All hands on Deck

Question 1

What is the general fermentation process?

Answer 1

Biomass pretreatment to convert cellulose and hemicellulose into fermentable sugars (glucose)

Fermentation: Yeast converts sugar to ethanol, which is a fuel source

Question 2

What are some pretreatment methods?

Answer 2

Physical: Crushing, milling etc

Thermal: steam explosion

Chemical: alkali, acids, oxidizing agent

Question 3

Advantages/Disadvantages of batch fermentation?

Answer 3

Advantages:
simple and easy to control
more flexible of handling high ethanol conc

Disadv
Cleaning is accomplished with clean-in-place equipment
Cleaning takes 50 min
Lower fermenter usage and higher cleaning cost

Question 4

Continuous fermentation advantages

Answer 4

conditions dont change with time
Higher fermentation efficiency and productivity due to highly homogeneous fermentation medium
Flexibility to run in batch mode

Question 5

Challenges of fermentation

Answer 5

Contamination

Biomass: low conversion efficiency due to lignin
and low energy efficiency

Starch and sugar: low energy efficiency, competing with food supply

Question 6

Fermentation sources

Answer 6

Biomass

Sugars/starch

Question 7

Definition of anaerobic digestion

Answer 7

Biological process uses microorganisms to break down biodegradable materials in the absence of oxygen

Question 8

Conversion processes

Answer 8

Hydrolysis: break large molecules into monomers
Acidogenesis: monomer to VFA’s
Acetogenesis: VFA’s to acetic acid, CO2 and hydrogen
Methanogenesis: Acetates to methane, CO2 but consumes hydrogen

Question 9

Important factors

Answer 9

Volumetric loading rate: COD
Mass yield: measure of cell growth within a substrate
Specific biological activity
Hydraulic retention time (HRT)
Solids retention time (SRT)

Question 10

Types of anaerobic processes

Answer 10

Temperature based:
Mesophilic
Thermophilic

Wet vs Dry
Dry produces more biogas

Batch vs continuous
Continuous is better controlled thus conversion efficiency is high

Question 11

why Pre treatment, and some methods

Answer 11

Enhance biodegradability:
Thermal
Mechanical
Chemical

Question 12

Advantages/Disadvantages of pyrolysis

Answer 12

Advantages:

• Mobile: processing technology can be moved to biomass locations
• No agent required
• Fast (short residence time)
• High yield of vapours and liquids

Disadvantages:

• Properties of the liquid
• Stability
• Viscosity
• Miscibility