A study published yesterday in the renowned scientific journal Nature warned that power consumption used to power bitcoin transactions alone could send global warming to critical danger levels specified during the 2015 Paris Agreement. The magnitude of this problem would depend on the rate of future bitcoin adoption and usage, the paper said.

The issue of bitcoin’s power consumption, necessary to complete the cryptocurrency’s Proof of Work (PoW) challenge, has been often cited in media as a critical weakness of person-to-person transactions.

The paper’s lead author, associate professor Camilo Mora of the University of Hawaii’s Department of Geography and Environment, based this outlook on the examples of historical mass adoption rates of new technologies, such as credit cards and dishwashers.

Arraying bitcoin’s potential adoption against those historical rates, the study stated that “if [bitcoin’s] rate of adoption follows broadly used technologies, it could create an electricity demand capable of producing enough emissions to exceed 2 °C of global warming in just a few decades.”

Reducing emissions to keep warming below 2 °C is already regarded as a very difficult challenge given the increasing human population and consumption as well as a lack of political will. Then came Bitcoin.

Camilo Mora, et al


Methods and Accuracy

Mora’s paper used 2017 as a reference year for calculating the Bitcoin network’s energy cost in terms of CO2 consumption. To calculate their figure, the paper’s researchers chose randomly from a list of suitably modern (2017) bitcoin mining hardware for every block mined, and averaged together that electricity consumption.

The team then tracked the country locations of each block produced during that year, and using a formula of average CO2 emissions in every country where the each PoW calculation was “likely to be resolved,” applied a country-specific rate of CO2 emission to each block based on average power consumption. Adding these calculations together gave Mora a figure of 69 metric tons of CO2 consumed during 2017.

This figure is far higher than some other estimates, and indeed the rate of CO2 emission coming from the bitcoin network is a highly debated subject. But, critically, Mora’s study did not derive power consumption assumptions from an estimated percentage of profits used to pay for electricity as is common, but rather directly from mining machines’ averaged consumptions specs – sidestepping one of the most contentious disagreements on this subject.

A Bitcoin Cash Fan?

The paper reckons that improvements in bitcoin mining hardware could allay some of the impact of mining, due to an increase in efficiency, but cautions that “reducing Bitcoin’s carbon footprint should not rest solely on some yet-to-be-developed hardware but include simple modifications to the overall system, such as adding more transactions per block or reducing the difficulty or time required to resolve the proof-of-work.”

The battle of bitcoin block sizes is one of the issues that led to the Bitcoin Cash (BCH) fork of Bitcoin last year, with BCH opting for bigger block sizes. Bigger blocks equate to less competition for mining power, and thus lower difficulty PoW operations.

The reduction in difficulty of the PoW algorithm, in the event that bitcoin’s popularity and adoption continues to increase, seems unlikely however, as increased price will mean increased competition to mine blocks – even after next year’s halving.

Another unknown is how the Lightning Network, an in-work offchain payment protocol layered atop the Bitcoin network, will affect all of this if it manages to succeed and gain widespread adopting. It would necessarily draw some of the workload away from the miners, as this is its precise objective; but a widespread adoption of Lightning would probably mean much more overall use of the Bitcoin network, potentially maintaining – or even increasing – current levels of mining requirement. Simply put, nobody knows what would happen.

Other arguments

The bitcoin activist Andreas Antonopoulos is often asked about environmental damage caused by running the Bitcoin network, during his talks. He typically responds in two parts.

His first response is that much energy production is wasted in certain parts of the world, and that setting up mining operations at those locations can constitute a form of “energy arbitrage.” Secondly, he points to the banking and financial system that Bitcoin could stand to eventually replace, and draws attention to the enormous amount of energy gone into supporting its vast infrastructure – physical banks, office towers, data centers, and the like.

Others have taken to social media in the same vein, criticizing the study’s focus on bitcoin in particular as especially harmful.