A group of enterprising engineering students has developed a process for extracting combustible methane gas from cow manure (don’t worry, the exhaust is odorless).With a specially adapted internal combustion engine, the students claim that an automobile can be propelled 15 miles per day from the “cow gas” produced by a single cow. Their experimental car can travel 60 miles per day for an estimated cost of $5 (this is the allocated cost of the methane process equipment—the cow manure is essentially free)