I stumbled upon this interesting bit of technology while researching something else. It captured both my interest and my imagination. This unit is designed for use in underdeveloped areas to provide methane gas primarily for cooking. It is intended to offset the LPG normally used. It requires some effort, and the output is not much, but it is adequate for it's purpose. This is cool!
The unit is the size of a medium refrigerator, and reportedly costs about $200 USD. After setting it up, you provide it with about 4.5 pounds (2kg) of food waste, and 2 gallons of water. This is enough to produce 500 liters of methane gas a day. 500 liters is about 17 cubic feet of gas. Looking at my gas bill (heat & hot water) this would run my house for about 20 minutes. But, it appears to be enough to supply the cooking needs of a family. 17 cubic feet is equal to about 1/7 gallon of gasoline, so it is not for powering your CNG car unless you make really short trips! These units are apparently geting popular in India. Lets hope they catch on elsewhere. Below is a link to the ARTI Website, as well as a link to a technical analysis of the unit, and a very good Youtube video about the unit.
Video about the unit