**3.2 Waste Management:**

Types of waste (solid, liquid, gas) (organic and non-organic)

Sources of waste products (biological {human & animal} and
non-biological)

Collection, storage, and processing/disposal of waste products (Super
Critical Water Oxidation process )

Medical hazards associated with waste management

WASTE MANAGEMENT

Kira Bacal, MD PhD MPH

![](media/image1.jpeg){width="5.375694444444444in"
height="4.031944444444444in"}

Backdropped by Earth's horizon and the blackness of space, an unpiloted
Progress 14 supply vehicle departs from the International Space Station,
carrying its load of trash and unneeded equipment to be burned up in
Earth\'s atmosphere during reentry.
(http://www.nasa.gov/multimedia/imagegallery/image_feature_204.html)

**WASTE MANAGEMENT**

This chapter is designed to provide you with a basic understanding of
how wastes are handled in the spaceflight environment. Emphasis is
placed on understanding the sources and types of waste and their
potential effects on crew health. The chapter will also review how
wastes are collected, processed, stored, and/or discarded, as well as
the design considerations for both spacecraft hardware and crew
procedures.

![](media/image2.png){width="5.993055555555555in"
height="4.404861111111111in"}

Figure 1: This diagram shows the flow of recyclable (\"regenerative\")
resources in the Space Station\'s Environmental Control and Life Support
System (ECLSS).

**Waste Management**

**Types of waste**

Have you ever lived through a garbage strike or faced a delay before
Housecleaning came to a room in your emergency department, office, or
hospital? For most of us, the items we casually toss in the trash seem
to disappear magically, thanks to the garbage collection services at
home and work. Take a moment to think of the wide variety of things that
you throw or flush away in your own household -- discarded napkins,
banana peels, torn clothing, crumpled paper, used Kleenex... Now
consider the issue on a spacecraft, where there is no garbage pickup. In
the microgravity environment, your trash tends to stay with you -- even
contaminating the air you breathe, since the lint, dust, hair, eraser
rubbings, and all the other things we sweep off our desks or brush off
our clothing will not drop to the ground, but rather remain floating
around your person.

![](media/image3.jpeg){width="2.2916666666666665in"
height="1.7486111111111111in"}

Figure 2: Trash piling up during a Chicago sanitation workers' strike
(http://www.cnn.com/2003/US/Midwest/10/09/garbage.strike.ap/)

It is thus imperative for a spacecraft's environmental control and life
support system (ECLSS) to be able to handle all types of waste, be they
solid, liquid, or gaseous. Such waste accumulation also presents
considerable vehicle storage and crewmember handling challenges.

As occurs lamentably often in history, previous lessons were forgotten
when the ISS was designed and launched, and the experiences in trash
handling gained aboard the Mir and Skylab space stations were not
utilized. Instead, it was erroneously assumed that Shuttle flights would
be adequate to remove any and all accumulated waste from the ISS, though
little attention was in fact directed to the issue. It was even unclear
what types and number of waste stowage bags had been manifested.

The problem of waste accumulation, handling and disposal quickly became
so acute on ISS that NASA established a team tasked solely with
developing an ISS Trash Plan (SSP 50481), including procedures for the
management of ISS waste. This also included ground-based processing of
the Shuttle-returned trash at Kennedy Space Center which must comply
with OSHA regulations. For example, before ISS Expedition 1, there was
no flight rule to prevent the stowage of trash with food. In addition to
relearning the lessons from Skylab and Mir, NASA also sought help from
the US Navy's handling of trash on submarines. The Navy views trash in
this context as such a significant issue that the Chief of the Boat
(COB), who is responsible for habitability, sets the cleanup policy for
the vessel and has direct access to the captain.

The ISS Trash Plan included development of a label which could be
attached to a trash bag to enable the crewmembers to identify its
contents once the bag had been sealed, an issue that had not been
identified pre-flight.

![](media/image4.wmf)Figure 3: An ISS trash label.

