Equation 5.1 Emission factor approach for calculating
Table 5.1 Data collection principles11
GHG emissions GHG emissions =
Data collection principles
Activity data × Emission factor
Establish collection processes that lead to continuous improvement of the data sets used in the inventory (resource prioritization, planning, implementation, documentation, etc.)
Activity data is a quantitative measure of a level of activity that results in GHG emissions taking place during a given period of time (e.g., volume of gas used, kilometers driven, tonnes of solid waste sent to landfill, etc.). An emission factor is a measure of the mass of GHG emissions relative to a unit of activity. For example, estimating CO2 emissions from the use of electricity involves multiplying data on kilowatt-hours (kWh) of electricity used by the emission factor (kgCO2/kWh) for electricity, which will depend on the technology and type of fuel used to generate the electricity.
Prioritize improvements on the collection of data needed to improve estimates of key categories which are the largest, have the greatest potential to change, or have the greatest uncertainty
Data collection is an integral part of developing and updating a GHG inventory. This includes gathering existing data, generating new data, and adapting data for inventory use. Table 5.1 sets out the methodological principles of data collection that underpin good practice.
Sourcing activity data
It is good practice to start data collection activities with an initial screening of available data sources. This will be an iterative process to improve the quality of data used and should be driven by two primary considerations:
•• Data should be from reliable and robust sources •• Data should be time- and geographically-specific to the inventory boundary, and technology-specific to the activity being measured Data can be gathered from a variety of sources, including government departments and statistics agencies, a country’s national GHG inventory report, universities and research institutes, scientific and technical articles in environmental books, journals and reports, and sector experts/stakeholder
Review data collection activities and methodological needs on a regular basis to guide progressive, and efficient, inventory improvement Work with data suppliers to support consistent and continuing information flows
organizations. In general, it is preferable to use local and national data over international data, and data from publicly-available, peer-reviewed and reputable sources, often available through government publications. The following information should be requested and recorded when sourcing data:
•• Definition and description of the data set: time series, sector breakdown, units, assumptions, uncertainties and known gaps •• Frequency and timescales for data collection and publication •• Contact name and organization(s) It may be necessary to generate new data if the required activity data does not exist or cannot be estimated from existing sources. This could involve physical measurement12, sampling activities, or surveys. Surveys may be the best option for most emission sources, given the tailored data needs of city-wide GHG inventories, 11. Adapted from 2006 IPCC Guidelines, Chapter 2. 12. For example, direct measurement of point source GHG emissions from an industrial or waste treatment facility.
48 Global Protocol for Community-Scale Greenhouse Gas Emission Inventories