Mars Homestead – Waste Recycling Systems August 12, 2005 Mars Society Convention Presented by:...

August 12, 2005 Mars Society Convention

Mars Homestead – Waste Recycling Systems

Presented by:

Gary C. FisherTreasurer – The Mars FoundationSteering Committee – The Mars Society

[email protected]

Introduction



Mars Homestead Project seeks to develop a unified plan for building the first (mostly) self-sufficient settlement on Mars by exploiting local materials.Initially housing a population of 12.Population doubling every 2 to 4 (Earth) years. The goal is to prototype the entire initial settlement on Earth.

Introduction


Mars Homestead – Waste Recycling SystemsIntroduction



We want to take this barren Martian world

Introduction



And establish a civilization!

Introduction



Settlement Exterior

Settlement Design



Base Components

Settlement Design



Greenhouses & Recycling Area



Close up of Recycling Areas



B-B Cross Section Thru Greenhouse and Kitchen


Mars Homestead – Waste Recycling SystemsTwo level greenhouse


Mars Homestead – Waste Recycling SystemsOverview

The Waste Recycling System (WRS) consists of two major components:

An Ecological Processing Unit (EPU) that combines biological with various physiochemical systems to process gray water and,

A Composting System (CS) designed to process feces, food waste, inedible/unusable plant material, paper,

biodegradable plastics, and material collected from agricultural and aquaculture filtration systems.

All other waste products, including industrial process, medical, and laboratory waste are handled by other means.



Guiding Principle:

“There is no such thing as waste, there are only resources we are too stupid to know how to use.”

Arthur C. Clarke – to Walter Cronkite during launch of Apollo 13



For design purposes gray water is defined as the collected water from:

cleaning, clothes washing, showers, kitchen and lavatory sinks, and urinals.

It is expected to contain some amount of feces dissolved in the water used in the cleanup process after defecating and from the laundering of EVA suit diapers.

There are lavatories near the crew quarters that will receive the most use, that include showers, and have at least 4 toilets.

A sink and toilet will be adjacent to each main airlock.



The output of the composting system is used to make “composting tea” by percolating the treated gray water through finished compost to provide a leachate derived nutrient solution to the agricultural area.

It is expected that what remains from the composting tea making process will be mixed with Martian regolith to create a soil for soil-based agriculture at a later date, potting soil for plants distributed around the settlement, and other uses.

One of the essential uses will be the construction of air biofilters from mature compost.


Mars Homestead – Waste Recycling SystemsMAIN FUNCTIONS OF THE WRS

The primary function of the WRS is to provide an ongoing supply of agricultural water; and to recycle nutrients from the waste stream to agricultural production providing day-to-day independence of these processes from the well water supply and the need to add nutrients.

The secondary function of the WRS is to provide short-term availability of potable water in the case of loss of the ability to send humidity condensate through the primary water treatment system or an inability to produce water from the well.

The tertiary function of the WRS is to augment the agricultural area in the production of food and non-food plant and animal products.


Mars Homestead – Waste Recycling SystemsPOTABLE WATER REQUIREMENTS

From a macro-perspective the potable water availability to the inhabitants is predicated upon the water demands of the agricultural areas which are predicated upon the food and inedible plant requirements of the inhabitants.

The greenhouse area is assumed to contain of 880 m2 of growing area:

Two areas for food crops in opaque hydroponic greenhouses, Two areas for food crops in transparent hydroponic greenhouses, One area for non-edible crops in a separate opaque soil-based

growing space adjacent to the dining/meeting space.

In addition there are two greenhouse support areas in cylindrical pressure vessels of 30 m2 with a connecting circular pressure vessel of 10 m2.



The water flow to the greenhouse is dictated by the evapotranspiration rate of the greenhouse combined with the incorporation of water into growing biomass.

The major source of demand variation is the activation and deactivation of growing areas within the greenhouses.

The water demand for the greenhouses – both food and nonfood - is calculated to average 2710 L/d.

The evapotranspiration rate is assumed to average out to 3.0 L m2 /d.

The result is a total water requirement from evapotranspiration of 2640 L/d.

Both the crop selection, maturity, and other factors such as heat generated from the lighting (High Intensity Discharge (HID) lighting is assumed), and greenhouse atmospheric pressure all influence the evapotranspiration rate.



Fresh biomass harvested each day is assumed to be 91.89 kg/d.

