Biomass-based Fuel Cells - Application to Manned Space Exploration

Prof. Aarne HalmeDept. of Automation and Systems Technology

Helsinki University of Technology

Content:• Fuel cells – a short introductory

- chemical fuel cells- biocatalyzed fuel cells - what they are?

• Current status of research and practice- chemical fuel cells- biocatalyzed fuel cells

• Biocatalyzed electrolysis – a recent new innovation• Application to manned space flights• Summary

Fuel cells – a short introduction

Energy Conversion Schemes

Fuel cell technology• Chemical fuel cell concept is already 100 years old

innovation.• There are many different type of fuel cells, but they all

work accoding to the same main principle shown below.• Electrode reactions need a catalyst – Pt most comonly

used, but there are also other alternatives.

Chemical fuel cells

• Low temperature fuel cells- PEMFC (Proton Exchange Membrane Fuel Cell)- DMFC (Direct Methanol Fuel Cell)- AFC (Alcaline Fuel Cell)- PAFC (Phosforic Acid Fuel Cell)

• High temperature fuel cells- MCFC (Molten Carbonate Fuel Cell)- SOFC (Solid Oxide Fuel Cell)

• Most fuel cells operate with hydrogen gas. Exceptions are- DMFC, which operate with liguid methanol- high temperature cells (SOFC), which operate also with morecomplex fuels, like natural gas/methane, co, or even diesel

Reactions and ion flow in different type of fuel cells

Technology trends

• AFC is the oldest technology (used already in 60’s in Apollo program)

• Today development priority- PEM (car industry, small CHP-plants…)- DMFC (electronics etc applications)- high temperature fuel cells (SOFC, MCFC forCHP and larger power station applications)

Biocatalyzed fuel cells

• Opposite to chemical fuel cells biocatalyzed fuelcells are a quite recent innovation

• The early studies are from the beginning of 90’s• The basic idea is similar to PEM, but reactions

take place in liguid phase and are catalyzedbiologically either by living microbes orenzymes.

• A very recent close innovation is biocatalyzedelectrolysis to produce hydrogen

Biocatalyzed fuel cells – operating principle

• Above a bacterial fuel cell (BFC)• Enzyme fuel cells operates in the same way, only bacteria are

replaced with an enzyme• Most biocatalyced fuel cells need a mediator (above HNQ) to

transport electrons to electrodes

Biocatalyzed fuel cells vs chemicalfuel cells

Biocatalyzed fuel cells• Wide fuel selection, in principle

all biodegrable substrates• Final products water +CO2 +

anode process products• Low temperature (ambient)

operation only• Low power density

~ 1 mW/cm2• High operational time

acheivable (BFC)

Chemical fuel cells• Restricted fuel selection:

hydrogen, methanol, methane..• Final product water if hydrogen

is used as fuel, otherwise morecomplex (+C02+reforming side products)

• Low and high temperatureoperation possible

• Higher power densityDMFC ~ 60 mW/cm2PEM ~ 300 mW/cm2SOFC ~ 400 mW/cm2

• High operational time still a problem in many cases

Biocatalyzed electrolysis – a recent new innovation

Biocatalyzed electrolysis - Operation principle

• External electrical power source E is needed to make system Gipps freeenergy negative allowing hydrogen reduction going freely

• E is a very low voltage ~0,2-0,3 V. Energy of released hydrogen is (much) more than taken by the external power source.

Fuel: organic substrate

Fuel: Organic substrate

Biocatalyst

Ox

Re

Ox

Re

Mediator

H+

e-

H2

H+

Anode PEM Cathode

E

State of the art

• Biocatalytic electrolysis has been known only for a couple of yearsnow

• Published experimental results are available using a bacterialcatalyst using organic acids and communal waste water as fuel(2006, Prof. Logan, Pensylvanian State University, and DrRozendahl, Wageningen University).

• Unpublished experimental tests have been done by this authorusing fructose as fuel and fructose dehydrogenase (FDH) enzymeas catalyst (2007)

• Experiments clearly show that the method is working and worth of further development. Logan reports 92W/m3 reactor volumehydrogen production (burning value) with 288% electrical efficiency(Web-site information).

Application to manned space flights

• NASA and ESA have preliminary plans for manned exploration flights to Mars around the middle of this century.

• According to one scenario 6 astronauts make2,5 years return mission spending 1 year in a camp in Mars.

• Especially during the camp phase it is rational to establish a micro ecological life supportingsystem with plant cultivation, where organicwastes are recirculated and the related energy is recovered as electricity.

ARIADNA AO/1-4532/03/NL/MVresults

Menu: packaged food (565 g) and growth food (1000 g) per day per person

Menu:packaged food (1500 g) and growth food (67 g) per day per person

Six AstronautsSix Astronauts

Scenario II (on Mars)Scenario I (on Mars)

Input and output of an astronaut per day, all plants menu

* 97% of water is circulated. The rest 3% goes along with brines; ** Includes 10% of left-overs and 30% processing waste

0.60 kgDry trash (tapes, filters, packaging , misc.)

