Two environmental concerns come up most: emissions from electricity, and electronic waste from short-lived machines. Both are real questions with measurable answers.
Emissions
CCAF estimated about 39.8 Mt CO₂e a year (data 2024), about 0.08% of global emissions, with a possible range of 32.9–37.6 Mt in a more detailed analysis. The trend is toward cleaner power: coal fell from 36.6% (2022) to 8.9% of the surveyed mix.
E-waste: two estimates
- A 2021 peer-reviewed paper by de Vries and Stoll estimated 30.7 kilotonnes a year (May 2021), assuming machines last about 1.29 years before becoming unprofitable.
- CCAF's 2025 survey estimated about 2.3 kilotonnes for 2024: miners said 86.9% of retired hardware would be resold, repurposed or recycled. CCAF itself calls its method "markedly simplified".
The gap shows why this is debated: one approach models when a machine stops paying, the other asks miners what they actually do with it.
How Bitcoin answers
- Price signals: old machines move to places with cheaper power instead of the bin.
- Firmware: custom firmware can run chips cooler and extend their life.
- Energy choice: mining pays most where energy is surplus or wasted.
Bitcoin's footprint is not zero, and no honest page claims it is. It is measurable, it is shrinking per unit of security, and it buys something new: money without a central issuer.