Perhaps the most dangerous (at least in the sense of rapidly hazardous)
contaminant is the carbon dioxide produced by the crew. As described in
a previous lesson, CO~2~ levels can build up quickly, endangering crew
health and safety. The ECLSS system must utilize ventilation fans and
lithium hydroxide filters to maintain safe levels. Other airborne
(though not necessarily gaseous) contaminants that the system must
control include particulate matter (things like dust or nail cuttings),
trace contaminants (from off-gassing materials), biological compounds
(such as aerosolized droplets and bacteria from a sneeze), and
odors[^1]. Liquid wastes include urine, sweat, hygiene water (i.e. water
used for washing), and effluent from payload experiments. Solid wastes
include not only feces but also food refuse and non-biological waste,
from paper to metals.

Biological solid waste, such as those from food, are generally not
stable, as they contain 40-90% moisture and soluble organic compounds.
As a result, these wastes cannot be stored for extended periods, because
they will decompose, leading to the growth of undesirable anaerobic
microorganisms (which could pose a threat to crew health), produce
noxious gases (including N~2~O, NH~3~, H~2~S), and create foul odors
from volatile fatty acids. Unfortunately, with the current limitations
to ISS operations, this is an unavoidable fact of life. While the
Shuttle is grounded, waste can only be disposed of via Progress
vehicles. This has exacerbated the difficulties with waste stowage
already present on the ISS. Imagine if you could only have your trash
picked up once every three to six months and even then you could dispose
of only a small proportion. The ISS Trash Plan allocates a minimum
dedicated stowage volume for the accumulation of waste and trash of no
less than 75 cubic feet. This volume equates to 25 days of trash volume
for a crew of 3 based on a production figure of 1 ft^3^/day/crewmember.

In addition, wastes may be in mixed form (such as "semi-solid"), and
they may be handled by more than one ECLSS system, as when water
condensed from the ambient air by the atmosphere-management system is
then sent to the water-processing system for final disposition. Life
support designers must also take into account the need to conserve
resources wherever possible. Particularly on long duration and
exploration missions, wastes must be recycled and/or reused, and this
imposes requirements on how wastes are categorized and handled. For
example, liquid waste from food preparation might be able to be re-used
for hydroponics projects and should therefore be captured and stowed
separately from liquids contaminated by toxic chemicals, as might result
from certain payload experiments. Composting, the process of
accelerating decomposition in an aerobic environment, is also being
explored as an option for safely handling biological wastes.

![](media/image5.jpeg){width="3.0in" height="2.441666666666667in"}

Figure 4: Plant researchers at Kennedy Space Center's hydroponic Biomass
Production Chamber prepare to harvest a crop of lettuce.
(http://www.hydroponics.com.au/back_issues/issue58.html)

**Sources of waste products**

The following table, taken from [Human Spaceflight: Mission Analysis and
Design]{.underline} Chapter 17 "Environmental Control and Life Support
Systems", lists several types and sources of wastes in the spaceflight
environment.

  ----------------------------------- -----------------------------------
  **Waste Category**                  **Waste Sources**

  Liquid, biological, decomposable    Hygiene water, metabolic water,
                                      respiration/transpiration water,
                                      urine, liquid feces

  Solid, biological, decomposable     Solid feces, waste with bound
                                      water, solids from
                                      urine/sweat/hygiene water, clothes

  Gaseous, metabolic                  CO2, trace gases, methane

  Liquid, nonrecoverable              Medicines, payload/experiment
                                      products or effluent

  Solid, nonrecoverable               Spare parts, plastics, metals
  ----------------------------------- -----------------------------------

In short-duration missions, recycling is less of an issue, and wastes
can simply be collected in order to ensure they do not impair crew
health and performance. As mission length and distance from Earth (and
therefore the resupply chain) lengthens, more attention must be paid to
the ability to gain the maximum use from everything. On exploration
missions, such as Mars missions or Moon bases, the crew may grow some of
their own food themselves. This will create large amounts of inedible
plant material for the waste management system to handle, along with
additional liquid and gaseous wastes. A wider variety of microorganisms
may also exist, as a result of the more diverse organisms, and this
could require additional filtration systems to maintain air and water
purity. At the same time, the waste management system will grow in
complexity as other, recycled wastes will need to be diverted to the
growth chambers.[^2]

Particularly for exploration class missions, another category of waste
must be considered: contaminants from the external environment, such as
moon dust. The habitats used by crew on lunar and martian missions will
need to have systems, such as forced air blowers, sticky strips, or
other devices to remove any such "pollutants" from an astronaut's suit
or tools and to dispose of them in a safe manner. In addition, there is
a desire not to contaminate the external environments with terrestrial
compounds. For example, studies into the possibility of life (past or
present) on Mars could be confounded if terrestrial bacteria were
carried from a habitat module into the larger martian environment.
Accordingly, the waste collection and disposal system will likely be
used by astronauts as they leave the base, as well as when they reenter
it, creating (potentially) twice as much waste material of two very
different kinds, endogenous to the habitat and exogenous.

