algae photobioreactor for life support on space stations.
Current solutions for supporting humans in space are very inefficient and if we ever want to create permanent, self sustaining settlements in the orbits of Earth or other planets, we must create life support systems that are efficient and stable.
The ISS, largest space station that is currently in operation, has a life support system called the Environmental Control and Life Support System, or ECLSS. It provides the astronauts with clean water and oxygen and gets rid of CO2 and other human wastes. It provides oxygen with an oxygen generator. This machine runs an electric current through water, which causes a chemical reaction called electrolysis that separates the water molecules into oxygen and hydrogen. This process is bad as it wastes water, which can't be reclaimed from external sources in space. The hydrogen produced is just dumped in space, which also wastes resources. This was what we focused most on to improve. The ECLSS also has a system that reclaims the water wasted by the crew, and a CO2 scrubber, which is also inefficient as it just dumps the CO2. In addition to all these problems, the ECLSS also has frequent maintenance issues that slow down the research on the ISS. We wanted to create a life support system that fixed all these problems and stable so it could be used on a self sufficient space station. The best way to create a life support system that doesn't have any waste materials is to simulate the ecosystem on Earth. On Earth, plants photosynthesis and cellular respiration are always in balance. What we needed to do was either bring photosynthesis aboard the ISS or simulate it the best we could. We came up with several different solutions, using chemical reactions to create artificial photosynthesis, putting microalgae or cyanobacteria in the ISS, or using other plants. Artificial photosynthesis is still in its early stages and implementing this would be far to expensive. We then found that microalgae would be the best plant life to implement because of its high oxygen-production to mass ratio. Algae also grows much faster than other plants and needs less nutrients to survive. A containment in which algae is grown in high densities is called a photobioreactor. Our plan was to create a photobioreactor that pumps the waste CO2 from the astronaut's exhalation into the algae, which then photosynthesizes and creates oxygen for the crew to breathe. This was challenging because most photobioreactors are used to harvest algae for food and other uses, and we would have to come up with our own design. There were several different types of photobioreactors that we could have modeled ours after. There are tube bioreactors, plate bioreactors, and bubble column bioreactors. Tube bioreactors contain the algae in tubes, plate bioreactors do it in plate sections, and bubble column bioreactors have the algae in a tank with bubbles flowing through them. after some further research, we learned that most algae only photosynthesize in the air when they are exposed to it. this meant that the oxygen production rate of our photobioreactor was based on not the volume of algae, but the surface area. We then learned that one person needs 8m^2 of exposed algae to survive, this was discovered at a closed ecological system called Bios-3 at the Institute of Biophysics in Krasnoyarsk, Russia. Looking back at the different photobioreactor types, we saw that the bubble column would be the most effective, because each bubble would add to the area of exposed algae. The smaller the bubbles, the larger the surface area because more bubbles can fit in a given area, so we found out the size of the smallest bubbles that can be currently produced, which 0.9mm. Knowing this information, we calculated the surface area of the inside of one bubble to be 0.00000254m^2. a crew of twelve would need 96m^2 of exposed algae and when we divide this by 0.00000254m^2 we get 37,795,276. This is the number of bubbles that must be in the bioreactor at any given moment to provide enough oxygen for the crew. We decided that the optimum form factor for our bioreactor was a cylinder with a base diameter of 0.1m to allow for unrestricted lighting for the algae. We then had to calculate the height that our bioreactor needed to be to meet the 37 million bubble requirement. We approached this by calculating the number of pores, or bubble holes could be put at the base of the bioreactor. We knew that the base of the cylinder was 7,854mm^2, and we knew that a 0.9mm bubble needs a pore with an area of 0.36mm^2. When we divide those numbers, we see that each time air is pumped into our bubbler, it produces 21,816 bubbles in one "bubble layer." And when we divide 37,795,276 by 21,816 we get 1,732, This is the amount of bubble layers that are needed in our bioreactor. If each bubble is about one mm in diameter, then the bioreactor needs to be 1.7m tall. Because there is no gravity on the ISS, the bubbles wouldn't rise, that is why they would have to be pumped through the bioreactor with the algae and then separated out with a membrane at the end of the cylinder. the algae could then be strained and prepared as food. This system would also obviously need many cultures of algae nearby to keep the bioreactor running constantly. The entire bioreactor would also be lit by a large number of LED bulbs. This design could supply a space station with oxygen and food and get rid of CO2 and maintain water.
This was definitely my favorite project so far. This is because we were challenged to learn many things on our own in order to solve the problem. We did a great job coming up with a creative solution to the problem and we worked together quite nicely, But we did struggle with getting everything done on time and we could have made a nicer model or blueprint of the final design.
