For those averse to using herbicides and chemicals to kill weeds, they can be cooked to the roots instead:
No idea if this service is available in France, but there’s a fair chance someone is doing it, and there’s no reason it has to be exclusvely knotweed.
We’re in a “no chemicals” area of France and I seem to recall these cooker-weeders have been looked at in the past few years. Doubtless in use in some places.
Seems this gardening company has homed in on a good business angle in UK.
I wonder if you can but them, we are still battling ours 
Lidl does them once or twice a year, previously the ones requiring an aerosol can of gas, in recent years sometimes the 2000W electric wands.
Lidl says theirs can be used to strip paint and light barbecues too.
IIRC this month would be a likely time for them to be offered and, I think, late August. They are not expensive at all.
Hi Karen, I’m reasonably sure that’s the hot air/flame gun type. This uses high voltage to actually electrocute the plant by heating internally with electricity, which is a bit different.
Which would you consider the more humane? But more importantly, which would you consider the more effective killing device? (je ne suis pas très woke par les plantes).
I would expect the electric device to be most effective, because it should kill the roots. Probably the most humane thing for plants in general would be to eat vegans.
They do, in the long run.
Cremation not withstanding. 