Debate about the environmental effects of bitcoin mining has resurfaced following claims by an Australia-based sustainability think tank that bitcoin could eventually consume 60% of annual global electricity production.
"Bitcoin miners can get power cheaply for $0.05 per kilowatt hour (kWh) which means that they get 20 kWh per dollar spent," notes the website.
By multiplying these numbers (500,000 x 20 x 3,600 x 365) on its Bitcurrent calculator – an interactive spreadsheet – the foundation arrives at the conclusion that bitcoin mines would consume 13,140,000,000,000 kWh – or 13,140 terawatt hours (TWh) – per annum, or the amount of energy required to power 1.5bn homes.
Guy Lane, an environmental scientist and spokesperson for the foundation, said:
"While bitcoin is a virtual currency, it has very real economic, social and environmental effects […] Bitcoin has the potential to have an enormous impact on our global resources and energy use if not managed properly.”
Lane explained that the foundation’s bitcoin energy model assumes that miners will spend half the value of a potential million-dollar bitcoin on mining. “As their [bitcoin] value increases, more people will certainly look to create more bitcoins, the cost and energy used in this process will logically grow so long as people can make money.”
“There is a lot to be said for bitcoin as a currency, but it may ultimately be fatally flawed because of its growing energy consumption,” Lane concluded.
The think tank's findings have been widely contested by the bitcoin mining community.
Sam Cole, co-founder of KnCMiner AB, spoke to CoinDesk about the relative shortcomings in the foundation's research.
Lane said the foundation's argument rested on a "scientific theory based on an understanding of the bitcoin technology and economic system. The scenario of $1m bitcoins is just one of the many that can be applied to the Bitcurrent Calculator."
"If bitcoin replaces gold and the US dollar as a global currency, maybe $1m is a low figure. Even if bitcoin only gets to $400,000 it still consumes 23% of global electricity supply," he added.
Dave Hudson, author at HashingIt, a blog that looks at statistics of the bitcoin ecosystem, noted that although the essence of the foundation's argument was not fundamentally wrong, he thought that there were making a "very extreme argument more for effect than anything else".
Lane, however, rebutted the claims that the presented argument was extreme. "What is extreme is the possibility of a simple technology that did not exist a decade ago threatening to overwhelm global energy supply," he noted.
Despite this, Hudson agreed that if potential profit margins from bitcoin mining were large, this would incentivise people to continue reaping the profits and "one unfortunate consequence of this is energy use", he said.
According to him, one of the issues is that the foundation's calculations assume a daily production of 3,600 bitcoins, but Hudson pointed out that as of next year this would drop to 1,800 and in another five years it would be halved further to 900 bitcoins a day.
Hudson added: "For one thing at these sorts of levels the entities controlling mining operations would now be huge corporations (the infrequency of blocks means that a degree of block-maker centralisation is inevitable) and with that would come accountability.
Green credentials would need to be established otherwise we'd see governments elected with a remit to tax such unfriendly businesses of all profits."
Although he said that some of the more ardent decentralisation fans would potentially dispute his reasoning, Hudson believes that the only way to achieve mass-scale decentralisation would be to have hashing distributed over a vast number of devices and locations. In turn, this would mean that system-wide upgrades or protocol changes would be unpractical.
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