Energetische Nutzung von Mikroalgen: Status Quo und Entwicklungspotentiale
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Energetische Nutzung von Mikroalgen: Status Quo und Entwicklungspotentiale EnergieSpeicherSymposium 2013 13. März 2013, Stuttgart Dr.-Ing. Ursula Schließmann, Dr. Ulrike Schmid-Staiger Fraunhofer Institut für Grenzflächen- und Bioverfahrenstechnik IGB in Stuttgart Dr. Ulrike Schmid-Staiger Fraunhofer IGB Stuttgart © Fraunhofer IGB
Microalgae as energy feedstock
Algae are the most promising non-food source of biofuels –
can be cultivated in seawater or brackish water on non-arable land,
and do not compete for resources with conventional agriculture.
Growth rate may be 5 to 10 times higher compared to plants
Algae have a simple cellular structure
The biomass is homogenous and free of lignocellulose
A lipid-rich or starch-rich composition (40–80% in dry weight)
under specific cultivation conditions possible
Carbon dioxide emitted from combustion processes can be used
as a source of carbon for algal growth (1 kg of dry algal biomass
requiring about 1.8 kg of CO2).
Different waste water streams can be used as resource for nutrients
(nitrogen and phosphorous) and water
Water demand for algal biomass production is lower than for land © Ernsting, GEO
plants like rape seed
Microalgae biomass can be harvested during all seasons.
Algae biofuel contains no sulfur, is non-toxic and highly biodegradable
Net energy production is possible
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Renewable Energy Directive (RED 2009/28)
The “Renewable Energy Directive” (RED 2009/28) established mandatory targets of 10% share of
renewable energy in the transport sector by 2020. While the Fuel Quality Directive (FQD 2008/30)
introduced a mandatory target to achieve by 2020 a 6% reduction in the greenhouse gas emissions
of fuels used in road transport. The contribution of biofuels towards these targets is expected to be
significant, accounting for nearly 80% of the overall output.
further incentives to be provided by increasing the weighting of advanced
biofuels towards the RED 10% transport target compared to conventional
biofuels.
the contribution made by biofuels produced from municipal solid waste, aquatic
material, agricultural, aquaculture, fisheries and forestry residues and
renewable liquid and gaseous fuels of non-biological origin shall be
considered to count four times within the EU’s 10% target.
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Cost estimation of microalgae production
At 1 ha scale today: 10 € / kg
At 100 ha scale today: 4 € / kg *
What will be possible 0.4 – 0.7 € / kg *
© Ernsting, GEO
Too expensive for energetic use alone
Too expensive for chemicals production
Reduction of biomass production and processing costs
Valorisation of biomass
* according to Wijffels et al. 2010
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Main components of microalgae
Algae
Proteins Carbohydrates Lipids valuable
compounds
• high content • storage storage lipids • pigments
membrane lipids
up to 50% of products: • antioxidants
• mainly TAGs
dry weight in ά-(1-4)-starch • different lipid
growing • up to 50% of • fatty acids
ß-1,3-glucan,
cultures DW classes • vitamins
fructanes,
• all 20 amino glycerol • TAG as oil • up to 40% of • anti
acids droplets -fungal,
total lipids are -microbial
• 20 % soluble • Low cellulose -viral
80% membrane PUFA toxins
content
bound
Usable for valorisation of biomass
© Fraunhofer IGB 5
Dr. Ulrike Schmid-Staiger
Algal components as energy carrier
growing cells non-growing cells
hydrophilic lipophilic hydrophilic lipophilic
proteins membrane lipids proteins oil (=TAG)
cell walls carotenoids cell walls carotenoids
carbohydrates xanthophylls starch phytosterols
phytosterols
Carbohydrates as energy storage product
Storage products
valuable
pigments compound
lipids
proteins
valuable
pigments compound
lipids
N- ,P- and S-limitation carbohydrates
light, CO2
proteins valuable
carbohydrat pigments compound
es proteins
lipids
carbohydrates
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Algal biofuel conversion technologies
Algal Biomass
Conversion of Direct production Conversion of
whole biomass of biofuels extracts
Calvin cycle photosynthesis
pyruvate
NADPH
ethanol
butanol
secreted
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Algal biofuel conversion technologies
Conversion of
whole Biomass
Anaerobic hydrothermal Pyrolysis Gasification
digestion conversion
SynGas
Liquid or
vapor fuels Fischer- Higher
Tropsch Alcohol
synthesis
Catalytic Catalytic
upgrading upgrading
Biogas Transport. fuels Liquid Hydrogen MeOH,
CH4 + CO2 liquid or gas Hydrogen fuels EtOH etc.
