CAPCOA Issues New Guidance On Quantifying GHG Emissions

The California Air Pollution Control Officers Association (CAPCOA) recently published a report entitled “Quantifying Greenhouse Gas Mitigation Measures: A Resource for Local Government to Assess Emission Reductions from Greenhouse Gas Mitigation Measures” (August 2010). The Report provides local governments and environmental consultants guidance on how to quantify GHG emissions in the environmental review of projects and for planning efforts. The Report focuses on quantifying GHG reductions from mitigation measures in the areas of land use, transportation, energy use, recycling and waste management, among others. The Report suggests the methodologies used in the Report should also be acceptable for use to quantify GHGs for the EPA Mandatory Reporting rule, both inside and outside California.

The Report begins with a discussion of key programs and concepts associated with GHG quantification including: baseline, business-as-usual emissions, types of emission reductions, project scope, lifecycle analysis, accuracy and reliability, additionality, and verification. The report then provides specific guidance for quantifying GHG emissions for each source or activity associated with projects. For each source, the report provides emission factors that can be used quantify the amount of emissions released as a result of the source or activity. Project-related GHGs are determined by multiplying each project source metric by its emission factor. All project-related GHG emissions are then converted to carbon dioxide equivalent units by multiplying values by their global warming potential from the IPCC Second Assessment Report (SAR, 1996). The same general equation is used to determine the reductions from mitigation measures.

The mitigation measures are presented in Fact Sheets and broken into the following general emissions categories: Energy, Transportation, Water, Landscape Equipment, Solid Waste, Vegetation, Construction, Miscellaneous Categories, and General Plans. Several categories are further split into subcategories to properly address the effects of combining the mitigation measures (e.g., transportation). Step-by-step guidance for using the Fact Sheet to quantify a project’s GHG emissions and reductions for mitigation based on California regulations is provided. A discussion on how to modify and use the Fact Sheets outside of California is also provided.

To address the accuracy and the reliability of each quantification method, the report includes a discussion of the assumptions and limitations of the method. For projects where either the assumptions are not met, or the limitations are exceeded, CACPOA states that adjustments must be made to reflect the conditions of the specific project. If required adjustments are not made, the Report indicates the method will not be accurate, and the error can be very large. This in turn could undermine an agency’s CEQA document.
Where several mitigation measures apply to the same source, the Report cautions that estimation of the overall impact of the measures must be carefully evaluated. The Report states that while in some cases the emissions reductions are additive, in others cases emissions reductions must be evaluated sequentially. A detailed discussion of quantifying the combination of mitigation measures, as well as rules to prevent the over-estimation of reductions is included in the report. The report also states that any reductions resulting from compliance with existing laws or regulations cannot be counted as mitigation under CEQA and should be considered part of the existing baseline, or subtracted from the project. The report does not provide guidance on CEQA thresholds of significance.

A full copy of the Report (“Quantifying Greenhouse Gas Mitigation Measures: A Resource for Local Government to Assess Emission Reductions from Greenhouse Gas Mitigation Measures” (August, 2010)) is available at