0.26 kgWet trash (paper, wipes, 10% humidity)

4.025 kg (wet)**Plant biomass (from harvesting, cooking and left-overs)

0.254 kgBrine for shower/ handwash/ sweat

0.565 kgFood (packaged)

0.524 kgBrine for urine1.0 kgFood (grown)

0.053 kg (dry)0.143 kg (wet)

Feces + toilet paper(0.03 kg dry feces only)

27.58 kgH20 total *

1 kgCO20.83 kgO2

OUTPUTINPUT

Input and output of an astronaut per day, Extended Base, All plants menu,limited to items applicable for fuel-cell study

Input and output of plant field per day (per person)

*Energy (light) 2.6 k W/m2

26.8 m2Needed area

4.0 kgNon-edible biomass

69.7 k WEnergy (light)*

1.0 kgEdible food 86.5 kgH20

0.534 kgO20.735 kgCO2

OUTPUTINPUT

Input and output of plant field per day (per person), limited to items applicable for fuel-cell study, Extended Base, All Plants Menu.

Waste Biomass

25.04.17Overall volume (liter)

300Volume density (kg/m3)

7.501.25Overall solid biodegradable waste (kg/day)

130.221.7Overall energy (MJ/day)

24.904.150Overall mass weight (kg wet/day)

128.121.35Energy (MJ/day)

17.5Energy density (MJ/kg dry biodegradable waste)

7.321.22Biodegradable solid waste (kg dry/day)

24.04.00Rate (kg wet/day)

Vegetable residues and others

2.1240.354Energy (MJ/day)

11.8Energy density (MJ/kg dry biodegradable waste)

0.1800.030Biodegradable waste (kg dry/day)

0.0450.0075Ash (kg/day)

0.9000.150Rate (kg wet/day)

Faeces

Six personsOne person

Energy system

Solarenergy

Windenergy

Trans-portedenergyfromEarth

•Heating•Cooking•Lighting•Plant growth•Motors&engines•Electronicdevices

•…

Recycling energyfrom fuel cell

Recirculation balance: SOFC and PEM fuelcell system

DigestionProcess

Fuel ReformerBiomassCollection

SOFC or PEM FuelCell

Electricity(EnergyOutput)

Byproduct as Feed for Plant Growth

Net Energy Output (Energy Input – Output)

Energy Input to the System

Other Byproducts (Water and CO2)

Fuel CellSystem

Sequential batch anaerobic composting system for space mission

Biodegradables( Excluding Urine )

FeedCollection

5d New5d

Activated5d

Mature5d

Aerobic5d

Compost

Dewater

Ambient Air( CO2+H2 )

Organic Acid

Inoculumm

Biogas(CH4+H2O)Waste stream

Pretreatment Anaerobic Treatment Post-treatment

Particle size 2-5 cmadd wastewater to 35% TS compacted to 300 kg/m3

Mass Balance

Input: • 7.5 kg biodegradable waste• 6 kg oxygenOutput:• 1.5 kg methane (+4.1 kg CO2 + 1.9 kg

compost) (from AD process)• 4.1 kg Water + 3.3 kg CO2 (from FC)

Energy Balance

Input:130 MJ/day in biodegradable waste

Output:26.2 MJ/day after AD process (20 %)5.2 – 7.8 MJ/ after FC system (20-30%)

Overall energy efficiency:4 – 6 %

Recirculation balance: Biocatalyzedfuel cell system

Pretreatment(liquefaction)

Biomass Collection

Biological Fuel Cell

Electricity(Energy Output)

Byproduct as Feed for Plant Growth and others (water and CO2)

HydrogenProductionFermentation

Energy Input for Pumping and Rotating.

SOFC or PEM Fuel Cell System

Net Energy Output (Energy Input – Output)

Mass Balance

Input: • 7.5 kg biodegradable waste• 3.5 kg oxygen (100 % converted)Output:• 2 - 3 kg compost• 3 – 3.5 kg Water• 5 – 5.5 kg CO2 (from FC)

Energy Balance

Input:130 MJ/day in biodegradable waste

Output:39 MJ/day from the BFC system30 MJ/day comsumed for the process9 MJ/day or 104 W

Overall energy efficiency:6.9 %

Summary and conclusions

• Biomass energy can be recovered in electrical formwhen recycling waste in micro ecological life supportingsystem during long space flights.

• Net balance of recovery is not much but positive and seems little bit better when using biocatalyzed fuel celltechnology than classical diggestion, reforming and chemical fuel cells.

• A new biocatalyzed electrolysis to produce hydrogendirectly from biomass seems very promising and maybring a new dimension to this analysis.