I think the main problem with space colonization is the whole nutrient cycle - using and/or recycling every part of food that is grown and consumed, including h

I think the main problem with space colonization is the whole nutrient cycle - using and/or recycling every part of food that is grown and consumed, including human excrements and other organic waste (skin, hair, blood, etc.). I don't think that terrestrial farming practice focus on that, no matter how technologically advanced or futursistic.