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Photosynthesis to Fuels
ARPA-E Workshop on Applied Biotechnology for Transportation
Fuels
Tasios Melis, UC Berkeley
1
CO2
H2O
Photosynthesis Photons
Biomass
Fuels
O2
Feedstock and products
Process offers a renewable energy supply and mitigation of climate change.
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Properties and attributes of photosynthetic microorganisms
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• Microalgae • Cyanobacteria
Differential Interference Contrast Chlorophyll Fluorescence
The green microalga Chlamydomonas reinhardtii
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Edwards & Gantt
Sherman & Sherman
Thermophilic cyanobacterial strains Thermosynechococcus elongatus & Synechococcus lividus
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Features of microalgae and cyanobacteria
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High rates of photosynthesis
Easy to cultivate
Require “containment” in a photobioreactor
Chlamydomonas reinhardtii mass culture
Hydrogen production in a backyard
vent
8
P
Sunlight: Over-absorption and dissipation
NPQ
9
P
Sunlight: Improved
intra~culture energy flux
NPQ
P
PP
P
ARPA-E Workshop on T-Fuels (Melis)
10
Photosynthesis and Photovoltaics
From Blankeship et al. submitted
VISIBLE Green Algae
NEAR INFRARED
Photo Bacteria
300 500 900 700
Wavelength, nm
0
1
2
3
4
5
Qua
ntum
irra
dian
ce,
x101
2 qua
nta
m-1
s-1
nm
-1
45% of sunlight 20% of sunlight
Sunlight absorption & utilization
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A two-dimensional problem in sunlight utilization
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- Over-absorption and wasteful dissipation of excess sunlight at the surface.
- Steep gradients in sunlight penetration through a high density culture/canopy.
- Short range (400-700 nm) of photosynthetically active radiation.
- Possibility of extending PAR to 950 nm.
Tools required
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Transformation technologies for the genetic engineering of chloroplasts, microalgae and cyanobacteria: - Excellent in many cyanobacteria and in Chlamydomonas reinhardtii. - Poor in most other microalgae.
- Species-dependent in vascular plants.
Benefits to be accrued
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Substantially improved sunlight absorption and utilization.
CO2
H2O
Photosynthesis Photons
Biomass
Fuels
O2
Feedstock and products
The problem of carbon partitioning between fuel and biomass
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RuBP +
CO2
GA 3-P
3-PGA
Calvin Benson Cycle
Pyruvate
Acetyl-CoA
Fatty acids
Deoxy-xylulose-5-P
Terpenoids
Dimethylallyll~PP
Photosynthesis
2
3
1 SUGARS
C5H8 Isoprene
C30H48 Btc-oil Biodiesel
Biomass
Ethanol Butanol
Photosynthetic carbon partitioning in 3 pathways
RuBP +
CO2
GA 3-P
3-PGA
Calvin Benson Cycle
Pyruvate
Acetyl-CoA
Fatty acids
Deoxy-xylulose-5-P
Terpenoids
Dimethylallyll~PP
Photosynthesis
2
3
1 SUGARS
C5H8 Isoprene
C30H48 Btc-oil Biodiesel
Biomass
80‐85% of CO2
~4% of CO2
~10% of CO2
Ethanol Butanol
Photosynthetic carbon partitioning in 3 pathways
Productivity Features
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Fuel / Biomass carbon partitioning ratios are currently low (they need to be greater than 20%)
Tools required
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Metabolic engineering approaches to alter carbon flux toward fuel in photosynthetic organisms.
Benefits to be accrued
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Enhancing the Fuel / Biomass carbon partitioning ratio improves the economics of the process.
Thank you for your attention
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Photosynthetic Productivities
Theoretical productivity: ~75 g DW m-2 d-1
(8-10% solar energy conversion efficiency)
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Photosynthetic Productivities
Theoretical productivity: ~75 g DW m-2 d-1
(8-10% solar energy conversion E) -----------------------------------------------------------------
Measured productivities: Less than 25 g DW m-2 d-1
(3-4% solar energy conversion E)
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