This is an old technology that was widely used during World War 2.
Simply put, the flame you see in your fireplace is the gas coming off the fuel you are burning. In a gasifier this is captured, cleaned and cooled and used to run an engine; mainly petrol engines, but it can also be used to run diesel engines.
We have started work on a gasification project and in due course this page will be updated with pictures.
It is worth noting that one of the by-products of gasification is biochar.
Checkout the blog for updates.
Down Draft Gasifier