Life Support Systems
Section 4.3.5.
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Biological Recycling

This document outlines the proposed biological recycling scheme for the Artemis moonbase. The timespan covered starts with the arrival of the greenhouse on the second flight, and continues until the habitat becomes large enough to support a self-balancing ecosystem.

This is a purely qualitative analysis, and does not delve much deeper than a basic outline of the whole system. Crop types, air purity requirements, diet and so forth are discussed elsewhere.

Why Artemis Is Not Like Biosphere II

While much can be learned from Biosphere II, very little will be applicable to Artemis until power reseves and spare habitable volume are high. Biosphere II was designed as an experimental ecosystem enclosing an enormous area, holding hundreds of tonnes of biomass and water, supporting only 6 humans who did nothing but tend the farm, and was supplied with an external, regular 12/24 light cycle.

Our initial base will have perhaps a tonne or so at best of biomass, an enclosed area perhaps one half that of Biosphere II, a few of tonnes of water which will also be required for power storage, and a light cycle which consists of 14 continuous days of light and intense heat followed by a similar period of absolute dark and extreme cold.

Reclaiming Wastes

While our air could be recycled using chemical techniques, we need to recycle the human organic wastes into food. Instead of composting (which locks up recycled materials and creates waste gas), the energy of the sun is used to break down the wastes -- together with any pathogens and compounds that would otherwise accumulate in the system like dioxins -- into carbon dioxide and the components for chemical fertilizers.

The sun's energy is then used to form ammonia- and nitrate-based fertilizers from the waste gasses, furnace ash, and some hydrogen produced by electrolysis of water. Nothing is wasted. Excess oxygen from the electrolysis is introduced to the atmosphere, possibly supplementing the plants during the lunar night when lamps are used. The fertilizers are used to feed the plants hydroponically while they convert the carbon dioxide into oxygen and food.

As the solar furnaces have to shut down at night, "night soil" needs to be stored until daybreak. Dumped in external tanks as sludge, it will freeze, halting biological activity. Come daybreak, it will be defrosted and processed. This temporary shutdown prevents some carbon dioxide from being returned to the generator, compensating for the reduced efficiency of the plants under lamps.

Water Reclaimation

Water is recovered by distillation of the human and plant wastes, extraction from the air via air conditioning, and as a byproduct of burning the solid wastes with excess oxygen. As the furnaces shut down at night, our water storage system has to cope until daybreak. Some potable water will be produced by power generation, but that may be better left there. The water can be stored as "grey" water -- water good enough to bathe in once irradiated with UV light, but probably not quite good enough to drink. Potable water is produced by passing grey water through a reverse osmosis filter. This presents a physical barrier to pathogens and contaminants, providing safety and greater confidence to the users.

While the flowchart below may seem complex, this is a full, closed-cycle environmental system. Consideration needs to be given to duplicating vital components, possibly making sure that one part has several uses so that a working part can be shunted around the system in an emergency. As well as mechanical problems, there are potential biological upsets which could be catered for by using independent greenhouse systems with crops that will tolerate each other's diseases.

Waste processing flowchart

Life Support Systems

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