Raw materials for Bioethanol
Production
Cereal Grains
They are mostly used as food and feed.
However, due to their high starch content, they can be used as raw materials in biofuel production and in the production of
biologically based products.
From these raw materials, the only fuel commercially produced on a large scale is bioethanol.
Starch contents and theoretical ethanol yields of some cereal grains are summarized in the table.
Grain type starch % Etahnol L/kg
corn 72 0.52
wheat 77 0.55
barley 57 0.41
sorghum 72 0.52
oat 58 0.42
rice 79 0.57
Theoretical yield 0.51 kg ethanol / kg glucose
After hydrolysis, 1 kg of starch forms 1.11 kg of glucose !!!!!!!!
Starch is a glucose polymer consisting of two main structures called amylose and amylopectin.
Amylose is a linear polymer (glucose molecules bound by α-1,4 bonds)
Amylopectin is a larger and branched structure. It contains both α-1,4 and α-1,6 bonds.
Most starches contain 25% amylose and 75% amylopectin.
Starch can be converted to glucose by enzyme hydrolysis, the monomeric sugar that S.cerevisiae can use.
Today, hydrolysis of starch by enzyme is highly important in industry and low-cost hydrolysis is performed on the market.
Corn
In America and Canada, corn is the most important raw material used in ethanol production.
America is the largest corn producer in the world. China ranks second.
Wheat
Wheat starch is currently used only in two plants in the US to produce ethanol.
It is an important raw material in biofuel production in other countries.
In Canada, 15% of ethanol is produced from wheat.
Wheat is the primary raw material for starch-based ethanol production in Europe and Australia.
Barley
Barley is an alternative raw material used in ethanol
production in the USA, especially in regions developed in winter
Although it is an alternative raw material, there are problems in the production of ethanol from barley.
Barley has less starch content than corn, so ethanol yield is also low.
Barley contains a significant amount of β-glucan.
Beta-glucan is soluble in hot water. This
soluble beta-glucan causes viscosity in the fermentation process and makes mixing
difficult.
The presence of beta glucan in by-products makes it difficult to use as animal feed.
A number of studies have also been carried out to eliminate this viscosity. Enzyme
companies such as Novozymes and Danisco have developed commercial products that reduce viscosity.
Sweet sorghum
It has a starch content similar to corn.
The ethanol yields from sorghum and corn were similar.
The advantage of Sorghum is its high resistance to drought and heat. This is because the waxy layer on the leaves
holds the water in the plant. It is an important raw material that can be used in ethanol production in arid regions such as Africa and South Asia.
Oat
Oats are not used commercially in ethanol
production. This is because it contains relatively less starch and the ratio of the shell weight to the whole seed weight is as high as 34%. Beta glucan content also causes viscosity.
Rice
On the basis of total production, rice is the third product after wheat and corn in the world.
Starch content is high. (Even in Asia, many alcoholic drinks are produced from rice)
Another advantage is the easy separation of the rice husk.
However, rice is not used in bioethanol production in many countries. Because it requires a large
amount of water for production and is used as food. But in more developed countries like the
United States, damaged rice seeds can be used as raw materials for animal feed and ethanol
production.
Tubers and roots
Tubers and roots are developed in moist areas that are not suitable for the development of cereals.
Due to their high starch content, they are important raw materials in ethanol production.
The most notable of these are cassava and sweet potatoes.
Cassava: A tropical root. Low nutrient content and grows easily in arid areas. It is easy to develop. Africa and Asia have an important place in cassava production.
This root contains 22% starch and 70% moisture. When dried, the starch content is 73% and theoretically yields 0.45 L / kg ethanol.
Cassava starch is very easily hydrolyzable to fermentable sugars.
Sweet Potato: Carbohydrate content of dry weight is between 80 and 90% band.
Most of the carbohydrate it contains is starch, but also
contains glucose, fructose and sucrose. (these sugars can be converted into ethanol by yeast)
Ethanol is produced from this raw material in America, China and Thailand.
Sugar Raw Materials
Sugar cane: The most important ethanol raw material in Brazil.
Wet sugar cane contains 12-17% of total sugar by weight.
90% of the sugar is sucrose and 10% is glucose + fructose.
All of these sugars can be readily fermented to ethanol by S. cerevisiae.
Sugar beet: It is an important raw material such as wheat in ethanol production.
It is thought that its use will increase with some legal regulations in Europe.
Sugar beet contains 16-18% sugar.
Lignocellulosic Raw Materials
3 important components are cellulose, hemicellulose, and lignin.
The main sources of these three components are forest
products and residues, agricultural wastes and a number of energy products.
