The Covenant of Mayors for Climate and Energy initiative, hereafter called "Covenant" or "CoM", brings together local and regional authorities voluntarily committing to develop and implement a Sustainable Energy and Climate Action Plan (SECAP) containing measures to reduce their energy (and non-energy) related Greenhouse Gas (GHG) emissions. Within the CoM 2010 guidebook 'How to develop a Sustainable Energy Action Plan' (Bertoldi et al., 2010), Part II focuses on the compiling of local GHG emission inventories in the 28 Member States of the European Union (EU). This technical report provides an update of the CoM default emission factors, reported in Part II of the CoM 2010 guidebook and subsequently revised (CoM, 2014; CoM, 2016), together with information on the methodologies, assumptions and data sources, as well as recommendations for their application to the calculation of CO2 and GHG (CO2, CH4 and N2O) emissions due to local use or production of energy (fuel, municipal wastes, renewable energy sources (RES), electricity). As for previous versions, the CoM default emission factors - Version 2017 (expressed in tCO2 or CO2 equivalent/MWh), to be used to estimate standard direct emissions are the IPCC (2006) default factors for stationary combustion for the energy carriers and RES, the most commonly used in the European Union. The CoM default emission factors to estimate local emissions using the Life Cycle Assessment approach, which also includes emissions from the entire supply chain, have been updated using the lastest version (v3.2) of the European Life Cycle Database, as well as other Life Cycle databases and literature reviews. For indirect emissions from local consumption of electricity, national and EU annual factors have been calculated for the 1990 to 2013, using an updated methodological approach and an extended set of energy data (IEA, 2016). The GHG emission factors (in tCO2-eq/MWh) have been estimated using the 100-year time horizon Global Warming Potential factors from the IPCC Fourth Assessment Report (IPCC, 2007), which are the ones currently recommended to the EU countries for the national inventory reporting, in the frame of the United Nations Framework Convention on Climate Change. Regular updates of CoM default emission factors are foreseen for the future. New CoM signatories are therefore recommended to use the latest version of Annex I available from the Covenant on-line library1. It is important to note is that the emission factors used to calculate emission inventories should be consistent for the entire implementation process of the SECAP. In particular, since more recent knowledge and technologies can give substantial changes, it is strongly recommended when opting for the use of CoM default emission factors, not to modify the ones applied to the Baseline Emission Inventory during the monitoring phase, in order to identify the trends and changes in local emissions that are due to local energy production and consumption. When selecting the CoM default emission factors, it is also important to ensure that they are appropriate to local fuel quality and composition. If local authorities prefer to use emission factors that better reflect the properties of the fuels used in their territory for the calculation and update of their local emission inventories, they are welcome to do so, when more country specific or local data are available and reliable.
