Abstract
AbstractWater scarcity in hot deserts, which cover about one-fifth of the Earth’s land area, along with rapid expansion of hot deserts into arable lands is one of the key global environmental problems. As hot deserts are extreme habitats characterized by the availability of solar energy with a nearly complete absence of organic life and water, space technology achievements in designing closed ecological systems may be applicable to the design of sustainable settlements in the deserts. This review discusses the key space technology findings for closed biogenerative life support systems (CBLSS), which can simultaneously produce food, water, nutrients, fertilizers, process wastes, and revitalize air, that can be applied to hot deserts. Among them are the closed cycle of water and the acceleration of the cycling times of carbon, biogenic compounds, and nutrients by adjusting the levels of light intensity, temperature, carbon dioxide, and air velocity over plant canopies. Enhanced growth of algae and duckweed at higher levels of carbon dioxide and light intensity can be important to provide complete water recycling and augment biomass production. The production of fertilizers and nutrients can be enhanced by applying the subsurface flow wetland technology and hyper-thermophilic aerobic bacteria for treating liquid and solid wastes. The mathematical models, optimization techniques, and non-invasive measuring techniques developed for CBLSS make it possible to monitor and optimize the performance of such closed ecological systems. The results of long-duration experiments performed in BIOS-3, Biosphere 2, Laboratory Biosphere, and other ground-based closed test facilities suggest that closed water cycle can be achieved in hot-desert bioregenerative systems using the pathways of evapotranspiration, condensation, and biological wastewater treatment technologies. We suggest that the state of the art in the CBLSS design along with the possibility of using direct sunlight for photosynthesis and recent advances in photovoltaic engineering can be used as a basis for building sustainable settlements producing food, water, and energy in hot deserts.
Highlights
The general idea of using the closed-system bioregenerative life support technologies developed by space life support (SLS) to improve Earth's environment was formulated by Nelson et al (2003a) on the basis that the SLS science simultaneously addresses the problems of food, water, clean air, and energy supply
The productivity of higher plants in closed biogenerative life support systems (CBLSS) as a function of incident PPF is determined by the efficiency of four physiological processes: absorption of PPF by photosynthetic tissue, carbon fixation evaluated by photosynthetic efficiency, growth respiration evaluated by respiratory carbon use efficiency, and carbon partitioning evaluated by harvest index (Bugbee and Salisbury, 1989; Bugbee, 1992)
The review presented above shows that the technologies and experience developed and accumulated by the space life support science gives a way to design and build sustainable bioregenerative life support systems for hot deserts, the extreme environments with high solar energy input, a stock of minerals in the soil, and atmospheric air
Summary
The general idea of using the closed-system bioregenerative life support technologies developed by space life support (SLS) to improve Earth's environment was formulated by Nelson et al (2003a) on the basis that the SLS science simultaneously addresses the problems of food, water, clean air, and energy supply. The abundance of solar energy, minerals, and surface area in hot deserts offers us a way to revitalize them and put them to use by establishing a network of highly efficient closed bioregenerative systems accompanied by photovoltaic arrays over the desert surface Design of such systems involves the following major challenges: (1) Completely closed water cycle and the production of water by living organisms. In the SLS science, CBLSS is designed to provide food production due to crop cycling times much shorter than in nature, water-closed loop, fresh water production, removal of CO2 by plant and algae assimilation, oxygen production, and utilization of the solid and liquid wastes formed in the system (Gitelson, 1992) It should be completely powered by sources of renewable energy, such as sunlight. Its performance depends on light intensity [photosynthetic photon flux, PPF, 400 to 700 nm, which accounts for 32% of the total Sun irradiance (Sager et al, 1992)], temperature, carbon dioxide and oxygen concentrations, and air velocity over the plant canopy, which must be controlled and monitored in the system (Bugbee et al, 1989; Wheeler et al, 1996, 2008a, 2008b; Andre et al, 1989, 1999; Borodina et al, 2003; Nelson et al, 2003a, 2008; Qin et al, 2008; Kitaya 2003; Kitaya et al, 2008; McKeehen et al, 1996; Allen et al, 1999, 2003; Berkovich, 2008)
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