Bitcoin’s environmental impact subject of debate

Currency’s growth intensifies power use by computers

The growth of bitcoin is fueling speculation and debate about the environmental impact of the collective energy needed to power the virtual currency in the era of climate change. Some questions and answers about the issue:

A bitcoin itself is essentially a line of computer code. It’s signed digitally when it goes from one owner to another. The sustainability concerns about bitcoin, voiced by economists and environmentalists, stem from the process of “mining” that is central to its existence.

The “miners” use computers to make complex calculations that verify transactions in bitcoins. This uses a tremendous amount of energy via computers and server farms all over the world.

Bitcoin is a kind of digital money that isn’t tied to a bank or a government, and its value rose swiftly in the second half of 2017. The value of one bitcoin was about $16,500, in late December, compared with about $1,000 in March.

Bitcoin can’t exist without computers, and 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. The 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.

Some estimates say more than 60 percent of the processing power used to mine bitcoin is in China, where it relies heavily on the burning of coal.

Estimates vary, and a true figure could be impossible to come by because of the intentionally anonymous nature of bitcoin use.

But Dutch bitcoin analyst Alex de Vries, who operates a Bitcoin Energy Consumption Index on the website Digiconomist, has produced estimates he believes are alarming.

If bitcoin miners are using the most efficient machines possible, the lowest amount of electricity they could possibly be using is 13 terawatt hours, de Vries said in an interview. That’s about as much as the entire country of Slovenia.

While de Vries says bitcoin is consuming an “insane amount of energy,” others think the situation is not so dire.

Bitcoin investor Marc Bevand, of St. Louis, has written that bitcoin likely uses close to four or five terawatt hours, less than the annual electricity consumption for Christmas lights in the U.S.