# Open-data based carbon emission intensity signals for electricity generation in European countries -- top down vs. bottom up approach

**Authors:** Jan Frederick Unnewehr, Anke Weidlich, Leonhard Gfüllner, Mirko Schäfer  
**arXiv:** [2110.07999](https://arxiv.org/abs/2110.07999)  
**Date:** 2021-10-15  
**Summary page:** https://www.summarizepaper.com/en/paper/2110.07999v2/

## Key points

- Emission factors (EFs) provide a signal about the carbon intensity of electricity generation in the power system, which is crucial for tracking progress towards decarbonization goals.
- The authors present a bottom-up method that allows deriving per country and per technology EFs based on plant-specific power generation time series and reported emissions from the European emissions trading mechanism.
- The bottom-up method provides more accurate results by accounting for country-wise differences in per technology EFs compared to a top-down approach using statistical data on emissions and power generation on national scales.
- Other methods used to model EFs and resulting carbon intensities include process-based life cycle assessment (LCA) methods and balancing methods that use total emissions and total generated electricity.
- Transparent data sources and publicly available data are important to ensure replicability, adjustability, and expandability of analysis.
- Complementary approaches such as real-time signals provided by companies like Tomorrow through their “electricityMap” platform can also be useful.
- The bottom-up method presented in this study represents a valuable system-wide approach to calculating EFs for electricity generation from various technologies and countries without changing system boundaries or methods between technologies and countries.

## Summary

This article discusses the calculation and application of emission factors (EFs) for electricity generation in European countries. EFs provide a temporally resolved signal about the carbon intensity of electricity generation in the power system, which is crucial for tracking progress towards decarbonization goals. The authors present a bottom-up method that allows deriving per country and per technology EFs based on plant-specific power generation time series and reported emissions from the European emissions trading mechanism. They match 595 fossil generation units and their respective annual emissions, representing approximately 50% of power generation from fossil fuels in 2018. The resulting values for historical per country carbon intensity of electricity generation are compared with corresponding results from a top-down approach, which uses statistical data on emissions and power generation on national scales. The analysis shows that the bottom-up method provides more accurate results by accounting for country-wise differences in per technology EFs. The article also discusses other methods used to model EFs and resulting carbon intensities, including process-based life cycle assessment (LCA) methods and balancing methods that use total emissions and total generated electricity. Many LCA studies can be found for different power generation technologies but often use different LCA methods or system boundaries, making it challenging to compare results across studies. The article highlights the importance of transparent data sources and publicly available data to ensure replicability, adjustability, and expandability of analysis. It also discusses complementary approaches such as real-time signals provided by companies like Tomorrow through their “electricityMap” platform. In conclusion, the bottom-up method presented in this study represents a valuable system-wide approach to calculating EFs for electricity generation from various technologies and countries without changing system boundaries or methods between technologies and countries. This approach can help track progress towards decarbonization goals accurately while accounting for country-wise differences in per technology EFs.