Doris-Algal lipid based biofuels

Question 1

What is the basic idea of Algal biofuels?

Answer 1

Microalgae

• Algae are autotrophic and heterotrophic aquatic organisms
• amongst them: pro- an eucaryotic microrganisms with photosynthetic

activity

• Freshwater and marinewater species
• Growth by amitosis
• More than 40 000 species of microalgae identified (Zhu et al, Biofuel, Bioprod. Bioref. 9:801-814 (2015)
• Most studied for biofuel production: green algae

–> Biofuel production from Microalgae still R&D

Question 2

Give examples for common green algae ( single cells, eucaryotic)

Answer 2

1. Chlorella Spec
2. Scenedesmus Spec
3. Spirulina Spec

Question 3

How are Microalgae cultivated?

Answer 3

Basically growth and biomass accumulation by photosynthesis

Question 4

What are the reactor types of microalgae?

Answer 4

• Open ponds
• Photo-bioreactors:

1. Tubular reactors
2. Flat panel reactors

Question 5

Which of the algae reactors has the highest biomass yield?

Answer 5

Question 6

Limitations of photosynthesis

Answer 6

• Lack of photons (light) –>photo-acclimatisation
• Surplus of photons –>photo-inhibition
• Lack of carbon source (e.g. CO2 )
• High concentrations of O2 –>damage of chlorophyll reaction center (photo-oxidation)

Question 7

Back to high school :) give the biosynthesis reaction of glucose

Answer 7

6 CO₂ + 12 H2O + photons –> C₆H₁₂O₆+ 6O₂+ H₂O

• 8 photons per mole of CO₂ required
• Photosynthetically active radiation (PAR): λ = 400 - 700 nm

Question 8

What are the limitation to be considered for Flat panel reactors?

Answer 8

Lightning profil

• Absorption of light in the surface layers

of solutions with high density of algal

biomass

• High intensity of light on the reactor surface

–> photo-inhibition

• Low intensity of light in the center of reactors –> limitation

–> Design of reactors with low layer thickness

–> Directed transportation of algal cells to the

light (near surface) by mixing

Question 9

What are the phases of Microalgal growth for Lipid production?

Answer 9

Microalgal growth

• Exponential phase cell production, mainly protein
• Stationary phase accumulation of lipids, carbohydrates

Question 10

What are the types of Lipids in algal oils?

Answer 10

• Algal oils contain various types of lipids
• Composition depends on species and cultivation
• Stress cultivation enhances share of TAG in algal oil

Question 11

Draw that beauty microalgae cell while she is producing oils ;)

Answer 11

Demands on algal strains for algal oil-bases biofuel production

• High growth rates
• High trigylceride contents in lipids, well defined degree of unsaturated fatty acids
• Robustness, easy cultivation (nutrient requirements etc.)
• Cell structure: easy harvest, dewatering, drying and cell disintegration

–> Lipids of know algae stored IN the cells !!

Question 12

Draw the downstream processing of Microalgae:

Answer 12

Energy intensity of Drying in Algae producrion :(

• Improves storability
• Reducestransportation volume
• Ye it, has high energy demand

Question 13

What are the benefits and drawbacks of biofuels production from algal lipids?

Answer 13

Benefits

+ High energy yields per ha

+ No competition to food use

Drawbacks

• Still poor overall energy efficiency (downstream processing !)
• High costs  3- 30 €/kg dry algal biomass
• Technology still R&D

Question 14

What strategies could you suggest to improve the overall efficiency of biofuel production from algal lipids?

Answer 14

Strategies to improve overall efficiency

• Use of CO₂ from exhaust gases
• Use of waste water for cultivation
• Bio-refinery systems for high value co-product recovery
• Bio-engineering of microalgae

Question 15

What are the products of biorafineries?

Answer 15