Part 5: Biofuels Flashcards

1
Q

Def: Biofuel

A

Fuel generated from biological material

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2
Q

Define and evaluate 1st Gen biofuels

A

Produced directly from the field, directly related to edible biomass
Advantages: Renewable, cleaner emissions, no pre-treatment required
Disadvantages: Low energy yield, Food or fuel debate, may raise food prices

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3
Q

Define and evaluate 2nd Gen biofuels

A

Derived from dedicated energy crops and other lignocellulosic plants and residue
Advantages: Renewable, reduces organic land fill, eliminates food price problem
Disadvantages: High energy cost, food or fuel debate, still lower energy yield

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4
Q

What is bioethanol

A

A biofuel produced through the fermentation of glucose

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5
Q

Describe the process of producing bioethanol

A

1) Milling to release starch
2) Saccharification to produce glucose
3) Fermentation to form ethanol
4) Distillation and rectification
5) Drying

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6
Q

Def: Saccharification

A

The heating and addition of water and enzymes to milled grain to produce glucose:
⍺-amylase converts starch to oligosaccharides and dextrin
Glucoamylase converts oligosaccharides and dextrin to glucose

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7
Q

What must be done to lignocellulose before fermentation

A

Pretreatment: Solubilises hemicellulose ad increases hydrolysability of cellulose.
This is done mechanically, chemically and/or biologically

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8
Q

Why is lignocellulose difficult toproduce energy from

A

The structure consists of cellulose, lignin and hemicellulose arranged to give it a very strong and stable structure, making it hard to break down into glucose for fermentation.

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9
Q

Def: Isobutanol

A

Next generation biofuel with characteristics:
Good blending with petrol
Good volatility
Less phase separation
~82% energy content of petrol
Lower moisture absorption

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10
Q

Briefly describe the process of isobutanol production

A

1) Glycolysis: produces pyruvate
2) Valine biosynthesis: Metabolises pyruvate into KIV
3) Ehrlich Pathway: Degradation of KIV to isobutanol via the KDC enzyme

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11
Q

How can isobutanol yield be improved

A

Metabolic engineering:
1) Overexpression of KDC enzyme
2) Overexpression of limiting factor enzymes
3) Improve enzyme specificity to pyruvate
4) Remove competing metabolic pathways

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