Ember’s calculations for emissions are continually improving, but may be conservative or uncertain in the ways we describe below. These figures are intended to include full lifecycle emissions, including upstream methane, supply chain and production emissions, and include all gases, converted to CO2 equivalent over a 100-year period.
Emissions can vary over time as power plant efficiency changes and as different grades of fuel are used. Therefore, we report emission values by fuel type and emission intensity by country. These values are calculated by multiplying our generation numbers by emissions factors taken from various sources, detailed below. Our goal is, whenever possible, to capture variation across geographic regions and over time in the intensity of emissions from different fuels. We recently updated this approach and are actively working to improve it; If you have any comments or suggestions for improvement, please email us [email protected].
Our sources and methodology for different fuels are described below. All the factors we use are for net generation; where we report gross generation, we adjust our factors by 6% for thermal fuel sources and 1% for others.
The data is taken from Gibon et al. 2022 (UNECE) and the Global Energy Monitor Coal Plant Tracker (EGG YOLK). UNECE provides life cycle emissions factors for different fuel types for the year 2020 for each TO REMEMBER region. UNECE reports values for different technologies that use bituminous coal; We derive factors for different coal types based on IPCC 2005 direct combustion emissions factors. Using national annual technology and coal quality blends from GEM capacity data, we estimate combined emissions factors by country and by year for mineral coal and lignite. The range of factors used in the EU between 2000 and 2023 is
- Coal: 952-1045 g/kWh
- Lignite: 1033-1080 g/kWh
Country-level factors are taken from Jordaan et al. 2022, and are for generation for the year 2017. Two sets of factors are provided; we use ones that try to account for combined heat and energy. For smaller countries where data is not available, a global average number is used. The range of factors used in the EU is:
Nuclear and wind
We use regional-level data from UNECE. The values used are:
- Onshore wind: 12 g/kWh
- Offshore wind: 15 g/kWh
- Nuclear: 5 g/kWh
Bioenergy, hydro, solar, other renewable energy and other fossil fuels
We use data from IPCC AR5 WG3 Annex III (2014). These are global estimates for the year 2020; we use midpoint life cycle factors. These are:
- Bioenergy: 230 g/kWh
- Hydro: 24 g/kWh
- Solar: 48g/kWh
- Other renewable energy: 38/kWh
- Other fossil: 700/kWh
This approach attempts to explain some geographic and temporal variations in emission factors. It is a work in progress and numbers may differ from reality for several reasons. Some of them are listed below:
- Coal: UNECE base factors refer to coal plants in the year 2020. They do not capture operational efficiency losses associated with older plants or intra-technology efficiency differences. Finally, we make assumptions to derive factors for coal types other than lignite, including identical combustion efficiencies and upstream emissions per MWh generated.
- Gas: Our gas factors are specific to the year 2017, so they do not take into account temporal variations in plant efficiency or methane leak rates. The methodology in Jordaan et al. 2022 it also prefers to underestimate methane emissions when there are doubts. In general, there is very significant uncertainty surrounding methane emission rates, even in countries that prioritize collecting this data. Some authors believe that emission rates are significantly higher than assumed in our factors.
- Time horizon: Upstream methane emissions for gas and coal generation are calculated on a long-term basis, assuming methane is 21 times more potent than CO2. However, methane’s short-term impact is actually four times greater, with 86 times the potency of CO2 during its first 20 years in the atmosphere. To see This page For more informations.
- Solar and wind: Recent efficiency improvements have caused wind and solar emissions intensity to decrease as energy production increases relative to emissions from production. Our numbers may therefore be higher than reality. We also do not currently capture geographic variation in emissions intensity within TO REMEMBER regions; This could be significant as countries with lower annual solar capacity factors will have proportionally higher life cycle emissions.
- Bioenergy: It is very likely that our value is a significant underestimation of the actual emissions caused by bioenergy generation. The intensity of bioenergy emissions depends greatly on the raw material, how it was obtained and what would have happened if the raw material had not been burned to produce energy. The IPCC value we use is for dedicated energy crops and crop residues, rather than the much more commonly used woody or forestry biomass, which has been shown to have a higher risk of high-carbon outcomes. In certain cases, bioenergy may have a carbon intensity significantly higher than coal. Bioenergy is also often powered by fossil fuels; We have disaggregated them where possible, but in certain cases the recorded bioenergy generation may include some co-combustion. In these circumstances, actual emissions will be higher than we estimate.
- Hydro and other renewable energies: Hydropower emissions are generally very low, but can vary based on emissions during construction and biogenic emissions, and therefore in a small number of cases can be much higher than our value. Likewise, other renewable sources, such as geothermal, can, in rare and discrepant cases have high emissions.
- Gross and net generation: In the EU, we report net generation for monthly data and gross generation for annual data. For raw generation, we perform the conversion described above, which may present some errors.
- Combined heat and power (CHP): In many cases, thermal power plants produce heat and electricity. Our coal factors are based solely on the electricity produced by these plants, ignoring heat. Therefore, it may not be fair for our dataset to include all emissions attributed to co-firing plants, which actually have higher efficiency than reported when considering total useful energy production. Our gas factors are responsible for cogeneration.