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Algal biofuel conversion technologies
Conversion of
Extracts
Lipids Carbohydrates
Chemical Enzymatic Catalytic Fermentation
Transesteri- Conversion Cracking
fication
Diesel Biodiesel Gasoline, Diesel Ethanol
FAME Kerosene, Olefine
Aromatics
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger
Demands to sustainable microalgal Processes
Energy efficient algae biomass production process
strain selection, high rate of photosynthesis, fatty acid profile, photobioreactor, CO2-
utilization, net energy balance
Product recovery
use of whole biomass or use of extracts
solvents (which and quantity)
extraction from wet biomass, avoiding energy intensive drying steps
Residual biomass utilization
free of lignocellulose, conversion to biogas by anaerobic digestion,
Recycling of nutrients
CO2, nitrogen, phosphate, water
Water reuse
quantity and quality
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerDemands on an energy efficient and cost effective microalgae process
Strain properties
high growth rate and biomass productivity in fresh water, saline water or
waste waters
high productivity of metabolites for example lipids or starch
product concentration i.e. oil content (> 30% TAG) or starch (> 30% )
product composition (fatty acid profile, α-1,4 starch or ß-1,3 glucan)
high yield on light at high light intensities
robust algae strains adapted to local environmental conditions
especially temperature
ease of biomass separation and processing (harvest and rupture)
Chlorella vulg. lipid phase
14% 18%
10% 2%
C16:0
increase of lipid
C18:0
content by 35%
main fatty acid
C18:1n9c
C18:2n6c
C20:0
56% is oleic acid C18:1
total lipid content: 45 % of dry biomass © Fraunhofer IGB
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerDemands on an energy efficient and cost effective microalgae process
Process engineering
net energy production by optimization of energy input for
intermixing and distribution of high light intensities (full sunlight
intensity) for a high biomass productivity
one-stage production for conversion of complete biomass to
energy product
two-stage production for specific product formation like TAG or
starch after nutrient limitation
use of flue or waste gas as CO2 source
use of waste water streams as nutrient source
energy efficient downstream processes (harvest and extraction)
possibility of obtaining other valuable compounds to valorise
algae biomass
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerComparison between different Cultivation Systems
System Raceway ponds Tubular reactors Flat panel airlift
reactors
Light efficiency Fairly good excellent excellent
Temperature control None excellent excellent
Gas transfer Poor Low-high Low-high
Oxygen accumulation low high low
Biomass concentration low high high
Sterility low high high
Cost to scale-up low high high
Volumetric productivity low high high
Energy demand per kg high high low
biomass produced
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerTwo-stage process for lipid production
1. stage 2. stage
biomass production lipid production
sufficient nutrient nutrient deprivation
supply
accumulation of storage
maximum biomass lipids
productivity
Fatty acid profile Chlorella vulgaris
composition of lipid fraction
100%
80%
C18:3
60% C18:2
C18:1
40% C18:0
C16:0
20%
0%
11 % [w/w] 48 % [w/w] © Fraunhofer IGB
total lipid content
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerProduction of oil-rich microalgae biomass
Outdoor production of
oil-rich Chlorella biomass
in 25 L FPA-reactors
in Stuttgart
Two-stage process
• 1st stage – producing algal biomass
• 2nd stage – nitrogen and phosphate limitation, high light intensity
Oil production (triacylglycerides)
• Fatty acid content up to 55%
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerBiomass production phase
12
biomass concetration
Maximum Average
10
Biomass
[g DW L-1]
8
concentration 10.0 4.7
6 [g DW L-1]
4 Vol. biomass
productivity 0.98 0.57
2 [g DW L-1d-1]
0 Biomass
0 20 40 60 80 productivity
cultivation time [d] based on
21.2 12.4
illuminated
30 reactor surface
[g DW m-2d-1]
[MJ m-2 d-1]
irradiance
20
10
Light yield PAR
0.94 0.45
[g DW EPAR-1 ]
0
1 Einstein [E] equals 1 mol photons
0 20 40 60 80
cultivation time [d]
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerLipid production phase – lipid content
60
50
lipid content % (w/w)
40
30 100%
composition of lipid
20 80% others
10 60% C18:3
fraction
C18:2
0 40% C18:1
0 2 4 6 8 10 12 14 16
20% C18:0
cultivation time [d]
C16:0
initially 1.1 g DW L-1 0%
initially 2.3 g DW L-1 53.7%
total lipid content
initially 3.6 g DW L-1
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerBiogas from algae biomass
From Mussgnug et al. 2010
J.Biotechnology
Table 1 Summary
Problem:
hoher Proteingehalt führt zu hohen Ammoniumkonzentrationen (> 1,5 g NH4/l)
Problem:
• high protein content results in high ammonium concentrations (> 1.5 g NH4/l)
• composition and rigidity of cell wall influences degree of cell rupture and biomass degradation rate
© Fraunhofer IGB 18
Dr. Ulrike Schmid-StaigerHydrothermal gasification of microalgal biomass to methane
from Paul-Scherrer-Institut, Villigen- CH
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerHydrogen production with microalgae • unique, environmentally friendly energy carrier • currently 500x109 cubic meters of H2 per year are are used in industrial processes world wide • 90 % is derived from fossil resources (natural gas) • Hydrogen production via microalgae: development is on the level of research • green algae • actual H2-production with microalgae: 2 ml H2/L/h • current market price: 1€/kg H2 • yield of H2 with microalgae needs to be increased 100-fold • In comparison: cost of algae lipids need to be increased 10-fold © Fraunhofer IGB 20 Dr. Ulrike Schmid-Staiger
Water demand - comparison of energy crops and microalgae
Outdoor, solar Corn, Sugarcane Switchgrass Rape Tetraselmis Arthrospira
demonstrated values grains and mixed seeds suecica (Cyanob.)
