Closed loop
Astronauts on Mars will eat fish and fertilize plants with waste
Scientists of the Federal Research Center Krasnoyarsk Scientific Center SB RAS have developed a technology for processing fish waste to prepare a nutrient solution for growing plants. The technology will become one of the links of the future closed human life support system in space. The results of the study are published in the journal Life Sciences in Space Research (Tikhomirova et al., Incorporation of mineralized human waste and fish waste as a source of higher plant mineral nutrition in the BTLSS mass exchange).
The BIOS-3 closed life support system developed by Krasnoyarsk scientists is a prototype of a lunar or Martian base. At the heart of its work is an ecological cycle of a high degree of isolation coordinated by chemical elements. As a result of the vital activity of plants grown on mineralized human secretions and other organic waste, food is produced, oxygen and drinking water are restored. Autonomous closed ecosystems should make planetary bases less dependent on food supplies and, therefore, cheaper to use.
The long-term life of an extraterrestrial planetary settlement will be impossible without the production of animal food for humans. Fish is a promising candidate for inclusion in the bioregenerative life support system due to high-quality protein and high content of essential polyunsaturated fatty acids (omega-3 and omega-6). However, the appearance of fish food in the crew's diet will entail a new type of organic waste – scales, bones, entrails.
Scientists of the Institute of Biophysics of the FITC KNC SB RAS have developed a technology for processing fish waste as an additive in a nutrient solution that can be used for growing wheat. For this purpose, in the process of so-called "wet burning", the organic material was oxidized in an aqueous solution of hydrogen peroxide in an alternating electric field. As a result, organic matter was transformed into inorganic salts. Scientists expect that using this method, the space team will be able to completely recycle fish waste and use it to grow vegetables and other food.
Fish waste (left) before processing in a wet combustion reactor (right)
Carp waste was used as a prototype in the work. Crucian carp is an omnivorous freshwater bony fish that does not show special preferences in its habitat. Such fish, unlike marine species, does not need a large salt content in the water. It is important that fresh water can be easily obtained by transpiration of plants and condensation of water vapor in biological water. The researchers found that in the presence of mineralized human waste, the processing of fish waste is more efficient than with their direct oxidation. The re-processing of the resulting small sediment in the medium of hydrogen peroxide and nitric acid made it possible to transfer the remaining insoluble mineral elements into an accessible form for plant nutrition.
"We have shown that wheat plants grown on a nutrient solution prepared from mineralized fish waste and human waste produced a higher yield compared to the harvest obtained using only mineralized human secretions. In addition, fish waste has become a source of additional mineral elements for wheat," said Alexander Tikhomirov, Doctor of Biological Sciences, Professor, Head of the Laboratory of Phototrophic Biosynthesis Management at the Institute of Biophysics of the FITC KNC SB RAS.
In the future, Krasnoyarsk biophysicists propose to include other types of waste in the mineralization process, for example, household packaging and sanitary materials. The development of a physico-chemical method for the oxidation of human and plant waste with their subsequent involvement in the circular process in relation to closed ecosystems is supported by a grant from the Russian Science Foundation. Long-term research on the development of a closed life support system of a new type, in particular work on the mineralization of fish waste and their use for nutrient solution, is carried out within the framework of the state task under the program of fundamental scientific research of the state Academies of Sciences for 2013-2020.
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