Clean blue flame. NAT GEO tests emissions of wood fuel 

Wood fuel. This man gets 5000 miles on a cord of wood in a full-size truck. And can switch back to gasoline while driving

Builds a Gasifier using a book you can get on Amazon

Builds a Gasifier using a book you can get on ebay

NAT GEO  shows emissions with gasoline, then with wood. They also show a safety feature that is a must have