![](media/image6.jpeg){width="4.874305555555556in"
height="3.2493055555555554in"}

Figure 5: Dust is kicked up by the lunar rover during an Apollo mission.

Although external contamination is not seen as such an important issue
for missions to low earth orbit, even these can have the risk of outside
contaminants, as was seen during STS-98, when an EVA crewmember became
covered in ammonia crystals during the connection of the US Lab module
to the rest of the ISS. The EVA crewmember was safe, of course, but
there was great concern that upon reentry, ammonia remaining on his suit
could contaminate the cabin atmosphere and jeopardize the intravehicular
crew. A multi-step protocol designed to clean his suit was followed, and
there were no difficulties, but spacecraft designers and flight surgeons
must realize that waste management systems may be called upon to handle
more than the anticipated compounds; in the above case, the atmospheric
system might have needed to remove ammonia from the air, as well as the
more routine CO~2~, water vapor, and odors.

**Medical waste considerations**

Medical waste falls into a special category, as it can be more hazardous
to the crew than other wastes. To date, there have been very few cases
of illness (other than rare cases of Space Motion Sickness) in which
crewmembers have generated large amounts of medical waste. Eventually,
however, this "lucky streak" will end, and someone will become seriously
ill or injured and produce a large amount of medical waste. This could
be in the form of vomit, sputum, blood, teeth, diarrhea, or any other
potentially contaminated body fluid. As anyone who is familiar with an
emergency department is aware, bloody spillage is difficult to manage
and requires significant protective measures to be taken. Now imagine an
ER where waste products can float away or be suspended in mid air.
Microgravity significantly magnifies the problems associated with
medical waste and caregiver protection.

Currently, there are limited supplies for personal protection and
cleaning: latex gloves, alcohol pads, soap, bandages, etc.
Unfortunately, in the event of a serious medical event, these supplies
will quickly run out, and the crew may therefore be exposed to
biological hazards. For example, the ISS has a ventilator and
endotracheal tubes, so intubation is a possibility. Unfortunately, there
is no medical suction apparatus available for endotracheal suction, as
all such terrestrial devices make use of gravity to separate the air and
fluids. In the absence of such a device, improvised materials, such as
using a Foley catheter, will be needed, increasing the possibility for
unintentional release of biological materials into the cabin.

![](media/image7.jpeg){width="3.0in" height="2.0in"}
![](media/image8.jpeg){width="2.7098425196850395in"
height="2.6720472440944882in"}

Figure 6: At left, an IV bag in microgravity shows the lack of air-fluid
separation. At right, a picture of the ventilator currently flown on the
ISS

There is also the question of what to do with any medical samples. The
current ISS blood analysis device, the iStat Portable Clinical Blood
Analyzer, only uses a few drops of blood, which is wicked into a
self-contained cartridge. If longer duration missions have expanded
laboratory facilities, though, additional attention to the question of
discarded samples will be needed. Another question (that has to date
been largely avoided) is what to do in the event of a death on orbit.
Leaving aside the questions of how death would be ascertained and
declared, what effects such an event would have on the other crew
members, the impact for the mission, and other such matters, there
remains the issue of what to do with the remains. Are they to be
returned to Earth? While that might be feasible -- albeit unpleasant --
on the Shuttle, the tight quarters of the Soyuz make it much more
difficult to transport a body. And what about longer duration missions?
Even if a crewmember's death were to force the abandonment of the
mission, the time required to return to Earth might be too long to
permit the transport of an unpreserved cadaver. At present, there is no
procedure to handle a death on orbit.

