Graphical Abstract: The paper summarizes the research results on development national emissions factor for the Greenhouse Gas Inventory (GHGI) Source Category “6A Solid Waste Disposal on Land”. The obtained results offer the opportunity to improve the Intergovernmental Panel for Climate Change (IPCC) methodologies and Emission Factors for assessing the GHG emissions originated from waste sector. The article contains relevant information on composition of landfill gases at managed and unmanaged solid waste disposal sites, as well as the municipal solid waste composition results, investigated during one year in the Republic of Moldova: from autumn, 2004 to summer, 2005.