prairie (Alge) *
grasses
Produktivity (t DW/(ha*a) 7 73 - 87 3,6 - 15 2,7 38-69 27a; 60-70b
Produktivity raw energy 120 1230 - 1460 61-255 73 700-1550 550, 1230-
(GJ/(ha*a) 1435
Main components
Nonrecalcitrant 70 30 5 - 12 11c - 47d 15c - (50)d
carbohydrates (%)
Lipids (%) 4-6 13 1-2 42 (23)c - (15)d 5c - (13)d
Proteins (%) 6 -12 (68)c - (28)d 72c - (27)d
Water usage (L/ kg DW) 565 89 - 118 50 3390 310 - 570
Water usage per energy 33 5-7 3 200 18 - 34
(L/MJ)
a cultivationin seawater, not optimized; in Mexiko
Water demand in PBR : < 100 L / kg DW b optimized cultivation in raceway ponds in Israel
c growing algae with sufficent nutrient supply
or 5 L / MJ d with nutrient limitation results in accumulation of storage products
According to Dismukes et al. 2008
© Fraunhofer IGB Current Opinion in Biotechnology 2008, 19:235–240
Dr. Ulrike Schmid-StaigerConclusions and outlook
Biofuel quality
fatty acid profile, ethanol, hydrothermal processes, biogas
Protection of climate
CO2 mitigation
from flue gases or industrial fermentations
Costs
too expensive up to now
reduction of CAPEX and OPEX is mandatory
net energy production
Sustainability
Recycling of nutrients (CO2, nitrogen, phosphate, water)
Water usage valorisation of biomass
© Fraunhofer IGB
Dr. Ulrike Schmid-Staiger[www.meteonorm.com]
Energetic use of microalgae – projects all over the world
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerThank you for
your attention
Dr.-Ing. Ursula Schließmann
ursula.schliessmann@igb.fraunhofer.de
Dr. Ulrike Schmid-Staiger
schmid-staiger@igb.fraunhofer.de
www.fraunhofer.igb.de
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerLinks: Lichtmikroskopische Aufnahme der Mikroalge
Chlamydomonas reinhardtii. Rechts: Kleinere Labor-Photobioreaktoren
in denen Algen wachsen. Quelle: Kruse
Neben diesem Konsortium leitet Kruse auch ein Projekt, das sich mit der
Wasserstoffgewinnung aus der gentechnisch optimierten Grünalge
Chlamydomonas reinhardtii befasst – mit finanzieller Unterstützung durch das
Bundesministerium für Bildung und Forschung. Hieran sind ebenfalls
Wissenschaftler von den Universitäten Karlsruhe und Münster sowie dem
Max-Planck-Institut für Molekulare Pflanzenphysiologie in Golm (Potsdam)
beteiligt. „Für die Alge ist Wasserstoff ein Abfallprodukt,“ erklärt der 48jährige.
„Dadurch kann sie ihre nutzlosen Protonen loswerden. Zwei „Abfall“-Protonen
verbinden sich in der Alge zu einem Wasserstoff-Molekül, das flüchtig ist und
die einzellige Pflanze verlässt.“ Noch sei die Ausbeute an freigegebenem
Wasserstoff nicht sehr hoch, räumt Kruse ein, doch an der Optimierung
werde stetig gearbeitet.
© Fraunhofer IGB
Dr. Ulrike Schmid-StaigerBruttoenergieinhalt von Energieträgern hergestellt aus 1 kg Algenbiomasse
Gross energy content of products derived from 1 kg biomass
Annahmen:
20
18 biodiesel 35 % Lipidgehalt werden zu
16 + biogas
biogas 18
0,35 kg FAME umgesetzt
14
19
12 50 % Kohlenhydratgehalt werden
MJ/kg ethanol
10
algae biomass + biogas zu 0,225 kg Ethanol
8 12
6 biodiesel
10
ethanol 0,8 m³ Biogas aus
4 6
2 1 kg Biotrockenmasse
0
© Fraunhofer IGB 26
Dr. Ulrike Schmid-StaigerYou can also read
