In the level Power Plant
Left, after the room with the giant statue,
you should see 3 furnaces and a truck. Jump on top of the truck, push the lever forward the make it go, push it forward again to make it go faster
although harder to control. Grab on to the wheel to steer the truck left and right. Drive up the road until you get the truck's bucket under the hopper
connected to the conveyor belt. Now, get off the truck and walk forward until you see a cave to your right. Follow the cave
to a pile of coal. Throw at least 10 pieces of coal onto the belt
(I recommend a bit extra just in case). Now go back to the truck and drive it past the cave and to the right as the path connects with another road leading back. Once you're back to the main area with the furnaces
the achievement is yours!