Post on 22-Feb-2022
What is the maximum efficiency that What is the maximum efficiency that What is the maximum efficiency that What is the maximum efficiency that photosynthesis can convert solar energy into photosynthesis can convert solar energy into
biomass?biomass?biomass?biomass?
Light to Liquids: Improving biological energy captureLight to Liquids: Improving biological energy captureAdvanced Research Projects Agency Advanced Research Projects Agency –– EnergyEnergy
Dec 2Dec 2--3, 20103, 2010
Total solar energy
Conversion ffenergy efficiency
Wh = S i cWh
H d
S i c
Harvested yield
Partitioning efficiency
Interception efficienc
(Harvest index)
efficiency
i is determined by speed of canopy i s determ ned by speed of canopy closure, and canopy size & architecture
- top performing crops achieve i = 0.9
- little potential for further improvement
Partitioning efficiency ()- for some crops, yield increase
has been due in large part to has been due in large part to improved
H t i d ( ) f - Harvest index () for corn grain in modern cultivars is ~55% f d ( of above ground biomass (i.e. =
0.55)- little room for improvement in
major grain crops
Lignocellulosic Feedstock Harvest Index
F d t k C ll l H mi ll l Li i A h Oth HIFeedstock Cellulose Hemicellulose Lignin Ash Other HI
Hardwoods 39-50% 18-28% 15-28%
0.3-1 % 3–6% 0.65-0.82
Softwoods 41-57% 8-12% 24-27%
0.1-0.4%
5-9% 0.63-0.69
Miscanthus 43-48% 23-27% 9-22% 1.7-2.1%
? 0.78-0.89
is d t min d b mbin d ph tc is determined by combined photo-synthetic rate of leaves in the canopy corrected for respiratory loses.
Annual solar energy conversion efficiencies of C3 d C4 i l l and C4 agricultural crops.
Crop Type Yield EfficiencyCrop Type Yield Efficiency(t ha-1y-1) (%)
Pennisetum purpureum C4 88 0.8
Saccharum officaarum C4 66 0.6
Zea mays C4 27 0.4
Beta vulgaris C3 32 0.5
Lolium perenne C3 23 0.7
Solanium tuberosum C3 11 0.3
Triticum aestivum C3 12 0.2
C3 Potential εc = 0.046Maximum observed εc = 0.024cAverage observed εc = 0.007
C4 Potential εc = 0.060Maximum observed εc = 0.037Average Observed εc = 0.012
Modified from Zhu et al. 2008 Current Opinion in Biotechnology. 19:153-159.
Why is maximum observed below theortical Why is maximum observed below theortical εεcc??
-1)
J m-2
s
15
hesi
s ( 10
otos
ynth
0
5 75% of daylight hours
0 500 1000
Pho 0
Solar energy (J m-2 s-1 )0 500 1000
Raising the theoretical upper Raising the theoretical upper limit of photosynthetic limit of photosynthetic limit of photosynthetic limit of photosynthetic
efficiency.efficiency.yy
PGAPGACH2OPO3
2-
C HHO
CH2OPO32-
C HHO
G
CH OPO 2-
CO2
C
COO-
HHOC
COO-
HHOO2
CH2OPO32-
C O
COO-COO-
C
C
OH
H OH
H
C HHO
COO
CH2OPO32-
COO C
CH2OPO32-
H OH
CH2OPO32-
PGA2-phospho-glycolate
Ribulose-1,5-bisphosphate
glycolate
Effects of temperature and [CO2] on c of C3 vs C4 photosynthesis vs C4 photosynthesis
Zhu , Long, and Ort (2008) Current Opinion in Biotechnology 19, 153-159
Redesigning photosystem absorption Redesigning photosystem absorption to better match energetic to better match energetic
f H f H d d d d requirements of Hrequirements of H22O oxidation and O oxidation and carbon reduction to solar spectrumcarbon reduction to solar spectrum
Blankenship et al. submitted