Can Store $1500 of Credits
The Tiberium silo were structures used in the First Tiberium War.
The Tiberium silos can hold a large amount of Tiberium. If a commander captures a Silo, the amount of Tiberium that was given to the enemy would be lost and converted to the commander. Its fairly light armour makes it fairly vulnerable to enemy attack.
There is a way to bypass the need for building Tiberium Silos. Note that at the beginning of a mission, you are given an amount of credits which do not require any "storage space" in a Refinery or Silo. When you construct a building or unit and subsequently cancel it, the money is refunded to you in the form of storage-free credits rather than as Tiberium. Since the game prioritizes spending Tiberium before storage-free credits, this means that repeatedly building an expensive structure and canceling it will eventually convert all your Tiberium into storage-free credits and alleviate the need for Tiberium Silos. The same trick works in Red Alert 1 and Tiberium Wars, though not in Tiberian Sun (Tiberian Sun spends your storage-free credits first and refunds it to you in the same form).