Lecture 17 Flashcards
When did algae form
1.8 billion years ago (in the Proterozoic Eon)
What allowed early eukaryotic cells to harvest light energy
Incorporation of photosynthetic cyanobacteria (endosymbiotic theory)
What helped generate the oxygen levels needed for life to emerge
Cyanobacteria and algae
Do algae use photosynthesis
Yes
Algae photosynthesis
Use photosynthesis to generate organic carbon from CO2 and the energy of light (O2 is a byproduct)
Can algae produce lipids/oils
Yes, under certain conditions
What percent of their dry weight can algae produce in oil
70%
Other compounds that can be produced by algae
Butanol, hydrogen, etc.
Genera common for bioenergy purposes
Chlorella
Botryococcus
Dunaliella
Nannochloropsis
Scenedesmus
Growth conditions that algae can have
Phototrophic
Heterotrophic
Mixotrophic
Phototrophic growth
Requires light energy and inorganic carbon
Heterotrophic growth
Requires an organic carbon source for energy (e.g. glucose, glycerol)
Mixotrophic growth
Combination of light energy, organic carbon, and inorganic carbon (rarely used)
Nutrients required by algae
Nitrates, phosphates, potassium, calcium, zinc, iron, magnesium, manganese, molybdenum, copper, etc.
Why is it so expensive to grow algae for biodiesel
The need for nutrients
Strategy to keep the cost low for algae biodiesel
Use of human wastewater as a source of nutrients
Requirements of algaeal farms
Sunlight
Carbon dioxide
Moderate temperatures
Water
Nutrients
Land
The appropriate algael strain
Main types of algael farms
Open
Closed
Types of open system farms
Ponds
Raceways
Downside to open system farms
Less control of nearly every parameter
What type of system is more expensive to build and operate: open or closed?
Closed
Main types of closed system farms
Columns
Tubes
Control over closed system
Great control over parameters
What does the choice between open and closed systems usually come down to
How much you have to invest
Harvesting
Separating mature algae from water
Harvesting methods
Centrifugation
Flocculation
Sedimentation
Filtration
Centrifugation
Spinning at high speeds
Flocculation
Algae aggregate and clump (auto and induced)
Sedimentation
Gravity will cause algae to settle over time
Filtration
Use fine screens to separate algae from the water
Physical extraction of lipids from algae methods
Mechanical disruption
Electric pulse
Sonication
Osmotic shock
Expeller press
Chemical and biochemical extraction of lipids from algae methods
Solvent (hexane)
Enzymatic
Algae produces ____ that can be used to make biodiesel
Triacylglycerides
___ of algal lipids leads to FAMEs
Transesterification
Is the overall process of algae biodiesel production affordable
No
Cost per gallon of algae diesel
$8 per gallon
