Step 1: Fill the soda with water
Step 2: Get some urine
300/2000 is 0.15 or 15 percent of the total volume we need to fill a 2 liter bottle.
Say you only have 100 ml of urine. Divide 100 by 0.15 to get 666.6. This is the total amount of solution you need.
Now calculate how much water you need by subtracting 100 from 666.6 to get 566.6 ml of water.
Pour out the 1.7 ml of water and pour in the 100 ml of urine. Then measure 566.6 liters of water and pour it back in the soda bottle.
Now you have 666.6 milliliters of natural fertilizer solution you can water house plants with.
Be sure to label the soda bottle so no one will think it is lemon soda and take a drink by mistake.
You can also use this fertilizer solution to fertilize your lawn and other plants outdoors for free.
Step 3: Now make some of your own "Dark Earth"
Mix your soil and biochar and then soak it in the urine you have made so the carbon particles can become saturated with nitrogen and phosphorous and other minerals in the urine. Use this mixture as a very rich potting soil but be careful not to over concentrate the urine. One neat thing about this potting soil is that after bacteria start growing you will not have to add any more fertilizer and can reuse this potting soil over and over again without it becoming depleted.