There are way, way more than 10 explosives throughout the campaign and many enemies to take out with them. Your first opportunity will come after you drop in from the helo with FEAR squad, you'll open the gates and make your way into the building. After the worker dies on the floor move in and melee the guy with his back to you then shoot the yellow barrel he was facing (1).
If you want this achievement as quickly as possible or have already completed the campaign you can: Melee the first enemy from behind then kill the next enemy with the yellow barrel. Backtrack to the railing where you opened the gate and jump off until all health is lost. Rinse and repeat at this spot until the achievement unlocks.
(Thanks to rob25X
for confirming this works).
Otherwise proceed until you drop down over the fence, shoot the guy standing then wait for the other 3 enemies to go near the fuse box and shoot it killing them (2-4).
You'll soon come to a room with two guys standing there, quickly shoot them then a third guy will come from the right, shoot the fuse box there to kill him (3-5). Around the corner is a fire extinguisher and if you wait a second another guy will walk round (4-6).
Proceed for quite a while until you encounter Alma in the sewers and go up a ladder and in through a door with a broken bloody window. There'll be a clone standing there if you wait he'll walk round the walkway towards the fire extinguisher (5-7).
A little further after dropping from the grate you'll notice a fuse box on the wall, wait for the two guys to walk near it or shoot your weapon to coax them over (6-10).
You'll reach a room with large pipes on the floor and an office on the right, go into the office and wait for the two guys who come down the ladder, either wait for them to pass by the fire extinguisher or coax them over, its on the wall on your right in the dark (7-12).
You'll soon come to a double door leading to an outside area with around 4 enemies, there is an explosive barrel behind the box in front of you, wait for a them to go near it and shoot it (8-16).
The next enemy encounter will put you in a room with an explosive barrel near the centre and two clones right next to it (10-18).
Apart from these specific opportunities there are many others dotted around in the campaign and instant action maps. The key is often patience, wait for the enemy to move near a fuse box, fire extinguisher, or yellow barrel then shoot it. You can coax an enemy by firing your weapon then moving back and ambushing them.