Cryptocurrency Mining in European Electricity Systems: A Critical Review of Carbon Accounting, Operational Flexibility and Environmental Trade-Offs

Cryptocurrency-energy assessments often conflate electricity use, emissions attribution and avoided system emissions. This targeted, non-exhaustive integrative review separates these quantities and evaluates mining-flexibility claims in European electricity systems. A six-criterion appraisal links principal studies to supported claims and transfer limits. A general electricity-accounting benchmark uses secondary data to compare 2024 production-mix and residual-mix direct CO2 factors for 24 national European Union domains. Their unweighted means are 214.38 and 415.18 g CO2/kWh; the median within-country ratio is 1.95. The two orderings have a Spearman correlation of 0.670 and disagree for 68 of 276 country pairs. The residual factor exceeds the production factor in all 24 countries in both 2024 and a matched 2025 comparison; consumption-weighted contrasts also remain positive. For a fixed hypothetical 1 MW Hungarian load operating throughout leap year 2024, the two accounting descriptors yield 1556.5 and 2798.9 tonnes of attributed direct CO2, a 79.82% accounting difference. These descriptive, non-causal results compare accounting descriptors, which are not freely interchangeable facility reporting options. Conditional procurement scenarios and an explicitly assumed four-hour example distinguish reported emissions, electricity volume and operating schedules. Technical evidence supports curtailment and ancillary-service participation in specified settings, but price responsiveness alone does not establish lower emissions. The applied framework links European disclosure to claim-specific counterfactuals and specifies requirements for joint assessment of heat, methane, water, hardware and health impacts.