The UNFCCC has accepted the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories ,  developed and published by the Intergovernmental Panel on Climate Change (IPCC) as the emission estimation methods that must be used by the parties to the convention to ensure transparency, completeness, consistency, comparability and accuracy of the national greenhouse gas inventories.  These IPCC Guidelines are the primary source for default emission factors. Recently IPCC has published the 2006 IPCC Guidelines for National Greenhouse Gas Inventories . These and many more greenhouse gas emission factors can be found on IPCC's Emission Factor Database.  Commercially applicable organisational greenhouse gas emission factors can be found on the search engine, .