The Airizona terrarium experiment. An enclosed biosphere containing all the elements of earth. It has it's own arctic,desrt,rainforest, and even an ocean section. All mimicking the environments of earth. If i recall correctly a team of volunteers tried to live in the terrarium for a year but it resulted in failure because of steadily rising co2. A few things that came to mind were, I assumed the photosynthesis was taking place during the day time which would mean the process of making oxygen was taking place during a maximum of a12 hour period during the day and then the plants at night would create co2 as they naturally do. That and the volunteers breathing was adding to the co2 buildup at a rate faster than the plants could aborb. My theory would be basically an equivalent of a second level to the terrarium underground to be cultivated specifically during the night time so when one forest is asleep the other can be awake. Oxygen production could take place on a 24 hour basis and algea cultures could be cultivated in individual containers with their own timed light source to fill in the hours in between. This could also be applied to agriculture and potential expand production of food. Your thoughts everyone?