Technology Cost
Although blockchain can save users money on transaction fees, the technology is far from free. The “proof of work” system that bitcoin uses to validate transactions, for example, consumes vast amounts of computational power. In the real world, the power from the millions of computers on the bitcoin network is close to [what Denmark consumes annually
Despite the costs of mining bitcoin, users continue to drive up their electricity bills in order to validate transactions on the blockchain. That’s because when miners add a block to the bitcoin blockchain, they are rewarded with enough bitcoin to make their time and energy worthwhile. When it comes to blockchains that do not use cryptocurrency, however, miners will need to be paid or otherwise incentivized to validate transactions.
Some solutions to these issues are beginning to arise. For example, bitcoin mining farms have been set up to use solar power, excess natural gas from fracking sites, or power from wind farms.
Speed and Data Inefficiency
Bitcoin is a perfect case study for the possible inefficiencies of blockchain. Bitcoin’s “proof of work” system takes about ten minutes to add a new block to the blockchain. At that rate, it’s [estimated]that the blockchain network can only manage about seven transactions per second (TPS). Although other cryptocurrencies such as Ethereum perform better than bitcoin, they are still limited by blockchain. Legacy brand Visa, for context, can process 24,000 TPS.
Solutions to this issue have been in development for years. There are currently blockchains that are boasting over 30,000 transactions per second.
The other issue is that each block can only hold so much data. The [block size debate has been, and continues to be, one of the most pressing issues for the scalability of blockchains going forward.