![](media/image9.jpeg){width="1.2118055555555556in"
height="2.3756944444444446in"} ![](media/image10.jpeg){width="2.25in"
height="2.25in"} ![](media/image11.jpeg){width="2.123611111111111in"
height="2.123611111111111in"}

Figure 7: Images of (from left) the Portable Clinical Blood analyzer,
loading a typical sample, inserting the test cartridge into the machine
(http://www.amedical.com/istat.html)

**Collection, storage, and processing/disposal of waste products**

Generally speaking, waste collection is designed to be as simple for the
crew as possible. In some cases, crew members merely place the refuse in
a container and stow it. In other cases, the waste may be automatically
collected and stored, as is the case for the toilet appliance. In all
cases, however, the limited stowage space remains an issue which drives
disposal of the wastes.

On the short-duration Shuttle missions, "regular" trash is collected,
compressed into as small a volume as possible, and stowed for disposal
following return to the ground. Wet trash is defined as all items that
could off-gas and cause unpleasant smells. Overall, four trash
containers are located in the Shuttle\'s crew compartment (3 for dry
trash and 1 for wet trash). Each trash container has a trash liner
placed inside. If the liner becomes full, it is closed with a velcro
strip, removed and stowed in a stowage container below the middeck
floor. There are separate stowage containers for dry and wet. The wet
trash container is airtight, closed by a zipper and connected to the
waste management system by a venting hose. During stowage, developing
gases are vented through this hose, which helps to control odor
development inside the crew compartment. Overall, 8 ft^3^ of wet trash
stowage is available under the middeck floor. All wet and dry trash is
returned to earth for disposal. For longer duration missions, however,
this is obviously impractical.

![](media/image12.jpeg){width="1.5263888888888888in"
height="2.7506944444444446in"}
![](media/image13.jpeg){width="2.6756944444444444in"
height="2.6756944444444444in"}

Figure 8: At left, astronaut Kent V. Rominger uses an age-old trash
compacting method on the Space Shuttle. At right, a "football", trash
wrapped in plastic and duct tape, is an acceptable method of waste
storage for short duration Shuttle flights, but not for longer duration
station or exploration missions.

(http://liftoff.msfc.nasa.gov/News/2001/News-Housekeeping.asp)

Rather, the ISS crew collect trash in much the same way as Shuttle
crews, but then they remove it from the station either by sending it
back to Earth with a visiting Shuttle crew, or by placing it into a
Progress rocket which has delivered new supplies and will subsequently
burn up upon reentry. The hiatus in Shuttle flights has exacerbated
problems with this approach, however, and trash has built up
significantly.

For waste material that the crew should not handle for reasons of health
or safety, the appropriate systems usually collect and package the waste
automatically. One frequently asked question has to do with the handling
of biological wastes -- how do astronauts go to the bathroom? Generally
speaking, most current systems, Russian or American, work the same way:
as wastes exit the body, they are drawn away by a stream of air and
captured by the toilet.

The first American in space, Alan Shepherd, was given no toileting
options. Since his flight was only scheduled to last 15 minutes, this
oversight on the part of the ship designers and his flight surgeons can
perhaps be excused, but a lengthy delay prior to launch forced him to
urinate in his suit (which had the unwelcome side effect of compromising
his EKG electrodes). Later astronauts wore incontinence pads, similar to
adult-size diapers, until later, longer flights came along. For these
flights (through Apollo 12), a condom catheter-like device was used for
urination, with the urine passing through a valve and into a collection
bag, which could then be vented overboard. One problem with overboard
dumping was the resultant "haze" of ice crystals which could stay around
the spacecraft for some time afterwards; because of this, dumping did
not occur during mission critical phases of flight.

For defecation on these flights, the astronaut first had to secure a
plastic bag around his anus, and use a built-in finger cot to move the
stool further into the receptacle. When defecation was complete, he
removed the bag and cleaned the area with tissues that were then placed
in the bag. Because feces could not be dumped overboard as the urine
was, it had to be carried back to Earth for disposal. Accordingly, the
astronaut had to squirt a germicide into the bag, seal it, and knead the
contents together. The bag was then placed into a second bag in case of
leaks, formed into the smallest volume possible, and stored for
transport to Earth. This method was universally despised by the crew and
invariably led to soiling of the crew and environment, despite all
possible care. In addition, the process was time consuming, requiring up
to 45 minutes.