Plant material is approximately 85% water by weight we assume a daily water demand from incorporation into plant biomass of 78.10 kg (78.10 L).

Biomass water is recovered from the composting process as an evaporate, and from urine for eaten biomass.

Combining the evapotranspiration demand with the incorporation into biomass demand results in an average total daily greenhouse requirement of 2710 L/d.

All harvested biomass, with the exception of that used in construction or manufacturing, is eventually converted to compost, and the water component is mostly returned to the atmosphere of the settlement.

Therefore humidity corresponding to something less than, but close to 2710 L/d is available to be condensed from the atmosphere to provide a source for a daily potable water supply.



We assume that 10 L/d of water is removed either by leakage, incorporation in stored compost, or incorporation in plant materials used in construction and manufacture.

This 10 L is the daily makeup requirement from the primary water source (the well) to maintain agricultural operations.

This water demand of the greenhouse is large enough to translate into a generous daily potable water supply to the inhabitants of an equivalent amount of

2710 L/d or 226 L CM-d (60 gal CM-d) for a crew of 12.

If low-heat lighting is used for the greenhouse, e.g., LEDs, the evapotranspiration rate may be closer to 2 L m2/d that would still translate into a comfortable

147 L CM-d (39 gal CM-d).



Fig. 1 - Settlement Non-industrial Water Stores

Humidity in settlement atmosphere 38.4 L

Settlement volume approximately 4000 m3

WRS PotableWater Tank

#110,000 L


#210.000 L


#310.000 L

Potable Water Store 90% full

WRS Pre-process Gray Water Store 66% full

WRS Post-process Water Store 33% full

WRSOutflow Storage

Tank10,000 L

Harvestedplant biomass

? LStored Food

? L

Harvested Biomass water content

Greenhouse Water Stores 66% full

Nutrient Tank8,000 L

IrrigationWaterTank

8,000 L

AquacultureTanks 4 @2,000 L

Growingplant biomass

? L

Misc. Water Stores: Plumbing, Rovers, Beverages, etc.

Approx. 2,000 L

EPU Water Store 100% full- One Path of Two

EPU Tank #5Algal turf scrubber

250 LEPU Tank #3

TricklingFilter

EPU Tank #2Trickling Filter

Reservoir3,000 L

EPU Tank #4Turf Scrubber

Reservoir1,500 L

EPU Tank #7Aerobic3,000 L

EPU Tank #9Ozone/UV

Column200 L

EPU Tank #6Aerobic3,000 L

EPU Tank #1WRS Inflow

GrayWater Tank10,000 L

EPU Tank #8Clarifier3,000 L

Treatment Wetland

Approx. 20,000 L


Mars Homestead – Waste Recycling SystemsTHE ECOLOGICAL PROCESSING UNIT

In normal day-to-day operations the WRS is not the primary source of potable water. The initial supply of all water is assumed to be a well producing 38 L/min primarily for O2 and H production and industrial uses.

All water extracted from the well is treated by passing it through a filtration and treatment system which will likely incorporate filtration, a large Reverse Osmosis (RO) unit and/or a deionization (DI) unit and possibly ozone and UV treatment systems.

During initial operation of the well the starting inventory of water is collected within two large tanks and for non-industrial use is accumulated within the various water stores of the settlement.


Mars Homestead – Waste Recycling SystemsFig 2 - EPU Flow Diagram

WRS PotableWater Tanks

3 @10,000 L

WRSOutflow Storage

Tank10,000 L

Nutrient Tank8,000 L

IrrigationWaterTank

8,000 L

AquacultureTanks 4 @2,000 L

Tank #5Algal turf scrubber

250 L

Tank #3Trickling

Filter

Tank #2Trickling Filter

Reservoir3,000 L

Tank #4Turf Scrubber

Reservoir1,500 L

Tank #7Aerobic3,000 L

Tank #9Ozone/UV

Column200 L

Tank #6Aerobic3,000 L

Tank #1WRS Inflow

GrayWater Tank10,000 L

Tank #8Clarifier3,000 L

5 micronfilter

Potable Water Uses:LaundryCleaning

Food PreparationDrinkingShower,

Etc.

