Ok, well, my yellow bucket has been sitting in my locker at school for about 5 weeks now. I have not been using it that much lately as I am quite busy and a bit disorganized these days. The bucket contains a mix of urine, of course, as well as saw dust and bokashi (selected microorganisms in wheat bran) and is topped with straight bokashi. Can you imagine how tat bucket smells right now? I bet you can’t because it actually does not have much smell at all. This is important since it is the smell that really detracts a lot of people from this idea. So having peed in plenty of straight sawdust and experienced the smell when left for too long, I can confidently say it is the bokashi that is making the difference. Especially since the bucket has a tight fitting lid which usually makes things smell even worse. But the bokashi thrives under anaerobic conditions, so the bucket is ideal.
I did a bit of pee research and came across the paper below (and others). The researchers here (in Finland) used human urine to fertilize cabbage. Here is a bit of their intro about human urine (are you as excited as i am?):
The urea/ammonium in urine and urea/ammonium in artificial fertilizers are similar; that is, 90–100% of urine N is in the form of either urea or ammonium, as has been verified in fertilizing experiments (7, 8). The P and K contents in urine are almost totally (95–100%) in an inorganic form (6). These ions are directly plant-available; for example, the phosphate plant availability from urine has been demonstrated to be as good as that of chemical phosphate (7). Urine has been successfully used to fertilize barley (8) and cucumbers (5). The growth and yields were as good as could be obtained with mineral fertilization.
So this project has some promise after all. I will be using some of my sawdust and bokashi urine at my community garden plot which I hope to incorporate this weekend. I won’t be doing a control (space too small) but I’ll still be curious to see the results.
But human urine is not necessarily perfect. From another paper’s abstract:
Stored human urine had pH values of 8.9 and was composed of eight main ionic species (> 0.1 meq L–1), the cations Na, K, NH4, Ca and the anions, Cl, SO4, PO4 and HCO3. Nitrogen was mainly (> 90%) present as ammoniacal N, with ammonium bicarbonate being the dominant compound. Urea and urate decomposed during storage. Heavy metal concentrations in urine samples were low compared with other organic fertilizers, but copper, mercury, nickel and zinc were 10–500 times higher in urine than in precipitation and surface waters. In a pot experiment with15N labelled human urine, higher gaseous losses and lower crop uptake (barley) of urine N than of labelled ammonium nitrate were found. Phosphorus present in urine was utilized at a higher rate than soluble phosphate, showing that urine P is at least as available to crops as soluble P fertilizers.
So phosphorus seems to be the best benefit from human urine. But the N is important also since it is so mobile in the soil (due to it’s negative charge) and very important to plant growth. It would be interesting to see how things change after being mixed with sawdust and bokashi. Both are high C materials but the biological activity of the bokashi may have an effect on the nutrients in some way.