What you need is a soda bottle, a measuring cup or scale, a funnel, some water and some urine.
Step 1: Fill the Soda With Water
Fill a 2 liter soda bottle with water right up to the top of the label. This will give you about 1.7 litters.
Step 2: Get Some Urine
Pee is full of urine. Pee in a measuring cup until you have 300 ml. If you can not pee this much at one time hide the cup near the commode and try again later to add more pee to get a total of 300 ml, or get out your calculator and use the following formula to determine how much fertilizer solution you can make with whatever amount of urine you've got and how much water you need.
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"
If you really want to make stuff grow don't stop here by just using urine. To make stuff really grow add your urine to 2 part regular soil and 1 part powdered biochar by weight, not volume. Biochar is like charcoal but made entirely from organic waste matter with all the bio-oil separated and removed. Unlike some charcoal you buy at the store, biochar does not have special additives like oil that help it burn better.
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.