Ozone GeneratorInjector

GREENHOUSE

Condenser/RO + Makeup WaterTo Condenser/RO

Sludge to CS

Spent Sand to CS

P1

P2P3

P8

P4

P5P6

P7

COMPOST SYS

FilterThru

Compost


Mars Homestead – Waste Recycling SystemsTHE ECOLOGICAL PROCESSING UNIT

The function of the EPU is to:

• extract salts, • convert ammonia to nitrate, • reduce dissolved solids, • and degrade organics such as hair, soap, hormones in the urine, and food waste from kitchen utensil cleaning.

• The EPU has the capacity to extract heavy metals and other pollutants which would slowly build up in the water if the RO unit was not functioning. The build up of toxins such as metals, pesticides and other man-made chemicals will be far less likely than occurs on Earth. Water contact with the materials involved in its transport and processing are the only real sources for such pollutants. This needs to be considered when selecting materials.


Mars Homestead – Waste Recycling SystemsTHE COMPOSTING SYSTEM

The bulk of the material to be handled by the composting system is the unusable (inedible plus that which has no other use) biomass produced by agricultural operations and wastewater recycling in the EPU.

In most cases the majority of the nutrients required for agriculture, other than carbon, nitrogen and phosphorus, are contained in the unusable biomass.

When plant material is ingested most of the carbon, nitrogen, and phosphorus is assimilated, metabolized, and excreted as urine – containing nitrogen and phosphorus – or exhaled as CO2.



The production rate of fecal material is, by weight, about one tenth that of inedible biomass associated with the food consumed.

For a short duration stay on Mars it might make sense to merely incinerate the fecal material, but since the duration time of the Mars Homestead Project is long and indeterminate, the nutrient content of fecal matter must be recovered.

The best way to recover this from the standpoint of energy consumption and agricultural use is to compost the feces.

The assumed nominal rate of fecal matter production is 0.032 kg/CM-d dry matter plus 0.091 kg/CM-d of water, or 1.476 kg/d for a population of 12.



Compost Material Daily rate for population of 12, kg

Fecal Matter 1.476

Inedible biomass dried to 50% water 7.380

Unusable biomass dried to 50% water 0.231

Food waste, preparation waste 1.771

Biodegradable Paper, packaging, plastic 1.360

Aquaculture waste dried to 50% water 1.800

TOTAL 14.018



Nutrients have been shown to be easily leached from dried plant material; however, phytotoxic effects can occur unless there is degradation of unstable organic material in the leachates. For this reason the proposed system combines the composting of inedible biomass with human waste.

Composting is effective in addressing the phytoxicity issue if retention times of greater than 21 days are used.

Thermophilic composting will reduce pathogens.

The only dependable method of effective and total pathogen inactivation, including the most resistant helminthes (intestinal worms such as Ascaris (roundworm) eggs and all other bacterial and viral pathogens) is heat treatment to a temperature of 55 to 60°C for several hours. Thermophilic composting, properly done, can reach these sterilizing temperatures without the addition of externally supplied heat.



The aerobic processes which generate the heat consume oxygen, however, it has been found that it more effective to remove heat by on demand thermostatically controlled ventilation to ensure that maximum temperatures do not exceed 60°C than to attempt to maintain a correct oxygen level within the compost.

This system of heat removal in reference to temperature is known as the Rutgers strategy and is recommended for this system.



Soluble nutrient recovery from compost is less than 100 percent, particularly for P, Mg, and Ca.

By extending the agriculture from hydroponic to substrate based systems more complete recovery can be achieved.

The feasibility of this will depend upon the availability of a suitable Martian regolith (e.g., free of toxic materials) with which the compost can be mixed to create a soil.

Mushroom farming, which requires no light and cool temperatures, would be the logical first use of such a material.



Push flush lever.

This activates a fan that will cause air to be drawn into the compost bin and out through an activated carbon filter through a vent pipe that discharges into the greenhouse.

This thermostat controlled fan cycles on and off to draw oxygen rich ventilation air into the compost bin as needed through a one-way valve, however, during the flush cycle the fan always comes on.

The sealing trapdoor at the bottom of the toilet, on which the feces lays, swings down.

The feces slide off the sealing trap door into the compost bin. To assist the feces dumping a squeegee is automatically wiped across the

door while simultaneously squirting a supply of water. A minimal water amount is always used, but additional water may be used if

sensors indicate the compost is too dry. A measured amount of dried biomass/sand mix is dropped from the hopper

into the compost bin. The trap door in the toilet shuts.

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