Yudi Chen, Carnegie Mellon University

Catherine Groschner, Carnegie Mellon University

Brent Heard, Carnegie Mellon University

Avisha Shah, University of Pennsylvania

Matthew Vernacchia, Massachusetts Institute of Technology

Linear Nutrient Flow

Food Storage

Waste Storage

CrewO2

CO2

Cyclic Nutrient Flow

Current Solutions Sequential Batch Anaerobic

Composting (SEBAC) Anaerobic system→ CH4, not food

Research Space Bioconverter (RSB) Mainly for food waste

NASA JSC’s BIO-Plex Food storage and growth research

ESA’s Micro-Ecological Life Support System Alternative (MELISSA)

Critical Tasks

Food Crop Selection Composting Process Selection Proof-of-Concept Rate Balancing Microgravity Gas Exchange Automation Verification

Food Crop - Production

Algae advantages over macroscopic plants Whole biomass edible

No waste from stems, etc less harvesting machinery

Grow in Liquid Media Simpler growth chamber: bioreactor tank

vs. complex hydroponic farm Easier process automation

Food Crop - Nutrition Of algae evaluated, Spirulina Platensis shows best

nutritional properties Spirulina has soy-like nutritional properties Spirulina is a staple crop for several tribes around

Lake Chad, and was for the Aztecs (Ciferri 1983) Carb : protein balance alterable via changes in

growing conditions (Tadros 1988) UN FAO meta-study:

Rich in protein, vitamins (Becker 1994) and iron (Henrikson 1989)

Immune system resilience to radiation (Academy of Chinese Military Medical Sciences)

Food Crop - Preparation

Fresh foods + packaged garnishes/ flavorings Allow astronauts to process the Spirulina into a variety of food

products

Tofu Soy-like milk Flour for tortillas, noodles and bread

Composting Process

Spirulina can grow in aerated swine waste (Canizares and Dominquez 1993)

Process: Liquefaction Aerobic stabilization

Thermophilic stage (60C) reduces pathogens Sterilization by UV irradiation

Lower complexity than MELISSA’s anaerobic and nitrogen fixation process.

Carbon:nitrogen ratio = most important parameter

Proof of Concept Procedure

Feces, urine, food waste and paper, in ratio matching NASA effluents report

Mechanical liquefaction Aeration in 1L bioreactors (35 days) UV irradiation + 10 min at 100C Dilution Used as Spirulina growth media in 1L bioreactors

Compare composting performance at C:N ratios and concentrations

Gather metabolic rate data

Proof of Concept

3-Aug 4-Aug 5-Aug 6-Aug 7-Aug 8-Aug 9-Aug 10-Aug 11-Aug 12-Aug0

100

200

300

400

500

600

700

Spirulina Growth (25:1 C:N compost)

Reactor 1Reactor 2Reactor 3

Time (days)

Lig

ht

Absorp

tion b

y b

iom

ass (

NTU

)

10:1 dilution

50:1 dilution

25:1 dilution

Rate Balancing

O2 produced by algae = O2 consumed by compost

+ O2 consumed by crewCO2 consumed by algae = CO2 produced by compost

+ CO2 produced by crewCompost mass

= (waste produced/time)*(retention time)Algae mass

=(food needed/time) / (growth rate)

Rate Balancing

Rate Balancing

Rate Balancing

Assuming Algae produces 15 g O2 /day/kg algae media Compost consumes 15 g O2 / kg compost

slurry /day 3 week waste composting 6 person crew 75% of diet is grown

~290 kg compost slurry >530 kg algae media to provide food ~620 kg algae media to balance O2

Microgravity Gas Exchange Need to move gases into and out of

liquid media Normally done by sparing – this will not

work in microgravity

Membrane Gas Exchange (MGE)

Centrifugal Gas Exchange (CGE)

CGE/MGE Bioreactor10L capacity

Rotating growth chamber, up to 500rpm for CGE

Electrical connections for sensors, heating and lighting on rotor

Under DevelopmentUnder Development

Future Work

Microgravity CGE/MGE

Pursue experiments on parabolic flight aircraft NASA’s Reduced Gravity Education

Flight Program

Biological tests in CGE/MGE BioreactorInvestigate: Algae and compost metabolisms with

new gas exchange system Impact of biomass on gas exchange

effectiveness

Closed system

Components: Compost bioreactor

(x1) Algae bioreactors

(x2) Crew simulant (i.e.

mice) Confirm rate

balances Investigate

automation methods

Automation

Waste Input

Composting

Algae growth

Material Transfer

Alternative Product Applications

• Remote Locations

• Oil Rigs / Submarines

• Third World

Extensive Ground Proving

Acknowledgements

This research was funded by a Conrad Foundation Spirit of Innovation Award

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