Bitcoin relies on computers, which rely on electricity, to exist. The number of computers and the energy needed to power them is rising — the growing value of bitcoin is directly tied to the amount of energy it uses.
Bitcoin miners unlock bitcoins by solving complex, unique puzzles. As the value of bitcoin goes up, the puzzles become increasingly more difficult, and it requires more computer power to solve them. Estimates on how much energy Bitcoin uses vary.
A 2019 study by researchers at the Technical University of Munich and the Massachusetts Institute of Technology concluded that, in late 2018, the entire bitcoin network was responsible for up to 22.9 million tons of CO2 per year — similar to a large Western city or an entire developing country like Sri Lanka.
Plus the major bitcoin miners are now in China, so predominantly using 'dirty' energy from coal fired powerstations.BTC's energy used has increased massively, and is already higher than that of countries like Sweden and Argentina. Another significant statistic: to process one transaction in BTC takes a million times more processing cycles than to process a credit card transaction. This makes the BTC infrastructure incredibly limited: it can only process 10 transactions/second.