The chemical process uses toxic and hazardous reagents such as N,N-dimethylaniline (CH3)3SiCL and PCL5. It also uses chlorinated sovents (CH2CL2), needs inert gas conditions and has expensive waste gas cleaning. The composition of the wastewater prohibits or endangers conventional biological wastewater treatment and thus has to be incinerated. Some processes use zinc salts (with resulting problems of heavy metal disposal). The process uses very low temperature chemistry which gives rise to high energy costs