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singularity-energy / open-grid-emissions

Tools for producing high-quality hourly generation and emissions data for U.S. electric grids
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Should we adjust emissions for biomass? #130

Open grgmiller opened 2 years ago

grgmiller commented 2 years ago

The combustion of biomass releases greenhouse gases and other air pollutants into the atmosphere. However, the EPA's eGRID database includes a legacy calculation of biomass-adjusted emissions values. As they explain in the eGRID technical support document:

Prior editions of eGRID applied a biomass adjustment to the annual emission values based on an assumption of zero emissions from biomass combustion. This assumes that the amount of carbon sequestered during biomass growth equals the amount released during combustion, without consideration of other factors. For reasons of consistency, the same approach is applied in eGRID2020.

However, this approach of assuming zero emissions from biomass combustion is problematic for several reasons:

  1. There is much debate in the academic literature about the assumption of zero net emissions from biomass. This is far from a comprehensive literature review on the topic, but for example see: Johnson 2009, Cherubini et al 2011, Haberl et al 2012, Downie et al 2014
  2. This approach selectively applies a partial life-cycle accounting approach to biomass fuels (as it consideres the upstream emissions impacts of the fuel), which is inconsistent with the treatment of other fuels in this dataset

Based on our current understanding of this topic, it may not be appropriate to use biomass-adjusted emissions data for carbon accounting or other general uses, unless they are being used in a specific policy or regulatory context that treats biomass emissions as carbon neutral. Thus, biomass-adjusted emissions are only included in the OGEI dataset for consistency with eGRID and for use in these niche cases. All emissions data that has been adjusted for biomass emissions will include _adjusted in the name of the column.

We may want to consider removing the biomass adjustment from future versions of the data, but it would be useful to do more research on this and understand what the use cases for this adjusted data are.

grgmiller commented 1 year ago

The GHG Protocol Scope 2 Guidance (2015) notes in section 6.12 that:

While biomass can produce fewer GHG emissions than fossil fuels and may be grown and used on a shorter time horizon, it still produces GHG emissions and should not be treated with a “zero” emission factor. Based on the Corporate Standard, any CH4 or N2O emissions from biogenic energy sources use shall be reported in scope 2, while the CO2 portion of the biofuel combustion shall be reported outside the scopes. In practice, this means that any market-based method data that includes biofuels should report the CO2 portion of the biofuel combustion separately from the scopes.

For the location-based approach, most commonly used grid average emission factor—including those issued by EPA eGRID (U.S.), Defra (U.K.), and the International Energy Agency (for all countries worldwide)—do not note the percentage of biomass in the emission factor and do not separately report the biogenic CO2, effectively treating it as “zero” emissions. Companies should document this omission in any grid average emission factors used.

This seems to suggest that to be in compliance with the guidance, we would need to provide a "biogenic" and "nonbiogenic" emission factor, but only for market-based accounting? This seems to suggest that location-based accounting should include biogenic emissions?