We optimize the overall energy consumption of a Narrowband Internet of Things (NB-IoT) application created using a hybrid blockchain framework. We accomplish this by engineering the underlying hash function (SHA-256) that is used in different procedures (Unique ID generation, Device Join, and Device Transaction) of the blockchain-based NB-IoT system. In order to reduce the complexity of hash verification, IoT devices in the NB-IoT application are built to save the hashes of their authorized transactions as a linear hash chain rather than the entire Merkle tree. Furthermore, base station memory is dynamically partitioned to improve memory usage efficiency and scalability. Compared with the state-of-the-art approach, our approach considerably reduces the total energy consumption of the state-of-the-art application.