Development of Bioregenerative
Life Support for Longer Missions:
When Can Plants Begin to Contribute to
Atmospheric Management?
Raymond M. Wheeler
Surface Systems Office
NASA Kennedy Space Center
Florida, USA [email protected]
https://ntrs.nasa.gov/search.jsp?R=20150022488 2020-04-01T06:55:36+00:00Z
Plant Photosynthesis
light
CO2 + 2H2O* (CH2O) + H2O + O2
*
Edible (food)
(CH2O)
Inedible (waste)
For carbohydrate (CH2O) type crops, Assimilation Quotients (AQs) are ~1.0 (mol CO2 / mol O2)
For fat producing crops, AQ’s are lower, e.g., 0.8-0.9 (Tako et al., 2010)
Nitrogen, NH4 vs. NO3, can also affect AQ, with NO3, resulting in lower AQs (Bloom et al., 1989)
Factors Affecting Plant Photosynthesis and Growth
• Water and Nutrients—Assume these will be optimized but there
are challenges for micro and reduced gravity settings.
• Temperature—Assume this will be optimized for the given crop species.
• Carbon Dioxide—Optimal range for C3 crops probably 1000 to
2000 ppm (0.1 – 0.2 kPa); chambers open to cabin air might be
exposed to “super-elevated CO2”, which can cause some problems.
• Light
1) Light must be intercepted by the leaves or photosynthetic
organs. Light on the floors or walls does no good!
2) Most crops show a linear response of photosynthesis
to light across the lower light range.
NASA’s Biomass
Production Chamber
0
10
20
30
40
50
0 10 20 30 40 50 60 70 80
Photosynthetically Active Radiation (mol m-2 d-1)
Cro
p Y
ield
(g m
-2d
-1)
Total
Biomass
Edible
Biomass
Studies
Include:
Wheat
Soybean
Potato
Lettuce
Tomato
Effect of Light on Crop Yield(Data from NASA Biomass Production Chamber)
Wheeler et al. 1996. Adv. Space Res.
Canopy CO2 Uptake / O2 Production(20 m2 Soybean Stand)
6Wheeler, 1996. Plants in Space Biol. Suge (ed.)
CO2 Exchange Rates of Soybean Stands
-20
-10
0
10
20
30
40
50
0 10 20 30 40 50 60 70 80 90 100
Time (days)
CO
2E
xchange R
ate
(µ
mol m
-2s
-1)
Photosynthesis
Night Respiration
815 µmol m-2 s-1
HPS Lamps
477 µmol m-2 s-1
MH Lamps
Canopy Lodged
Harvest
High Temp
Event
7
Period of
Incomplete
Canopy Cover
Wheeler et al. 2006. EcoEngineering.
0
5
10
15
20
25
30
35
40
45
50
0 200 400 600 800 1000 1200 1400 1600
CO2 (mol mol-1)
CO
2E
xchange R
ate
(
mol m
-2s
-1)
CO
2C
om
pe
nsa
tion
Po
int
Fig. 6
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
90 100 110 120 130 140 150
CO2 Compensation Point
y = 0.15 x - 14.6
R2 = 0.99
CO2 (mol mol-1)
CO
2 E
x.
(m
ol m
-2 s
-1)
(97)
CO2 Exchange Rate vs. CO2 Concentration
Optimal Concentration
Wheeler. 2006. Potato Res.
Effect of Light on Photosynthesis
Wheeler, 1996, Plants in Space Biol. Suge (ed.)
Area for CO2 Removal / O2 Production
for One Person
Radiation
Use
Efficiency
PPF(µmol m-2 s-1)
250 500 750 1000
(g mol-1 PAR)
Daily Light
Integral(mol m-2 d-1)
14.4 28.8 43.2 57.6
0.50 94.4 47.2 31.5 23.6
0.75 63.0 31.5 21.0 15.7
1.00 47.2 23.6 15.7 11.8
* Biomass production data assuming Assimilation Quotient or AQ = 1.0 (i.e., biomass all CH2O)
** Assumes daily O2 requirement of 830 g / person-day (NASA SPP 30262)
*** Assumes a 16 h light / 8 h dark photoperiod
**** Radiation use efficiency data based on Wheeler et al. 2008. Adv. Space Res.
Area Per Person for O2
RUE = 1.0 g mol -1
RUE (Radiation Use Efficiency) Conversions based on Wheeler et al. 2008. Adv. Space Res. 41:706–713 .
Number of Plant Chambers for One
Person’s Oxygen
(with 500 µmol m-2 s-1 PAR and 0.75 RUE)
• VEGGIE (0.15 m2)
210
• Salad Machine (2.0 m2)
16
• Plant Module (10 m2)
3
A “Salad Machine” for Space Station and Transit Missions
MacElroy et al. 1992. Adv. Space Res.
One Human’s Oxygen from 11 m2 of Wheat !
Edeen and Barta. 1995. JSC No. 33636
Harvest Index (%) Ranges for Some Crops*
If inedible biomass recycled aerobically, this will consume some O2.
Hence high harvest index plants benefit gas exchange for life support
30 40 50 60 70 8020
Peanut
Rice
Cowpea
Radish
Sweetpotato
Spinach
Lettuce
Wheat
Tomato Potato Beet
* Data gathered from controlled environment tests at KSC Breadboard Project
and CELSS literature.
Oil Seed
Brassica
Soybean
Wheeler, 2004. Acta Hort.
Role of Bioregenerative Components
for Future Missions
Short Durations Longer Durations Autonomous
(early missions) Colonies
Bioregenerative
Stowage and Physico-Chemical
~1-5 m 2 total ~10-25 m 2 / person ~50 m 2 / person
Plant Growing Area
Wheeler, 2004. Acta Hort.
Conclusions
• Bioregenerative life support components will likely expand as
mission distances and durations increase.
• Near-term missions can benefit from the production of fresh
foods to supplement the crews’ diet.
• Contributions of plants to O2 production and CO2 removal will
be minimal with small, food production systems.
• A plant production module in the range of 10 m2 could begin to
contribute to O2 production.
• The O2 production and CO2 removal by plants is strongly
affected by light.
• Radiation (light) use efficiency (RUE) is an important aspect to
plant performance in future life support systems. Levels up to
1.0 g biomass / mol of photons have been documented and
should be achievable.
Thank you!
Astronaut Steve Swanson
Harvesting Lettuce on the ISS
Light, Productivity, and Crop Area Requirements
0 10 20 30 40 50 60 70 80
Light (mol m-2 day-1)
Are
a R
eq
uir
ed
(m
2/ p
ers
on
)
0
5
10
15
20
25
30
Pro
du
cti
vit
y (
g m
-2d
ay
-1)ProductivityArea
0
20
40
60
80
100
120
140
Bright SunnyDay on Mars