2:22 PM - 2:39 PM
[HCG24-03] Problems on Physicochemical and Bioregenerative Processing in Material Circulation in Closed Ecological Life Support System
★Invited Papers
Keywords: Controlled/Closed Life Support System, Physicochemical Processing, Bioregeneratieve Processing
An Environmental Control and Life Support System (ECLSS) supplies substances necessary for human survival and maintains an environment in which human can survive in the ultimate environment such as outer space. The controlled/closed life support system (CELSS) is one type of ECLSS and aims to maintain the environment while regenerating and circulating the necessary materials in the system as much as possible. The CELSS is one of the ultimate form of the ECLSS.
The functions to material regeneration in the ECLSS are "regenerate oxygen from carbon dioxide", "reproduce pure or grey water from waste water", "process wastes to carbon dioxide and plant fertilizer", "separate harmful gases", and so on. There are two way to concrete these functions: one is based on physicochemical processes and the other is bioregenerative processes. For example, the physicochemical processing of "regenerate oxygen from carbon dioxide" is divided into the following three actions: 1. Separate carbon dioxide from atomosphere.2. Carbon dioxide is converted to water using Bosch or Sabatier reaction. 3. Electrolyze water to generate oxygen. On the other hand, the same function using bioregenerative method are achieved by photosynthesis by plants. As another example, a function to "process wastes to carbon dioxide and plant fertilizer" based on physicochemical process are realized wet-oxidation method or combustion/incineration method. The same function based on bioregenerative is to process waste by microorganisms, for example methane fermentation method
Generally, in the methods based on physicochemical process, one element (equipment) covers one function, and the amount of treatment can be designed freely from small to large amounts. In addition, there is little change in throughput with the same equipment. On the other hand, because one device implements one simple function, the number of device type and the number of devices tends to become much large as becoming amount of process necessary larger. Furthermore, there are some reactions that are feasible at laboratory level but cannot be used in actual operation due to the excessive temperature required, (such as Sabatier 2nd reaction. On the other hand, the equipment based on bioregenerative process achieve multiple functions with one element. For example, cultivation of plants realize following functions: separation of carbon dioxide, regeneration oxygen from carbon dioxide, supply food, reproducing water through transpiration, and so on. In addition, it may be possible to regenerate some of the trace substances that would lost in physicochemical processing. On the other hand, the treating time of bioregenerative process is much longer than the physicochemical processing, and it is much large that fluctuation of the amount of processing that due to the individual difference of the living body. In addition, there are following characteristics: a large growing space is required in spite of the small amount of processing, however, compare to physicochemical processing, it often does not require large equipment even if the through is quite large.
The methods applied in the past ground experimental facilities were mainly methods based on physicochemical processing, and some facilities used both physicochemical and bioregenerative processing. In the current ECLSS on the International Space Station (ISS), carbon dioxide is regenerated into oxygen and water is regenerated by physicochemical processing. Other non-regeneratable materials dispose to and supply from the outer system. This replenishment/disposal-based method can be realized because it is near the earth. However, if we need an ECLSS that can withstand a long period of time and long distance from the Earth, such as living on Mars, we need to increase the types and amounts of materials that can be regenerated, and make it closer to CELSS. Therefore, although it depends on the how many human live in the system, part of the equipment based on physicochemical processes should be replaced with bioregenerative equipment step by step.
In this presentation, I will summarize the current situation and problems related to physicochemical and bioregenerative processing, and discover what kind of problems will occur by replacing physicochemical equipment with bioregenerative ones from the viewpoint of material circulation using numerical simulation.
The functions to material regeneration in the ECLSS are "regenerate oxygen from carbon dioxide", "reproduce pure or grey water from waste water", "process wastes to carbon dioxide and plant fertilizer", "separate harmful gases", and so on. There are two way to concrete these functions: one is based on physicochemical processes and the other is bioregenerative processes. For example, the physicochemical processing of "regenerate oxygen from carbon dioxide" is divided into the following three actions: 1. Separate carbon dioxide from atomosphere.2. Carbon dioxide is converted to water using Bosch or Sabatier reaction. 3. Electrolyze water to generate oxygen. On the other hand, the same function using bioregenerative method are achieved by photosynthesis by plants. As another example, a function to "process wastes to carbon dioxide and plant fertilizer" based on physicochemical process are realized wet-oxidation method or combustion/incineration method. The same function based on bioregenerative is to process waste by microorganisms, for example methane fermentation method
Generally, in the methods based on physicochemical process, one element (equipment) covers one function, and the amount of treatment can be designed freely from small to large amounts. In addition, there is little change in throughput with the same equipment. On the other hand, because one device implements one simple function, the number of device type and the number of devices tends to become much large as becoming amount of process necessary larger. Furthermore, there are some reactions that are feasible at laboratory level but cannot be used in actual operation due to the excessive temperature required, (such as Sabatier 2nd reaction. On the other hand, the equipment based on bioregenerative process achieve multiple functions with one element. For example, cultivation of plants realize following functions: separation of carbon dioxide, regeneration oxygen from carbon dioxide, supply food, reproducing water through transpiration, and so on. In addition, it may be possible to regenerate some of the trace substances that would lost in physicochemical processing. On the other hand, the treating time of bioregenerative process is much longer than the physicochemical processing, and it is much large that fluctuation of the amount of processing that due to the individual difference of the living body. In addition, there are following characteristics: a large growing space is required in spite of the small amount of processing, however, compare to physicochemical processing, it often does not require large equipment even if the through is quite large.
The methods applied in the past ground experimental facilities were mainly methods based on physicochemical processing, and some facilities used both physicochemical and bioregenerative processing. In the current ECLSS on the International Space Station (ISS), carbon dioxide is regenerated into oxygen and water is regenerated by physicochemical processing. Other non-regeneratable materials dispose to and supply from the outer system. This replenishment/disposal-based method can be realized because it is near the earth. However, if we need an ECLSS that can withstand a long period of time and long distance from the Earth, such as living on Mars, we need to increase the types and amounts of materials that can be regenerated, and make it closer to CELSS. Therefore, although it depends on the how many human live in the system, part of the equipment based on physicochemical processes should be replaced with bioregenerative equipment step by step.
In this presentation, I will summarize the current situation and problems related to physicochemical and bioregenerative processing, and discover what kind of problems will occur by replacing physicochemical equipment with bioregenerative ones from the viewpoint of material circulation using numerical simulation.