![](media/image14.jpeg){width="2.7506944444444446in"
height="2.102777777777778in"}

Figure 9: Apollo era fecal bag
(http://history.nasa.gov/SP-368/s6ch2.htm)

Although the lack of toilet facilities during launch and landing still
require crewmembers to wear "adult diapers" during those phases of
flight, during the rest of the mission Shuttle and ISS crewmembers have
an actual toilet. The Shuttle version is known as the WCS (Waste
Collection System) and is located immediately aft of the ingress and
egress side hatch. The compartment door is used as the ingress platform
when astronauts crawl into the orbiter before launch (the vertical
position of the orbiter on the launch pad makes the rear wall the
floor). When it is used during flight, its door is opened and two
curtains, attached to the top and the side of the door, are deployed to
provide privacy. The WCS is actually a multi-functional system used to
collect and process all biological wastes. The main function of the
system is to collect and store fecal wastes and to process urine and
transfer it to the waste water tank. It also processes condensate and
waste water from other Shuttle systems. One of the first tasks of the
astronauts after reaching orbit is to activate the WCS for operations.

Technically, the WCS consists of a commode, urinal, fan separators, odor
and bacterial filter, vacuum vent quick disconnect, and controls. The
commode that processes the fecal wastes is 27 by 27 by 29 inches and is
used like a regular toilet. The WCS compartment also has many stowage
lockers located along the inside walls. These are stocked with towels,
washcloths, urinal funnels, wet wipes, dry wipes, tissues, disposable
gloves, and emesis bags. The back of the door has color coded rubber
grommets (four for each crewmember) to restrain towels and washcloths
used by the astronauts. For each day in orbit, a Shuttle astronaut
typically uses two washcloths (12 inches by 12 inches) and one towel (16
by 27 inches) for personal care. A water hose, located next to the
Shuttle\'s galley, dispenses water if needed.

The urinal is essentially a flexible hose with attachable funnels. Every
astronaut has a personal funnel, which are differently shaped for men
and women. The urinal can be used in either a \"standing\" position or
while the astronaut is \"sitting\" on the commode. Urine is collected in
a funnel, carried along by the airflow from the WCS fan-separator. The
air/urine is pumped through a flexible hose to a chamber below the
toilet seat, where an assembly of rotating vanes creates centrifugal
force that pushes the liquid to the walls of the chamber. The liquid is
drawn off to the wastewater tank under the deck, and the air returns to
the crew cabin after passing through an odor and bacteria filter. The
wastewater tank can be dumped overboard, just as it was in the earlier
days of the space program, though this is less frequently done nowadays.

To handle feces, the toilet has a cylinder system where a plastic bag is
placed in the toilet before use. Crew use two foot restraints and two
body restraints (bars positioned over the thighs) to position and hold
themselves on the toilet seat, ensuring a good seal with the contoured,
soft seat. The good seal is a requirement, ensuring that the toilet's
airflow will be able to draw the waste away. The hole for solid wastes
is only 10 cm (4 inches) in diameter, and crewmembers actually practice
positioning themselves on a toilet trainer before flight[^3]. A camera
placed within the toilet trainer, directly beneath the hole for solid
waste, allows them to see if they are positioning themselves correctly.

Feces enter the commode through the seat opening and are drawn in by air
flowing through holes under the seat. This downrushing airflow (850
L/min) substitutes for gravity in collecting and keeping the waste
material inside the commode. The wastes are then broken up by rotating
vanes and deposited along the walls in a thin layer. A hydrophobic liner
inside the commode prevents free liquid and bacteria from leaving the
collector. The plastic bag is then sealed, and a plunger attached to a
lever forces it to the bottom of the cylinder. A new bag is then placed
in the toilet for the next astronaut. When the cylinder is filled, it is
replaced by a new cylinder.

Because of the toilet's limited volume, toilet tissues are temporarily
placed in a small canister which is installed on the wall and later
moved to the wet trash compartment. When the astronaut is finished using
the toilet, he or she then opens a valve which exposes the solid waste
container to space, instantly freeze-drying the stool. During the
mission, it may also be necessary to compact the solid wastes to avoid
overflow.

