Wood is a standard bio-mass used for heat and power. Ships and trains used to be wood-driven, the wood being burned to create steam to drive the steam engines. Wood Gas is a way to use wood to power our 'modern' internal combustion engines.
There are a couple of ways to use turds as fuel. First is to dry them and burn them like any other bio-mass. And second is to turn them into methane. Methane (also known as natural gas) is an eco-fuel made from bio-mass that can be used to power our 'modern' internal combustion engines.