If you could invent one thing to help mankind, what would it be? [Daily Journal]

        I would invent cars that run off garbage. So you could put garbage inside of them or old clothes. And it could convert them into energy somehow. So that people wouldn't have to worry about gas or the pieces for gas and garbage and stuff could be reused as fuel. You could even have old cars converted so that they can run off of garbage as well. Then no one would need to worry about gas because the "fuel" you need can come from your own home.