Biofuels

Question 1

Importance of biofuels

Answer 1

Less greenhouse gases, More readily available, designed for liquid type fuels used in transportation

Question 2

Properties and origination of 1st and 2nd gen biofuels

Answer 2

Low in energy density
High moisture content
low compatibility

1st gen are from food crop
2nd gen are from feedstocks

Question 3

Process of bioethanol production. stage 1

Answer 3

Milling -the mechanical crushing of the cereal grains to release the starch components

Question 4

stage 2

Answer 4

Saccharification- Heating and addition of water and enzymes for conversion into fermentable sugar

Question 5

stage 3

Answer 5

Fermentation of the mash using yeast, whereby the sugar is converted into bioethanol and CO2

Question 6

stage 4

Answer 6

Distillation and rectification, i.e. concentration and cleaning the ethanol produced by distillation

Question 7

stage 5

Answer 7

Drying (dehydration) of the bioethanol

Question 8

Saccharification of Starch

Answer 8

1. Starch mixed with water at 60 degrees for 5-10 min
2. Starch dissolves in water to form a mash
3. Liquefaction process, a-amylase added at 70-80 degrees for 2 hours. This degrades starch to oligosaccharides and dextrin
4. Glucoamylase added at 60-65 degrees for 30 min. this converts oligosaccharides and dextrin into glucose

Question 9

Fermentation

Answer 9

In yeast fermentation, the glucose solution obtained from starch saccharification or cellulose hydrolysis is cooled to around 32C.
Yeast culture is added into the solution under aseptic condition
Glucose (nutrient) is metabolised (enzymatic reactions) to eventually ethanol, CO2 and energy.
Some of the released energy and glucose are utilized by the yeast cells to support their growth during fermentation.
The rest of the energy becomes heat to the fermentation broth and may increase the temperature if not taken out of the system.
Both ethanol and CO2 secreted out of yeast cells.
CO2 readily dissolves in water, but can easily be saturated in fermentation broth.
The excess CO2 bubbles out of the liquid and can be collected for food and soft drink preparation.

Question 10

three constituents of biomass ?

Answer 10

cellulose,hemicelluloseand lignin

Question 11

What do these do?

Answer 11

strong linkages between molecules resulting in a complex structure

Question 12

What does pre-treatment do?

Answer 12

Helps in separation of main biomass components (cellulose, hemicellulose and lignin)
Increase available surface area
Reduce particle size
Solubilizes hemicellulose
Increases enzymatic hydrolysibility of cellulose

Question 13

Physical pre-treatment involves

Answer 13

Milling which is Time consuming, intensive, expensive

Irradiation (microwave heating) which is slow, substrate specific, expensive

Question 14

Biological involves

Answer 14

Lignin-solubilizing microorganisms
No chemicals
Slow
Consumption of cellulose and hemicellulose

Question 15

synergistic effects

Answer 15

Chemical followed by biological

Physical followed by biological

Question 16

Acid chemicals involves

Answer 16

Using concentrated acids such as H2SO4 and HCl
Dilute sulfuric acid pretreatment could achieve high reaction rates and significantly improve cellulose hydrolysis.
There are two types of dilute acid pretreatment process:
High temperature (T > 160C), continuous-flow process for low solids loading (5%-10% [w/w])
Lower temperature (T < 160C), batch process for high solids loading (10%-40% [w/w])
Cost is higher than steam explosion
A neutralization of pH is necessary before enzymatic hydrolysis or fermentation process.

Question 17

Alkali chemicals involve

Answer 17

Alkaline pretreatment can disrupt lignin structure and decrease crystallinity of cellulose and degree of sugar polymerization.
Compared with acid pretreatment, alkaline pretreatment has less sugar degradation and inhibitory compounds (furan derivatives) formation
NaOH and lime can be recovered or regenerated.
NaOH is very efficient in removing lignin from lignocellulosic materials at a temperature of 100C for 15-30 min.

Question 18

Advantages of isobutanol

Answer 18

Blend properties in gasoline/petrol
Volatility
Phase separation
Energy content
Blend wall
Ideal platform molecule to produce renewable iso-paraffinic kerosene (IPK), a blendstock for jet fuel

Question 19

Blend Properties in Gasoline/Petrol

Answer 19

Does not increase vapour pressure when added to gasoline/petrol

Question 20

Phase separation qualities

Answer 20

Isobutanol is less polar than ethanol

Can be more easily transported through pipelines

Question 21

energy content qualities

Answer 21

Isobutanol has approximately 82 percent of the energy value of gasoline-higher energy content = greater fuel economy

Question 22

Three parts of the isobutanol pathway

Answer 22

1) Glycolysis to provide pyruvate
2) Valine biosynthesis to metabolise pyruvate to KIV
3) Ehrlich pathway which is required for degradation of KIV to isobutanol

Question 23

ways to increase isobutanol production

Answer 23

Introducing a promiscuous 2-keto-acid decarboxylase and an alcohol dehydrogenase into E. coli produced isobutanol in high yields through the 2-keto-acid pathway.

Overexpression of 2-ketoisovalerate biosynthetic genes

Deletion of multiple pathways competing for pyruvate consumption and the replacement of the endogenous acetolactate synthase enzyme with one from B. subtilis — which has a higher specificity for pyruvate — resulted in increased isobutanol

Overexpress alcohol dehydrogenase enzymes including Adh2 from S. cerevisiae and AdhA from Lactococcus lactis for isobutanol production in E. coli