As of today, an estimate of Bitcoin’s carbon footprint has been added to the Bitcoin Energy Consumption Index. Many readers requested for the addition of this number, as it gives a more detailed understanding of Bitcoin’s environmental impact. This impact is significant, as the electricity going into the Bitcoin network is mostly coal-based (mining is primarily based in China which relies heavily on coal). This type of electricity has an emission factor of up to 1 kg CO2e per kilowatt-hour (KWh).
The estimate featured on the Bitcoin Energy Consumption index applies a more conservative emission factor to the network. This factor is based on the emission factor of China’s national electricity grid (including electricity from all sources) of around 0.7 kg CO2 per KWh. This factor is then applied to only 70% of the total electricity consumed by the network (the remaining 30% is assumed to be based on clean energy). Effectively, the applied factor would then amount to 490 grams of carbon dioxide equivalent per kilowatt-hour (gCO2eq/kWh).
Support for this number was later found in the most detailed available report on cryptocurrency mining facilties (by Garrick Hileman and Michel Rauchs in 2017). In this study, they surveyed facilities representing roughly half of the entire Bitcoin hash rate, with a total (lower bound) consumption of 233 megawatts. Chinese mining facilities were responsible for about half of this, with a lower bound consumption of 111 megawatts. This information can be used to get a rough idea of the actual carbon emission factor in grams of carbon dioxide equivalent per kilowatt-hour (gCO2eq/kWh) that applies to the electricity used for mining.
The table below features a breakdown of the energy consumption of the mining facilities surveyed by Hileman and Rauchs. By applying the emission factors of the respective country’s grid, we find that the Bitcoin network had a weighted average carbon intensity of 475 gCO2eq per kWh consumed.
|wdt_ID||Location||Power consumption (megawatts)||% of surveyed facilities||Carbon intensity (gCO2eq/kWh)|
|8||Total / Weighed Average||233||100.00||475|
The resulting estimate can be found here.