algae: fuel for the future? · 3 presentation_name . why should you care about algae? • diverse,...
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ORNL is managed by UT-Battelle for the US Department of Energy
Algae: Fuel for the future? Teresa Mathews Environmental Sciences Division
2 Presentation_name
Why should you care about algae? • Diverse, aquatic, ancient, photosynthetic (and beautiful!)
Red Algae
Green Algae
Diatoms
Blue green algae
3 Presentation_name
Why should you care about algae? • Diverse, aquatic, ancient, photosynthetic (and beautiful!)
• Important for global cycles of carbon dioxide, oxygen, nitrogen, etc.
4 Presentation_name
Why should you care about algae? • Diverse, aquatic, ancient, photosynthetic (and beautiful!)
• Important globally for biogeochemical cycles of carbon, nitrogen, oxygen
• ~40% of net primary productivity globally—important source of food!
Try some day! Spirulina, Chlorella
5 Presentation_name
Why should you care about algae? • Diverse, aquatic, ancient, photosynthetic (and beautiful!)
• Important globally for biogeochemical cycles of carbon, nitrogen, oxygen
• ~40% of net primary productivity globally—important source of food!
• Water quality issues (e.g. harmful algal blooms, “dead zones”)
6 Presentation_name
Why does the Department of Energy care about algae?
7 Presentation_name
Georgiana et al., Nature, 2012
energy.agwired.com Why does the Department of Energy care about algae?
Land area required to replace 100% of U.S. petroleum needs with biodiesel
Lipid productivity much higher than
other energy crops Short
generation time Captures CO2 and can
grow in wastewater
8 Presentation_name
Challenges for algal biofuel commercialization Cost (2500-5000 gallons biofuel intermediate/acre/year @ $3/GGE) -Increasing biomass and lipid productivity Crop protection: minimizing algae death from grazers or pests Limiting resources: - Water supply - Nutrients demands (N, P, CO2)
Improve economics through using wastewater.
Heathy pond
Crashed pond
www.laprogressive.com
Pond crash due to pest (adapted from Sapphire Energy Inc., CA)
9 Presentation_name
Cyanotech Corporation, Hawaii
Algal biomass production: Monoculture vs polyculture
Specialist pathogen
www.waterontheweb.org Seasonal succession of phytoplankton populations
In nature, algae exist in polycultures
Biofuel industry focus is on growing monoculture
Polycultures can provide crop
protection against specialist pests
10 Presentation_name
Does increased species diversity lead to increased productivity?
Shurin et al., 2014
Overyielding can occur if polycultures include species with complementary traits or that occupy different niches
11 Presentation_name
Creating niche differentiation with nutrients
• 106 C: 16 N: 1 P – Nitrate (NO3) – Ammonia (NH4) – Urea (NH2)2CO
• How do algal growth rates differ when given different nitrogen sources?
• Do different algal species prefer different nitrogen sources?
• Can polycultures grown in mixed nutrient media outperform monocultures?
Culture media
Waste water
12 Presentation_name
Outcome: Decreased cost and increased
annual biomass yield
Complementarity can reduce competition among species for
nitrogen.
Our hypothesis: Algal polycultures in wastewater produce
more biomass Ammonium uptake (9 mol/L/day)
Tetraselmis Chlamydomonas
Navicula
Raphidocelis
Scenedesmus
Urea uptake (3 mol/L/day)
Nitrate uptake (5 mol/L/day)
Algal species showed complementarity in forms of nitrogen use
13 Presentation_name
Polyculture
Monoculture NO3
media
NH4 media
Urea media
NO3+NH4+urea media
(simulated wastewater)
16 algal species communities
Experimental design
1-species cultures: 5
2-species cultures: 10
5-species culture: 1
4 media (all containing
equimolar nitrogen) Algae cultures
in lab
14 Presentation_name
Overyielding (polyculture yield – monoculture mean) occurs most often in wastewater media
Biomass yield: Monocultures vs polycultures
128 82 161 0
30
60
90
120
150
180
B E BE
Bio
mas
s (m
g/L)
Positive overyielding polycultures
56 Monoculture mean = 105
128 112 93 0
30
60
90
120
150
180
B C BC
Bio
mas
s (m
g/L)
Negative overyielding polycultures
-27
Monoculture mean = 120
Spe
cies
co
mbi
natio
n
Over yielding = polyculture yield – mean of mono cultures
15 Presentation_name
The rate of increase in biomass production
is highest in wastewater with polycultures
Biomass production vs species richness
300
200
100
0
Bio
mas
s (m
g/L)
1 2 3 4 5 Species richness
Nitrate
Wastewater simulated
Urea
Ammonium
0
10
20
30
Slop
e
16 Presentation_name
NUE =Biomass
Nitrogen in biomass
Nutrients use efficiency (NUE) is much more
pronounced in wastewater with polycultures
30
20
NU
E (b
iom
ass/
N)
0 1 2 3 4 5
Species richness
Nutrients use efficiency (NUE) vs species richness
Nitrate
Wastewater simulated
Urea
Ammonium
0
1
2
3
Slop
e
17 Presentation_name
What mechanisms are responsible for over yielding?
Ammonium Nitrate Urea Wastewater A B AB AB
Complementary effect
Selection effect
Over yielding= Complementary + Selection effect
Bio
dive
rsity
effe
ct µ
m3 /m
L
Overyielding in wastewater was mostly explained by
complementary effect
18 Presentation_name
We see promising
evidence of increased
productivity in algal
polycultures, especially with
wastewater
Polyculture in wastewater
can reduce the nutrients cost
by increasing nutrients use
efficiency
Next steps: Feasibility study to
use wastewater resources in US.
Crop protection
using algal polycultures
Conclusions and future direction
19 Presentation_name
Questions?
20 Presentation_name
Extra slides
21 Presentation_name
Can GM algae survive outdoor settings and express engineered
phenotypes?
How far would GM algae disperse?
What risks do GM algae pose to native ecosystems?
Acutodesmus dimorphus
Addition of 2 genes: • C14 fatty acid biosynthesis • Green fluorescence protein (GFP)
Genetic modification of Acutodesmus dimorphus
First EPA-approved GM algae in open ponds
Genetically modified (GM) algae: Realizing the potential and weighing the risk
Dispersal tank
22 Presentation_name
GM phenotypes translated from lab to field
Wild type
GM
Alga
l bi
omas
s (g
/L)
GM pond
Wild type
Harvest 1
Harvest 2
Harvest 3
3-fold increase of C14:0 fatty
acids in GM strain
GM pond performed similar to wild type
GFP expressed in both lab and field
23 Presentation_name
-10 0 10 20 30 40 50
-10
010
2030
4050
4226 34
34
21
59
3259
y
>
>
Distance: P=0.0003 Distance* direction: P=0.004
Dispersal in different directions
GM algae can disperse with no apparent effect on native algae
Mur
ray
Mira
mar
Pow
ay
indo
ante
e
ControlWTGM
Lake Murry Miramar Poway Lindo Santee N
umbe
r of a
lgal
spe
cies
5
10
15
0
ContrWTGM
Colonization in natural water bodies without effect on native algae composition
Dis
tanc
e no
rth (m
)
Frequency of counts by wind direction (%)
W
S
N
E 2%
6% 10%
14% 18%
22%
mean = 0.681 calm = 15.8%
0 to 1 1 to 2 2 to 3 (m/s)
Frequency of counts by wind direction (%)
Distance east (m)
A- days to invasions
Increasing productivity
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