Calculating Emissions from Biofuels, Waste Fuels, and Biomass
The LGO Protocol requires local governments to identify, quantify, and report biomass CO2 emissions as biogenic emissions separate from fossil fuel emissions. CO2 emissions from biomass combustion (e.g. wood, landfill gas, ethanol, etc.) are tracked separately because the carbon in biomass is of a biogenic origin – meaning that it was recently contained in living organic matter – while the carbon in fossil fuels has been trapped in geologic formations for millennia. For additional information, please refer to Chapter 4.5 in the LGO Protocol.
Examples of biogenic emissions sources and their quantification guidelines are below:
Biofuels (e.g. landfill gas, biosolids, wood, and wood waste)
The same step-by-step procedure for determining GHG emissions from fossil fuel applies to non-fossil fuels. Note that CH4 and N2O emissions from biomass combustion are included in Scope 1 and are not treated differently from CH4 and N2O emissions from fossil fuel combustion.
Waste fuels (e.g. municipal solid waste)
For facilities that combust municipal solid waste (MSW), CO2 emissions resulting from the incineration of waste of fossil fuel origin (e.g. plastics, certain textiles, rubber, liquid solvents, and waste oil) must be quantified and included as Scope 1 CO2 stationary combustion emissions. CO2 emissions from combusting the biomass portion of MSW (e.g., yard waste, paper products, etc.) should be separately quantified and reported as biogenic CO2 emissions from combustion.
The LGO Protocol recommends any of the following three methodologies to calculate these emissions:
- Site-specific information on the biomass portion of MSW obtained from a local waste characterization
- ASTM D6866 “Standard Test Methods for Determining the Biobased Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis.”
- Methodologies in ARB’s Regulation for the Mandatory Reporting of GHG Emissions, Section 95125(h).
Biomass Co-Firing in a Unit with CEMS (continuous emission monitoring system)
If biomass fuels are combusted in any of a local government’s units using CEMS to report CO2 emissions, calculate the biogenic emissions associated with the biomass fuels (Equation 8.2) and subtract this from the total measured emissions (Equation 8.3).
Alternatively, instead of first calculating biogenic CO2 from biomass combustion, calculate CO2 from fossil fuel combustion. To do this, multiply fossil fuel consumption by an appropriate fuel-specific emission factor from Table G.1 and Table G.2. After deriving total CO2 from fossil fuel combustion, subtract this value from total CEMS CO2 emissions to obtain CO2 from biomass combustion.
As a third option for separately calculating the portion of CO2 emissions attributable to fossil fuel versus biomass, use the methodology described in ASTM D6866-06a (see above).