The ISS, largest space station that is currently in operation, has a life support system called the Environmental Control and Life Support System, or ECLSS. It provides the astronauts with clean water and oxygen and gets rid of CO2 and other human wastes. It provides oxygen with an oxygen generator. This machine runs an electric current through water, which causes a chemical reaction called electrolysis that separates the water molecules into oxygen and hydrogen. This process is bad as it wastes water, which can't be reclaimed from external sources in space. The hydrogen produced is just dumped in space, which also wastes resources. This was what we focused most on to improve. The ECLSS also has a system that reclaims the water wasted by the crew, and a CO2 scrubber, which is also inefficient as it just dumps the CO2. In addition to all these problems, the ECLSS also has frequent maintenance issues that slow down the research on the ISS. We wanted to create a life support system that fixed all these problems and stable so it could be used on a self sufficient space station. The best way to create a life support system that doesn't have any waste materials is to simulate the ecosystem on Earth. On Earth, plants photosynthesis and cellular respiration are always in balance. What we needed to do was either bring photosynthesis aboard the ISS or simulate it the best we could. We came up with several different solutions, using chemical reactions to create artificial photosynthesis, putting microalgae or cyanobacteria in the ISS, or using other plants. Artificial photosynthesis is still in its early stages and implementing this would be far to expensive. We then found that microalgae would be the best plant life to implement because of its high oxygen-production to mass ratio. Algae also grows much faster than other plants and needs less nutrients to survive. A containment in which algae is grown in high densities is called a photobioreactor. Our plan was to create a photobioreactor that pumps the waste CO2 from the astronaut's exhalation into the algae, which then photosynthesizes and creates oxygen for the crew to breathe. This was challenging because most photobioreactors are used to harvest algae for food and other uses, and we would have to come up with our own design. There were several different types of photobioreactors that we could have modeled ours after. There are tube bioreactors, plate bioreactors, and bubble column bioreactors. Tube bioreactors contain the algae in tubes, plate bioreactors do it in plate sections, and bubble column bioreactors have the algae in a tank with bubbles flowing through them. after some further research, we learned that most algae only photosynthesize in the air when they are exposed to it. this meant that the oxygen production rate of our photobioreactor was based on not the volume of algae, but the surface area. We then learned that one person needs 8m^2 of exposed algae to survive, this was discovered at a closed ecological system called Bios-3 at the Institute of Biophysics in Krasnoyarsk, Russia. Looking back at the different photobioreactor types, we saw that the bubble column would be the most effective, because each bubble would add to the area of exposed algae. The smaller the bubbles, the larger the surface area because more bubbles can fit in a given area, so we found out the size of the smallest bubbles that can be currently produced, which 0.9mm. Knowing this information, we calculated the surface area of the inside of one bubble to be 0.00000254m^2. a crew of twelve would need 96m^2 of exposed algae and when we divide this by 0.00000254m^2 we get 37,795,276. This is the number of bubbles that must be in the bioreactor at any given moment to provide enough oxygen for the crew. We decided that the optimum form factor for our bioreactor was a cylinder with a base diameter of 0.1m to allow for unrestricted lighting for the algae. We then had to calculate the height that our bioreactor needed to be to meet the 37 million bubble requirement. We approached this by calculating the number of pores, or bubble holes could be put at the base of the bioreactor. We knew that the base of the cylinder was 7,854mm^2, and we knew that a 0.9mm bubble needs a pore with an area of 0.36mm^2. When we divide those numbers, we see that each time air is pumped into our bubbler, it produces 21,816 bubbles in one "bubble layer." And when we divide 37,795,276 by 21,816 we get 1,732, This is the amount of bubble layers that are needed in our bioreactor. If each bubble is about one mm in diameter, then the bioreactor needs to be 1.7m tall. Because there is no gravity on the ISS, the bubbles wouldn't rise, that is why they would have to be pumped through the bioreactor with the algae and then separated out with a membrane at the end of the cylinder. the algae could then be strained and prepared as food. This system would also obviously need many cultures of algae nearby to keep the bioreactor running constantly. The entire bioreactor would also be lit by a large number of LED bulbs. This design could supply a space station with oxygen and food and get rid of CO2 and maintain water.
This was definitely my favorite project so far. This is because we were challenged to learn many things on our own in order to solve the problem. We did a great job coming up with a creative solution to the problem and we worked together quite nicely, But we did struggle with getting everything done on time and we could have made a nicer model or blueprint of the final design.