Common story at present of gasification for waste from energy (particularly mixed waste). It is a global phenomenon:
1. Promote a system as doing what it cannot, with no detail of the technology.
2. Employ lots of gas clean up systems which fail.
3. Company goes bankrupt.

Downdraft gasifiers work on single feedstocks and only then if they are designed with the correct air intake settings and internal configuration. Outside of these feedstock ranges (which depending on the system can be ridiculously narrow), the temperature of the reactor will oscillate, and tar will be produced in qualities and/or quantities too excessive for the clean up processes to function. There are two ways to solve this, either throw more and more effort into clean up stages, or simply go to the root cause and adjust the temperature of the reactor along with uniformity in the feedstock!