Dynamite is an item that can be used to remove boulders that are too big to break with the basic hammer. It can be crafted at the 3D printer after buying the blueprints from the online blueprints terminal.
The recipe for Dynamite is 9 Fertilizer, 9 Sawdust, and 1 Copper Ore.
Copper Ore can be mined in the cave in the mountains, Fertilizer is made in the Grinder by processing Niter, also found in caves, and Sawdust is produced by grinding Lumber.
To use a piece of Dynamite, open your inventory, click the Dynamite, then click on the boulder you wish to remove. You do not need to move your character away from the resulting explosion.