  The data collected from Internet of Things (IoT) devices on various emissions
or pollution, can have a significant economic value for the stakeholders. This
makes it prone to abuse or tampering and brings forward the need to integrate
IoT with a Distributed Ledger Technology (DLT) to collect, store, and protect
the IoT data. However, DLT brings an additional overhead to the frugal IoT
connectivity and symmetrizes the IoT traffic, thus changing the usual
assumption that IoT is uplink-oriented. We have implemented a platform that
integrates DLTs with a monitoring system based on narrowband IoT (NB-IoT). We
evaluate the performance and discuss the tradeoffs in two use cases: data
authorization and real-time monitoring.
