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The main objective of the activities of the Closed Ecology Experiment Facilities (CEEF) is to construct a mathematical model to predict the transfer of radiocarbon (14C) released from a nuclear fuel reprocessing plant in the village of Rokkasho into the local ecosystem. For this purpose, an artificial ecosystem, including crops, domestic animals, and human inhabitants, needs to be maintained in the CEEF for several months. As a preparatory study, two-week habitation experiments using the CEEF were planned in 2006. In the first habitation experiment, a CO2 separator was continuously operated with a cycle of 60-minute adsorption and 60-minute desorption periods in order to remove excess CO2 from the habitation room, and the maximum CO2 concentration of air in this room slightly exceeded 5000 ppm, which was identical to the maximum 8-hour exposure permitted for industrial settings.

The Closed Ecology Experiment Facilities (CEEF) have been under construction in northern Japan since 1994. These facilities contain the Closed Plant Experiment Facility (CPEF), as well as other facilities, in all of which, Controlled Ecological Life Support Systems (CELSS) research and development can be conducted. The CPEF includes two Plant Cultivation Modules (PCMs), which contain a PCM consists of three 30m2 closed cultivation rooms illuminated solely by lamps and a 165.1m3 preparation room, and a PCM consists of a 60m2 closed cultivation room illuminated by natural light and supplemental lamps and a 88.8m3 preparation room, and a Material Circulation System (MCS). Measured rate of air exchange between a 30m2 cultivation room and the preparation room was 0.48% hour-1, and that for a 60m2 cultivation room was about 0.11% hour-1. Air leak rate of the PCM as a whole was less than 0.01% hour-1 under isothermal and equal pressure condition.

Rating of daily amounts of CO2 and O2 exchange of crops, animals and humans to be involved in the long-term habitation experiments using the Closed Ecology Experiment Facilities (CEEF) were carried out. Daily amounts of the CO2-absorption and O2-generation of crops including rice, soybeans and other 27 vegetables were estimated from data obtained from a sequential crop cultivation experiment conducted from August to December of FY2001. Daily amounts of O2-consumption and CO2-expiration of two female Shiba goats to be involved were estimated based on gas exchange determination conducted in FY2002. Daily amounts of CO2-expiration and O2-consumption of two persons to be involved were estimated based on correlation between respiration rate and heart rate, heart rate data during the simulated habitation in the CEEF and a tentative work schedule.

Three 1-week experiments were conducted from September to October of 2005 in which two human subjects called as eco-nauts were enclosed and worked in an airtight facility called Closed Ecosystem Experiment Facilities (CEEF). The test involved connecting a Plant Module (PM) with 23 crops, including rice, soybean, peanut, and sugar beet, to an Animal & Habitation Module (AHM), which included the eco-nauts and two Shiba goats. Although only 34% (by weight) of the food consumed by the eco-nauts was produced by crops in the PM in the first experiment, it was 81% in the second and third experiments. As for feed for the goats, although all was Timothy hay was supplied from outside in the first experiment, all of the feed (rice straw, soybean leaf and peanut shell) was produced in the PM in the second and third experiments. In all these experiments, the crops produced more oxygen than the amount consumed by respiration of human and animals.

In the Closed Ecology Experiment Facilities (CEEF), an artificial ecosystem including crops, Shiba goats, and human inhabitants is to be constructed in order to conduct long-term habitation experiments. For carbon circulation in this artificial ecosystem, CO2 needs to be recovered from the air of animal breeding and habitation rooms using a CO2 separator and to be injected into growth chambers for consumption in crop photosynthesis. Moreover, daily crop yield from the growth chambers needs to be stabilized to drive carbon circulation in the artificial ecosystemwithout huge buffers. Because crops are cultivated in a staggered manner, controlling atmospheric CO2 concentration in the growth chambers at a constant level during light periods throughout crop cultivation is necessary for stabilizing daily crop yield.

The first seven-day air circulation confinement experiments were repeated three times at the Closed Ecology Experiment Facilities (CEEF or the so-called “Mini Earth”) of the Institute for Environmental Sciences in Rokkasho, Aomori, Japan. Energy expenditures have been estimated for habitants of the CEEF (known as Eco-nauts) in the experiments. This paper presents the calculations of the Eco-nauts' energy expenditures using records of life activities during the experiments and compares them with the values estimated in previous preliminary experiments.

The Closed Ecology Experiment Facilities (CEEF), designed to simulate material circulation, is an artificial closed agricultural ecosystem with plants, humans, and animals. The drying toilet system “DRI-LET®” had been installed in the habitation module as a human waste processor for material circulation by carbonizing. Carbonizing of human waste has advantages in life support systems because it can minimize the total volume and weight of human waste. However, this toilet system releases many gases during processing. In particular, NO2 concentration in the habitation module increased up to 4 ppm when one person used the toilet system. In this paper, we report NO and NO2 behavior in the habitation module during experiments and a method to reduce their concentrations by using NO and NO2 adsorbent.

A mathematical model was developed in order to predict quantities of CO2 and O2 gas exchange, transpiration, biomass production, food production and nutrient absorption by candidate crops in Closed Ecology Experiment Facilities (CEEF) in which material recycling in a controlled ecological life support system (CELSS) is to be made. This model includes effects of physical parameters such as light intensity, air temperature, humidity and atmospheric CO2 concentration on these processes and plant aging effect on these processes. Using results from experiments in which candidate crops were grown under controlled environment and data from literature, mathematical models for each crop was given physiological parameters. Then, changes in biomass and food accumulation, gas exchange and transpiration of each crop with time were calculated.

Closed habitation experiments are to be carried out using Closed Ecology Experiment Facilities (CEEF) from 2005 to 2009. The last target of duration of closed habitation is four months. Preliminary study and testing have been conducted in order to start the closed habitation experiments. In 2004 as the last year of the preliminary test phase for the 2005–2009 experiments, periodical harvesting from staggered cultivation of 23 crops including rice, soybean, peanut, and sugar beet was continued during 103 days. In order to balance with metabolisms of humans (named as “eco-nauts”) and animals, it is necessary to stabilize production of edible and inedible biomass, CO2 uptake and O2 production of crops. Although biomass production decreased rapidly during first five weeks of the 103-day period, it was relatively stable during last ten weeks. Average major foodstuffs in the harvested edible biomass met the requirement of two Eco-nauts although several minor ingredients were insufficient.

Preliminary seven-day habitation experiments without complete closure of the habitation module were performed in the Closed Ecology Experiment Facilities (CEEF) to obtain information for the closed habitation and to prepare for the actual closed habitation experiments to be launched in September 2005. Energy requirements have been estimated for habitant candidates in closed habitation experiments (to be called Eco-nauts). This paper presents the calculations of Eco-nauts' energy requirements using records of life activities during the preliminary experiments and compares them with the expected energy supply from the CEEF.

The Closed Ecological Experimental Facilities (CEEF), designed to simulate material circulation, is an artificial closed agricultural ecosystem with plants, humans and animals. In the experiments starting from FY2005, habitants referred to as eco-nauts will be exposed to complex workloads and various CEEF environmental factors, which may influence their physio-psychological state, and lower their performance. Therefore, preliminary experiments were conducted on the workload-matched (11.1h work, 168h, airlock open) and the environment-matched condition (6.9h work, 24h, air circulation) to monitor physio-psychological changes. As a result, both experiment types were conducted as scheduled without any major problems, and no serious physio-psychological disorders were observed in the eco-nauts. One week closed habitation experiments will be performed as a preliminary step toward much longer (max. 4 months) experiments.