Everyone knows how bitcoins is proved based on the workload. So the world will have tens of thousands of absenteeism calculate the hash value and huge energy consumption. Now, the PoS does not need to really dig. All the NxT always exist and have already exists, so now the client wallet mining get the transaction fees. Subsequent trend is to use the word "forging" instead of "mining". These can download to the PC (CPU) mining and client wallet to complete, it is very friendly to the environment and efficient.