Biomass-based Fuel Cells - Application to Manned Space Exploration

Prof. Aarne Halme Dept. of Automation and Systems Technology Helsinki University of Technology Content:

• Fuel cells – a short introductory -chemicalfuelcells - biocatalyzed fuel cells - what they are? • Current status of research and practice -chemicalfuelcells - 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 more complex 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 for CHP and larger power station applications) Biocatalyzed fuel cells

• Opposite to chemical fuel cells biocatalyzed fuel cells 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 catalyzed biologically either by living microbes or enzymes. • A very recent close innovation is biocatalyzed electrolysis to produce hydrogen Biocatalyzed fuel cells – operating principle

•Abovea 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 chemical fuel cells Biocatalyzed fuel cells Chemical fuel cells • Wide fuel selection, in principle • Restricted fuel selection: all biodegrable substrates hydrogen, methanol, methane.. • Final products water +CO2 + • Final product water if hydrogen anode process products is used as fuel, otherwise more • Low temperature (ambient) complex (+C02+reforming side operation only products) • Low power density • Low and high temperature ~ 1 mW/cm2 operation possible • High operational time • Higher power density acheivable (BFC) DMFC ~ 60 mW/cm2 PEM ~ 300 mW/cm2 SOFC ~ 400 mW/cm2 • High operational time still a problem in many cases Biocatalyzed electrolysis – a recent new innovation Biocatalyzed electrolysis - Operation principle

E

e- Ox Ox

Fuel: H Fuel:Organic organic Biocata 2 substrate substrate lyst Mediator

H+ Re Re H+

Anode PEM Cathode • External electrical power source E is needed to make system Gipps free energy 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. State of the art

• Biocatalytic electrolysis has been known only for a couple of years now • Published experimental results are available using a bacterial catalyst using organic acids and communal waste water as fuel (2006, Prof. Logan, Pensylvanian State University, and Dr Rozendahl, Wageningen University). • Unpublished experimental tests have been done by this author using fructose as fuel and fructose dehydrogenase (FDH) enzyme as catalyst (2007) • Experiments clearly show that the method is working and worth of further development. Logan reports 92W/m3 reactor volume hydrogen 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 make 2,5 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 supporting system with plant cultivation, where organic wastes are recirculated and the related energy is recovered as electricity. ARIADNA AO/1-4532/03/NL/MV results Scenario I (on Mars) Scenario II (on Mars)

Six Astronauts Six Astronauts

Menu: Menu: packaged food (1500 g) packaged food (565 g) and growth food (67 g) and growth food (1000 per day per person g) per day per person Input and output of an astronaut per day, all plants menu

Input and output of an astronaut per day, Extended Base, All plants menu, limited to items applicable for fuel-cell study INPUT OUTPUT O2 0.83 kg CO2 1 kg H20 total * 27.58 kg Feces + toilet paper 0.053 kg (dry) (0.03 kg dry feces only) 0.143 kg (wet) Food (grown) 1.0 kg Brine for urine 0.524 kg

Food 0.565 kg Î Brine for shower/ 0.254 kg (packaged) handwash/ sweat Î Plant biomass (from 4.025 kg (wet)** harvesting, cooking and left-overs) Wet trash (paper, wipes, 0.26 kg 10% humidity)

Dry trash (tapes, filters, 0.60 kg packaging , misc.)

* 97% of water is circulated. The rest 3% goes along with brines; ** Includes 10% of left-overs and 30% processing waste Input and output of plant field per day (per person)

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

CO2 0.735 kg O2 0.534 kg

H20 86.5 kg Edible food 1.0 kg

Energy (light)* 69.7 k W Non-edible 4.0 kg biomass Needed area 26.8 m2 Î Î

*Energy (light) 2.6 k W/m2 Waste Biomass

One person Six persons

Faeces Rate (kg wet/day) 0.150 0.900 Ash (kg/day) 0.0075 0.045 Biodegradable waste (kg dry/day) 0.030 0.180 Energy density (MJ/kg dry biodegradable waste) 11.8 Energy (MJ/day) 0.354 2.124 Vegetable residues and others Rate (kg wet/day) 4.00 24.0 Biodegradable solid waste (kg dry/day) 1.22 7.32 Energy density (MJ/kg dry biodegradable waste) 17.5 Energy (MJ/day) 21.35 128.1 Overall mass weight (kg wet/day) 4.150 24.90 Overall energy (MJ/day) 21.7 130.2 Overall solid biodegradable waste (kg/day) 1.25 7.50 Volume density (kg/m3) 300 Overall volume (liter) 4.17 25.0 Energy system

Solar •Heating energy •Cooking •Lighting Wind energy •Plant growth Recycling energy •Motors&engines fromfuelcell •Electronic Trans- ported devices energy from •… Earth Recirculation balance: SOFC and PEM fuel cell system

Biomass Digestion Fuel Reformer Collection Process

Energy Input to the System Byproduct as Feed for Plant Growth Fuel Cell System

Other Byproducts Net Energy (Water and CO2) SOFC or PEM Fuel Output (Energy Cell Input – Output) Electricity (Energy Output) Sequential batch anaerobic composting system for space mission

Pretreatment Anaerobic Treatment Post-treatment

Biogas Waste stream (CH4+H2O)

Dewater

Feed Compost Collection Biodegradables New Activated Mature 5d Aerobic ( Excluding Urine ) 5d 5d 5d 5d

Particle size 2-5 cm Organic Acid add wastewater to 35% TS compacted to 300 kg/m3 Ambient Air

( CO2+H2 ) Inoculumm Mass Balance

Input: • 7.5 kg biodegradable waste • 6 kg oxygen Output: • 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: Biocatalyzed fuel cell system

Pretreatment Biological Fuel Energy Input for (liquefaction) Cell Pumping and Rotating.

Byproduct as Feed for Plant Growth and others (water and CO ) Electricity Biomass Collection 2 (Energy Output)

Hydrogen SOFC or PEM Fuel Net Energy Output (Energy Production Cell System Input – Output) Fermentation 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 system 30 MJ/day comsumed for the process 9 MJ/day or 104 W Overall energy efficiency: 6.9 % Summary and conclusions

• Biomass energy can be recovered in electrical form when recycling waste in micro ecological life supporting system during long space flights. • Net balance of recovery is not much but positive and seems little bit better when using biocatalyzed fuel cell technology than classical diggestion, reforming and chemical fuel cells. • A new biocatalyzed electrolysis to produce hydrogen directly from biomass seems very promising and may bring a new dimension to this analysis.