👨🔬Ethereum (Proof of Work)
Note: Post-merge, Ethereum has become a PoS chain – all transactions occurring post-merge will be calculated using the PoS methodology.
Return Protocol calculates Ethereum’s carbon footprint using a bottom-up approach. This is achieved in three parts (see excel doc here):
Energy Consumption: To calculate total energy consumption, Return Protocol leans on user-reported GPU hash rate and power draw data.[1][2] Return Protocol then uses information from Hive OS to understand which GPUs were most popular to compute a weighted average hash rate and power draw. Lastly, four other relevant factors (power supply efficiency, hardware overhead, datacenter overhead, and grid loss) are applied to compute a final value for each year since 2015. To calculate the daily energy consumption of the Ethereum blockchain the daily hash rate is divided by the estimated average GPU hash rate. The result gives an estimate for the total number of GPUs needed to create Ethereum’s daily hash. That figure is multiplied by estimated GPU power draw to calculate Ethereum’s estimated daily energy consumption (MWh).
Grid Emission Factors: The Ethereum Blockchain relies on a global community of validators. To calculate Ethereum’s carbon intensity, the Grid Emission Factor (GEFs) of each country/region where Ethereum is mined are needed. These factors are subject to their own imperfections – while developed economies like the United States provide reasonably up to date GEFs, nations with less robust economies may provide little to no information at all. Additionally, some nations may provide misleading or inaccurate GEFs. For this reason, Return Protocol only uses GEFs provided by trustworthy institutions[1][2][3] or the UNFCCC. Lastly, many nations did not start calculating GEFs until relatively recently. Unfortunately, this forces Return Protocol to make some assumptions about historical GEFs that may impact accuracy.
Node Geolocation: While many websites show daily, or weekly node geolocation data, very few store historical information. To overcome this, Return Protocol uses the Wayback Machine to search Etherscan.com’s Node Tracker, which provides updated daily heat maps of validator locations. Etherscan.com has data going back to late 2018. For all previous years Return Protocol applies the same GEF mix as the oldest date.
GEF Weighted Average: A weighted average GEF is calculated from the daily snapshot of validator geolocations. This final value is multiplied by the estimated daily energy consumption to get an estimated daily carbon intensity (tCO2e) of the Ethereum blockchain.
Emission per Transaction: Finally, estimated daily carbon emissions are divided by the total transactions on each equivalent day. The product represents the estimated carbon intensity per transaction per day (Tx/tCO2e). To calculate a user’s individual on-chain carbon footprint, the Tx/tCO2e is multiplied by the quantity of transactions the user made on the equivalent day. The process repeats for all days the user made transactions on the Ethereum Blockchain. The products are summed to calculate the user’s total lifetime carbon footprint.
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