![](media/image15.jpeg){width="2.9305555555555554in"
height="3.6145833333333335in"}
![](media/image16.jpeg){width="2.707638888888889in"
height="2.692361111111111in"}

Figure 10: Shuttle toilet
(http://www.abc.net.au/science/slab/shuttle/nature.htm and
http://lsda.jsc.nasa.gov/kids/L&W/hygiene.htm)

On the ISS, the ASU toilet used is in the Russian built Service Module
block. This looks like a more earth bound toilet that uses metal
containers. Prior to use, the containers are stored rather like empty
buckets, however once full they present considerable stowage and hygiene
issues.

![](media/image17.jpeg){width="3.375in" height="2.834722222222222in"}
![](media/image18.jpeg){width="2.1166666666666667in"
height="2.9159722222222224in"}

Figure 11: The ASU toilet at left. At right, as part of routine
procedures, cosmonaut Yury V. Usachev, Expedition Two mission commander,
changes out a solid waste container in the Zvezda/Service Module in
2001. (http://www.nasa.gov/missions/science/f_compost.html)

As described above, virtually all forms of waste disposal currently make
use of the Earth, both by returning some trash to the ground for final
disposal and by utilizing the atmospheric reentry to destroy other trash
in the Progress rockets. Unfortunately, these options are not ideal for
long-duration exploration missions, where Earth will not be available.
In these situations, waste will need to be reused or destroyed in more
efficient ways, so as not to take up valuable storage space.

**High efficiency waste destruction**

Rather than planning to create a garbage dump on the Moon or litter the
way to Mars by periodically jettisoning trash, NASA is investigating
other methods to dispose of wastes. Ideally, these would facilitate
reuse of whatever useful components remain.

Supercritical water oxidation process (SCWO) is one method under
investigation to destroy hazardous organic waste in a completely closed
system. It uses an oxidant in water at extremely high temperature and
pressure (374 C and 218 ATM). Under these conditions, organic molecules
can be rapidly and completely oxidized to CO2, water, and inorganic
salts, which could easily be recycled.

SCWO is currently being investigated as a way to dispose of terrestrial
toxic wastes, such as chemical warfare agents and solid rocket fuels, in
a safe manner. While the efficiency of the process makes it attractive
for use in space, the associated temperature and pressure that are
required may pose too great a hazard in such close quarters. However,
the development of a compact unit for use onboard US Navy ships may
overcome some of these design challenges and holds out hope for use of
the process even in the tight quarters of a closed environmental system.

**Medical hazards associated with waste management**

Any system of waste management has certain hazards and regulations
associated with it. Here on Earth, waste handling is regulated by OSHA;
while OSHA rules may not apply on the ISS, they are in effect when the
waste is offloaded from the Shuttle MPLM at Kennedy Space Center.
Depending upon the amount of contact the inflight or ground based crew
must have with the assembled wastes, there could be bacterial
contamination, sharp edges, and/or exposure to biohazards. As a result,
designers generally try to minimize the need for crew interaction with
the systems, making them as self-contained as possible.

On both the Shuttle and ISS, the galley and toilet are geographically
close to each other. In the event of an illness, therefore, good hygiene
could be compromised and food consumption areas contaminated. In the
Shuttle's cramped environs, there is no dedicated location where a sick
crewmember can be placed in order to avoid contamination of the rest of
the crew -- or merely to decrease what is often (particularly for
non-clinicians) the provocative stimulus of someone vomiting nearby.
These close quarters can thus pose both public health and performance
hazards.

![](media/image19.jpeg){width="3.280708661417323in"
height="2.1251968503937007in"}

Figure 12: Crew Medical Restraint System (CMRS) will be deployed in the
US Lab module and provide not only a place for ill/injured crewmembers
to be located but also the restraint straps necessary for caregivers.

The ISS, with its larger internal volume, does have a dedicated location
for casualties, complete with "bed" (in the form of a foldout,
electrically isolated crew medical restraint system). Interestingly,
however, the ISS medical system is based in the US Lab module, at the
other end of the station from the toilet facility. This suggests that if
someone is seriously ill, they may have to choose between having access
to medical supplies (including medical oxygen) or a toilet. Not only
will this increase the amount of care other crew members will have to
provide to a casualty, but it also creates additional challenges for
managing medical wastes.

