Talk:Azolla and Duckweed Calculations

The downside with a very "tight" nutrient cycle involving humans is the risk of retaining in the system: pharmaceuticals, hormones, microbes/other pathogens. The larger the number of people using this toilet, the higher the likelihood that somebody will be on some antidepressant or birth control pill. Possible solution: dry all waste and burn it. Collect urine with sawdust, dry it, burn it. Collect humanure, dry it, burn it. Use the resulting ashes to fertilize the duckeweed/azolla pond. Some nitrogen would be lost but that's OK, it's minimal. Urine sawdust could be continuously aerated to keep it dry. My suggestion: use human urine and humanure in other ways (e.g. fertilize trees, biomass plants). --Rasmus (talk) 22:32, 13 April 2016 (CEST)

What specifically are the hormones and drugs of interest? Do these persist? Could try mycoremediation in the loop somewhere?

The drugs that are most often mentioned in this context are antibiotics, antifungals, antidepressants and estrogens (from birth control pill). Wastewater treatment facilities now have an increasingly difficult time getting rid of these. Different drugs have different breakdown characterististics of course, which also depend on the system. You are right, a mycoremediation step (i.e. biofilter) could solve most of the problems. Another way would be to not connect the human waste system immediately back to the aquaponic system. The biomass plants and fruit trees need fertilizing anyway, so we might as well divert it that way. This still leaves some chance of creating drug effects in the environment, such as antibiotic resistance, although probably reduced. Another possibility is a greenhouse for cattails. Then the cattail roots can be used for ethanol and the rest of the plant can be burned for energy. --Rasmus (talk) 19:28, 14 April 2016 (CEST)

Clarification for my first comment above: burning may actually destroy *most* of the fixed nitrogen in the burned biomass. By "...that's OK, it's minimal" I meant to say that the overall amount of nitrogen lost is not that much. The Azolla system produces plenty of fixed nitrogen, so no big deal. --Rasmus (talk) 19:31, 14 April 2016 (CEST)