Yeast is a living, eating, breathing and reproducing organism. They consume sugar and water and excrete carbon dioxide and alcohol. Yeast is used in the production of alcohol. Buy some brewers yeast at a make-your-own-beer/wine store. You will have to get a large jug with a small mouth, a rubber cork with a hole in it that will fit in the mouth of the jug, and six to ten feet (your decision) of flexible tubing in which the carbon dioxide will travel. All of these can be found at the one store. You are basically reviving the dry yeast in the package so that they will eat the sugar you give it and produce carbon dioxide meanwhile. Ask the person at the store that you want to produce carbon dioxide for some house plants. They will give you what you need.
1. Fill the large jug with slightly warm water. Not hot, not even warm, just a bit warmer than lukewarm. The warmth wakes up the yeast.
2. Now add sugar to the water . One part sugar to every five parts of solution.
3. Empty the packet of yeast in the jug and stir.
4. After a few hours the yeast should be active and producing carbon dioxide. The production of carbon dioxide can be observed by actual bubbles floating to the surface.
5.The only thing you have to do now is maintain the life of your yeast population. Dump out some of the solution and add fresh water so that is does not become stagnant. Add a few teaspoons of sugar. Do this every week or two.
6.Theoretically, your yeast population can last for an eternity!