (3 min):
https://www.youtube.com/watch?v=V5fWCkFPZT8
Ethanol (in liters) per 100 kg of the feedstock
https://wgbis.ces.iisc.ac.in/energy/paper/Third-generation%20bioethanol%20status,%20scope,%20and%20challenges/materials.htm
In the EU, bioethanol is produced from wheat (3.9 million tonnes), maize (4.1 million tonnes), sugar beet (12.1 million tonnes), barley (0.4 million tonnes) and rye (0.4 million tonnes).
In the USA, the most used cultures are corn and sugar beet, wheat, barley and rye.
In Brazil, the main culture is sugarcane.
Video (5 min):
https://www.youtube.com/watch?v=ZitcSUdqmhM
https://www.eubia.org/cms/wiki-biomass/biofuels/bioethanol/
Forest Feedstocks
Two types of forest feedstocks are available for bioethanol production: those are hardwoods and softwoods.
Softwoods, such as pine, spruce, cypress, fir, and others have lower density and can grow on a higher rate, while hardwoods, such as oak, willow, poplar, cottonwood, and others are angiosperm and mostly deciduous.
Cottonwood is believed to be the most suitable woody feedstock for bioethanol production, since it is the most productive tree with several important advantages, such as a large amount of clones, restoration possibility by multiple cuttings, and uniformity in planting material quality. Different forest feedstocks possess more lignin and less ash content, which makes such woody feedstocks a very attractive raw material to improve and increase bioethanol conversions in its production processes.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7867074/
Cottonwood (poplar), several fast-growing trees of North America, members of the genus Populus, in the family Salicaceae, with triangular, toothed leaves and cottony seeds.
https://www.britannica.com/plant/cottonwood-tree
Video (5 min):
https://www.youtube.com/watch?v=HlWsLKOui_0
As an alternative to agricultural cellulosic residues, a good candidate for raw materials that has potential for bioethanol production is municipal solid wastes, which can solve the household garbage disposal and therefore limit the environmental problems that may occur due to such problem.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7867074/
Video (4 min):
https://www.youtube.com/watch?v=vmjaYPlzlDE
Biomass pretreatment:
https://biologyreader.com/production-of-bioethanol.html
Sample preparation�
For the sample preparation, it is essential to prevent pre-fermentation and bacterial contamination once the feedstock is delivered to the ethanol plant. The raw materials must include washing, cutting and drying stages for up to three days. Then transfer the mixture to the milling unit, and store the dried biomass inside a sealed bag at room temperature.
Pretreatment�
Feedstock having lignocellulosic content requires a pretreatment to separate cellulose from lignin and hemicellulose. In the case of lignocellulosic sources like the milled grasses are suspended in 75% anhydrous peroxide, to which NaOH is added to adjust the pH to 11.5. The mixture is then incubated at 35 degrees Celsius and then centrifuged at 250 rpm for 24 hours.
Then, concentrated HCl is added to adjust the pH to 4.8 before hydrolysis. Filtration is not required after the pretreatment. The liquid phase with solubilized hemicellulose and solid phase with the cellulose of the sample is subjected to enzymatic hydrolysis. Thus, the feedstock is first delignified to make cellulose accessible to the hydrolysis step. The pretreatment step makes the use of acid, alkali, organic solvents, heat treatment etc.
https://biologyreader.com/production-of-bioethanol.html
Hydrolysis
The degradation of starch content like corn, wheat etc., involves the association of amylase enzyme. In contrast, degradation of cellulosic material like wheat straw, grasses etc., consists of the association of cellulase enzyme.
In 10 grams of dried sugarcane, 200 ml of distilled water is added. Then add the above solution into a solution containing 0.5 ml of NaOH at a pH of 4.5. After that, 0.2 µl of enzyme α-amylase is diluted with the phosphate buffer, and the temperature is maintained at 50 degrees Celsius. The mixture is then cooled to 32 degrees Celsius.
The hydrolysis of starch requires alpha-amylase and glucoamylase under high-temperature conditions.
The hydrolysis of cellulose involves steam explosion and dilute acid prehydrolysis, followed by enzymatic hydrolysis. To improve the solubilisation of hemicellulose, H2SO4 and CO2 are often added, releasing simple sugars like xylose, glucose etc. As a result of hydrolysis, acetic acid, H2SO4, inhibitors are produced, which must be removed. Second stage hydrolysis, the cellulose biomass into glucose by concentrated or dilute acid or cellulase enzyme.
https://biologyreader.com/production-of-bioethanol.html
Fermentation
Mediates the conversion of simple sugars into ethanol via the association of microorganisms like yeasts and bacteria. Saccharomyces cerevisiae and Escherichia coli are the most common organisms that are being used in the fermentation stage. S. cerevisiae can ferment the simple sugar into ethanol and carbon dioxide at a temperature of 37 degrees Celsius at a pH ranging from 3-5.
But in the case of starch and cellulose, the fermentation process can carry out in two possible ways. The enzyme hydrolysis and the fermentation can occur separately and simultaneously by a method known as separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The SSF process yields much ethanol with reduced formation of inhibitory end products comparative to the SHF method.
https://biologyreader.com/production-of-bioethanol.html
Distillation
After fermentation, the recovery of ethanol from the whole suspension or fermentation broth refers to the process of distillation. This stage filters out the fermentation broth to extract bioethanol from the remaining residue through Whatsmann filter paper. Then boil the liquid mixture of water and ethanol.
As the water has a high boiling pressure (100 degrees Celsius) than the ethanol having 78.3 degrees Celsius, so the ethanol will get separated from the solution mixture as vapours via the rotary evaporator. During this process, all the co-products and impurities or residues, enzymes, ash etc., settle down at the bottom of the distillation column.
Bioethanol from green algae Enteromorpha intestinalis
https://wgbis.ces.iisc.ac.in/energy/paper/Third-generation%20bioethanol%20status,%20scope,%20and%20challenges/materials.htm
Example
Seaweed biorefinery
https://wgbis.ces.iisc.ac.in/energy/paper/Third-generation%20bioethanol%20status,%20scope,%20and%20challenges/materials.htm
Example
Solid waste management
Example:
Video (6 min):
https://www.youtube.com/watch?v=A9BB-A2uc0I
Video (34 min):
https://www.youtube.com/watch?v=9P_4b6kuVTc
Microorganisms in bioethanol production:
https://www.sciencedirect.com/science/article/abs/pii/S2589014X23002141
https://amb-express.springeropen.com/articles/10.1186/s13568-021-01257-x
https://www.sciencedirect.com/science/article/abs/pii/S0960148119302125
End of Lecture 1
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