Personally, greenery insupposes me much less than this obsession with maximum sterilization, but I can understand that for some is psychologically reassuring (there may be other reasons for this requirement) ...
There are quite a few ways to deal with the problem. The easiest way, at least on a theoretical level, is to take this aspect into account when designing the aisles, depending on their functionality and also on your idea. In this hypothesis, the modalities vary according to its "degree of allergy" to chlorophyll. It goes from the grassy and more or less mowed passage, to the same one, but with slabs passing through, or, at the other end, a hollowed out ground, covered with a "bidim" (non-woven geotextile) and backfilled. with crushed stone or equivalent. This last case will see very little grass implantation and its rooting remaining superficial greatly reduces the difficulty of elimination (provided you do not wait too long before reacting!).
The general case is not this, however, and you have to do with the aisles in place and find curative solutions. Janic mentioned thermal weeding, a solution that works very well at the weed seedling stage, but remains poorly suited to well-established herbs: we only get a tedding of the aerial parts. This mode of action is energy intensive and if you choose it, you should not forget that the goal is not to burn the leaves, but to cause a thermal shock which will then lead to drying, therefore, do not insist too heavily: the slight sag under the flame of affected organs indicates that the goal has been reached. It is still possible to destroy adult plants in this way, but it should not be concealed that several passages will be necessary.
A transparent (or opaque?) Tarpaulin briefly spread over the grassy parts will play the same role as the butane / propane torch, provided that the sun is very active (so it depends on the season and the cloudiness) and the exhibition of the place ...
Harvesting gives good results depending on the type of weed and the type of support, but can be very laborious, if not impossible.
A last solution consists in using boiling water: on condition of operating with caution and in hot and dry weather, this generally gives very good results since the thermal action is not limited to the aerial parts, but extends to root zones. Another advantage compared to the gas torch is that it is possible to act at the foot of a thuja hedge (or other sensitive place) without setting it on fire!
I voluntarily limit myself to physical processes, knowing that plant-based weedkillers are starting to be marketed and that usual household products are also taken from their usual use, without this guaranteeing perfect safety ...
