[datr]

Unfortunately I don't think there's an easy component x which you could test for.

How about weight though? I imagine most bombs are considerably heavier than normal refuse. Could we add scales to bins and notify authorities that it should be examined if the weight suddenly increases by 2+ standard deviations, say.

I suppose this could be worked around by dropping explosive material piecemeal into the bin so this would have to be paired with an effective surveillance system to pick up on this behaviour.