In one oft-described case, the Shuttle toilet broke down, requiring two
crew members (including the commander) to break up the solid wastes by
hand in order to try to repair it and avoid an early deorbit or the use
of the always unpopular Apollo fecal bags. As unpleasant as such work is
in a terrestrial environment, it is infinitely worse in the confined
volume of the Shuttle, with the lack of gravity making any stray
particles instantly airborne.

When, as is inevitable, other plant and animal life exists in the
spacecraft, there will be additional wastes produced, both in terms of
quantity and types, with the associated new microbial flora as well.
This will further increase the hazards to crew health in the event of
improper waste management.

**References and Suggested Readings**

1\) Clement, G. (2003). [Fundamentals of Space Medicine. Space
Technology Library.]{.underline} El Segundo: Microcosm Press.

2\) Harding, R. (1989). [Survival in Space.]{.underline} London:
Routlege.

Office.

3\) Stine GH. (1997). [Living in Space: A Handbook for Work and
Exploration Stations Beyond the Earth's Atmosphere.]{.underline} New
York: M. Evans and Company.

4\) Larson WJ and Pranke LK (Eds.). (1999). [Human Spaceflight: Mission
Analysis and Design.]{.underline} New York: McGraw Hill.

5\) Nichols, M. (2001) "The Next Step: Mars or Bust", [Practical
Hydroponics and Greenhouses]{.underline}, issue 58,

http://www.hydroponics.com.au/back_issues/issue58.html

6\) NASA Research Award: Denitrification Composter to Stabilize Space
Mission Trash, http://lssc.ksc.nasa.gov/als/projects/nra.php

7\) Heiney A, "Not Your Back Yard Compost Heap", NASA Feature article,
http://www.nasa.gov/missions/science/f_compost.html

8\) Kneir, G. (2001) "Housecleaning in Space",
http://liftoff.msfc.nasa.gov/News/2001/News-Housekeeping.asp

9\) "Solid Waste Handling trade Study", Advance Life Support Systems,
http://advlifesupport.jsc.nasa.gov/documents/simaDocs/MSAD-00-0501.pdf

10\) "Guidelines and Capabilities for Designing Human Missions", NASA
Exploration Team, Human Subsystem Working Group (2002)
http://research.hq.nasa.gov/code_u/nra/current/NRA-02-OBPR-01/HSSWG.pdf

11\) Kruszelnicki, K. (2003) "Great Moments in Science: Space Toilet",
http://www.abc.net.au/science/k2/moments/s348188.htm

12\) "The History of Household Wonders: The Space Toilet",
http://www.historychannel.com/exhibits/hometech/spacetoilet.html

13\) "Hazardous Waste Destruction: Supercritical Water Oxidation",
http://demil.ga.com/haz/scwo-haz.html)

14\) Halvorson T. (2001) "Destiny Installed Despite Toxic Coolant Link",
Space.Com Spaceflight News,
http://www.space.com/missionlaunches/missions/sts98_eva1pm_010210.html

15\) Sauer RL and Jorgensen GK. (1975) "Waste Management System" in
[Biomedical Results of Apollo]{.underline} SP-368, Johnston RS, Dietlein
LF, and Berry CA (Eds), http://history.nasa.gov/SP-368/s6ch2.htm

[^1]: The effect of odors should not be underestimated in the relatively
    confined environment of spacecraft. Cases of flatulence or
    gastrointestinal distress can, particularly on the crowded Shuttle,
    create a highly unpleasant atmosphere for the entire crew and, at
    the very least, affect morale. Even in the absence of illness, odors
    tend to build up in the small environment, albeit usually so
    gradually that the crew do not recognize them. However, ground
    personnel who are among the first to enter the Shuttle following
    landing and wheel stop have often commented upon the strong odor in
    the cabin even after relatively short duration missions.

[^2]: In order to obtain the maximum possible use of hydroponically
    grown plants, efforts are underway to use exogenous enzymes to break
    down normally inedible compounds, like cellulose, into more simple
    sugars that humans can digest. If a human could obtain nutrition
    from more of the biomass (as, say, a rabbit can) then in situ
    agriculture would be much more efficient and it would reduce the
    amount of vegetative waste produced.

[^3]: A video showing proper use of the Shuttle toilet can be found at
    the website: http://edspace.nasa.gov/text/livespace/gottago.html
    Please note: The video is intended for use by schoolteachers, not
    clinicians.