Laboratory for Energy and Materials Cycles - LEM 5232 Villigen PSI, Schweiz

a: PSI – Catalytic Process Engineering Group , * martin.brandenberger@psi.ch, http://cpe.web.psi.ch

b: PSI – Chemical Processes and Materials Group,

c: EPFL-PSI – Joint Professorship on Solid Waste Treatment

M. Brandenberger a*, M. Schubert a, J. W. Reglera , A. Haiducc C. Ludwig b,c, F. Vogel a

SunChem – Bio-Synthetic Natural Gas from Microalgae

SunChem Process: Closed-Loop System with Respect to Nutrients

Why Microalgae? Why Bio-Synthetic Natural Gas?The production of liquid biofuels from food crops such as corn, soya, and

sugarcane are in direct competition with food production for human consumption.

In contrast, microalgae grown in photobioreactors, offer the following advantages:

• Microalgae are the most productive photosynthetic organisms on earth and grow several times faster than other energy crops.

• They can grow in reactors on non-fertile land, thus not competing with food production.

• They require less water for growth than land cultivated crops.

• They can directly convert industrial CO2 emissions into organic matter.

Wet biomass feedstocks can efficiently be converted into Bio-Synthetic Natural Gas (Bio-SNG) through catalytic hydrothermal gasification. The major advantages are:

• Bio-SNG can be used in the existing infrastructure (natural gas grid).

• It can be sold as transportation fuel in the form of natural compressed gas.

• Technology with high efficiency for power production is available (CHP).

• No biomass drying or product distillation steps are necessary.

400°C, 30 MPa,catalyst

+

CH4

CO2

H2

catalytic hydrothermal gasificationBEFOREAFTER

1. Microalgae use sunlight energy, CO2and H2O for growth. They are cultivatedin photobioreactors.

2. Bio-active chemicals can be extracted from the microalgae, before feeding them into the hydrothermal process.

3. The biomass is converted into Bio-SNG by catalytic hydrothermal gasification. Nutrients and water are separated during the process from the Bio-SNG.

4. The recovered nutrients and water are transferred back into the photobioreactor.

Conclusions

Photo source: Courtesy of Marine Biotechnology Group, UR Wageningen

If proved feasible, SunChem is an innovative way to produce renewable transportation fuel and power.

Nutrients can be recovered from the microalgae feedstock in the form of a concentrated salt brine.

Microalgae can be produced at high specific rates in photobioreactors, surpassing the area yield of crops and other plants.

Technical challenges such as the coupling of the biological process with the hydrothermal process need to be tackled in the future.

The economic feasibility of the SunChem process has to be assessed and demonstrated.

The Hydrothermal Laboratory Plant

Nutrient Recovery from Feed: Recovery of Salts from an Artficial Salt Mixture Composed of K2SO4 and Na2CO3

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0 0.250.50.751 1.251.51.752 2.252.52.753 3.253.53.754 4.254.54.755 5.255.55.756 6.256.56.757

Time [h]

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Feed LF [uS/cm] LF1 [uS/cm] LF2 [uS/cm]

Pressure 300 barV Feed 960 ml/h

Start of Experiment

End of Experiment

390 °C 430 °C 500 °C470 °C

Salt Concentration of Feed

Salt Concentration at Salt Separator

Salt Concentration of Process Effluent Water

Salt Separation Begins

• 1 kg feed stream per hour

• Concentrations up to 20 wt % organic material

• Operated almost fully by remote control

• The rig consists of three sections:

• Preheating

• Salt separation

• Fixed bed catalytic reactor

• In order to remove the nutrients quantitatively, the salt separator is the hottest part of the rig

• Project-Partners: Velux-Stiftung, Axpo Naturstrom Fond

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CB400A70 ZB400A71 ZB400A01 CB400A02 CB400A03 CB400A07Experiment

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Gasification Efficiency Bio-SNG Yield CH4, C2H6, C3H8

C: 2% Ru/CZ: 2% Ru/ZrO2

Increasing Catalyst Load High

Hydrothermal Gasification of Spirulina Platensis (Microalgae): Gasification Efficiency and Bio-SNG Yield at Different Catalyst Loads

Low