There is no risk in terms of taking too much CO2 out of the atmosphere. Over the last couple of hundred years, humans have put several trillion extra tonnes of the stuff in (by burning material sequestered over millions of years). Further, this tech carbon neutral, not carbon negative. The advantage is that when the fuel is used, it's just putting CO2 back into the air that was there before, not adding more.

Hopefully this kind of thing, in addition to switching the electricity grid to zero emissions tech will allow us to halt global warming where it's at.