Last week I posted a short series on my blog about the need (or lack thereof) for nitrogen-fixing plants in small plots where the residents recycle their urine into the garden. Based on Martin Crawford's figure of one pee (half a litre) containing about 5.6 grams of nitrogen, and using his numbers for nitrogen demand of different food forest canopy plants, I calculated that one person's annual urine should meet the nitrogen needs of 4100-5100 square feet of forest garden."One adult on an ordinary diet will produce from 100 to 250 grams of feces per day. On a vegetable diet, an adult will produce from 300 to 400 grams per day. (Respectively, 0.22 to 0.55, and 0.66 to 0.88 pounds per day.) Feces are usually neutral to slightly alkaline in pH, 24% to 27% TS [total solids] (dry weight), with a C/N [carbon-nitrogen ratio] of 6 to 10, nitrogen 4% to 6% of TS, VS [volatile solids] is 85% of TS. Normal values for urine are 1 to 1.6 liters volume per day, average pH 6.0, 4% to 6% TS, with a C/N of 0.8, nitrogen 15% to 18% of TS, VS is 72% of TS. (That's 1.06 to 1.69 quarts volume produced daily). Every liter of urine weighs about 1,020 grams. Every quart of urine weighs about 2.9 pounds." [The Complete Biogas Handbook, p 69.]
You can read the full post at: http://farmerscrub.blogspot.com/2007/12/nitrogen-fixers-vs-liquid-gold.html
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