What I am concerned about is the fact that Proton Technology are running (or proposing to run) unbounded reactors underground, with I suspect only the haziest idea about what is actually happening inside them. They will contain many temperature zones that might not produce hydrogen but in my opinion some of those zones are likely to produce both toxic and/or mutagenic compounds that will inevitably migrate into the water table.
"It's not the reactions you want that are the proble, but the side reactions you don't."
i guess that is why they call it 'syngas'. The core IP should be about separating hydrogen from the rest. It can also create cavities underground etc. The biggest hurdle could be obtaining env. Assesment but compared to tarsands ravage they can be considered as green solution